Is Air Recirculation A Problem With Air Source Heat Pumps?

[@pete_pump]

A cracking experiment. What I take away from it is that we have to test things for real far more often than we do. Thank you for that. Let’s keep experimenting and learning. I will do a smoke test on an install now which has massive icing issues because I think it is recycling flue gases from a neighbours non-condensing gas boiler

[@waqasahmed939]

Especially when the ambient temperature inside will be at least 8C

[@jonblacklock1052]

Often wondered what an ASHP would be like if it was in a lean to greenhouse with manufacturers clearances all round but venting the exhaust out of the greenhouse.

[@inh415]

Big enough double glazed greenhouse should increase scop

[@robcuthbert8257]

If a partially buried solar thermal storage system was incorporated into your greenhouse, could the ASHP use the greenhouse space as a buffer, while the thermal storage would backfill (radiation/convection) the greenhouse volume as needed while the ASHP was running ? Thank you

[@jsjs6751]

What are you wondering? Every degree you can add to the temperature of the input of the outdoor unit will decrease the amount of electrical power needed, everything else being equal. But the greenhouse only has so much energy to give. More if the sun is shining, of course. If the exhaust is vented to the outside, the greenhouse will of course at some time be emptied of heated air, and this would make the HP work much as if it was mounted outside. But, since the air in a greenhouse is usually very humid, there will probably be more ice buildup if the evaporator gets below freezing.

[@inh415]

Air volume is lightly a lot less important than sun faceing surface area. Also insulation would help. A feasible way of adding more heat from the sun to the cold side of a heat pump would be triple wall pollycarb sheet laid with an air gap over a black insulated steel sheet. Use the air in the air gap to feed the heat pump outdoor unit. Air inside will easily get over 100c on a sunny day. I know of a swimming pool that heats their water using the same construction, only with a black pipe laid in the air gap as a heat exchanger . Would still want a nice large area to make a significant difference. Probably 10's of square meters angled at around 45+ Deg to be most effective in the winter months (dependent on where you live)

[@jonblacklock1052]

@@jsjs6751 it would be interesting to see what the improvements in CoP would be. Presumably enough airflow onto the greenhouse or covered area would counter humidity issues but I guess that’s something that could be measured.

[@tomplayer]

I believe the diagram at 9:40 is my system which we are currently in the process of altering. The microclimate effect is commonly -2C difference, and what wasn't included on the diagram were some temporary scaffolding boards 12ft above which were creating near-enclosure conditions. The walls are 50ft / 10ft either side. Everything still within manufacturers spec (we wouldn't have installed it otherwise). - The main struggling points (which I see briefly mentioned in the video) are the de-icing cycle length, which was around 25-35 minutes in the cold weather. I'm told it should be more like 90 minutes. And the flow temps could only reach 35-36C (design target is 40) before it got iced up and restarted the cycle. - House therefore struggled to reach 18/19C on the coldest days, but most irritating was any additional demand for hot water causing the whole house to drop in temperature for hours, as the heat pump only operates at low (~25% power output) until DHW demand satisfied. Can't figure that one out. nb. system efficiency is usually excellent in other conditions, well above 400% Proposed solution = I put a gym fan in the alleyway to exchange air, and it extended the cycling time from 30 mins to 90 mins and the flow temperatures got up to 39C, so clearly an airflow/micro-climate issue. We are going to raise the heat pump to 3m, and possibly upgrade to a 7kW unit. Currently a 5kW unit for a four bed semi detatched property which is on the low side. tl;dr Good work on the video, but consistent flow temps are the most important metric

[@Richardincancale]

My tumble dryer has a built-in heat pump. I have it in my plant room so it recycles heat escaping from pipes and hot water tank 👍

[@tanyac.c.macbean4707]

In the 70's, my Dad ran our dryer vent to our unfinished basement for "free" heat. He drooped the vent & added an ice cream bucket to the bend. He poked a couple holes in the vent & the moisture dripped into the bucket. That water was collected & saved from outdoor plants. He never took anything for granted & recycled what he could.

[@waqasahmed939]

That's not a bad shout. My parent's one is in the cellar lol but it very very rarely gets below 5C

[@CH11LER.]

We should put them in garages / sheds and have a vent just for the air outtake. That should improve efficiency.

[@HeDzsz]

In my previous house, I created a surround around the heatpump, with and entrance on one side, and the exhaust blowing into a shed with 1 side open. It worked great. Also significantly quieter.

[@jsjs6751]

Why? And what exactly "worked great"?

[@Lfreeman98]

This highlights the main issue I often experience with air to water HP - AC engineers have limited knowledge & experience (and often interest) in the hydronic circuit & vice versa for the plumber/mechanical engineer. When your A2WHP goes wrong - what trade do you call first? Unit there is a specific trade that trains a dedicated air to water HP engineer - with all the skills to install/commission/diagnose both sides of the circuit (wet & refrigerant) - there is going to be issues.

[@stevechambers8869]

So next is to try the aftermarket prettying up covers and see if they screw it? Pallets!

[@jwheeler91]

Is love to see an experiment with a green house, where the fan expels the air out through a cutout, and various sized inlets to see if solar gain could help at all

[@jwheeler91]

(As in a modified / custom lean to style greenhouse)

[@timballam3675]

@@jwheeler91 is you have a South facing wall you can create a lean-to greenhouse with solar pannles for the roof to use the high summer sun for electricity and the low winter sun for thermal gain. You can pump the heat directly from the greenhouse into the house without the need for a heatpump.

[@Antony-4Q]

I was thinking the exact same thing, maybe some side vents for added airflow into the back of the unit ?

[@waqasahmed939]

I'd love to see it in a cellar tbf, and therefore the COP from there I say a cellar because the temperature typically is just above 5C so it'd be interesting to know what the COP is in such a scenario

[@jsjs6751]

@Waqas Ahmed In that case the outside unit will remove heat from the cellar, until the temperature there falls below the outside temperature, after which you will be better off placing the unit outside.

[@nsevaslidis]

It would have been great to compare the fan speed and the sound levels in those deferent scenarios because noise sometimes can be a problem. The unit might manage to capture almost the same energy by the outside air by increasing its fan speed. Great video!

[@constructioneerful]

Does the COP Calc include the running costs of the fan?

[@HeatGeek]

@@constructioneerful ofcourse

[@HeatGeek]

Fab speed will be the same

[@glightsolutions]

I was getting a tour of a Swedish heat pump factory once and they tested heat pumps in sealed cabins. Also used to warp the units in cling film 😂

[@pjttaylor7186]

on really cold days could you feed warmer air via a duct or other, say a small woodburner [warm air from around the flue , not the smoke fumes] to boost heat transfer, yes i know it isn't eco but just for sub zero days?

[@cipur11]

They would never tell you "yes you can" beacous that would beat the whole point of heat pump and you may as well have stove in your house !!!

[@ScrapKing73]

I’m thinking about getting a waterproof portable heat pump for my small suite, putting it indoors during the winter where the heat of its operation is a benefit, and outdoors in the summer when the heat of its operation is a negative. Hiding it in the shade outdoors, naturally. Just changing which hoses are hooked up to the window. I can’t use a window-mount unit as the windows open horizontally.

[@ngbc5342]

Hi, I once considered putting an ASHP in my large lean-to conservatory (25m l x 4m w x 3m h) to heat my small indoor swimming pool. Given most conservatories are too hot in the summer, and cold in the winter it seems logical to me that they would be mutually complementary, but when I spoke to Mitsubishi they said "computer says no" I think they're wrong. Nick

[@jsjs6751]

Every temperature increase of the input air for the outdoor unit will save on electrical costs. But the heat pump will remove heat from the conservatory, and if that temperature falls below the outside temperature, it will cost you more money. If the air in the conservatory is more humid, it will increase de-icing frequency when freezing.

[@Roedy_Coedy]

I've wondered for a while if you managed to mitigate vibrations would a loft space work? Drain condensate out through the eaves, ensure vent tiles are installed or even better eave vents to drop the cooled air out of the loft, easy pipe runs into the house/airing cupboard (where most people now house their utilities). Any poor loft insulation goes to help raising loft temps/inlet temps (I know it's not a perpetual energy system, if you lose more than you generate you still lose) and increasing cop? I'm the summer it's likely to be off anyway unless it helps towards hot water in which case it would realllly help that cop...?

[@leonhardtkristensen4093]

One of the things you probably haven't thought about is that by incasing the unit you also save the energy that is used to drive the compressor and defrosting it. That energy would normally get lost I think. If it wasn't for the noise we should actually install the main unit indors and the indor part outdoors and then run it in reverse exept of cause you can't defrost the indoor unit.

[@HeatGeek]

This is a misunderstanding of the first law of thermodynamics

[@leonhardtkristensen4093]

@@HeatGeek I am sorry but I don't get that. As I understand it the heat that is being moved into the house by an air conditioner is what is taken away from the outside air that surrounds the external collector/radiator. What I am talking about are the heat losses in the compressor that may or may not heat up the air going through the collector normally but must do that if it is all incaged. Also I am assuming electricity is used to defrost the collector should it be iced up.

[@leonhardtkristensen4093]

@@zImdragon Yes that is what I talked about. I have played around with old heat pump water heater trying to use it to heat water in the daytime using solar and then circulating that water into and old caravan to keep it warm doring the night. From that I know that the compressor gets pretty hot. Not all the energy goes into compressing the gas to fluid. (My result was not so good. I ran out of heat at about 2am. Not enough water heated up and losses of about 50%) The live feed is very interesting to me. I just lack one thing. The COP varies a lot through the days and overall it is far from max COP. I would have liked to know the outdoor temperature (Really the temperature difference) on the days as well to be able to compare it to my conditions. I live in Melbourne Australia and we currently use gas for heating and hot water as it has been the cheapest in the past but the difference gets less and less and additionally we are exporting solar power in the daytime for no profit so when the gas heating breaks down we will probably swap to heat pumps. Here of cause we rarely get temperatures lower than zero centigrade. Earth loop is basically out of the question due to space restrictions so it has to be air to water. The video was very interesting and informative as we have about 1.5m between the house and the fence. I was worried about the short distance but not so much now. Have you or any body else got any info about using CO2 as the gas instead of the more normal ones. It is advertized as being more efficient.

[@leonhardtkristensen4093]

@@zImdragon Thanks. That gives a lot more information then. In regards to CO2 they do advertize them for heating including including hydronic heating as being the best of the best here in Australia.

[@leonhardtkristensen4093]

@@zImdragon No I haven't. I hope my final decision is some time of. I hope my gas heaters will last some time still and that the gas prices won't rise too much. Allready I have been told that we should expect to pay at least A$600 more for gas nest year. I am just gaining information.

[@Coupe100]

I think you're definitely right about flow temp being the determining factor for efficiency. My installers left the weather compensation set pretty much as default (50 degrees at -3, to 35 degrees at 15), no underfloor heating, just new radiators. I found the pump was cycling too much as it reached temperature in the house too quickly and my COP was around 3.2 at zero degrees outside. After some experimentation I now have my flow temp set at 39 degrees at -3, to 29 degrees at 15, and now have a COP of 4 at -3 up to 4.5 at 8 degrees, and the house stays at a constant 21 degrees in the main living areas, and 18 to 19 in the bedrooms. There may still be a little more efficiency to gain, but will see how it performs in the milder weather.

[@Coupe100]

@@zlmdragon. Panasonic Aquarea J Series 7kW

[@Coupe100]

@@zlmdragon. yes it is - I’m not convinced I have the weather compensation quite right further up the scale yet, I’m sure there is still more efficiency to come. The only downside to the Panasonic is that the weather compensation only has 2 points that you can adjust, a low and a high (you can move these along the scale), so you only ever get a linear scale for temperatures in between, whereas ideally I think it should be a curve

[@Coupe100]

@@zlmdragon. according to the Panasonic control panel at the time, yes.

[@Coupe100]

@@zlmdragon. bear in mind, this is maintaining a constant temperature, not heating up to achieve a temperature. It never gets turned off or down at all.

[@RustyWalker]

Can you duct the air from a greenhouse, and if you do, how much volume would the greenhouse need to make a difference to the heat differential?

[@markbarrett2321]

heat pumps will work in enclosed spaces but the issues would be the defrost cycle and condensate unless run with trace heating, but one problem with 'boxing it in' is it can/will make it louder

[@thomasmcdonagh43]

Agreed. It will need to defrost more in an enclosed space

[@jsjs6751]

I don't think so. If you remove the condenced water from the system, the result would be a very dry environment. Should be enough to drain it out of the system (down a drain, for example).

[@markbarrett2321]

@jsjs by that theory you'll be getting no new air to replenish the heat pump meaning you've put it in a completely sealed airtight container which will just get colder and colder unless heated by something

[@ngbc5342]

I should have added in the summer months, they will cool the conservatory, while heating the pool. Nick

[@Thermahexx-ThermaPANEL]

We placed our Chiltrix heat pump in our factory where we manufacture our hydronic radiant ThermaPANEL's. This unit is for heating and cooling our offices. The factory operations produce a great deal of heat that we exhaust out of the building in winter and summer. In summer, the ambient temperature of the location of the unit is comparable to outside temps. We connected the outflow to a 24" duct which is part of our exhaust system for our other operations. This duct system has its own exhaust fan which provides about 10 extra CFM through the unit. We have not measured the COP, but we suspect that it is off the charts. being that it is inside, glycol is not required in the system.

[@_3ntity_]

As you pointed out, you'll probably start to struggle at some point to get to a comfortable temperature inside, especially if the sizing of your heatpump was done correctly and you're now getting quite a bit less energy output. The only thing that would have a detrimental effect on COP here is if your outside temperature meter is too close to the heat pump, as then the compensation would start to kick in way harder than it should. You're also testing in a condition where the house is already warmed up, so the losses in output are managed by the not so high demand to keep the flow temperature up. I think it would struggle a lot more if the system actually had to do some heating instead of just keeping a temperature. Personally I think it's a bit dangerous to put out the assumption that installs like these are decent without more extensive testing (heatpumps got enough of a bad rep as it is due to bad installs).

[@HeatGeek]

If you watch the video we literally state that this is not conclusive and not recommended. Secondly nearly all heating systems should 'maintain' rather than heat up for max effy. Please research stable state heating on jg dot com

[@ChristopherSmith-im5hc]

Guys great content as usual -Physics always prevails -experiments take a long time to think about and there correct design is critical -remember also wind speeds and characteristics are different at ground level vs height from grade. A reminder to turn your phone to landscape when making a video which has use on multiple viewing platforms (especially KZbin!). Image having your TV turned on its end to watch a movie?

[@PeterJFlower]

I wondered what happened to the humidity around the heat pump. Theoretically the humidity would rise as the temperature drops. Enclosed, the heat pump would condense that moisture out quite quickly, the air around the unit should therfore be much drier than the ambient air. I understand that in drier and colder countries than the UK heat pump efficiencies are quite good and they don't defrost very often so maybe that is improving COP. Facinating stuff, I wish I had a heat pump to play with...

[@briangriffiths1285]

I have a similar arrangement with a fence round 3 sides and a house wall behind. To mitigate the issue of air pooling I took the boards off one side of the fence and refitted them with gaps like louvres. Either we get a breeze pushing through the fence or the air passes out of the louvres on a still day. The unit is a Mitsubishi 14kW.

[@HeatGeek]

Did you notice any difference or did you do this from the start?

[@briangriffiths1285]

@@HeatGeek I did it before the metering was working but but it probably helps. If the air is still I get a cold draught coming through the fence.. The louvered panel is only about 4 ft long but will allow breeze from the west to pass through the panel across the front of the heat pump. Either way it offers an escape route for air pooling. The fence is a close board fence like the one outside your premises. I think it probably helps to reduce sound noise but we are on the A31 just outside Alton anyway, plenty of other noise! My installer was very impressed by my handy work! Thanks for your picing this up. I got into plumbing when my 2 year old broke an 8mm pipe by staring on it 45 years ago. I subsequently fitted a couple of full systems when it was legal for the amateur to do it back in the 80s. Someone, somewhere needs to get heat pump installation moving ahead rapidly. I have had quite a few thoughts on issues and think that 3rd parties or charities should get behind helping those who can't cope with the upheaval. Love to discuss that with you.

[@salibaba]

This reminds me of when the top gear team tried to kill a Toyota hilux. Have you dropped it off a building yet? 🤣

[@zelozejn]

Great content, great video, an on screen recap chart for those that aren't that good at listening would be awesome.

[@GhitaA]

I'm thinking to put the monobloc heatpump INSIDE a 400 m3 glasshouse, with only the fan side blowing outside. The glasshouse is also where the ventilation system exhaust bad air from inside the house (800m3/h) . It's a passive house with 6kwh heatpump+underfloor hearing running 24/7 - so nowhere close to maximum power/airflow. If there's not enough airflow I can always leave a small window cracked in the glasshouse. Was thinking during the sunny days the COP should be significantly better and less (or no) defrosting. Do you think it'd work?

[@Themiddleagedman53]

What would happen if you put a heat pump in a car port 1 metre from one end? Is this possible? Cheers great video

[@Candisa]

Good do know if I ever get a heatpump the location I have in mind isn't a problem. The location I have in mind is a tiny courtyard of about 2.5 by 2.5 meters (8ft by 8ft) with 3m (10ft) high walls or fencing all around with one side that is about half open to the garden. I would put the heatpump about 3ft off the ground (there is a flooding risk). That location would allow me to tie in with the location of the combiboiler to make a hybrid system.

[@diatonicdelirium1743]

If you vent the exhaust air into the (half)open side you should be OK, air will be drawn in from above to reach the intake.

[@jboutdoors7019]

I've wondered for a while how well one would do in like a root cellar, say a 10x10 room below frost level, dirt sides and gravel bottom.

[@jsjs6751]

The heat pump will remove heat from the cellar. After some time, the temperature in there will probably fall below outside temperature, after which you will increase your electricity bill.

[@EdthePlumber]

I am now very curious, what size vent and exhaust would you need for an internal heat pump?

[@simonposkett1753]

One that shift the air. That single fan Vaillant shift around 2500 3000m3/hr

[@johntisbury]

Did the fire brigade turn up with all that smoke? LOL

[@IanCope-jv1dt]

1/I would question how airtight the makeshift box is.2/Are the circulating air currents pulling in additional warmer air. 3/Regards incoming air temperature the heatpump is still working within range, as the temperature bottoms i.e - 20C. I think a different scenario will be observed???. The temperature will drop to this point quicker than a unit located in an open space.

[@yeahright3348]

With the graph at @14:17 you can see that the outdoor temperature rose considerable, from -2.5 degrees C to 0 degrees C, i think this maybe offsetting any negative you might see because of increased recirculation.

[@HeatGeek]

Frosting happens from 4c downward…

[@yeahright3348]

@@HeatGeek and? Just because ice will start to accumulate doesn’t mean a heat pump won’t be more efficient at 0 than at -2.5c. There is simply more heat energy per cubic meter of air relative to the working temperatures of the refrigerant, it will boil easier, thus require less work to force the phase changes, thus the compress will do less work, thus more efficient.

[@anthonyhodson]

Entropy (2nd law) would be my guess having seen this (hot travelling to cold). Though very surprised how little the re circulation matters. Thanks for your experiment!

[@lancashirebob3]

I had a friend on holiday in Thailand. No Aircon in his hotel room so he opened the mini fridge to cool the room down!

[@HeatGeek]

Lol

[@cjmartin9579]

What was the temperature of the air coming out of the fan. Wouldn’t expect it to be much low than ambient temperature. Probably would have a worse effect in summer as temperature differences would be large

[@nlmoin990]

@HeatGeek I honestly want to know if I should put a a air-to-water heat pump in my basement, I'm planning on having my home server on the same room, it's not completely underground, like.. 80% underground, why/why not would this work?

[@richH1625]

What is the power consumption of the server? What is the temperature of the cellar?

[@nlmoin990]

@@richH1625 Insulated cellar, normal temperature 15C, the server uses around 200W and the temperature goes slowly up to 20 degrees, already testing with a hybrid water heater/heat pump, so far the temperature stays stable above 15 degrees C

[@davidoxnam]

How about running air pipes under the garden to deliver pre warmed air to the pump in a box ?

[@GWP-UK]

regarding wind, westerly and south winds are warmer than north or east. So intake should be facing S -W

[@HeatGeek]

The wind reaches all sides of the house

[@dinendale666]

Ideal place is a roof , a traditional cold vented roof. As long as you have somewhere to run condensation.

[@crcurran]

When can we expect the circulation test again but under heat load? Is there a way to improve efficiency by having a fan with a solar panel that blows air towards or away from the heat pump to improve circulation. I'm thinking it wont. What about putting a heat mass in the air intake area using wood outside. You keep the combustion outside the home but feed the heat from it into the heat pump intake (must only let heat in and not smoke or any air with particulates in it from the fire.

[@laserjim]

I was wondering just last week if I could gain from putting a heat pump in a greenhouse... This make me think it might just work 🤔

[@jsjs6751]

If you place the outdoor unit in a space that is warmer than the ambient temperature, you will save electricity. You will, however, probably at times exhaust the limited heat accumulated in the greenhouse. When that happens you will lose electricity.

[@anderwpool3419]

I have an area around the side of my house which has a 6 foot fence on an angle exactly like you had in your scenario with a heat pump placed exactly as yours was, how much worse is the cop on something like this and is it worth the cost of moving it?

[@theirisheditor]

The difference will likely be more drastic when it's not cold enough outside for the condensation to freeze on the coils. By enclosing the heat pump, the drier recirculated air produces less ice build-up that insulates the coils and obstructs air flow through them, so this is likely helping it perform better despite operating a few degrees lower temperature from being enclosed. Once it's warm enough for the condensation to not freeze, the heat pump performs better from extracting latent heat from the condensing water vapour that drips away instead of insulating the coils, reducing air flow and requiring defrost cycles. In this scenario, enclosing the heat pump will reduce the amount of latent heat it collects from condensation and the lower recirculated air temperature will likely cause what condensation forms to freeze leading it to perform defrost cycles.

[@GWP-UK]

If client has a large open garden, how about a heat pump that rotates as per prevailing cold wind????

[@dmcolemanmarc647]

My cellar is the only place I could put one due to limited garden space and the loft now used as a bedroom. Will it work as long as it is well ventilated?

[@waqasahmed939]

I wonder this too tbf. It'd certainly be nice to have one indoors

[@rtfazeberdee3519]

I know zero about heat pumps but i have always wondered why the intake is not protected from the wind chill as wind chill is generally the reason we have really cold days.

[@jsjs6751]

In most circumstances, wind will just increase ventilation around the unit. This could improve efficiency a little, unless it by chance lowers the amount of air going through the evaporator (heat exchange coil).

[@patrickchan2503]

Hello, why is the heat pump installed outside the house and not inside? Thanks.

[@mermer2359]

I wonder what surface area the fins of the heat pumps heat exchanger have compared to the boxing in surrounding it?

[@adamdevine7375]

I watched this video when you first posted but re-watched it today after the environmental protection officer on my planning application insisted I enclose my heat pump using a surrounding with sound absorbing materials on the inside and louvres on the front to let the air out. This is for an a2a, 10kW Toshiba multisplit. I had purposefully planned to put the heat pump where there was really good air flow unlike down the side of my house (where it is 1.2m wide and enclosed with 6ft fencing) and now I am being forced to enclose it for noise reduction. Question and concern I have is how much will louvres on the front affect SCOP. Do you think it would be significant?

[@HeatGeek]

Never heard of anyone enforcing this! I have no idea! Seen mixed resukts

[@adamdevine7375]

@@HeatGeek it is very annoying that noise impact is put so far above climate change! What hope have we got of meeting net zero targets when planning enforces rules like this. Unfortunately I think this means my application is dead in the water. Would be interested to hear of anyone who has implemented a surround either for acoustics or aesthetics and what their experience has been

[@leosmit1835]

If proper airflow is not that big of a deal, then see what happens when you disconnect the fan. Maybe that could be an option a night to reduce noise complaints in some months (open windows)

[@marcwilkinson3249]

You can actually get fan less evaporator heat pumps. They are basically just black radiant panels. You just have poor control of superheat and risk damaging the compressor.

[@Benblyth]

Brilliant video, really interesting, thanks guys. Definitely getting more knowledge on heat pumps from you. Definitely NOT ever getting you to build an extension for me… 😂

[@ianmurray250]

This is easily the funniest video I've seen this year. Tomorrow I might just go and buy a shed to hide my heat pump in, or perhaps one of those plastic garden boxes designed to store bikes or mowers in.

[@iainmalcolm1]

The system may well keep operating and maintain the desired inside temp, but what is the end result on the fuel bill? If the average COP reduces by 0.2 (or even 0.1), how much more power do you use over a year? This change in cost will also look much bigger when looking at the differential cost between conventional gas heating and a heat pump system, In purely monetary terms, looking at the extra cost of changing to heatpump vs straight boiler replacement, a small change in average COP will have a huge impact on the marginal cost / payback period.

[@HeatGeek]

A change in scop of 0.1 will result in about 100 pounds a year currently.. remeber this isn't scop though. Its cop at 0. A 0.1 of cop at 0c will likely be about 0.02 scop change.

[@davidfellowes1628]

Have you now had a conversation with the likes of Daikin who are a player in AC and heat pumps. I think they wouldn’t be so surprised with you findings. Love to understand your follow up findings

[@HeatGeek]

Had loads of conversations with diakin.. many are on here

[@marcwilkinson3249]

The main problem is that it will go into defrost more frequently which causes the efficacy to drop off a cliff over the day.

[@leonhardtkristensen4093]

But that heat is heating up the surrounding air in this setup.

[@MagicianMan]

As an advocate for the use of Heat Pumps..... When will we see some content around the use/benefits/downfalls/costs etc of "Heat Pump Hot Water Cyclinders"??? We have a 2year old house, well insulated and are currently paying off our loan for Solar PV & Battery but Taylor Wimpey installed microbore pipework meaning that we are ineligible for any of the subsidised upgrade schemes ie. Octopus (£2k)/British Gas (£3k)etc. As a result we would have a much larger install cost to pipework alterations. Using a Heat Pump Hot Water Cylinder in conjunction with the Solar PV would reduce our reliance on gas significantly - potentially almost to zero during April/May through Sept/Oct and offsetting a decent portion during the colder periods. There is almost zero content on these devices up-to-date, online and relevant to the UK market/climate currently. Are they a good idea? Too expensive? They seem to be around £2kish - Orion/Vaillant/Ariston (maybe/not available in UK), Daikin (NOT available in UK currently). Having considered replacing our existing 2year old indirect unvented Hot Water Cylinder with a Mixergy Cyclinder the cost implication to achieve only 100% efficiency (1:1) and the ROI on the investment just doesn't make sense - also around the £1.5k mark. Plus Mixergy doesn't have a retroactive upgrade option to add a Mixergy Solar Immersion Diverter to their product unless you custom order this with the Integrated Immersion Diverter from the start. Alternatively you can purchase their 3rd party Solar Immersion Diverter product @ approx £200 but that's in addition to the outlay for a Eddi/Solar iBoost etc. Edit: Mixergy confirmed that they have untangled the AI features from the Grid Assist resolving this potential issue now.

[@tom.jacobs]

Thank you for this very surprising experiment, so the next installation advice is to place one unit in a isolated area, the other in a non-isolated area.. ;-)

[@normanboyes4983]

You clearly had a lot of fun.

[@johnfreshwater3790]

Just a thought why not fit the ashp in the loft and have a large duct in inlet and outlet to grills in the roof. Would certainly get round the problem of terraced houses. And guess that if you have the outlet the shortest duct it shouldn't be much of a problem. Maybe na experiment worth considering?

[@ZionistWorldOrder]

loft, put the exterior part in the cold loft, to heat the house under?

[@NickAskew]

My neighbour has a bunch of smaller heat pumps on his property. Something I noticed, however, was that in the recent cold snap, he fired up his pellet stove in the living room. This meant that his living room was lovely and warm but presumably other rooms still relying on a heat pump were running less efficiently. Given that all his heat pumps are reversible (can be airco in summer) it occurred to me that it would be great if heatpumps could be arranged to share the coolant circuit and take heat from the overly warm rooms and deliver it to the cooler rooms. Obviously an external unit is still required for sourcing heat or dumping it in airco mode. Is this just a silly idea?

[@keinzitat]

Aren't VRF/VRV units just that?

[@richardc1983]

Already exists, vrf, vrv is heat recovery moving heat about to rooms that need heating from the rooms that are in cooling. Great for north south window facing properties.

[@jdickson242]

Take heat from warm... Just use mvhr which recovers heat fron the outgoing air you could then passing the final vent through the heatpump.

[@NickAskew]

@@jdickson242 That is a good point. Those units are quite common in modern Dutch houses (where I live). The ventilation system in our house, however, does not have a return side from the exhaust. Air extracted is replaced by air sucked in through vents and other leaks in the house. However fitting a return side could be achieved I suppose although in the scenario I gave, the living room is not ventilated directly.

[@YearRoundHibernater]

Do you guys know much about the heat pumps that are intended for internal installation? the all-in-one heatpump and water tank systems that have started to hit the market? they seem much cheaper especially if you're replacing a combi boiler and currently don't have a tank and well sized for terraced homes. I think Daikan do one but not available in the UK and a UK company Cool energy but I last looked into them about a year ago and I think a bunch more have popped up since then. Was difficult to find reliable sources as to whether or not they're any decent or not, they use ducting to bring fresh air in and dump cold air out.

[@tedtenny]

Try an AERMEC unit, NLC, NXW, etc.

[@andrewcunningham1]

I think these 'internal' units would still be ducted to the outside air

[@davidbillingham166]

Hi I was wondering why my vaillant thermostat is set to a desired temperature of 21 degrees but it's been getting up to 23 degrees how do I control the heat do I turn the trv down from 5 to 4 or is the heat curve to high mine is set to 0.6?

[@kadmow]

Obvs putting the heatpump in a single communicating space will be suboptimal- as the cold side will be cooling a space/ room (pick a different room, with controlled night temps and potentially equalised daytime temps, OR an earth coupled cellar - it should have more temperate temps than an outdoor "free stream" siting), the hot side warming... In any single closed space, equilibrium will be achieved with net increase due to consuming energy within the envelope. - (siting the heatpump in an insulated conservatory will at least reduce icing - and solar gain / thermal storage will be beneficial - also re. noise)) Blowing exhaust vertically should enhance mixing - ... (keeping inlet temps within the working range of refrigeration (system) capacity is important, we always need sufficient energy remaining to reduce instances of inefficient (defrost / deicing) resistive modes.

[@billsmith5166]

The only way to test this is to raise the heat pump off the ground and seal it up completely (bottom too) in a very well insulated box. The bottom needs to be sealed because of the ground temp and mass. If what you seem to be trying to test is true, the manufacturer's clearance requirements are pretty much moot as the sealed air will eventually reach the same temp over time no matter the size of the box. Of course you will also need to adjust for the heat generated by defrost and motor. You will eventually find that the enclosure will approach the temperature of the heat exchanger coil, and that's cold. It will no longer produce heat through compression and expansion of the refrigerant. As this temperature is approached the efficiency will decrease to zero. So, as we know, the lower the temps, the lower the efficiency, AND as you increasingly contain the circulating air, the air temperature drops. There's no magic. Your enclosure isn't an enclosure.

[@billsmith5166]

@@zlmdragon. They were trying to create a barrier that was meant to contain some of the cold air generated by the exchanger to see if the cooler air would reduce efficiency. My test would show that cooler temperatures ALWAYS reduce efficiency, and further, it ultimately reduces it to the point that no heat is produced. In a controlled environment with proper measurement, the reduction in efficiency could be graphed and show how much efficiency is reduced for every degree the temperature drops. Therefore, if the air around the exchanger is contained to the point that it begins to be cooler than the air outside the enclosure it is less efficient in heat mode. It may be hard to primitively measure the difference in an unsealed container, (their test) but it's an undisputed fact that you are NEVER as efficient in a cooler environment. There are no exceptions.

[@billsmith5166]

@@zlmdragon. So, what were they doing?

[@ricos1497]

​@@billsmith5166 they were measuring the impact of different types of covering to simulate potential siting of heat pumps, I thought? They were larking around a little, trying to get it to fail with varying degrees of cover, without going to the extent of your proven experiment. The idea being that perhaps you can place heat pumps in locations that might have previously been perceived as off limits.

[@billsmith5166]

@@ricos1497 The thumbnail is "Can we put heat pumps indoors now", they made it appear as if they were lowering the surrounding temperature by enclosing the exchanger, and then implied that it may not reduce efficiency and made him question everything he knew about heat pumps. The correct, non-misleading thumbnail should have been "You should NEVER put a heat pump indoors", create an enclosure that wasn't flapping in the wind, placed sensors properly, and provided a large enough sample that would represent the truth. There are people that see these things and believe them. Why would anyone want to make a video like this unless they wanted views? He's smart enough to know this stuff!

[@billsmith5166]

@@zlmdragon. Read the title?

[@justinhalsall4077]

Looks like you need a blower door test for your heat pump

[@francishead8939]

Fun video. Not the outcome I was expecting either but some useful insights. I have memories of looking at the performance charts for the Mitsubishi CHAV units (I know it’s not their real name but I refuse to call them anything else) and it does back up your point about flow temps. (Ext -20 flow 25 COP 2.1 vrs Ext 10 flow 80 COP 2.18) You also see sharper declines in COP over the section of external temperature where air is relatively cool but still reasonably wet (3-7degC). Once you drop enough I guess the air gets drier - meaning less cycling of defrost to make up for the compressor working against the cold external. I suspect if you wanted to screw your heat pump over maybe put some saturated coldish air over it?

[@basneutel]

How do you get this trend your showing on the laptop? Whit the VR921 connected to the bus?

[@sorbetingle]

Can a HP be positioned in a greenhouse, with ventilation to let cold air out, but have the unit running in the comparative warmer air of the greenhouse ?

[@leonhardtkristensen4093]

Of cause. This is the opposite of a portable air conditioner that we use a bit in Australia. They are very ineffecient as they leave all the heat coming from running the compressor indoors beside of cause they suck in external hot air to replace the air blown out. I once made one heat a caravan by cycling the air -input and output - to the outside. It worked very fine untill it iced up.

[@87vortex87]

Can you solve this problem by creating a ramp in front of the heat pump where the air gets pushed up?

[@HeatGeek]

We would have, had we have found a problem to solve in this senario

[@CrashUK28]

Manufacturers are working on heat pump that fits the loft. This stops the need for defrost cycles.

[@MarkoCosic]

Most of your air movement is for air>evaporator heat transfer purposes. You don't need to bleed in a large fraction of the air to replenish the heat within the enclosed space?

[@JonnyR1981]

By the time the air leaves the units and mixes with the turbulent air it has picked up ambient air heat before going back into the unit. Yes it's a short cycle in terms of airflow but in terms of heat/cold air the difference will be minimal should have measured the off coil temperature vs the on coil. Fitted them in indoor plant rooms with louvre walls. Up on rooftops with 2.4m high parapets roofs. Roof top louvre enclosures. What you need to avoid the most is the cold/off coil side of one unit blowing directly into the back of the on coil side. There is no time for the air to gain heat before hitting the onside of second heatpump. To be honest efficiency can be increased planned right. Say you have a chiller room at -20 the outdoor unit will be throwing heat off the coils. Then if you have that blowing into back of heatpump you get better efficiency.

[@danoneill8751]

Just a thought, but I think you aren't seeing the efficiency drop much in the time you gave it because the heat capacity of the air is far higher than you think. I suspect your imagined systems with say the cool air in a pool trapped in that roof area are accurate, and I suspect they have the effect you think they do, but to a far lesser extent and far slower than your experiments could show. Remember the fallacious argument gas plumbers give you about how they (ASHPs) can't possibly produce heat during the winter when the air temp is below freezing (They think the frezzing temp of water has something to do with it all) or even just when the air temp is lower than the flow temp? While of course the temperature difference between the air and the flash point of the refrigerant under pressure is the vital bit. Well, take that temperature range and multiply it by the specific heat capacity of air (or don't) and think about how much more energy the air has to give when it has dropped by a a degree or two, and you'll see that the air could cycle through the machine many times, still giving energy each time. Yes it would get a tiny bit less efficient to get that energy out, but not much. I suspect that if you could run the experiment for longer, on a very still day, then you would see the effects you are picturing in your head coming true, albeit with a very small effect. As you so often say, I think the efficiency of a heat pump viewed as a whole is dictated by: the flow temp, the general outside temp, the hydraulic design, the emitter source-load matching (although this has such a strong tie-in to the flow temp...), system loss (by which I mean insulation of flow outside domestic envelope) and then, only then perhaps the pneumatic design. Obviously there are rare bizzare effects that could be an issue for the pneumatics - I did my PhD on FEA (finite element analysis) design of misting sprinkler systems (fire suppression in offices, getting the mist around corners essentially) and I remember after discovering the 600th surprisingly stong edge case where fluids do something curious you wouldn't expect, a colleague reminding me "tornados are just explained by reasonable-sounding conjecture, any (computational) models to back up even the most well-established rationale for twisters fail to bear out the conjecture. If we haven't actually proven how a ruddy tornado works, its hardly surprising that air movement - that stuff humans cant see - keeps creating stable shapes we'd never guess at."

[@danielbell1973]

We don't know the flow temp and as he said the closer the flow and outside temps the higher the COP, but also the more capacity Heatpump has to cope with poor air flow. It could be the heat pump isn't working very hard and once the airf flow or temp is compromised the HP just increases fan speed or if on weather comp increases flow temp, those two adjustments prob account for why the system is still achieving a good COP. Seeing the smoke flying around more is a good sign the fan has picked up its speed. On a more fundemental note the Heat exchanger doesn't have anywhere near a big enough surface area to extract all the heat energy from the air on a single pass, that's compensated by the fan blowing alot of air over the fins. This means your experiment will need to run much longer, but with standard air pressure, long run times will allow the air to mix through any gaps and holes, exchanging energy.

[@garywright8846]

Hi guys, coming in a bit late on this one, interesting experiment yes, but frankly it’s madness. I can assure you that you cannot in any way build in an air cooled heat pump, what you didn’t take into account is the variables, i.e the weather, which as you know changes not only daily but hourly. Re circulation is a killer, especially in extreme temperatures, although my experience is mainly in air to air heat pumps the fundamentals are the same. We are looking at two temperatures, air on, the ambient air being dragged in at the back and the air off, the ambient plus the rejected heat, coming off the front, it’s normally about a 12C difference. So with an ambient of say 5C, you have air off at -7C, this is low enough to start freezing of the coil, then the enemy of all heat pumps kicks in, defrost. So, my advise is this, stick to the manufactures instructions, they have after all spent thousands testing these units,they will be conservative but you can’t go wrong as long as you follow them. You want to avoid any chance of recirculating, what might work today may not work at 4am tomorrow morning. One other thing, unit placement, the unit on the cafe roof was fine, why because it was up above ground, be wary of installing these units in dips, below ground level as the air drops and may be 6 or 7 degrees lower than just 2mts up, that I can assure you can give you untold pain. So as I used to say to all my staff “ follow the instructions} you can’t go wrong.

[@NickRobbins-lb9ec]

Great presentation - but "cold hollow" effect can be an issue after there have been several days of cold weather - and on commercial systems where there is a lot of fresh air ventilation. I have dealt with several VRF Systems "fails" where the plant has been installed in a "pit" to meet planning , architectural conditions on visibility requirements. The defrost cycles just would not clear cold air from the hollow! The heat load and capacity of the heat pump in relation to the area and depth of the pit is quite complex. The solution on one of the systems was to lift the Outdoor units clear of the pit - problem resolved but planning condition compromised! On a few other systems we have simply reduced the fresh air supply quantity / rate - and added some direct electric heat to the fresh air supply. I think you would need to do some more work on your experiment before drawing any conclusions just yet.

[@HeatGeek]

That's exactly what we say in the video. This in no way even remotely convlusive

[@NickRobbins-lb9ec]

@@zImdragon top fan

[@KangoV]

I'm wondering when Stirling Heat Pumps will come out. Way more efficient.

[@HeatGeek]

I think if they were they'd be out already

[@onlyscience7120]

Why not an underground airflow geothermal style a2w heat pump?

[@jacharyzones]

Heat transfer from the ground is very slow so wouldn't really work. That's why geothermal heat pumps need such long lines running through the ground

[@paulrattray8121]

Surely fan pointing upwards eliminates all this?

[@HeatGeek]

Unfortunately these heat pumps don't point upward. The fridge gas will settle incorrectly. Same for most heat pumps, only a few are upwards.. as per the video it may not have any effect anyway

[@GrumpyOldGamer9221]

Has anyone tried a cover over the top and sides? Basically a canopy over the top for snow protection, and vented sides so air can still circulate. Front still exposed as normal.

[@wattsupmike7593]

Have you seen reports that replacing gas heating with ASHP will lower a house EPC rating because they consider electricity as inefficient compared to gas.

[@echamings]

This is true, especially if on single rate electric. Dual rate electric came out as the same score as a gas combi on our house. This is probably being addressed in SAP11 (the framework used in EPCs), due to be released in 2024. EPCs are all about cost to user (currently) rather than carbon savings though, and usually a heat pump costs a similar amount to run as a gas boiler (although can be a bit less and probably will be cheaper still in the future). The reason current EPCs suffer is they are based on heat pumps having COPs of 2 or something I think. Old data.

[@wattsupmike7593]

@@echamings very interesting and informative, thanks. I have always thought that EPC very confusing because they are a measure of cost of heating not efficiency which are not the same. My all electric heating system is rated below F but is 100% efficient. I recommend a recent KZbin video by Kathyn Porter wattlogic for her views on EPC.

[@muckfone5775]

Hi lads, great experiment, and this gives me an idea ? Your going to have to have an open mind for a couple of minutes,,,,, would I be right to assume that similar to a car's air con design, i.e. it operates most efficiently when the cold air is recirculated within the can so it isn't trying to cool outside warm air, it, after a while cools the already recirculated cold air. Therefore, could the air intake from an air source heater, DRAW ALREADY WARMED AIR FROM INSIDE A BUILDING. The warmer the inside temperature rises, the warmer the air feed into the air source heater, obviously improving efficiency and reducing running costs, better for the environment etc. Now that is an experiment I would like to see 👍👍👍

[@muckfone5775]

I just think i have thought of the first hot air heat recycling system for heat pumps 🧐👍

[@neilashdown6854]

Your thinking is ahead off the curve Combined ASHP with MHRV loft mounted ducted supply air and extract kills two birds with one stone. Could come with radiator circuit option for retrofits and fully ducted for new builds. As they say what goes in must come out and to recover potentially 80 to 90% of the energy within the house cannot be a bad thing.

[@muckfone5775]

@@neilashdown6854 The system could be taken one step further and place a "car like radiator" (with multiple fins) heated by the heat pump system, placed in front of the induction side of the heat pump, to assist drawing in warm air ?

[@codeforme8860]

As soon as the air is evacuated from the chamber and is outside, the air should equilibrate with the outside temperature

[@JimCassidy-xy1il]

Interesting stuff (and entertaining) to check this you should really have two identical set ups inthe same location - one is your control and is left as is, the other is your test bed where you can tests and compare the variables (height of wall, clearance distances, lid etc etc). This should allow you to do direct comparison of results and draw measured conclusions. This recent experiment just provides the incentive to investigate further.

[@michelmillette9218]

Indoor heat pump....LOL The only way to get a gain is to put the outdoor unit southside, you'll be a winner in autumn, in winter and in spring but for air conditionning in summer it will be less efficient. A southside unit will be a winner overall.

[@764pj]

You would see when people have built boxes over their pumps here in Sweden when it is 20 minus or 25. even though they need the same supply temperature, they just die with boxes and they run on electric cartridges. You are so hot that you don't notice it. just tell me :)

[@brianholding4357]

Interesting, not what i expected, i have a walled garden, and will still put my heat pump on a stand, also i will have a very cold back garden that sees no sun in winter. IF my grant application ever gets allowed, I have a Sun amp, and they say i don't qualify because i don't want a hot water cylinder?????? WTF!!!

[@timballam3675]

Aren't you required to keep the heatpump > 1m from any boundary so most alleyways are out of bounds?

[@HeatGeek]

For domestic permitted planning yes. This is commercial.

[@MrRednas24]

This might interest you @KetelKlets. Also as in the area I live I sometimes also see weirdly installed external units... :)

[@johnfreshwater3790]

Hi I font know if you have seen it but your friend the skill builder had a video on years ago showing him fitting one in someone's loft. Which I suppose as long as there are good ventilation in the loft it maybe OK but who wants to make their loft even colder. I do question his skills!

[@paulgoffin8054]

I've wondered about that - if the exhaust is ducted outside, then the loft ought to be warmer than outside air as, no matter how good the insulation, there will be some heat from the building getting up there.

[@johnfreshwater3790]

@Paul Goffin if your loft space is cooled it will lose heat quicker so best to duct to the outside I think with both inlet and outlet of fan

[@leonhardtkristensen4093]

@@johnfreshwater3790 I disagree. If the cold air is blown outside there is nothing to cool down the roof space. It will never cool below outside air that will be sucked in to replace the air blown out. In fact you should be able to keep the inlet air warmer as all the heat losses from the unit will stay under the roof. The heat harvested is only harvested in the heat radiating element that the air is sucked through. The mobile aircon's used in Australia show that all the time but in reverse of cause. All the heat from the unit is keept inside and even though hot air is blown out is is replased with hot air from outside. Here the COP is very low.

[@johnfreshwater3790]

@leonhardt kristensen yes but even a well insulated loft will lose a little heat so the loft space would be warmer than outside.

[@leonhardtkristensen4093]

@@johnfreshwater3790 That is what I am saying. In the heating cycle we will want to have the inlet air as warm as possible and get rid of the cooled air so outlet outside the roof and inlet inside. The heat pump is not generating heat in its gas/fluid cycle. It is just moving it. The actual compressor is powered by electricity and any electric motor has losses. The electric energy is split between compressing the gas/liquid and losses. losses are heat but that is no put into the gasses unless it goes through the absorbtion section.

[@abelfaber4457]

how did you're neighbours react to you're smoke test?

[@ElectricVehicleMan]

Good at heat pumps, terrible at using a phone in landscape! 😁

[@RB-eg7mj]

Perpetual motion!

[@neilhardy8211]

What is the refrigerant?

[@HeatGeek]

R290

[@paulwebb3569]

Propane

[@Allegedly2right]

Spot on

[@marcuswayman1628]

So why don’t you put the heat pump in a big loft? Thereby, recirculating inevitable house heat despite 300mm of roof void insulation. If a big loft then have everything up there and using gravity to reduce pump energy? Would it work? Now that’s an experiment and utube discussion to have!

[@adamadiallo845]

I am thinking putting the heat pump inside a small utility room where Solar powerwalls batteries are placed to get their heat transferred to the house. 23:56 23:56