Let's chat about the Mixergy iHP cylinder

[@craigknight2764]

I have an old cottage which only has a water supply and electricity, currently heated by bottle gas combi boiler and woodburner. Im hoping to gutt and iternally insulate the solid walls and floor and run A2A heating but was stumped for the right product for water heating. This looks absolutely perfect!

[@TimAndKatsGreenWalk]

Certainly looks like a neat product and the sort of thing we were after, so hopefully it'll do the job.

[@richarddixon6354]

Excellent news, looking forward to the upcoming videos. Just re-watched your video going through the different options available to produce hot water. Technology is progressing so fast in this sector these days.

[@TimAndKatsGreenWalk]

It sure is an interesting time. I wonder what's going to come along in the future and make all of this redundant!

[@richarddixon6354]

@@TimAndKatsGreenWalk But technology has always done this from VHS players, including Betamax, through DVD players and onwards. If you waited for the latest tech you will never get it. You are making the right choice, The EV Puzzle KZbinr has been impressed with his Mixergy. I am holding back at the moment as I want to move in a few years time and don’t want to invest in solar, batteries, ASHP etc and leave it behind!

[@TimAndKatsGreenWalk]

Very sensible. We bought this house a couple of years ago and figured it was the right time to do all this stuff since we plan on being here a good long while.

[@johnhunter4181]

Good to hear what you guys are up to now - I was definitely encouraged by your Green Walk to go air to air and that has worked perfectly since June and through winter for space heating. Our gas boiler was knackered but we got by with the immersion for hot water. Then I thought we're VERY reliant on Octopus Cosy and Solar batteries to make it economical. What happens in a few years time when everyone wants to charge their EV overnight? The iHP is expensive and probably won't have the best COP when heating water to 60°; it will incur service charges for the warranty and may only last 10 years - it will reduce CO2 but it won't be cost effective. So I'm afraid we bought an 11kW gas boiler to only do water heating and so far it's used about the same as the pilot light on the old boiler. There's a few other pros for it - 1. we can heat water at any time of the day, not just off peak or overnight. 2. It heats the entire cylinder which the immersion didn't do, so we can have baths again. 3. I'm contemplating using it to heat towel rail radiators in the bathrooms and turn off all the other house rads-that would also get some heat where the a/c doesn't quite reach. 4. It would give us a backup if the outside temp ever got to -20°. 5. It's cheaper than the immersion which of course the Mixergy also has and the whole installation cost less than the cheapest Mixergy.

[@TimAndKatsGreenWalk]

Fair enough.

[@daviddawson9099]

Be interesting to see the install and results of how well it works.

[@TimAndKatsGreenWalk]

Yup, we'll cover all that in great detail.

[@bobbazley5376]

Really interesting and thank you for sharing, I think the garage is the best option but you will be well aware of the need to ensure its insulated well during the winter time as the garage is not something you would normally heat (regardless of it maybe being within the main body of the house). I'm obviously keen to see how the tech is advancing and while I already have my own Dimplex ASHP system but the Mixergy was always an option, they just didnt have an ASHP available when I needed to do my install. Look forward to the "data"

[@TimAndKatsGreenWalk]

I've been keeping an eye on the temperature in the garage over the Winter and it doesn't usually get below about 10-12 deg, so I'm hoping that's going to be fine. It is insulated but obviously has a very large garage door too, so it's never going to be toasty warm in there.

[@arfansheikh]

Looking forward to the install videos

[@TimAndKatsGreenWalk]

I'm looking forward to filming them!

[@geoffreycoan]

Exciting times ahead Tim & Kat. Personally I think I’d not want to be at the bleeding edge of a new product, one that’s been trialled but the refrigerant is then changed, and one where the company is saying they’ll be training up engineers to fit it. I’d be a bit more pessimistic, want to see more of a track record and let other people do the early product testing. There is of course always a better thing just round the corner and you have to decide to buy at some point, but a bit later I think

[@TimAndKatsGreenWalk]

Well, someone's got to be the first to try something new, right?

[@colingoode3702]

I think I pointed out the R134a refrigerant issue with the Mixergy iHP when you first started looking at these cylinders so it's good to hear Mixergy have made the switch to R290. I'm also looking at Mixergy & SunAmp Thermino phase change hot water options to replace my vented HW tank. ATM I'm still undecided about which way to go. Ideally I want to move the cylinder / SunAmp unit into the loft from the airing cupboard because I have no space left in my garage. However, the Mixergy tank (& most of the other makes) would require a larger loft hatch which is not the end of the world but just another bit of hassle to consider. Going to unvented mains pressure hot & cold water also means I will have redundant power showers & pumps to deal with as well.

[@TimAndKatsGreenWalk]

There are always so many things to consider! It does take a lot of effort to get it all figured out, for sure. Best of luck with your project!

[@ChrisJakins]

I’m watching with interest. At some point we need a similar solution here. Choosing a location for the cylinder is a concern for us. We used to have a cylinder in the airing cupboard before we moved to a combi boiler. If we use that space then Henry the hoover faces eviction from his cupboard home. Space is a consideration too as it is tight in there. We also need to consider the duct work for the vents as it isn’t on an external wall. 🤔

[@TimAndKatsGreenWalk]

Yes, indeed, all valid concerns. We'll be discussing the various options with Mixergy when they come to visit us, and I'll ask about the practicalities of the different placement options, including the airing cupboard, so hopefully I'll have some more details to share in due course.

[@ChrisJakins]

@@TimAndKatsGreenWalk This is maybe a silly question but I’ll ask it anyway… can these things be installed in a loft space? I’m assuming the heft of them is the limiting factor. Also, even if your installer is an olympic power lifter they probably don’t fit through the hatch. Just thinking if you could use waste heat that escaped into the roof to heat the water it would be nice and the whole arrangement is out of the way.

[@TimAndKatsGreenWalk]

@@ChrisJakins I don't know, I'll ask when Mixergy come to visit us. You'd still need to vent to the outside though, or at least the output vent, otherwise you'd end up with recirculation of the exhaust air which would reduce the efficiency.

[@ChrisJakins]

Yes indeed. We have a very long flue on our boiler that takes that path currently. I wonder how long the exhaust vent is allowed to be. I’m sure that sort of thing is in the specs somewhere.

[@TimAndKatsGreenWalk]

@@ChrisJakins yup, this page shows you the effect that vent length (and bends) has on the CoP, which you might find interesting: support.mixergy.co.uk/ihp-faq

[@Umski]

They do indeed have the online ship open now - very transparent but nothing in stock it seems which is a shame

[@TimAndKatsGreenWalk]

Oh yeah, that is odd. It's been open for a while now, perhaps they just sold out?

[@rigel1632]

I was looking at Mixergy and still am. I saw a video maybe 12 months ago that suggested you lose the smart element (zonal heating in the cylinder) when using solar divert (or something like that). Be interested to see if this is still the case when you get yours done, assuming you’ll have solar divert on 😊

[@TimAndKatsGreenWalk]

Well, possibly not, it depends a lot on the tariff, as the export rates could be very favorable meaning solar divert isn't as beneficial as exporting the excess instead (Octopus Flux has exceptional export rates). In either case, the iHP works a bit differently, the stratification is used in boost mode so that you get usable hot water at the top of the cylinder quickly but the CoP of the heat pump isn't as good in that mode. In eco mode the heating is done from the bottom to achieve the highest CoP. So the strategy is to heat up overnight in eco mode, then use boost mode later in the day if required. Solar divert will then run whatever mode you set, I believe.

[@metalhead2550]

Hey, thanks for the update Tim & Kat. Will you be getting the R134a or waiting for the R290 variant?

[@TimAndKatsGreenWalk]

The R143a variant won't be going on sale, they only exist as pre-release models. Any that are sold from now on will be the R290 version, so we'll be getting one of those.

[@stevescott9289]

Did I miss a discussion around "why mixergy" vs the others you mentioned?

[@TimAndKatsGreenWalk]

I mentioned it in the stats comparison video that my preference was for the Mixergy due to the faster heat-up time and the split cylinder/heat pump.

[@stevescott9289]

@@TimAndKatsGreenWalk Aah, hadn't taken this as decisive.

[@TimAndKatsGreenWalk]

@@stevescott9289 gotcha. Yeah, I guess we decided properly once we'd gone to visit them but I was pretty confident beforehand, just needed to ask them some questions about it to confirm.

[@MrKlawUK]

Curious on expected energy savings. It should be sized for its needs and have a decent COP, and obviously your HP can dedicated to heating so COP stays high. But ultimately you’re heating X litres of water so energy in may not be that different?

[@TimAndKatsGreenWalk]

The CoP of these cylinders is similar to what you'd get with an external heat pump when used to heat hot water, so you wouldn't save energy relative to that setup. But compared to an immersion heater you'd be using only a third of the electrical energy to get the same amount of heat energy into the water. I've got lots of historical data for the immersion heater, so I'll be able to do a good comparison in due course.

[@MrKlawUK]

ah I'd forgotten you're A2A so this isn't a 'vs wet HP' situation! @@TimAndKatsGreenWalk

[@TimAndKatsGreenWalk]

No, indeed. If we had A2W I wouldn't be bothering with a heat pump cylinder, for sure.

[@julianguy5510]

Do you have an installation date for this?

[@TimAndKatsGreenWalk]

Not yet. Still waiting for the installer to become available.

[@KavanOBrien]

I’ve just rang the company and they said they don’t sell them only sold through retailers, did I miss understand that you mentioned we can buy it from the actual company ?

[@TimAndKatsGreenWalk]

I said the shop is coming soon, but it isn't available yet.

[@KavanOBrien]

@@TimAndKatsGreenWalk Sorry , you know I can’t watch and listen, I thought multitasking was a myth, I know an hour on the naughty step again , I did speak to a charming sales lady though are we allowed to say lady these days ? Sales human being is that ok ? Sorry I digress, both of you know me by now , oh yes the human sales person mentioned that they are in development of a tank with a box on the side called X that would also do the heating = sounds ideal for me , I did mention when I rang is because I follow your channel I didn’t mention how much whiskey you both need to get through one of my messages, take care you two = me.

[@TimAndKatsGreenWalk]

No problem, and I expect it won't be long before the shop lets you purchase the iHP directly. In fact the shop has now gone live for their existing products and the iHP is currently listed as "unavailable". I think it's only a few weeks away though. shop.mixergy.co.uk/

[@KavanOBrien]

@@TimAndKatsGreenWalk Thanks guys and for putting up with me.

[@jameswestcott4191]

Am I right in thinking pros are 1/3 energy consumption compared to immersion heater, know exactly how much hot water you have left, can connect to home automation (via cloud service?), 2 heating modes: can heat top of tank first to get some hot water quickly or if heating whole tank it’s more efficient to heat from the bottom. Cons: cost, no 300l tank, takes ages to heat whole tank as heat energy output only about 2200w, noisy (compared to immersion heating).

[@TimAndKatsGreenWalk]

Pretty good summary, yeah. Most people wouldn't need 300l, tbf, and the fast reheat in boost mode would help if needed. The eco mode could be used overnight so you'd have a full cylinder at the start of the day and then top-up later if required.

[@Aethid]

The efficiency is more complicated (worse) than that. It is pulling heat out of your house to put into the tank. All of that heat will need to be replaced by your home’s space heating system. So you are paying to put the heat into the house, and then paying some more electricity to move some of that heat into the water tank. The quoted efficiency is only for the 2nd step. These integrated heat pump tanks only make sense in hot climates.

[@TimAndKatsGreenWalk]

@@Aethid no, you'd typically have vents to pull the air from outside and then exhaust back outside after, you wouldn't pull the air from the house.

[@Aethid]

@@TimAndKatsGreenWalk Ah, well that would make it a lot more reasonable then. It is frustrating that the mixergy tanks do not play well with external heat pumps, for those already using one for space heating.

[@TimAndKatsGreenWalk]

@@Aethid the regular Mixergy tanks can be used with an external heat pump to great effect. Take a look at this blog post, for example: energy-stats.uk/mixergy-heat-pump-performance/

[@clarkfinlay78]

running the numbers this device doesn't seem to make sense. it costs more to buy it costs more to install (needing pipes outside the house) where as a direct cylinder does not and if it's like the American ones they lose efficiency over time because of dust and whatnot in the fins against simple tank and immersion with over night "charging". It will be really interesting to see if it truly is a cheaper option and can cover the extra costs in savings

[@TimAndKatsGreenWalk]

I've never claimed this was to save money. I'm doing it to reduce energy use. But you're right, it almost certainly won't "pay for itself". Mine won't need pipes outside of the house though, our garage is part of the house so all pipes will be internal, and in fact no new pipes should be needed, it'll use the existing ones, hopefully

[@USA-GreedyMenOfNoIntegrity]

Remember, everything crammed in that tight little package is not gonna be fun to work on down the road. So you’ll pay dearly when it breaks.

[@TimAndKatsGreenWalk]

Ok, no need for such a pessimistic outlook. I'm guessing you missed the fact that the head unit is separate from the cylinder so that it can be easily removed and repaired/replaced if necessary. It does also come with a warranty, much like any other piece of complicated equipment you might purchase. I wouldn't be doing repairs myself!

[@TommysDaddy]

I'd be very interested in how loud/quiet they actually are ! If we had one it would probably have to go in an airing cupboard (garage is 3 floors down !)

[@TimAndKatsGreenWalk]

I'll certainly be covering that in a future video, rest assured.

[@Jaw0lf]

Glad you have found a hot water solution and thanks for the update.

[@TimAndKatsGreenWalk]

Hopefully it works!

[@martinhibbert1428]

Will be following with interest. I own a 2 bedroom flat that has an electric immersion water heater (no gas). It’s currently costing around £1400 per year just to heat the water. From my rough calculations I think this would be £300 to £400 per year with a heat pump water heater. We are top floor so can draw and exhaust to the loft. Have some concerns about noise levels, as it will need to go in the airing cupboard.

[@TimAndKatsGreenWalk]

You can get sound proof boards that you can fix to the inside walls of your airing cupboard to help reduce the noise. It's an extra job but probably worth doing if the noise is a concern at all. I hope it works out for you!

[@denisbassom172]

Hurry up and get it installed, I waiting on you before ordering something on these lines!

[@TimAndKatsGreenWalk]

Patience, grasshopper. We'll get there as soon as we can ;)

[@asabriggs6426]

Thanks for the update on this missing link in your full (efficient) electrification give you went for A2A heat pumps. I wish you a smooth installation!

[@TimAndKatsGreenWalk]

Thank you, I hope it goes smoothly too. Given it's a new product I'm sure there will be a few problems to solve along the way but hopefully Mixergy will learn some useful things from the process to help streamline the process for others down the line.

[@asabriggs6426]

@@TimAndKatsGreenWalk That's a great way of looking at it. It will definitely be interesting to see how the control side (phone app, tank capacity and demand estimation) will develop, as that is what Mixergy are particularly known for (and issues there will be a software update away from being resolved which is nice).

[@Eggnog3000]

We're in exactly the same boat, just waiting for the release date then ours will be in too....

[@TimAndKatsGreenWalk]

Not long to go, hopefully.

[@Eggnog3000]

Finding mixergy a little disorganised to deal with, been told it's not released, it is released, mixergy shop isn't going live for the foreseeable, we're changing the design, we're changing the gas etc etc.... Bit worried that they might be a bit too busy or small to be able to deal with the demand.... Worried if it goes wrong I'll be stuck...we're installers so well versed at dealing with renewable manufacturers etc, mixergy isn't quite what we were expecting. That might not be a bad thing but initial impressions aren't great tbh.

[@johnh9449]

So will it fill the bath?

[@TimAndKatsGreenWalk]

Should do, yeah. Depends what size you get, I guess. There are quite a few options to choose from.

[@johnh9449]

​​@@TimAndKatsGreenWalkI was meaning your bath Tim. I was just thinking that with the gubbins on the top reducing overall water tank capacity you might end up being limited on tank size or location options. I have a 300 litre unvented cylinder coupled to my heat pump as part of my wet system which fully fills a full size bath before running cold - but only just - it drops three or four degrees at the tap toward the end as the cold water refills the tank from the bottom - and I struggled for space. I ended up putting it in the loft with millimetres between the top and the rafters and that was after changing make and model to one 50mm shorter and larger diameter but still with a high transfer coil suitable for a heat pump. Options were limited. I don't know if they do one with the heat pump gubbins on the side - that could give them more install options. Another alternative is a horizontal cylinder but they have issues.

[@TimAndKatsGreenWalk]

@@johnh9449 our current cylinder is 250l, which is way bigger than we need. We usually use less than 150l per day between us, closer to 100l most days. The largest iHP I can see on their website is currently 210l, but I expect we'd need no more than the 180l version. There are no heap pump cylinders of any kind that I know of that are as large as 300l. We never have baths anyway, so that's not a consideration for us, and I doubt we'd want it fully to the brim even if we did! The advantage of this particular cylinder is that if we needed a bit more hot water later in the day the boost mode is very quick to give you some extra usable hot water without having to reheat the whole tank and still with decent CoP (although not as good as the eco mode where the whole tank is heated).

[@johnh9449]

That sounds Ok then👍 I usually have showers that are powered from the home battery but I do like a hot (as I can bear) bath every now and then and with me in it the water can only come up to the overflow. Hot soaks are good for thinking and solving problems I find 🤔

[@John-FourteenSix]

Have you compared consumption data to heat your hot water using an ASHP against the Mixergy cylinder? Thank you.

[@TimAndKatsGreenWalk]

You mean using a standard external heat pump compared to using the iHP? They have similar coefficients of performance so the amount of energy used to heat the hot water is about the same. Compared to the regular (non-heat pump) Mixergy cylinder both an external heat pump and the iHP will use about half to a third of the energy.

[@John-FourteenSix]

Apologies yes, compared to a standard hot water cylinder. ASHP and Mixergy cylinder have a similar CoP, that’s good to know thank you. My thinking was, as I have Solar, I do not divert this power to the cylinder, as I believe it is prudent for us to export the excess at 15p. I re-charge both batteries overnight at 7.5p, so it’s a 2:1 scenario from the grid, and free off the excess Solar. I could be overdoing it with a Mixergy cylinder on top. Horses for courses I suppose.

[@John-FourteenSix]

PS Hope the install goes to plan.