Maximizing Your Condensing Gas Boiler's Efficiency

[@richardhanmer]

This is by far the most interesting and original heating related video I've seen in a very long time. ~My mind has been blown. A real eye-opener and give how insightful this info is I'm puzzled as to why other UK-based plumbers on KZbin haven't talked about it. Really glad you made you the video.

[@3GreeneBJ]

Oh I do so agree. This explains so much which is often muddied. The plume, condensing, the sizing and the likely spec and settings your boiler will need to be. Thanks.

[@irenemarwood7425]

This is the best vid on this topic ive ever seen. Discussing issues that virtually nobody talks about

[@3GreeneBJ]

Agreed and even I can understand it... !

[@raimundassmalstys9042]

Probably the smartest engineer in this country!!!

[@givemethejob3293]

The word engineer is very over used. Only a few are engineers associated with an engineering institute, the rest are fitters, see monkey do, its the way we have always done it, a percentage of those will be cowboys.

[@HDEFMAN1]

Am in the market for a new boiler so this was eye opening stuff ! This guy introduced topics I was completely unaware of. This allows us consumers to grasp the concepts and principles behind condenser boilers.

[@dermotnangle3648]

An excellent technical and professional presentation. This is by far the most comprehensive technical explanation of Condensing Boiler functionality I have viewed. Congratulations Czesc Szymon on a wonderful piece of work.

[@DaanPol]

Thank you so much! There is a dire gas crisis going on in the Netherlands and this video is already saving me money. I also now know why my gas boiler dies every 10 years!

[@CommercialGasEngineerVideos]

Excellent video. Had a long debate with a colleague on boiler efficiency and this settled it. Thanks, saved us a boxing match.

[@schrodingerscat1863]

What an absolutely brilliant video, so much information to think about and so many ways to greatly improve efficiency on existing systems. My own boiler is hugely over rated for my home all because the installer talked me into having the much larger boiler. Now I know that all the steam I see billowing out of the flue is really bad for efficiency and essentially negates the whole point of a more expensive condensing boiler to begin with.

[@Martindyna]

You still gain by having a condensing boiler since the minimum efficiency is typically 85% with a hot return temperature. My installer said it was good when the flue started exhausting plenty of fog, I thought it better not to correct him.

[@pault1289]

Agree, this is an excellent explanation. Wish I knew this when I've replaced a few boilers over the years in my last three houses.

[@tonyclough9844]

No a bigger boiler means you can turn down your boiler stat, so try nudging it down. Fitting a bigger engine in a car can cut your fuel consumption, believe me.

[@schrodingerscat1863]

@@tonyclough9844 It won't modulate down low enough except on really cold days so it is always running inefficiently and cycling all the time.

[@claudiahamminger-stone3274]

Great, and here you can use this DIY solution to save another 30% of your heating bills: www.dropbox.com/s/16zwaq7q3u4r2g7/22%20save30%25ads-1.jpg?raw=1

[@jassinghIG45]

Love the knowledge and ease of explanation. Very few are aware of this hence the epidemic. Especially amongst the older veterans that don’t want to learn.

[@jamb027]

Thank you so much for this information. I'm someone who puts a lots of care & attention into my work & expect other to give me that respect when doing work for me, unfortunately though in life most people are mediocre in their knowledge, skills & care. The number of plumbers who don't care enough to even make sure the boiler is the correct capacity, let alone talking to customer about setting the temperature controls to efficient settings or even understanding thermostats that work with modulation.

[@imc9301]

What an informative video. I have just had a new heat only 24 kW gas condensing boiler fitted. Had I watched this video first I could have saved a heap of money by ordering one much smaller grrrr!

[@nilsfrahm1323]

The boilers have adjustments inside for gas pressures for minimum and max modulation, then it can modulate for intermediary values. Thus you can call a technician to lower the pressure for minimum level, to get lower heat output. Of course, there is some minimum level, just mentioning there is still some room for adjustment. I think also the radiator size, number of radiators and room temp will influence the return temperature.

[@UrbanPlumbers]

@nilsfrahm1323 zero governor boilers do not have gas pressure adjustment - the boilers you talk about have been discounted since 20005 and the adjustment on most of them was minimal - making them still hugely oversized

[@malcolmwatson6127]

Great, clear video. You're spot on about the over-sized boiler 'epidemic'.

[@CommercialGasEngineerVideos]

It must be a money making thing and lack of knowledge that pushes this epidemic. It's interesting to see how a few commercial boilers and a powerful pump can supply thousands of people with hw and ch. Compared to thousands of overrated boilers. Well, keeps thousands of engineers in a job I guess.

[@claudiahamminger-stone3274]

thankfully boilers now have massive turn down ratios, although I notice that no figures for fuel efficiency are ever published for a gas boiler that's running at just 7% of its rated output... Does anyone else here suspect that they're horrendously inefficient at these burn rates?

[@Ian-gf8id]

I've learnt a huge amount from your excellent videos. Making sure that our boiler/water/heating are operating efficiency has become a bit of a 'thing' for me because I don't like waste, whether that be food / energy / money / time. My whole house heat loss calculations indicate that, using -3C outside / 21C inside / 1 air change per hour, we need 12KW for heating. We have a Vaillant EcoTec Plus 630 + 250L Megaflo and yesterday I called Vaillant Technical to talk through a few things. They guided me through the process to Range Rate the boiler and what did I find ? No prizes for guessing...boiler was set to 30KW. Yes it will modulate, to a degree, nevertheless it was set far too high. I've now set it to 12KW and will monitor the effect on temperatures and gas consumption. Keep up the good work 👍

[@robi4387]

Erm. Yes and no, my friend. You may want 21oC inside but unless you run your boiler 24/7 temperature will fluctuate. This is why most programmer come set with at least two basic programmes 7-11pm 7 days for retired and home workers and M-F 6-9 and 4-11 s/s 8-12 for people who go out to work. Why because there is no point heating an empty house. AND it follows that when the boiler comes on it has to heat a cool house up to your 21. That (and needing spare to heat water on demand) is why a boiler has to have greater power than the average heat loss. That and many places saw -15 and who want a house at 9o for a week.

[@Ian-gf8id]

@@robi4387 Everything is working very effectively at 12KW. Tado (which I've been using for several years) room schedules ensures that each room is heated according to need (i.e. bedrooms pre-heated for when the children are getting up in the mornings) and is off during the day, every room is capped at 19C, we don't use water on demand (system boiler + Megaflo), flow/return 58/46C respectively. I haven't updated and analysed gas usage for a couple of months - that's on my to-do list.

[@3GreeneBJ]

Interesting! A large step change. You can tell much by the rate of cycling.

[@takearidewithme3589]

I have been in Heating and cooling for 20 years in the USA northeast and always love to see how things are done elsewhere. I think you have great knowledge in hydronic heating systems and heat loss.

[@stephendoherty8291]

How do US furnaces compare (excluding the often massive heat losses that US homes are built and sold with). Its not like the showers are that much bigger or baths. I presume the heat loss return from the greater number (or much bigger) US home radiators. I see Heat pumps getting more US traction even if gas prices are tiny compared to Europe.

[@rmsearle4564]

Excellent video. Stuff I "ought" to have known years ago. There's a there's a lack of technical training in the UK: even if you go on the boiler manufacturers' courses you won't get this level of understanding as they're only interested in pushing their own products (in my experience). Thanks for producing this.

[@UrbanPlumbers]

You are welcome !

[@CommercialGasEngineerVideos]

Well said bud. There is a lack of technical training.

[@marksmith5977]

@@CommercialGasEngineerVideos Other parts of Europe you need a degree to be a heating engineer, over here, lorry driver one week, 6 grand course, heating engineer the next. No offence meant to lorry drivers, without you, the pubs would run dry.

[@CommercialGasEngineerVideos]

@@marksmith5977 wish there was a degree to become a gas man although I'm not sure I want a 30-40k student loan debt.

[@marksmith5977]

@@CommercialGasEngineerVideos if it needed a degree here, I would still be driving lorries.

[@hansv.d.p.8679]

Great info again, good subject again. I bought my self a vaillant boiler ecotec plus, the smallest because it can run/burn at low kw. So you are verry right in your video i hope peole will understand. But we need also to investing in isolate our homes...I just invest in isolate my apartment from the 60..good video..greetings from Rotterdam

[@UrbanPlumbers]

At least in Netherlands you can get VR33 and use open therm on your Vaillant !

[@hansv.d.p.8679]

@@UrbanPlumbers yes i check it is standard installed now i fitted a honeywell touch..easy peasy

[@yuriradomskyi7966]

Nice. Thank you for explaining! I wish I knew it when buying my boiler...

[@qbasz]

Czesc Szymon, great video. This should be a compulsory learning video for all boiler fitters. In regards to boiler size in Uk homes, I think the size is often related to the number of bathrooms and a possible number of taps with hot water open at the same time, where we all know that water flow in the network and pipe sizing is not good enough to manage that. Therefore, as you said over -sizing boilers is a plague in this country.

[@valroberts3828]

Thanks for the very informative video. Although I'm not in the business, I needed a new boiler to replace my old Baxi solo heat only boiler open cylinder, everyone initially wanted to replace with a 30kW combi which I insisted I did not want for several reasons. Firstly I had already calculated that my heat loss was between 8 - 10kWhr, we have 2 showers at the same time and a bath and as I had solar power to my immersion heater I wanted to retain my open vent cylinder for the free hot water. I initially looked at a Viessmann 12kW heat only boiler, but its turn down ratio was poor 12kW max 7.2kW minimum. This would as you say in this video mean it probably would not condense for most of its operation. In the end I went with the Vogue system 15kW (the smallest they do), its minimum is 3kW which as you say again in the video less that 50% (5kW) of my heat loss which should be fine. The boiler has only been fitted a few days and is fine, but ASAP I will get the installer back to turn my Y-valve round and wire it to Hot Water priority, and fit a Weather compensator so I can run the CH at the lowest temperature to achieve heating requirements, and have hot water at the cylinder temperature of 65C. You mention in the video, that for hot water priority it may be better to have this on continuous, is that correct? I'm also looking at upgrading my thermostat to either Hive or Nest, but favoured Hive because my family are a little 'old school' liking the Hot Water Boost control which I think is easier to operate on the Hive than the Nest, but I guess if the system becomes Hot Water Priority continuous it matters less. Thanks again for the vindication regarding my thinking over the years, now we just need boiler manufacturers to manufacture smaller system boilers with a minimum turn down ratio of 5!

[@UrbanPlumbers]

Check my other video about how to do Ideal on DHWP

[@3GreeneBJ]

Tell me more about your HW solar heating. Can you use DC directly from the solar panel without an inverter on a low voltage immersion element?

[@jacbisgood2221]

This is absolute gold mate, I've been learning about this on a number of courses but you do a great job of explaining it in a way I can understand. More please!!

[@UrbanPlumbers]

Ohhh thank you. I am doing my best to make as many vids as possible, but I also want to keep them high quality and that takes time, which is in short supply, especially now in the cold season when I am mad busy fixing and installing boilers!

[@cuckingfunt9353]

" Where are you from Mr. Knash ? " ..... " Lots of different places " .

[@3GreeneBJ]

@@UrbanPlumbers Keep it coming. Its grand stuff. You won my respect for sure. Thanks.

[@thetroopersk]

i decreased the power output on my previous gas boiler to minimum...job done...

[@SwedeEad]

Very interesting and useful. I know which direction to go now. I was kind of heading that way but you added a lot of information that will make sure I can make the right decisions about our heating system - which is a bit of a Frankenstein's monster as it has been added to over the years , like the house. Most people don't know what you say in this video so are easily sold systems that are inappropriate. The system we have came with the (old) house. Radiators get hot, water gets hot, what more do we need to know? Well, a lot! Thanks for this valuable information. BTW we have an Ideal Vogue C40 (we live near Hull where Ideal is based). When we lived in London the heat loss from the flat was so low we seldom turned the heating on had the windows open most of the time to cool the place down!

[@DinkyDoughnut]

Excellent, One step done towards the understanding of Heating efficiency.! 😊

[@martinwarner1178]

Brilliant, interesting video. Thank you. Peace and goodwill.

[@Benblyth]

Best video on the subject I’ve seen. Fantastic work, thank you.

[@UrbanPlumbers]

Glad it was helpful!

[@Kulvinder1974]

Hi there, thanks for your videos. As a user, I have learnt a heck of a lot about efficiencies. I have now realised that I have been running my heating system way too hot. I love these videos, they are so informative. Thanks again.

[@jayseabie215]

This is the best video I've seen that explains all this. Well done! This guy really knows his stuff! I would give u a call mate but I doubt u travel north of the river!!

[@UrbanPlumbers]

Email me. All depends on type of work.

[@ecowarrior4355]

Really good explanation of how things are. Hopefully some if not many may be inspired to change things for the better!

[@UrbanPlumbers]

Kim, thanks for your comment. Anyone who wants to know more about the topic go to Kim’s web site and check his training. Link in the description.

[@douglasstalley6475]

Top advice for sure,despite being over 3 years old right. So far ahead of anyone 😊

[@davidramsay7020]

Excellent video of a heating engineer that is at the top of his game. If I may suggest next time you explain latent heat of condensation you may wish to describe the opposite that being the ,agent heat of vaporisation, easier for people to grasp. For water taken from 1 degree C to 100 degrees and boiling it takes 75% of that energy to vaporise the boiling water and boil it off as steam. As your chart and description clearly shows the return temperature and the mass flow rate along with modulation combine to optimise boiler efficiency and reduce the steam cloud exiting one’s flue. I use an IR thermometer to monitor my return temperature and optimised on a flow temperature of 60 deg C which is of course dependent on my system radiators and pipe work. I fitted Honeywell WiFi thermostats on all but three radiators and also time the radiators to operate offset room by room to ensure there is always another heat sink coming on and keeping the system balanced against modulation, heat flow temp and rate. Great videos keep them coming your the smartest plumber on the internet.

[@foppo100]

Our first little boiler was a Small glowworm system.A tank in the loft and an emergen heater in the cupboard.That little boiler lasted twenty years it got replaced because of the water tanks in the loft.Igo to old climbing in there to check the systems out once in a while.I still miss that system sometimes that Glowworm boiler was so easy to serve,It heated 8 radiators never let us down.

[@chrissmith2114]

When we moved into our UK newbuild house in 1997 all the radiators were too small ( and they were imperial sized, not metric ) ... but the builder had fitted a very nice Vaillant condensing boiler ??? Within 5 years of moving in I replaced every radiator with a double panel one, this made the boiler much more efficient by lowering the boiler return temperature...

[@runrideski6003]

I'm from Canada and don't even have a boiler yype of heating system. Most homes around here used forced air (natural gas) heating systems. I happened upon this channel because I'm looking into upgrading my central air conditioner (30 years old) with a modern heat pump. Overall, I have found these videos extremely well done and surprisingly entertaining, given the subject matter. Very, very well done! I did note one minor error in this video related to heat loss calculations of homes, the units given in some of the graphics were kWh (energy), but I believe they should be kW (energy flux or power). This is such a common mistake - basically that the unit for power, W, already has time in the denominator - that even the pros do it ;-)

[@pinarellolimoncello]

I wouldn't claim to be the expert but like you say power is measured in Kw, consumption/usage or loss in this case is measured in Kw/h. So average Uk home loses 6 kw/h per day, at present prices of 10p for gas (government subsidies ) that is 60 p a day over 5 winter months is about £90, doesn't sound like a massive deal but with 20 million households the figures soon add up, (not all on gas, but would just be another loss of oil or electricity which is also produced by gas)

[@runrideski6003]

@@pinarellolimoncellounits of "kilowatts per hour" does not really make any sense for use in this context. Did you mean kilowatt hours (kWh)?

[@pinarellolimoncello]

@@runrideski6003 Yes kwh, is a measure of consumption, also written in UK as Kw/h, the forward slash denoting 'per' hour ie my cooker consumes at 4 kw on for an hour ..4 kw/h. Have just looked at my utility bill, I might be out of date, there is no slash in it but it was what we wrote in physics lessons.

[@Space-O-2001]

I don't know how KZbin videos are found but this video deserves a lot more views given the production quality and information communicated. Maybe a better title?

[@Burak-lz9jk]

That's an amazing video and very informative. Thanks and greetings from Ireland!

[@UrbanPlumbers]

No worries

[@tried2call260]

Excellent, excellent, excellent !!! Outstanding knowledge base and ability to communicate it !

[@UrbanPlumbers]

😮 thank you so much

[@TheZippyMark]

Really great video mate, you get the information across well. One thing though, I'd say the primary reason most boilers are oversized is that the vast majority of gas boilers in small/medium properties (that as you say require say 6-10kw) are combi boilers, and the minimum size combi is 24kw. I feel like the instead of the boiler plus legislation, they'd have had a much better outcome if a minimum 1:10 modulation was required from the boiler manufacturers, say. The other factor I have to deal with (working in London too, primarily rental properties), is that a lot of controls aren't going to make a blind bit of difference if the tenants still use them like a switch, I'd say at least 90% of the tenants I work for don't even have the timer set up, let alone optimised in any way. At least a high modulation would have an effect in all situations.

[@claudiahamminger-stone3274]

thankfully at least Viessmann boilers now have massive turn down ratios, although I notice that no figures for fuel efficiency are ever published for a gas boiler that's running at just 7% of its rated output... Does anyone else here suspect that they're horrendously inefficient at these burn rates?

[@jonathanarnold9409]

Have been following since you worked on my son's heating in South London. Love your work. I wish you were in Birmingham!

[@UrbanPlumbers]

thanks! not sure I will ever move to Birmingham though ;)

[@MrAvant123]

Brilliant video. I am not a heating engineer but have spent a great deal of time understanding mine and my mothers worcester boilers and this has helped me further as I believe I will need to replace my Greenstar 42 soon.

[@bluenapalm123]

Can I sue my plumber who installed my system then? 2x 30kW boilers.. (One disabled currently and notice my heating still works fine) Constantly cycling.. Just about to replace a EV for puncturing. (Boilers less than 5 years old, serviced) They didn't explain Opentherm/modulating feature which my boilers have. Didn't explain or setup any DeltaT. No offer for weather compensation. Can I sue the plumber who has 'serviced' my boilers each year and not spot the blown EV and an empty EV without charge? I am learning all these things from your videos, HeatGeek and SkillBuilder predominately.. absolute game changer for my knowledge. Thank you for sharing and increasing the knowledge across the country.

[@darlapurvis1439]

Excellent explanation and details on condenser boilers…thank you!

[@UrbanPlumbers]

You are welcome. I am glad you liked it

[@simonstones1918]

I love to fully understand what you’re saying in this video 😄

[@larkhill2119]

You're a superstar mate. Learned so much from that video.

[@Chris_at_Home]

Great video. I am getting ready to put in a five zone system in a duplex I am building and this explains a lot on sizing my boiler. The structure has 6 1/2” /16.5 cm of closed cell foam in the walls and R-60 in the attic. I live in a place where I am allowed to,do my own work.

[@UrbanPlumbers]

no electrical , plumbing or gas regulations in Alaska?

[@Chris_at_Home]

@@UrbanPlumbers Yes there are and the utilities won’t connect if they see something amiss. We don’t have building inspectors or building permits. I’m not using a bank so they aren’t involved either. The plumbers want $154 an hour here.

[@johnburns4017]

@@Chris_at_Home Can't you do it, then get someone to sign it off after inspection?

[@Chris_at_Home]

@@johnburns4017 I am going to do it myself after getting some quotes. I can do it for less than $20,000 and all the quotes came it at about $35,000, I’m going to use those Morris Beacon heaters in the floor and under cabinets and baseboard in the basements. The garage has Pex in the slab.. The borough I live in doesn’t have construction inspections. The only thing they are concerned with is property line setbacks and how the driveway connects to the road. No banks are involved as the project is out of pocket. One half of the duplex is finished. It is only 592 sqft of living area and has a full basement. We have been heating it with a Toyo Lasar 30 for 8 winters and only use about 150 gallons of heating oil a winter. The other half is larger at 784 sqft with a full basement. There is a 24x28 garage in the middle just for the larger unit. We have been heating that for a few years now with another Toyo 30. It doesn’t keep up when it is about -20F but other than that it works great. This time of year when the sun is out we don’t need heat it in the day as there is 200 sqft of windows on the south wall.

[@brianhof7599]

@@Chris_at_Home America F yeah!

[@richardmcmaster9389]

The method I use to maximise efficiency while heating the hot water tank is to set the room stat low at the same time so the boiler is not heating the rads. Great video.

[@romanpikuzinski3434]

Wow! Excellent video. Thank you for very clear explanation how the system works.

[@martinblondell9797]

Fantastic video the knowledge you have is astonishing. Cheers.

[@uhtredthebold2]

Instant subscribe. I had my boiler replaced a year ago and I've noticed it's not been condensing and cycling often. Unfortunately I'm on s plan with new radiators which are not particularly big. The boiler is Worcester so opentherm is off the table without losing my warranty. I've been experimenting with fans under the radiators to lower the return temperature and I also want to lower the pump speed to see if that helps. According to the manual it's set to high by default. This is quite the rabbit hole...

[@UrbanPlumbers]

Which model worcester is it? Some of them can do pDWH and also can work with modulation. Pumps are also adjustable on some WB boilers.

[@UrbanPlumbers]

Check this video on how to adjust the pump on WB boiler kzbin.info/www/bejne/rpi7pWyfjrlnnNk

[@uhtredthebold2]

​@@UrbanPlumbers It's a greenstar 24i Systemp ErP. When I turn the hot water on I only see the radiator symbol so I take that to mean there is no diverter kit installed. I've established the pump is set to 4 out of 0-4 available so I will try to reduce that.

[@nuppard]

Excellent video & thanks for all the useful advice. A few thoughts though. I live in a detached house with solid brick walls & a cavity walled extension to two sides. Heat loss is noticeable after only a few hours on cold days but the temperature drop overnight only usually amounts to 2-3 C over 8 hours or so before the boiler fires again in the morning. So does this still justify load compensating controls? I like the idea of weather compensating for my regular boiler & can see that it would probably be better to combine this with hot water priority. Although I know this a 'how long is a piece of string' question but roughly how much would you expect weather compensating, combined with a properly sized boiler, to improve boiler efficiency by? I've also noticed that boiler manufacturers like Worcester Bosch don't seem to mention what their boilers can down modulate to. Do you know of a central source that can list such specs for a number of different boilers? Thanks 😊

[@hotbeefymcd8162]

I learned so much from this video, thank you

[@nicholasstephens208]

I don't normally comment on KZbin videos. Superb explanation of the dire state of the gas boiler industry in the uk. Installers who are unable to adequately size boilers based on heat loss calculations for the property. Manufacturers who develop their own standards for heating controls to ensure you need to use their products. Installers seem unaware of the importance of heating controls and correct boiler sizing. When a new boiler is required, I have never known any installer who has given me a quote to do a heat loss calculation. The workforce needs to be better trained.

[@Tod_Unctious]

What a helpful video, a lot of info shared and superbly presented. Thanks

[@biggig06]

Hello Continue posting, great value content Learning a lot

[@UrbanPlumbers]

Thanks

[@jimroberts6456]

Interesting video. The question I’m left with is around boiler sizing. If I want a shower at 10l/m @40degC (pretty standard shower conditions) this works out at about 26kW (@ 80% efficiency). This then sets the combi boiler size as ~30kW whatever the house heat loss is. Of course you can fit a cylinder you can get round this but isn’t this why condensing combi boilers will never run at the condensing efficiencies claimed?

[@millomweb]

I've designed and installed my own CH system. Radiators are well-oversized (3-panel with convectors) (biggest: 2m long, 67cm tall) I have 5 zones - house, DHW and 3 bedrooms. Only the House zone is on TRVs ("high pressure" = restricted flow by TRVs!). This could run at a lower temperature. 1 bedroom, not used, is only heated to a cool temperature and the heat is limited to 1 hour but 15 minutes is about as long as it's on for. DHW and the three bedrooms on 22mm pipe. Easy flow "low pressure". My bedroom stat is set at 17°C. Rad overshoots to 24°C - great for going to bed & getting up. Heating period 1.5 hours at night and 2.5 hours in the morning. I liked the idea of 24kW going into my bedroom (old new boiler). Current boiler, sized by me is 9-19kW Viessmann - I wish it had dual set point and a lower minimum power level. House coolstat set to 18° and mainstat set to 18

[@UrbanPlumbers]

Yes, what is your Design flow temp?

[@millomweb]

@@UrbanPlumbers Whatever was necessary to get a good water temp for bathing. Boiler moderates to 68 but continues to rise to 75 before shutting off the burner.

[@mickinmerton8053]

Great video. I wish I'd seen this video a few days prior. I've just had a Valiant boiler fitted and I have Nest controls, if I had known I would of specified a different boiler. Luckily I did resist the pressure from the heating engineer to up my boiler from 16kw to 24kw.

[@UrbanPlumbers]

Good. Not many do as people usually think that bigger is better

[@UrbanPlumbers]

If you have a vaillant boiler, have a look at installing vaillant wiring centre (VR66 or similar) and converting the system into hot water priority with weather compensation. You will need to change Nest for Vaillant controls, but this will make the system more efficient and will extend the life of the components.

[@georgeturner6648]

Brilliant Thank you. I have heat only with stored HW with solar thermal input. The boiler needs changing soon. You’ve given me a lot to consider. I think the hardest part will be finding a competent engineer like you!

[@UrbanPlumbers]

Check ‘heat geek map’ on google! There will be one near you !

[@stephenrichards5386]

I could listen to your videos for hours and frequently do. Sad ! I know 😇

[@problem9]

thanks for great video! great explanation and info. i was using nest + combi condens protherm (vaillant group) + outdoor sensor, so heating wasn't that terrible (based on outdoor temperature), but nest wasn't used as it should be. so I ordered vaillant vr 33 from Netherlands, connect to protherm via x32 port and everything is working even with hot water heating.

[@iheggis86]

Thanks for uploading again - Great to see 👍

[@UrbanPlumbers]

No problem 👍

[@VathSok]

Thanks for the great and detail explanation. Great knowledge and experience you are sharing here. We've just installed a new Combi boiler last week, Lochinvar NKC199N. I've noticed the installer set the outlet temperature to 180F/82C and the return temperature to inlet is somewhere around 169F/76C. To me, this temperature set point is way to high but with the fact that it was cold out side last week 5F/-15C, we are in Massachusetts. We have 4 zones, 3 zones control forced hot water baseboard and the other zone controls radiant floor (concrete slap for our greenhouse, we use a mixing valve to reduce water temp to 130F/54C for floor). So while the other 3 zones satisfied the room temperature, the 4th zone for the radiant floor seems to keep running most of the time to keep the slap warm with this cold temperature outside, but since the outlet set point is180F/82C, I feel that we are wasting the energy. So my question is should I change the outlet set point to 130F/54C? so we can just send 130F/54C straight to radiant floor, ignoring the mixing valve, and I expect the return temperature to drop to somewhere 110F/43C. Is "130F/54C" good enough for baseboard heater ?

[@CrashUK28]

I had same. installed new boiler at set point temp was 85c. heating the house in 5 mins.

[@deano-qj9tj]

its probably about right if the outside temp is -15c . mine is on weather compensation and it would automatically run at that sort of flow temp if it -0c or less. when your outside temp reaches 11c or above try setting it to 65c and see how it goes

[@richardc1983]

Set to 55c see how you get on, if its still heating it well, lower it to 50c and see again, keep going until the boiler is set low enough that it keeps your home warm. The lower you can get the flow temp the boiler condenses even more and you get even more efficiency.

[@marloweye9188]

Well done on this information. Just a brilliant example of what I have been telling my own clients for years. A smaller Boiler working flat out is more efficient and lasts longer than an oversized one. What I didn't know until watching your video was by how much. That's an awful statistic.

[@joes250]

Excellent video. Very clear and well explained

[@johndevlin980]

Brilliant!! Great explanation, I wondered where you had got to? 😂 thanks 👍🏻

[@slygen6074]

You are legend my friend. So much much information! Brilliant

[@UrbanPlumbers]

Thank you for watching !

[@dave0smeg]

When we moved in here, the central heating system with a boiler around 40 years old and had a hot water tank. The home was always warm despite the boiler rarely needing to run. When it developed a fault it was reolaced with a super efficient A+ rating condensing boiler. This new boiler uses 3 times as much gas as the old D rated boiler, and the house is much harder to keep warm.

[@UrbanPlumbers]

there is no way any gas boiler will use 3x times the amount of gas. Unless your fitters left you with a gas leak on the system.

[@dave0smeg]

@@UrbanPlumbers Odd that our gas bill more than doubled as soon as it had been installed. It does seem a very wasteful boiler, running the gas through for 5 seconds before trying to ignite it, then regulating it down once it detects the heat.

[@UrbanPlumbers]

@@dave0smeg the difference in efficiency between boilers cannot be more than 10-15% and it's usually in condensing boiler favour. It may be that your supplierhiked the prices, or you have some very serious problem with your installation or maybe a leak on the installation. Get a decent gas engineer to check it for you. Check heat geek map for someone in your area. (google heat geek map)

[@richardc1983]

What's your flow temp set to?

[@bradymdj]

Two plumbers wanted to increase the gas pipe size (19mm to 22mm) to support a big boiler (24kwh). This had to run around the outside of the house. I can see many houses around with these ugly copper pipes running around the house from front to back (usually where the boiler is situated) and its something I wanted to avoid. Using the principles articulated here, I managed to put a smaller boiler in and heat my home perfectly well.

[@pumpkinhead456]

Great info thanks, in some ways it has put my mind at rest. We had a 46kw vaillant ecotec plus with 3 zones and controls installed, which seemed really silly for a house needing about 27kw. However it has weather comp and modulates down to 9kw, so usually just ticks over. It's not condensing much based on your info, flow and return at 62 and 54, but otherwise sounds like it might be quite efficient. Costs us £8 a day currently for 15 hours of heating - the joys of living in a draughty old house with a small baby!

[@UrbanPlumbers]

27kW heat loss - that must a 20 bedroom mansion!

[@pumpkinhead456]

@@UrbanPlumbers not quite, but it is bloody cold, I can hear the wind whistling through the floor just now... I just calculated that £8 a day is 11kw per hour of actual use. Will keep driving it down as I insulate and draught proof more and more...

[@3stevieb1]

Mind numbing but answers the real issues. Brilliant.

[@johnstewart1011]

1st class video thank you, I just bought a Worcester greenstar boiler, supposed to be the highest selling boiler in the UK, they also don't support open therm, so again they want you to buy their not so good controls but their latest controller that works with weather compensation sensor (and it comes included in the box) but it can't work with smart TRV's. so if you do decide to go for Worcester you are probably better off going for 3rd party modulating controls, maybe the Drayton, wiser software which is very good using it's own mesh network to communicate with smart wireless TRV's, which doesn't rely on your internet connection to communicate with the system component's, or manual TRV's on all radiators except for possibly a towel rail for heat dissipation when the boiler turns off. but I don't know if the Drayton wiser system communicates properly with the Worcester modulating controls or just acts as an on / off switch. That's the trouble manufacturers don't want you to be able to use 3rd party controls so there's limited information available. Thanks again for this video to explain the basics.

[@ellon118]

great video. very informative.

[@pb871]

Brilliant video. Clear and well explained. Thank you!

[@OggyGTA]

Great video! This has given me a lot to think about!

[@barriewright2857]

Thank you for the education and information 🙏.

[@chrissdavey]

Excellent info. Very interesting. This guy really knows his stuff!

[@UrbanPlumbers]

Glad you enjoyed it

[@richardc1983]

Combi boilers are sized based on the hot water demand. A smaller boiler will not provide the same flow rate of hot water than a larger. Unfortunately that means the heating side of it is usually oversized.

[@DouglasFurlong]

Came here to say just that. The over sizing is down to the dhw requirements for showers.

[@richardc1983]

@@DouglasFurlong yep or multiple bathrooms.

[@ItsFriscoBaby]

Na man you're doing it wrong. You need to start throwing in 6kw boilers and telling the customer they have to wait 7 hours to have a bath. Don't you know what your doing?

[@richardc1983]

@@ItsFriscoBaby it would be like being in a static caravan.

[@ItsFriscoBaby]

@richardc1983 yep. Talk here of sizing boilers based on the maintenance load of the heating only. Customer walks into a cold house and wants the heating and hot water, they're in for a wait but at least it'll be efficient.

[@paradoxni]

Great vid. I've a Worcester Green Star that had a Wave and compensation. Now using a Nest on/off, but was considering getting the EMS to Opentherm adapter to allow the Nest to compensate, but can't find concrete proof it works well.

[@andyxox4168]

Simplest easiest advice to any home owner, ensure your boiler wares temp (out) is 50-55C then whatever happens in your radiators your boiler will be operating in condensing mode.

[@GeneralTJP]

Absolutely brilliant video, clear and concise with so much knowledge, Thank you.

[@UrbanPlumbers]

Thank you for your kind words sir!

[@GeneralTJP]

@@UrbanPlumbers No Thank you, I feel like I've just discovered gold. Ps, I've sent you an email

[@anthonyschofield7807]

I enjoyed this clear and well presented explanation but could I ask whether a smaller combi boiler could provide the amount of hot water necessary to fill a large bath?

[@marcusjt]

Surely any boiler can fill any size bath, but the power of the boiler (and its efficiency) will determine how *quickly* it can supply a given volume of water at a given temperature. So really you need to work backwards from the volume of water needed, the temperature you want it to be at, and how quickly you want it to fill the bath to calculate the size/power of boiler that you need to achieve that level of performance.

[@Martindyna]

A small Combi could take 20+ minutes to fill a large old bath I would guess (120 litres) as against about 5 minutes from a airing cupboard hot water cylinder. My parents had a Worcester 280 Combi (non condensing) which was very reliable but took its time filling the bath. The 280 was unusual if not unique in that it was suitable for connection to an old radiator system since it didn’t need to be pressurised so could use a conventional F&E tank. Why they claim that F&E tanks cannot be used and the boiler must be pressurised nowadays is beyond me.

[@paperaduck9058]

very interesteing video, thanks for sharing. All correct, except for the confusion you made on kWh and kW. kWh is energy not power, boilers are rated for power (that is energy / time)

[@alipaulstagram]

When I had my boiler fitted, I made sure that I picked a boiler that would work via opentherm with my nest device to modulate. After it was installed, the electrician hadn't even wired it up for opentherm. When I asked him about it, he didn't even know what opentherm was! I hate to think how many boilers he has wired up incorrectly and how much waste has been created simply by that electrician.

[@BlueMoon130512]

There are people who know their subject inside out and there are people who can expain things concisely. But it's very rare to come across someone who can do both. Great video. If you can take the time to reply to this I'd be grateful. Is my nest thermostat then just a fancy on/off switch when connected to a Worcester 8000 Life? And basically, my fancy new boiler is not modulating?

[@UrbanPlumbers]

Yeah, get a Worcester own controls for better performance

[@BlueMoon130512]

@@UrbanPlumbers Thanks very much.

[@craignixon4468]

Or...try to get hold of a Nefit EMS-OT OpenTherm converter for your 8000. Similar to the one mentioned in the video. I believe they are very difficult to find but google is your friend. Someone should petition the Government to force the Manufacturers to do same as Netherlands do!

[@SiandMads]

@@craignixon4468 @Urban Plumbers have you seen Nefit EMS-OT OpenTherm converter working on a WB boiler and am I correct in thinking that it will invalidate my warranty if installed?

[@BoxerfanUK]

New subscriber. Great video, thoroughly enjoyed that. Can you move to Milton Keynes please we need an engineer like you around here. 👍😀

[@Land-of-reason]

Fascinating. Have you done a video on heat loss?

[@johnf3326]

I like control. iTemp Terriers on every rad. Oversized radiators on internal walls if possible. Crono proportional thermostat with target temperature and variable preheat time. Radiators balanced by digital flow and return thermometers. Serious underfloor pipe lagging. Flow temp 50 or 55 in very cold weather

[@billybobhouse9559]

I was told that it's OK to oversize a combination boiler as it will provide better hot water pressure at the tap. I always thought that the boiler would modulate down during a central heating demand according to the heat output required. I didn't know that there was a limit to how much that boiler can modulate down too. Very interesting video.

[@stephenrichards5386]

I don't know but I don't think the boiler size influences the water pressure. The big issue I have with condensing boilers is that the need for central heating influences the hot water negatively. I've always had system boilers

[@MrMutt1960]

Hi Richard, its not pressure its ,volume of hot water delivery,ie 35kw gives much more hot wtr than a 24 kw

[@IMBlakeley]

I've currently left UK but if I come back this will be useful. I am thinking my last place was better than average, it was a large 5 bed detached approx 180m2 and the installers recommended and put in a 15KW boiler.

[@danielradu7386]

Thanks for your great insights.

[@stevecraft00]

Combi boilers are sized for the hot water output. It takes a lot of energy to instantly lift water from 2 degrees to 60 degrees! I had a conventional boiler in my old house. 11kw. I had it replaced with a combi boiler, 24kw. Because it now had to heat the hot water.

[@bikeman123]

Or you could set the timer to bring on ch and hw at different times.

[@stevecraft00]

@@bikeman123 combi boiler.

[@Group51]

@@bikeman123 exactly what I plan to do. No idea if my combi boiler is under or oversized, but it clearly struggles to do heat and shower at the same time in winter. I only need a 1 hour block out for showering.

[@kevinhill1851]

To my knowledge, combi boilers cannot continue to keep the heating water at the desired temperature whilst producing hot water - they can continue to pump the heating hot water around the system, but cannot heat water for taps at the same time as heat water for heating.

[@stevecraft00]

@@kevinhill1851 correct. Nobody is disputing this?

[@kevinphillips8504]

Great video, great engineer. Not sure if you have before but I think you’d really enjoy the commercial market

[@UrbanPlumbers]

Commercial market ? Like charging money for the work? Never! I am a true communist mate.

[@stephendoherty8291]

I have read that removing all pipe insulation from return flow pipes means the chances of a condensing delta rate rise. Especially if the existing boiler was over sized. This dumps the heat into the house so it's a cooler return temp. In my case, I'll be adding a weather compensator and a water adjustment feature that only on reading the manual after, do I realize it offers much more hot water control.

[@DGQ1Q2]

Very good explained

[@olliec1319]

Thanks for this. You talk about an epidemic of oversized boilers. But if you have a combi, then surely you need a 30kw or 36kw to get decent flow for the hot water?

[@ChristianBHough]

That's the same thing my mate will say. You need the bigger KW Combi for the water. Not all properties have space for an invented cylinder or the water pressure isn't good enough for one. It will always be a trade off. Either a bigger Combi that can work with lower water pressure and give you the water output or an invented cylinder with an accumulator or booster pump. I'd love to hear how to overcome this issue as I'm doing my gas training and will need to know this for the future.

[@olliec1319]

@@ChristianBHough if you're training I'm sure you'll come across lots of people who know the answer. I'm not a plumber so I don't know. But I do know my neighbours have a 24kw combi boiler and they get a cold shock if someone touches a tap while showering. And we get a much higher flow rate of hot water with our 36kw combi.

[@steveducati996]

Spot on! So any people have boilers sized correctly for the CH and struggle to get a decent shower in winter I’ve got a 38kw Vaillant which is a bit oversize for my house CH, but have never struggled with shower temp or volume I’m glad I did it this way. Surprised this point wasn’t acknowledged in an otherwise excellent video👍🏼

[@olliec1319]

@@steveducati996 Those were exactly my thoughts. An excellent video, just a bit baffled why needing more power for good hot water flow wasn't even discussed. As I'm sure as a plumber he's having these conversations every week.

[@UrbanPlumbers]

Hi guys. I will do a follow up video to explain combi boiler confusion!

[@christoy5429]

Excellent video, thank you! I have a question about return flow temperature. I have some radiator pipes running in a crawl space under my home. It is advisable to insulate only the flow pipes and leave the return pipes uninsulated so get the return flow temperature as low as possible, or is it still more efficient to insulate all the pipes?

[@theoldgaffer]

Personally I’d say, insulate them as that’s just wasted heat. No matter how you look at it, you are heating loft space. Once insulated, maybe you could reduce the flow temp on your boiler?

[@ashoktewary4151]

Thank you, your explanation seemed logical and I reduced the boiler temperature to reduce cycling (I have underfloor heating) which reduced the plume. Two weeks ago Worcester Bosch sent their engineer for a repair. When I mentioned this to him, he explained that this was not correct. He explained that in the morning when the radiators are cold and return temperatures are lowest, the plume is the longest! I am now confused. Do heating engineers go through a formal course and pass examinations? Why then such diametrically opposite information for something so basic?

[@UrbanPlumbers]

Engineers have no training in efficiency usually. Even when they do it is usually next to useless. Keep your flow temp at 60c if you also have rads or 50 if ufh only or lower unless it gets very cold. Best to install weather comp or load comp on worcester

[@aidensholeh3696]

Incredible video. Thank you.

[@UrbanPlumbers]

you are welcome, thanks for watching

[@fredericguyon1449]

That is a very interesting video with good technical details. One thing I have been wondering is that for combi boiler, the power is also based on the need for hot water flow rate. However, you only talked about the heating what about the hot water. You might want to under sized based on the heat loss calculation based then it might not provide enough hot water flow rate.

[@hempcacaogoji831]

One way to extend the life of a condensing boiler is by using a programmable schedule thermostat. If the thermostat set temperature changes a few times per day, then the boiler will spend more time on and more time off, as opposed to turning on/off more times.

[@misterbeetz]

excellent video. well done!