01 Radiator Sizing

[@Pspsps5]

At last someone who is giving a true explanation of heat loss and what you need regarding system design. It’s not all about the heat source you must fully design a heating system. Great stuff very well done 👍

[@andrewmillwardwatford9410]

Great to see another great source of learning on utube.

[@hvaccuffingit6471]

Thanks Andrew.

[@m0aze611]

This is top notch, now I understand. I will be moving homes soon to a traditional boiler /radiator system, this helps me to ensure that when we move I will need to consider the current installation, trial using the boiler at the optimum temperature etc at the same time work out my heat losses per room and take what I’ve discovered here and put it into practice. Not at the ASHP stage yet. Regards Mike

[@Ifitaintbrokedontfixit]

Great presentation that has saved me some work! It's clear and concise and something I can point customers towards when we tell them that times are changing.

[@kevinschoales844]

We compliment you on your presentation on this subject, after reading or watching many articles on this same subject yours is the most comprehensive. Whether customers can fully understand or even agree due to installation costs is the major problem, so far installers are suggesting a suck it and see approach to keep heat pump install costs down, customers go along with that. I totally agree you have the correct approach, congratulations.

[@hvaccuffingit6471]

Thanks for your feed back, please share to spread the word. Thanks👍

[@yogbert]

Great video, clear and precise explanations on how heating works and how sizing needs to be done. Many thanks.

[@brendanfisher2528]

really good video! I'm glad someone is going indepth with this kind of stuff! keep them coming mate!

[@lewisprice3663]

Answered a lot of my questions I had on radiators. Thanks for that Black Mountains

[@alfypierri8022]

Fantastic video. Really done well. Thanks

[@dilshadahemad-f8o]

perfect explaination

[@neo_265]

Fantastic explanation and detail. I've been trying to lower my flow temperatures on my Baxi Plat combi as low as possible but can only get as low as 61oC as Im probably hitting the boilers minimum output for my system design.....yet my boiler still cycles as my heat loss is obviously lower than the boiler can go to (manually). My return temps are around 50oC so my boiler is only just condensing. Is there anything I can do to lower this further with my current boiler? I'd love a modern load comp boiler but cant justify it considering my boiler works perfectly.

[@ejp3245]

Awesome video. Is it really ok to connect flow and return top and bottom on the same side. Will this even work on a rad 1600 wide x600 tall.

[@scottk2765]

Great video. Concise and easy to follow. You do mention a 10 degree difference on the stelrad site but then go on to use a 20 degree difference between flow and return later on, why is this?

[@hvaccuffingit6471]

All modern boilers are dt 20 to maximise condensing. Rad companies don’t seem to keep up with this. Mean water temp is the main factor though.

[@jezlawrence720]

My house is annoyingly hard to heat throughout despite being quite small. In order for the hall and bathroom areas to stay warm, the flow rate needs to be 5c higher than the rest of the house needs. Its not too bad, i have smart trvs throughoutnso no room overheats, but it means i still have to run at 60c if its below 3c outside. 60c will then cope with that area down to -3, but below that id have to turn up to 70c. Vexing. I know the problem: bathroom radiator is undersized and sucks heat out towards that side of the house, and the landing above has no radiator. ...but theres no room to put a bigger rad in the bathroom or one on the landing! My hallway rad is oversized now which has helped - last winter i had to run at 60c below 7 and 70c below 0, but the bathroom remains stubbornly between 16 and 18. Bah. I think im going to have to get an IR panel or something in there. If it wasnt for that bathroom i think i could run the house at 55c flow rate or below all the way down to -3, which would be at least heat pump ready, if not heat pump perfect.

[@paulgoffin8054]

Very interested in the comment about radiator piping. In the illustration of the "European Way", you have hot entering at the top. Does it make a difference if hot enters at the bottom (which feels more logical to me)?

[@hvaccuffingit6471]

As far as I can remember it’s just states the pipe arrangement and doesn’t specify flow/return. I could be wrong and you’ll get some form of stratification naturally. I’m sure someone would have written a paper on it at some point. 😉

[@doodie84]

Very interesting. Do you recommend any courses for learning about heatloss when considering low temp systems? Do you have to be MCS registered?

[@handle1196]

Another great video. I have two questions on the content. 1. So at 15:46 Would you design bedrooms for 18°C and then they always have to be used as a bedroom, or at 21°C and add TRV's as a limiter so it's warm during the day but with a 3°C set back at night it would become 18°C anyway. This way the bedroom can be used for other in the future? 2. At 20:03 you say to try & stick to the same MWT throughout. Does having UFH ground floor with radiators 1st floor make a difference to this because the UFH will be blended down via the mixing group and would be a lower MWT?

[@hvaccuffingit6471]

1. I’d design at 18 for bedrooms as per the design guide, however someone may want them designed differently for office use and then you could use TRV’s to limit the output. 2. UFH is usually controlled with a mixer so it would have a lower MWT and would be designed for this. Sticking to the same MWT design is aimed at radiators so you don’t have hot and cold rooms at the same MWT.

[@handle1196]

@@hvaccuffingit6471 thanks for your reply and advice.

[@giacomobonetti9134]

To increase heat transfer, what about having blown air on the radijators, aka fancoil

[@markcharlesworth2528]

I'm trying my combi flow rate set at 56 degrees. I have heating at 18 degrees when on and turn it down to 16 degrees when off or out. I'll see how goes through winter.

[@mrfish2064]

This was very well explained. However, you never took into account how the house is used. In my house, other than the bathroom, none of the internal doors is ever closed.

[@Havana-man]

Are you unable to close them, and if you are, is there a reason you don't?

[@normanboyes4983]

Interesting that Part L specifies flow of 55 when a return temp of 55 is the start of the condensing phase. Did they get confused?

[@hvaccuffingit6471]

If you have a flow of 55 then on a gas appliance your return will be 35. So you’ll be condensing more and it takes less energy to heat to 55 than 70. 55 return is just dipping a toe into the condensing range.

[@normanboyes4983]

@@hvaccuffingit6471 Hi Yes - I totally get that, I just wondered about the ‘coincidence’.😉 Incidentally at - 3 I am flowing at 49 (V200).

[@hvaccuffingit6471]

I’d guess it was decided on 55 so properties are heat pump ready. 55 at dt 20 gives a 45 mean water temp which could be achieved with a 47.5 flow at dt 5 on a heat pump.

[@Nawas-radiator-2013]

❤

[@peterconnolly4608]

Hi, does this leave the 4 time flow rate now needing 28mm pipes installed all around ?

[@hvaccuffingit6471]

What’s the kw loading?

[@peterconnolly4608]

@@hvaccuffingit6471 11 kw and 22kw ,

[@hvaccuffingit6471]

@@peterconnolly4608 28mm will take you to 10.5kw at a velocity of 0.9m/s. 22kw at dt5 would require 42mm pipe. Feels a large heat load.

[@peterconnolly4608]

@@hvaccuffingit6471 hi, that is 28 mm from heat unit to distribution cylinder coil then to distribute to heat emitters (radiators) in 28 mm to ?

[@hvaccuffingit6471]

@@peterconnolly4608 no, you headers carrying all of the load will be sized accordingly. Each radiator will have a fraction of the load and the pipework size required will adjust with the load.

[@dontmissaday]

Why can't we use mixers on the return water

[@hvaccuffingit6471]

@@dontmissaday to achieve what exactly?

[@dontmissaday]

@@hvaccuffingit6471 to bring the temperature down to 55 c for the wall hung boiler

[@hvaccuffingit6471]

@@dontmissaday the flow at say 70 would need to be mixed with return water to bring it down to a temperature for say a 35 degree for under floor heating for example. You’d need to mix it with something cooler to get it down. Mixers can be used on say oil boilers to raise the return with some flow to avoid corroding the shell. Check out ESBE for applications.

[@kylebrowning7469]

How do you convert from a dt of 50 once I’ve worked out the wattage needed to what wattage will be needed with a dt of 24/25?

[@hvaccuffingit6471]

You need the F1 factor table in the domestic heating design guide to calculate the new out put. The video is more pitched at customers so they have an understanding that radiator outputs change depending on system design temperatures. Also to highlight that you can’t calculate a radiator size or design a system without knowing the heat loss.

[@hvaccuffingit6471]

kzbin.info/www/bejne/n5iviGlppJtje7s This video goes more into the maths which is all in that section of the book. Hope this helps👍

[@kylebrowning7469]

@@hvaccuffingit6471 perfect thanks bud I’ve just done half a quote for a huge place done all the heat loss working on a dt50 I honestly wasn’t aware of this new regulation change I’ve spend the last few days getting up to speed while being on paternity, so what would the case be if you’re going to do a boiler change and the customers don’t want to update the radiators? Just run it at 55 and tell them it isn’t going to get hot or you just cannot do the job? Or can you still run them at normal flow temps as it’s an exciting system? And if you were to say replace a radiator would you tell them they need to replace all of them or just replace the single one with a new ones installed ready for dt20 if they ever update it?

[@hvaccuffingit6471]

@@kylebrowning7469 my interpretation is new systems would need to be designed at 55 degrees. Boiler changes would be on the existing system and would not require updating. However with the introductions of more ASHP’s and rising gas prices then you may find more system design changes. Time will tell.👍

[@kylebrowning7469]

@@hvaccuffingit6471 ahh okay, and yeah suppose more work haha not that I think anyone worth their money is in need of it with this boom going on, really appreciate your fast response mate, got a subscriber here:)

[@SuperWayneyb]

🤘😎🤘

[@bethanypattison9842]

12:19 DT for the boiler should be 12 not 11

[@hvaccuffingit6471]

Thanks for the comment☝️feels a very minor difference to highlight. Can you reference it in any technical document for me to look into it? Thanks

[@noelburke6224]

You are all gone pear shaped.ypu have and are being pulled into climate hysteria. Sure the world is warming we don't need heat

[@hvaccuffingit6471]

Thanks for your comment. Feels like you need to point this opinion towards building regulations. 👍

[@stupidusername38]

When would you take into account the BTU of the radiator?

[@hvaccuffingit6471]

I personally would just use Watts. BTU’s are just a unit of measurement like using gallons or litres.