Should I make my radiators smaller?
A deliberately provocative title, forgive me.
The question is really about how important it is to have equally sized radiators in each room, in relation to specific room heat loss.
I had a heat loss calculation done, and with my current radiatiors at a design temperature of 50C flow and -3 OT, some are clearly undersized, the worst being -47%. Okay that needs upgrading, no brainer.
But how much to upgrade it, just to 100% the heat loss of that room, or to match the most oversized radiator in any other room?
What if thats not possible, and room A is sized with 100% of power output to heat loss, and room B is sized to 158% of power output to heat loss; I assume room B is going to get much too hot?
The modern advice is not to have TRVs and to go as "open circuit" as possible, so how do we mitigate the oversized radiator in room B? Should we make it smaller? What % of size deviation can be handled without adding flow restrictions and controls?
Everyone seems to say bigger radiators are better, but should that advice come with the caveat that sizing needs to be equal throught the heating zone?
TIA
Bonus question; if you open up all the radiators in a reasonably balanced system, and let the heating come to equielibreum with OT, and measure the temperature within each room; is that a better way to calculate heat loss? Is there a method for that?
Posted by: @scalextrixWhat if thats not possible, and room A is sized with 100% of power output to heat loss, and room B is sized to 158% of power output to heat loss; I assume room B is going to get much too hot?
The modern advice is not to have TRVs and to go as "open circuit" as possible, so how do we mitigate the oversized radiator in room B? Should we make it smaller? What % of size deviation can be handled without adding flow restrictions and controls?
The deviations can be handled by
a) the lockshield valve. this restricts the flow rate through the rad in question which increases the deltaT for that rad which reduces the average temperature and hence the output.
b) the fact that rooms tend to share heat anyway because the thermal separation is poor.
I had mismatches of 150% plus, no problem
Posted by: @scalextrixBonus question; if you open up all the radiators in a reasonably balanced system, and let the heating come to equielibreum with OT, and measure the temperature within each room; is that a better way to calculate heat loss?
No, you wont leave it like that for long enough to overcome all the other variations that mother nature throws at us.
Posted by: @scalextrixIs there a method for that?
yes, (a) measure it over several weeks monitoring individual radiators and the heat pump, Adia Thermal make the kit to do this or (b) plot your gas/oil usage vs average OAT for several months or preferably a whole season, estimate the efficiency of your boiler, and work from there (gives you whole house only).
4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.
@jamespa thanks for the reply, so really in this case we have to reduce the flow to the radiator to achieve it.
In my specific case the oversize radiators are upstairs which isn't really the best from a heat sharing perspective, but I get your point.
Posted by: @scalextrix@jamespa thanks for the reply, so really in this case we have to reduce the flow to the radiator to achieve it.
In my specific case the oversize radiators are upstairs which isn't really the best from a heat sharing perspective, but I get your point.
Mine are also upstairs because I upgraded them before I realised how much the heat pump industry overestimates house losses. Still not a problem although the lack of 'valve authority' with the very old LSVs on a couple of the rads in question makes for a slightly tricky, but not impossible, adjustment . Of course that is my house, yours may be different. The 'excess' upstairs capacity helped my installer to be happy to leave the bathroom well under-provided for, thus I could retain my exiting towel rail rather than replace it.
That said if you can make the downstairs ones bigger go for it. Lower flow temperature = lower cost and greater comfort, as you clearly know!
4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.
- 22 Forums
- 2,070 Topics
- 45.3 K Posts
- 17 Online
- 3,343 Members
Join Us!
Trusted Installers
Struggling to find a reliable heat pump installer? A poor installation can lead to inefficiencies and high running costs. We now connect homeowners with top-rated installers who deliver quality work and excellent service.
✅ Verified, trusted & experienced installers
✅ Nationwide coverage expanding
✅ Special offers available
Latest Posts
-
Fair enough. With R290 heat pumps, which seems to be...
By JamesPa , 1 hour ago
-
RE: Heat pump installation and BUS Grant timings
EPC no longer necessary Here is the link to the part...
By JamesPa , 4 hours ago
-
RE: Getting the best out of a heat pump - is Homely a possible answer?
@benson Ours is ‘resting’ for the summer now (unless we...
By Toodles , 5 hours ago
-
RE: Home energy storage & battery register
@jamespa To a certain extent, by exporting to the grid ...
By Toodles , 7 hours ago
-
RE: Jokes and fun posts about heat pumps and renewables
@transparent ‘Protein’s extra Luv’.
By Toodles , 14 hours ago
-
RE: Forum updates, announcements & issues
@editor Fairy Nuff Mars, I doubt that my ramblings woul...
By Toodles , 1 day ago
-
RE: Antifreeze top up for my heat pump - is this a rip off?
@johnmo You are correct, standard Ethylene glycol used ...
By Brendon Uys , 1 day ago
-
RE: Confusion about heat pump sizing
We’ve published a deep dive into heat pump sizing, and ...
By Mars , 2 days ago
-
We’ve published a deep dive into heat pump sizing, and ...
By Mars , 2 days ago
-
RE: Kensa GSHP finally installed - now to start the optimisation process
Just had a quick scan of the manual and should be weath...
By Johnmo , 2 days ago
-
RE: Potentially more choice including air to air heat pump grants
Hi all, I agree, the consultation documents are alway...
By madbilly , 2 days ago
-
RE: Commencing on an ASHP Installation Process
I think those are pretty much the standard figures that...
By JamesPa , 2 days ago
-
RE: Load Compensation and Weather Compensation
I think that maybe what the adia thermal system does, b...
By JamesPa , 2 days ago
-
RE: Enabling WiFi: Samsung ASHP on Smart Things App
@old_scientist @profzarkov thanks to you both for the v...
By Grahamh-uk , 2 days ago
-
RE: Nibe F2040 periodic warm water increase fails
@tribol here's an official reply from NIBE on your case...
By Mars , 3 days ago
-
RE: Vaillant & OVO partner up to offer Heat Pump Plus
@ecodan-efficiency On the other hand, the fact that the...
By Richard24738 , 4 days ago
-
RE: How accurate was your heat loss survey?
@scalextrix for our house 1950s detached the air leakag...
By Judith , 4 days ago
-
-
RE: Air Changes per Hour - ACH and the MCS requirement
@matwin If you plan to commission one it might b...
By JamesPa , 4 days ago