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Central Heating Pipe Sizing and Fitting Control System

Postby sbanks88 » Sat Jul 04, 2020 10:09 am

A couple of years ago I had a new central heating system installed as part of a full modernisation. Unfortunately I’ve been having problems with other aspects of the renovation so for a while I’ve been running it without a control system or TRV’s (I have a Honeywell EvoHome set ready to go but didn’t want these damaged by other work going on). Another reason is that I don’t have downstairs doors fitted yet so wouldn’t get the benefit of that extra control..

Now that I’m nearing completion, I would just like a bit of a sanity check on the plumber’s workmanship before I start fitting the control system and carpets etc.. I’m a bit concerned that some radiators feel cold lower down, I’m more accustomed to them being cold at the top if they need bled. Here are the specs;

- BAXI 28kW Combi boiler feeding 7 radiators in 3 bed terrace house with 2 receptions.
- Boiler located in kitchen.
- 10mm O/D speedfit pipes to all radiators
- I believe these all branch off 12 or 15mm speedfit pipe from the boiler (would need to lift boards to check).

Basically, I’m a bit concerned that the 10mm O/D pipe is too small and causing the cold spots lower down the radiators? Although this seems to be more of a problem downstairs than up? And could it be that they just need to be balanced properly and all will be well once TRV’s fitted?

Appreciate input from any experienced plumbers/heating engineers out there, also are there any relevant British Standards for selection of pipe sizing for heating systems you could point me to?


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Simply Build It

Postby stoneyboy » Sun Jul 05, 2020 4:55 pm

Hi sbanks88
Increasing the size of your pipework will be expensive so try fitting your TRVs, balance the system and check your pump is on its highest setting. If this fails you could upgrade your pump or replace pipework.
My only other thought is that if you have designer radiators some of these are handed as far as supply and return connections are concerned.
Regards S
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