Central Heating - Pipe Sizing?

[Deleted member 116030]

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?

Thanks

Steve

 

[Scott_D]

It would depend on the size of the radiator, length of pipe and number of elbows etc.
Are you leaving the heating on long enough for it to fully heat

 

[SJB060685]

Are you sure your primaries are in 15mm?

 

[SimonG]

I would 22 or 28 from boiler, depending on size of boiler. 2 zones for heating in 22. 22 distribution dropping to 15 to run upto 2 radiators.