Central Heating Pipe Diameter

[D_Hailsham]

Hi,

Total rad btu is 10,000 - 12,000

The run from tee off upstairs to furthest rad is about 10m, 2 pipe system so say 20m total, plus teeing off to each rad.

That's 3 to 3.5 kW. Assuming an 11C differential the flow rate is 0.076 litres/sec giving a resistance of no more than 0.6 m to the farthest rad. The velocity would be approx 0.5 m/sec. Nothing wrong with that. It will make balancing much easier as you won't have to close down the lockshields so much to get the correct drop across each rad.

 

[chameleon001]

Hi,

UPDATE:

So as things have progressed I've ended up taking down the entire kitchen ceiling etc etc. I have decided whilst we're in such a mess just to replace this 15mm feed return with 22mm to future proof if we ever add more rads downstairs for any reason. My plan is to cut into the main 22mm pipes upstairs, solder on a T to each then feed down wall under the house in 22mm copper. Once under the house would it be reasonable to change to 22mm speed fit (just easier getting the stuff under the house) and then 15mm speedfit closer to rads with copper on the last part coming up through floor?

I assume this would be a reasonable plan, I know speedfit internal diameter is less than 22mm copper but surely will give me more flow than 15mm right from upstairs?

I've watched plenty of youtube videos and as a competent DIYer feel I could probably tackle this myself, or am I being naive? I've got all the kit available to solder/ bend pipes anyway.

Cheers