15mm heating pipework

[DIYlabGuy]

Hi all ,

I'm planning on installing 2 radiators in my living room/dining room. I noticed after lifting the floorboards that the CH pipes are 15mm the whole way. I'm lifting as little as I can as it will cause too much disruption otherwise, but I'm guessing it's the same everywhere in the house.
The pipework coming off the boiler are all 15mm.
My question is whether I will get enough flow to the 2 new radiators as they will be a reasonably long run/end of run. The boiler can handle the btu as we only have 3 single panel radiators in the house and its 25kw. But I worry the rads may not get warm enough. Oh and they're both vertical rads just to make the issue more fun!

Any thoughts will be appreciated. Thanks

 

[ajohn]

You'll need to balance up the flow through each rad with the lock shield valves to accommodate the pipe flow resistance changes along the pipe lengths. That likely to mean changing the settings of the ones you have when the new ones are fitted.

When the systems are designed radiator parameters should be used. Heating water temperature and it's drop when it passes through the radiator. That can give the expected kw output. So the lock shield valves are set to achieve this drop. Each one is done in turn. This can only be done if a feed and return pipe runs throughout the system with each rad T'd off them. It would be unusual to find anything else. 15mm throughout isn't that unusual. The details on my now rather old boiler needs runs of a larger diameter. Manuals on them should point this out if needed.

The heating water spec temp used in the rad data is as far as I know ilikely to be 80C but could be 60C with larger rads for the same kw. I believe more modern systems may work at a lower temp.

Anyway this is how the rads can be balanced up. The plumbing section may have other ideas on how it could be done.

 

[DIYlabGuy]

That's really helpful, thank you. I definitely have flow and returns. So hopefully your advice will get them all working nicely. Thanks again