I have a feeling there’s a limit to how any rads should/could be powered effectively off 15mm pipes. Is there a magic number for this please?
Thanks
Thanks
How many rads off 15mm
- Thread starter chriselevate
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Depends on your remaining pump head, effective length of pipework and Max desired water velocity, also on the total radiator efficiency ie wattage and the temp difference you're aiming for.
But if forced to guess I'd say around 6 or one floor of a semi.
But if forced to guess I'd say around 6 or one floor of a semi.
There sounds like quite a few factors that affect it then but like you say it sounds like 6 or less is s good number to aim for. Thanks for that.
Old rule of thumb was 3 rads up to 6kw. Ultimately depends on ΔT, and heat load etc.
If I'm planning a system from scratch, I'd aim for no more than 2. If adding more rads for an extension, i'd go to 3 depending on rad size, and pipe runs. By following this simple rule, the system tends to have similar resistance to all rads and there is rarely a need for balancing. In my opinion, 6 is asking for trouble.
Six is a lot. My parents bought a 3 bed house in early 60s and had 4 medium sized single rads and a very small one in the bathroom - piped in 15mm throughout for ch (or background heating as the builders called it). One of the first things I did when I got into plumbing was change the very undersized rad in their bedroom for a large modern double. In those days, I knew nothing of the heat carrying capacity of pipe sizes and the downstairs rads were immediately starved. So I ended up ripping out everything and doing it properly.
From my experience, approx. 4 medium singles is about it, but less is better. May work better in other instances though, as the old flow and returns were 15mm. If they were 22mm, maybe would have worked better. I realise there are a lot of other variables at play. Trouble with undersized supply pipes is careful balancing becomes even more important. Can be a bit tricky.
From my experience, approx. 4 medium singles is about it, but less is better. May work better in other instances though, as the old flow and returns were 15mm. If they were 22mm, maybe would have worked better. I realise there are a lot of other variables at play. Trouble with undersized supply pipes is careful balancing becomes even more important. Can be a bit tricky.
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H
Hot&Cold
Max 3 radiators unless supporting testing with documents are available 
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