I've just fit a brand new rad into a garage conversion. Supply has been taken from the rad in the neighbouring room which was fed with 10mm pipe. However new rad valves were 8mm and the pipe work reduced accordingly. Problem is the rad won't warm up. When the system is fired up (Combi boiler) all rads warm up except new one. Flow pipe upto this rad is hot then nothing. Return is cold. Since problem I've undone the valves and opened them up. When i do this hot water is pulled through the return but when shut off immediately cools down back to the branch. The return valve has a drian off which when the system was refilled i've opened up. This pulls heat through the rad and return pipework but cools down once again when the drain is closed. Hope this makes sense! Guys where have I gone wrong other than coverting the garage in the first place.
Newly fitted rad is cold
- Thread starter williz
- Start date
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hazard a wild guess
Okay my bad but I can't understand why the flow to the rad is piping hot, things are working upto there. The downside for me is the return won't warm up unless I release it via the drain off. Can someone enlighten me with out blowing my mind with physics!!!
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Yes
The problem is that the circulating hot water will flow through the easiest path it finds. This will be the old pipework because it will be the shortest route. The fact that you have run the new pipework in even smaller tube means that the flow is still more impeded. The tiny amount of hot water flowing through is enough to make the supply pipe warm, but not enough to heat up the radiator, so the return pipe will also be cold.
If you rerun it in 15mm pipe and valves it will be a bit better, depending on the length of the extra pipework you have added. If you throttle down all the other radiators to impede flow through them, some may be forced into the new rad.
If your radiators are individually fed from a manifold (instead of coming off a 22mm pipe circuit) then you are pretty well doomed to failure.
The problem is that the circulating hot water will flow through the easiest path it finds. This will be the old pipework because it will be the shortest route. The fact that you have run the new pipework in even smaller tube means that the flow is still more impeded. The tiny amount of hot water flowing through is enough to make the supply pipe warm, but not enough to heat up the radiator, so the return pipe will also be cold.
If you rerun it in 15mm pipe and valves it will be a bit better, depending on the length of the extra pipework you have added. If you throttle down all the other radiators to impede flow through them, some may be forced into the new rad.
If your radiators are individually fed from a manifold (instead of coming off a 22mm pipe circuit) then you are pretty well doomed to failure.
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