I have one radiator that does not work at all (although it has worked in the past). Unlike all the other radiators that come directly of the main supply and return pipe from the boiler I can see that one end of the radiator is connected to a pipe that runs directly to the bottom of the hot water tank. I cannot trace where the other pipes goes, it seems to run towards the back of the hot water tank but cannot see where it goes after this point. Because this radiator is newly installed we don't actually know which pipe is the supply and which is the return, both pipes are stone cold. Its replacing a previous one but the installer didn't make note of which end had the thermostatic valve before he removed it and redid the pipes.
My questions are:
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Why has this radiator been attached directly to hot water cylinder
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Will the pipe attached to the bottom of the hot water cylinder be
supply or return ? -
Where logically should other pipe attach.
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What could stop it from working ?
Best Answer
Seems like a bodge to me.
Traditional UK systems have the radiators completely separate from the hot-water (which supplies taps only). The radiator system is usually a closed loop - with some means of topping up the water - either a header tank in the loft (US: attic) or a valve next to a pressure vessel with a pressure gauge.
Source: Honeywell
The hot water tank usually has four connections, two for supply and return from boiler which connect to an internal helical loop, there is no transfer of water from this loop into the tank, only a transfer of heat.
The tank is supplied with cold water at the bottom (e.g. from a separate header tank) and hot water to taps is drawn out the top.
Source: Potterton, modified to show pump, three-port zone-valve, vents and cold water to taps
Generally you remove hot water from the top and supply cold water into the bottom.
Your arrangement seems illogical. Probably the top of the cylinder.
† I believe some very old heating systems used natural convection but I've never seen one‡.
‡ I'm not a plumber.