Strange CH problem, downstairs rads only get hot with hot water off


R

russ.elliott

Strange CH issue, when the hot water is off at the control panel, the
rads are all working fine and are hot, if the hot water also comes on
at the control panel the downstairs rads become cold. I have bled all
rads flushed the system, balanced the system and turned up the pump to
setting 3....any ideas much appreciated..Thanks
 
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J

John Stumbles

Strange CH issue, when the hot water is off at the control panel, the
rads are all working fine and are hot, if the hot water also comes on
at the control panel the downstairs rads become cold. I have bled all
rads flushed the system, balanced the system and turned up the pump to
setting 3....any ideas much appreciated
Is it a new problem or has it always been like this? If the latter I'd
suspect balancing, and that the hot water is taking flow from the system
enough to starve the upstairs rads but not the downstairs ones. There may
be a balancing valve - probably a wheel-head gate valve with - in line
with the HW cylinder which you can adjust to balance.

If it's a new problem I'd check the cylinder thermostat which may
be failing to switch off and stop water going round the HW circuit when
the programmer is calling for HW.
 
G

gasman pete

sure sounds to me that the cylinder is robbing the pressure of the
pump, see if there is a valve on the return of the cylinder coil and
open it only a couple of turn... not fully.
 
R

russ.elliott

John said:
Is it a new problem or has it always been like this? If the latter I'd
suspect balancing, and that the hot water is taking flow from the system
enough to starve the upstairs rads but not the downstairs ones. There may
be a balancing valve - probably a wheel-head gate valve with - in line
with the HW cylinder which you can adjust to balance.

If it's a new problem I'd check the cylinder thermostat which may
be failing to switch off and stop water going round the HW circuit when
the programmer is calling for HW.
Thanks chaps, John can you elaborate on your last paragraph? I don't
quite understand as CH is a new area for me....Cheers
 
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J

John Stumbles

Thanks chaps, John can you elaborate on your last paragraph? I don't
quite understand as CH is a new area for me....Cheers
Systems are often set up so that when water is going round the cylinder
the rads don't necessarily heat up very well since the cylinder is taing
most of the flow, but it doesn't matter since by the time you notice it
the cylinder has heated up and the flow to the cylinder has cut
off again. If the cylinder stat is stuck on then water will always
be going round the cylinder so circulation to the rads continues to suffer
and you do notice it. That's why I asked if it's a new problem.

If you turn the cylinder stat control down does the pipe taking water into
the cylinder coil from the CH system (via 2- or 3-port valve) cool down
after a while (maybe 1/2 hour)?
 

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