Any motorised valves fitted?
Help!!! No heating after changing rad valve
- Thread starter flutterbye
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Well, funny you say that but you were spot on! There are two single-port valves. I took the CH actuator off and the spindle underneath couldn't be turned by hand! Unfortunately, I can't say for 100% whether the valve was open or closed when I took off the actuator but certainliny as soon as I opened it with a spanner water gushed through, the pump made more "normal" noises and the rads all started heating up!
What I don't understand is why me bunging up the pipes in the FE to change a rad valve should cause the CH valve to stay stuck shut. Could it be I dislodged some crap near the CH feed in the header tank which then got stuck in the MV ?
One thing I do know is I've been having trouble with the MVs recently. On some days I'd come to the airing cupboard, the progammer would say heating and HW should be off but the pump was still running! The whole system seems riddled with gremlins!
Thanks again for your help.
What I don't understand is why me bunging up the pipes in the FE to change a rad valve should cause the CH valve to stay stuck shut. Could it be I dislodged some crap near the CH feed in the header tank which then got stuck in the MV ?
One thing I do know is I've been having trouble with the MVs recently. On some days I'd come to the airing cupboard, the progammer would say heating and HW should be off but the pump was still running! The whole system seems riddled with gremlins!
Thanks again for your help.
You did get the bung back out again?? 
Its not floating round the system upsetting the MV's? Probably pure coincidence though.
MV's dont have an indefinate lifespan, especially on a dirty system. If they're showing signs of failure maybe an idea once better weather arrives to replace. (Its your money but mine would go on Honeywell.)
Its not floating round the system upsetting the MV's? Probably pure coincidence though.MV's dont have an indefinate lifespan, especially on a dirty system. If they're showing signs of failure maybe an idea once better weather arrives to replace. (Its your money but mine would go on Honeywell.)
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Yes makes sense.
In the meantime, I've removed the head (actuator) from the central-heating MV and left the copper valve itself in the open position.
From what I can understand, that should mean the CH should work normally when the HW is off (CH stat turning pump off and on) and when the HW is on too, then the CH thermostat won't be able to turn off the valve so might need to turn it off occasionally if house gets too hot. Does that sound about right?
Will look up honeywell...although not a straight swap. The current ones are Drayton ZA5.
In the meantime, I've removed the head (actuator) from the central-heating MV and left the copper valve itself in the open position.
From what I can understand, that should mean the CH should work normally when the HW is off (CH stat turning pump off and on) and when the HW is on too, then the CH thermostat won't be able to turn off the valve so might need to turn it off occasionally if house gets too hot. Does that sound about right?
Will look up honeywell...although not a straight swap. The current ones are Drayton ZA5.
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Assuming you have standard 'S' plan system, I think you may find CH will only come on when HW is calling.
Normally, roomstat (when CH is 'on' at programmer) will send call for heat to MV. MV opens, activating microswitch to supply power to boiler and pump to run. Once stat is satisfied, it cuts power to MV, MV closes breaking microswitch contact and cutting supply to pump/boiler. Unless the power to pump/boiler is supplied from the HW valve then neither boiler or pump will run and you'll have no CH.
If the valves seem free then you may be able to just change the Actuator (head), (avoids draining down), otherwise the Drayton ZA5 valve should be to industry standard, so the Honeywell V4043H would be a straight swap.
Normally, roomstat (when CH is 'on' at programmer) will send call for heat to MV. MV opens, activating microswitch to supply power to boiler and pump to run. Once stat is satisfied, it cuts power to MV, MV closes breaking microswitch contact and cutting supply to pump/boiler. Unless the power to pump/boiler is supplied from the HW valve then neither boiler or pump will run and you'll have no CH.
If the valves seem free then you may be able to just change the Actuator (head), (avoids draining down), otherwise the Drayton ZA5 valve should be to industry standard, so the Honeywell V4043H would be a straight swap.
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Great advice about the straight swap - will do that in summer (if I can last that long).
Re operation of valves etc, as far as I can tell, the pump+boiler is activated if _either_ of the two valves opens. So if HW stat calls for water and is on at the programmer, the pump&boiler will run. Likewise, if the CH stat calls and central-heating is on at the programmer then the pump will run. Does that sound right?
Assuming that to be the case, then with HW off and the CH on at the programmer, the pump is entirely managed by the CH room stat and so it should behave normally even though the CH valve is forced open (with the actuator plugged in but lying on the floor).?
Re operation of valves etc, as far as I can tell, the pump+boiler is activated if _either_ of the two valves opens. So if HW stat calls for water and is on at the programmer, the pump&boiler will run. Likewise, if the CH stat calls and central-heating is on at the programmer then the pump will run. Does that sound right?
Assuming that to be the case, then with HW off and the CH on at the programmer, the pump is entirely managed by the CH room stat and so it should behave normally even though the CH valve is forced open (with the actuator plugged in but lying on the floor).?
Ignore top half of my last post, wasn't thinking straight.... Trying to occupy brain and ignore toothache, its not quite working out as I planned!
Yes, actuator should work as normal if its been taken off the valve, assuming it wasnt faulty in the first place! Room stat will control things as its supposed to, just means the valve wont be physically opened/closed by the actuator. So, if CH is satisfied but HW is calling the CH valve wont shut off, and as you've said the house could get too hot. (Also will take longer for HW to be satisfied as its sharing flow with CH).
There's a fantastic flow diagram here showing how the power travels through a 'S' plan system. http://octaveblue.co.uk/c_heating/index.htm
Yes, actuator should work as normal if its been taken off the valve, assuming it wasnt faulty in the first place! Room stat will control things as its supposed to, just means the valve wont be physically opened/closed by the actuator. So, if CH is satisfied but HW is calling the CH valve wont shut off, and as you've said the house could get too hot. (Also will take longer for HW to be satisfied as its sharing flow with CH).
There's a fantastic flow diagram here showing how the power travels through a 'S' plan system. http://octaveblue.co.uk/c_heating/index.htm
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Many thanks Hugh.
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