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Discuss CH flow pipework still hot even with CH turned off in the Central Heating Forum area at PlumbersForums.net

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StuartA

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Hi, I’ve had a problem recently since I moved the pipes to my radiator from one side of the room to the other (in a bungalow so pipes go through ceiling into loft).
Even with the CH turned off I still get hot flow pipes to all radiators, the rads are just slightly warm at the top & all return pipes are cold. In this warm spell I’ve had to turn off all the rad valves on the flow side to get rid of the heat out of the pipes, but as soon as I open them the flow pipes heat up again. I have a standard oil boiler & 3 port motorised valve in my system if that helps for any info. Thanks in advance for any help.
 

jtsplumbing

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Sounds like your 3 port valve is faulty (Letting By) depending on age may be better to replace complete valve, as it could be the motor or the body that is at fault, but get it tested first as other controls could be causing the fault, Controller, Room stat,
 

fixitflav

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Hi, I’ve had a problem recently since I moved the pipes to my radiator from one side of the room to the other (in a bungalow so pipes go through ceiling into loft).
Even with the CH turned off I still get hot flow pipes to all radiators, the rads are just slightly warm at the top & all return pipes are cold. In this warm spell I’ve had to turn off all the rad valves on the flow side to get rid of the heat out of the pipes, but as soon as I open them the flow pipes heat up again. I have a standard oil boiler & 3 port motorised valve in my system if that helps for any info. Thanks in advance for any help.
All the heating return pipes must be commoned before joining the HW return pipe, otherwise your symptoms will happen. If everything was OK before you moved the pipes, is it possible it's now piped wrong?
 

doitmyself

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All the heating return pipes must be commoned before joining the HW return pipe, otherwise your symptoms will happen.
If reverse circulation is occurring then the return pipe will get hot, not the flow which is what the OP is experiencing.
 

garygvl

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Leave all the rads on except the one you repiped. If prob goes away you've got your return from this rad connected wrong
 

fixitflav

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If reverse circulation is occurring then the return pipe will get hot, not the flow which is what the OP is experiencing.
If the connection is wrong, one rad (or set of rads) gets warm on the returns, the other rad (or set) gets warm on the flow. But it could be either way round, depending on which way round the connections are. So if all the flows are warm and all the returns cold, after running like that for a while, that would rule it out. But I'd still be interested in OP confirming the pipe routing is correct. And is he sure which are the flows and returns? Maybe he is, but I wouldn't know offhand on my rads, if I needed to find out I would have to switch on from cold and feel the pipes.
 
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StuartA

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ok, I’ve been in the loft & traced out the pipework & im connected correctly with flow/return. I thought it may be the motor in the valve so replaced that (cheap option as was only a tenner) but problem still the same. I have recently installed a new Salus IT500 thermostat. I’m now wondering if it may be the valve not quite operating fully & is passing as suggested.
Thanks for the help so far by the way

E55CF310-D401-487F-84BB-F6143F7B4637.jpeg
 

fixitflav

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ok, I’ve been in the loft & traced out the pipework & im connected correctly with flow/return. I thought it may be the motor in the valve so replaced that (cheap option as was only a tenner) but problem still the same. I have recently installed a new Salus IT500 thermostat. I’m now wondering if it may be the valve not quite operating fully & is passing as suggested.
Thanks for the help so far by the way

View attachment 33633
OK it seemed like a coincidence that the problem started after the pipes modded, but coincidences do happen!
These 3-port valves can give problems, mine is a Honeywell clone, with a rubber ball on a lever, covering either of the ports, don't know if yours works same way. Had one where the lever broke off the shaft, another where the shaft through the ball fell out - poor design, just threaded in. I put Loctite on it and rivetted the end over, then I got symptoms like yours. I had to bend the arm slightly to cure it, took several tries and was a pita. It might be worth dismantling yours and see if it gives any clues.
 
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StuartA

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Ah ok fixitflav, thanks for that, I’ll get the valve out tomorrow & have a look at it or if needed get it replaced
 

garygvl

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as i said earlier just turn off the rad you repiped and leave the rest on. if prob goes away youve got your return wrong on your repiping. why are you taking out the 3 port. just start everything from cold with hot water on only and feel the heating pipe as far away from the 3 port as you possibly can, youll soon know bif 3 port is letting by
 

fixitflav

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as i said earlier just turn off the rad you repiped and leave the rest on. if prob goes away youve got your return wrong on your repiping. why are you taking out the 3 port. just start everything from cold with hot water on only and feel the heating pipe as far away from the 3 port as you possibly can, youll soon know bif 3 port is letting by
Good point, easier than taking the valve apart. I should have thought of that as that's how I checked mine when getting it to work properly. But the pipe shouldn't get warm more than 2-3 ft from the valve should it?
 

Chester

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i'm not sure why getting his flow and return pipework the wrong way round would cause the specific issue that he is having?
 
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StuartA

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as i said earlier just turn off the rad you repiped and leave the rest on. if prob goes away youve got your return wrong on your repiping. why are you taking out the 3 port. just start everything from cold with hot water on only and feel the heating pipe as far away from the 3 port as you possibly can, youll soon know bif 3 port is letting by
Fair comment, easier/quicker option than removing the valve so will give it a go & let you know how I get on
 
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StuartA

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as i said earlier just turn off the rad you repiped and leave the rest on. if prob goes away youve got your return wrong on your repiping. why are you taking out the 3 port. just start everything from cold with hot water on only and feel the heating pipe as far away from the 3 port as you possibly can, youll soon know bif 3 port is letting by
With the repiped rad switched off (fow & return), CH turned off, just the hot water on, the flow pipes to every other rad in the bungalow heated up inside 10mins. So do you think the next step is the valve passing?
 

fixitflav

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With the repiped rad switched off (fow & return), CH turned off, just the hot water on, the flow pipes to every other rad in the bungalow heated up inside 10mins. So do you think the next step is the valve passing?
Did you feel the pipe from the 3-port valve to the rads, as garygvl suggested?
 
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