I have had a new Worcester boiler and 3 way valve installed recently. Sometimes if I turn down the CH room stat the radiators still stay on. The room stat is a honeywell with an indicator LED and when I turn down the stat I notice that the led stays on but dims. Also noticed by chance that this only seems to occur when the tank stat is at temp. If I turn the tank stat temp up ie to make it work then the led on the room stat will go off. Is this likely to be a faulty 3 way or could it by wired up wrong ? Any advice welcomed. Thanks
Room stat not shutting off heating
- Thread starter M1ewk
- Start date
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Possibly or a back feed from the valve. Do you have a means of testing the voltage ( multi meter )?
Update on my problem..
On the wiring to the room stat I have red on t1 , blue on t2 and yellow on t3. When I start the heating from cold every thing works ok for both ch and water, ie if I move the room stat high the led comes on and if I turn it down the led goes off.
However , once the tank stat reaches temp then it seems that if I turn down the room stat, the led on the stat just dims rather than goes off and the radiators continue to get hot,
I measured the voltages at the room stat at this point and when I turn down the temp and the led dims, in fact the voltage at t3 (yellow) drops from 235 to 128 and the led is dimmer. If I then turn up the tank stat to make it work then the led on the room stat goes out. However if I then immediately turn down the tank stat the led on the room stat stays off. Weird . any good ideas ? Thanks
On the wiring to the room stat I have red on t1 , blue on t2 and yellow on t3. When I start the heating from cold every thing works ok for both ch and water, ie if I move the room stat high the led comes on and if I turn it down the led goes off.
However , once the tank stat reaches temp then it seems that if I turn down the room stat, the led on the stat just dims rather than goes off and the radiators continue to get hot,
I measured the voltages at the room stat at this point and when I turn down the temp and the led dims, in fact the voltage at t3 (yellow) drops from 235 to 128 and the led is dimmer. If I then turn up the tank stat to make it work then the led on the room stat goes out. However if I then immediately turn down the tank stat the led on the room stat stays off. Weird . any good ideas ? Thanks
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When wired correctly these problems don't exist. So my advice is to check the wiring, but thats not easy if you don't know how the 3port valve works. So first find out how it works.
Now that in itself is not straight forward, but there is plenty of information on it on this forum.
I'll try to explain how the valve operates, which is over two ranges.
In addition to the earth wire yellow/green and neutral wire blue there are 3 other wires White Grey and Orange.
I'd ignore HW operation for the moment and just deal with CH, but you do need to understand the following
Although the cylinder stat which is like a two way switch does play a part if HW is involved. (not satisfied terminal and satisfied terminal)
It should be pointed out that the HW switch on the programmer is also like a two way switch. This means there are two terminals with a wire from each but only one of them can be live at a time.so you have HW ON and HW OFF.
When both CH and HW are not on there is no power coming from the CH ON terminal or the HW ON terminal, but there is power from the HW OFF terminal.
Another thing to remember is the boiler gets its power from the cylinder stat when HW is called for, but if not called for or called for and satisfied, then the cylinder stat can't supply, so the supply comes from the valves 'orange' wire.
OK!. So for CH the programmer supplies the room stat and switched live from room stat supplies the 'white' wire of valve.
The white feeds two micro switches, one deals with driving the motor/quadrant to mid position and on the other micro switch it supplies a PCB, but when the PCB is no longer needed it diverts to the orange wire to supply the boiler.
Having got to mid position the first micro switch cuts off the 'white' but connects to the 'grey'. Now because HW is not involved the grey is live because of a wire from the HW OFF terminal.
So now the grey drives the motor/quadrant to the CH only position and triggers the second micro switch making the orange live.
Point of interest here is that both white and grey are both live, so when room stat is satisfied power to the white is cut off and boiler stops but the valve stays where it is, because the motor is still energised and will stay like that till HW is called for which could be the following day.
You'll realize how important the wire from the HW OFF teriminal is in feeding the 'grey'.
When HW is involved there is also a wire link from the cyinder stat (satisfied terminal) to the 'grey'
Now that in itself is not straight forward, but there is plenty of information on it on this forum.
I'll try to explain how the valve operates, which is over two ranges.
In addition to the earth wire yellow/green and neutral wire blue there are 3 other wires White Grey and Orange.
I'd ignore HW operation for the moment and just deal with CH, but you do need to understand the following
Although the cylinder stat which is like a two way switch does play a part if HW is involved. (not satisfied terminal and satisfied terminal)
It should be pointed out that the HW switch on the programmer is also like a two way switch. This means there are two terminals with a wire from each but only one of them can be live at a time.so you have HW ON and HW OFF.
When both CH and HW are not on there is no power coming from the CH ON terminal or the HW ON terminal, but there is power from the HW OFF terminal.
Another thing to remember is the boiler gets its power from the cylinder stat when HW is called for, but if not called for or called for and satisfied, then the cylinder stat can't supply, so the supply comes from the valves 'orange' wire.
OK!. So for CH the programmer supplies the room stat and switched live from room stat supplies the 'white' wire of valve.
The white feeds two micro switches, one deals with driving the motor/quadrant to mid position and on the other micro switch it supplies a PCB, but when the PCB is no longer needed it diverts to the orange wire to supply the boiler.
Having got to mid position the first micro switch cuts off the 'white' but connects to the 'grey'. Now because HW is not involved the grey is live because of a wire from the HW OFF terminal.
So now the grey drives the motor/quadrant to the CH only position and triggers the second micro switch making the orange live.
Point of interest here is that both white and grey are both live, so when room stat is satisfied power to the white is cut off and boiler stops but the valve stays where it is, because the motor is still energised and will stay like that till HW is called for which could be the following day.
You'll realize how important the wire from the HW OFF teriminal is in feeding the 'grey'.
When HW is involved there is also a wire link from the cyinder stat (satisfied terminal) to the 'grey'
Further investigation of the wiring revealed all sorts of issues.
The programmer is a centaur c27
Neither the ch off nor hw off are connected
There is a link wire in the programmer between the ch on and hw on so if I just put hw on then ch comes on as well. Time to get the person who installed it back ...
One thing though .. When the house was built about 25 yrs ago the programmer at the time only had hw or hw+ch, ie no ch only even though it is a fully pumped system with 3 way valve,so I don't think there is enough cabling (cores) between the programmer which is in the kitchen to the junction box which is upstairs in the airing cupboard to be able to have it fully wired to have separate control of ch and hw so maybe the installer has bodged it using the limited cable available but anyway he is coming back next week. See what happens
The programmer is a centaur c27
Neither the ch off nor hw off are connected
There is a link wire in the programmer between the ch on and hw on so if I just put hw on then ch comes on as well. Time to get the person who installed it back ...
One thing though .. When the house was built about 25 yrs ago the programmer at the time only had hw or hw+ch, ie no ch only even though it is a fully pumped system with 3 way valve,so I don't think there is enough cabling (cores) between the programmer which is in the kitchen to the junction box which is upstairs in the airing cupboard to be able to have it fully wired to have separate control of ch and hw so maybe the installer has bodged it using the limited cable available but anyway he is coming back next week. See what happens
At leased you're making some headway!
There needs to be a HW OFF wire, but there is no need for a CH OFF wire.
Make me wonder if the cylinder stat is also missing the link between the 'satisfied terminal' and the 'grey' of the valve.
As you say see what happens
There needs to be a HW OFF wire, but there is no need for a CH OFF wire.
Make me wonder if the cylinder stat is also missing the link between the 'satisfied terminal' and the 'grey' of the valve.
As you say see what happens
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