Fused connection unit. You may not have one.
Room Stat
- Thread starter Dan6206
- Start date
Fused connection unit. You may not have one.
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I'm afraid that you will need someone electrically competent to inspect the installation and determine which wire is being used for which purpose before making the connections, and to check for possible damage you make have caused. Otherwise we are all guessing.
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If we disregard other posts and picture then we have no information about which wire does which function.
To give accurate advice requires knowing how the old thermostat was connected and ( to be 100% certain) what type the old thermostat is.
Do you have a multimeter?
OK
Suggest that you terminate the three wires and earth in an insulated terminal block for safety.
Set the heating controller for heating ON.
First test between the earth and the three wires. You should see 230v (ish) on one of the wires - probably the brown
That will be your live in.
Then test between the live and the other two wires. One of those should show 230v - probably the grey with a blue sleeve. That will be your neutral.
The other wire - black with a brown sleeve. will be the call for heat.
Turn the power off. Connect the brown to the black/brown and turn the power back on. That should start the boiler.
If it works then connect the new stat up as below.
Live to 1
Neutral to 2
Call for heat to 3
If it doesnt start, then you have either scrogged the programmer, or the boiler control board.
Suggest that you terminate the three wires and earth in an insulated terminal block for safety.
Set the heating controller for heating ON.
First test between the earth and the three wires. You should see 230v (ish) on one of the wires - probably the brown
That will be your live in.
Then test between the live and the other two wires. One of those should show 230v - probably the grey with a blue sleeve. That will be your neutral.
The other wire - black with a brown sleeve. will be the call for heat.
Turn the power off. Connect the brown to the black/brown and turn the power back on. That should start the boiler.
If it works then connect the new stat up as below.
Live to 1
Neutral to 2
Call for heat to 3
If it doesnt start, then you have either scrogged the programmer, or the boiler control board.
Don't you think the call for heat wire will also show mains voltage through the lowish impedance of the boiler?
Agreed, though it will be through the 3 port valve valve motor not the boiler.
Your wiring in the first photo appears correct, the fact that swapping 2 and 3 trips the power proves this, however, the programmer and or thermostat may now be damaged. (combi boilers with designated room stat terminals would have had their main PCB destroyed if you had done that, a very expensive mistake)
Leave the wiring as it is, switch the programmer to heating only and carefully check for:
240V AC between brown and earth
240V AC between brown and grey
0V AC between black and earth when thermostat turned down, 240V present when the thermostat is turned up.
If the above checks out go to where the 3 port valve is wired in. With the room stat turned up there should be 240V AC measured between the valves white and blue wires, if there is, the valve should move fully open and the boiler and pump should start, if there is 240V and the valve has not moved, the valve motor has failed, or is jammed.
If the motor moves to the mid position only and the boiler/pump doesn't start, the hot water off signal is not getting to the grey wire on the valve, or the valve is faulty.
If there is no 240V here there is either a loose connection or wiring error somewhere between.
Has this heating system worked properly before?
The plumber suggested you replace the stat rather than them because they couldn't find the real fault.
Leave the wiring as it is, switch the programmer to heating only and carefully check for:
240V AC between brown and earth
240V AC between brown and grey
0V AC between black and earth when thermostat turned down, 240V present when the thermostat is turned up.
If the above checks out go to where the 3 port valve is wired in. With the room stat turned up there should be 240V AC measured between the valves white and blue wires, if there is, the valve should move fully open and the boiler and pump should start, if there is 240V and the valve has not moved, the valve motor has failed, or is jammed.
If the motor moves to the mid position only and the boiler/pump doesn't start, the hot water off signal is not getting to the grey wire on the valve, or the valve is faulty.
If there is no 240V here there is either a loose connection or wiring error somewhere between.
Has this heating system worked properly before?
The plumber suggested you replace the stat rather than them because they couldn't find the real fault.
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Agreed I thought the same, however, given expertise but lack of equipment, I'd probably connect a light bulb or something of a moderate wattage to those terminals instead of the voltmeter and see how it glows. Bright is neutral, dim is switched live.
In reality I'd disconnect at the cu and do it with dead testing and an ohmmeter.
My boiler controls just the heating only its a **Ideal Logic Heat 12 model**
My boiler just controls the Heating its not a combi boiler. Its a **Ideal Logic Heat 12 model**
The boiler was working fine before we turned the heating off down by the stat for the spell of good weather we had. went and turned the Room stat up when it got chilli and then noticed it was not turning the heating down once room reached the temperature.
Thats when i spoke to the people who installed the boiler they come out (then warranty expired 2 days later) done some digging around as they thought it may be the 3 port valve but on inspection that was working. and that when the engineer traced it to the thermostat.
He said to change it myself as they wanted £140 to do so.
My boiler just controls the Heating its not a combi boiler. Its a **Ideal Logic Heat 12 model**
The boiler was working fine before we turned the heating off down by the stat for the spell of good weather we had. went and turned the Room stat up when it got chilli and then noticed it was not turning the heating down once room reached the temperature.
Thats when i spoke to the people who installed the boiler they come out (then warranty expired 2 days later) done some digging around as they thought it may be the 3 port valve but on inspection that was working. and that when the engineer traced it to the thermostat.
He said to change it myself as they wanted £140 to do so.
OK, what was the results of the tests? I assume the hot water or whatever is on the other port of the valve is working properly?
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