Combi Boiler Room Thermostat Operates in Reverse

[stevethom2]

Hi

We recently moved into a property with a combi boiler system comprising a Camay 5 boiler, Drayton SM1 programmer and Danfoss RET230VF2 room thermostat.

The system seems to work ok except that the room thermostat will only switch on when temperatures are increased at the dial (or actually increase - which is obviously rare)

ie if the thermostat is indicated as being off when the dial set asking for 25deg, moving the dial down to 15deg turns on the system. Likewise when the system is indicated on(and we know it is because the radiators are warm) then if the temperature is set at dial to ask for 15deg, then turning up to say 18deg will turn the system off.

I've attached a photo of the thermostat wiring in its current state. Can anyone suggest how it can be operating in reverse and a solution?

I've also attached the wiring schematic I found online.

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• stevethom2
• 26 Feb 2013
• 1

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• stevethom2
• 26 Feb 2013
• 1

 

[Robin0577]

From the diagram, I'd expect that setup to work as it is, but swapping the black wire from terminal 3 to 4 should reverse the way it operates.

 

[EFLImpudence]

As above.

There seem to be conflicting diagrams.

http://heating.danfoss.co.uk/PCMPDF/294c08.pdf

 

[PrenticeBoyofDerry]

Unless reverse polarity is existing at the FCU or plug?

 

[RF Lighting]

Reverse polarity will make no difference what so ever.

There's usually a diagram on the back of the stat which might clear up the confusion.

 

[stevethom2]

Switching black from 3 to 4 has no effect.

 

[stevethom2]

I've posted here imaged of:
The inside of the room sensor showing the circuit diagram
The internal connections to the programmer
The wiring diagram for the programmer

There is a link in the programmer diagram ( L to 1) that doesn't seem to have been done - could this be any cause?

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• stevethom2
• 26 Feb 2013
• 1

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• stevethom2
• 26 Feb 2013
• 1

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• stevethom2
• 26 Feb 2013
• 1

 

[EFLImpudence]

The wiring diagram for the programmer

That must be the correct one.

There is a link in the programmer diagram ( L to 1) that doesn't seem to have been done - could this be any cause?

No. The boiler may be operating on 24V.

It would appear the thermostat is broken.

 

[stevethom2]

Confirm faulty thermistat replaced and all in order. Thanks all for your help.

 

[EFLImpudence]

Very good.

Thanks for letting us know.