No heating from Danfoss thermostat

[DevonDragon]

Looking for confirmation that joining the 2 wires (COM and N/O) should bypass the thermostat and trigger my heating.
Im trying to isolate the problem.
Pics attached.
This is a Danfoss TP4000

TIA.

 

[terryplumb]

What makes you think the thermostat is the cause of lack of heating ?

 

[DevonDragon]

We have underfloor heating downstairs and thats working fine; with zonal thermostats; its only upstairs that is failing - hence looking at the thermostat first. Am I right to assume joining these wires should bypass the thermostat and call for heat ?

 

[RandomGrinch]

Am I right to assume joining these wires should bypass the thermostat and call for heat ?

Yes you are. Isolate power safely before doing so - these wires are likely carrying mains voltages.

Edit for clarity - the stat itself doesn't call for heat, but it provides a switched live (combined with the programmer), that drives a zone valve, which in turn calls for heat, from the boiler.

 

[terryplumb]

More likely to be a zone valve issue. Are you competent to take voltage readings ?

 

[polesapart]

Am I right to assume joining these wires should bypass the thermostat and call for heat ?

No. Joining the wires has the same effect as setting the programmer to "on", i.e. sending the switching voltage to the thermostat.

 

[RandomGrinch]

More likely to be a zone valve issue

Yes, but linking out the stat is a completely legitimate first step in fault finding; it takes no time to do, involves no test equipment and could instantly rule out the stat as a problem - sticky relays still occur.

 

[RandomGrinch]

No. Joining the wires has the same effect as setting the programmer to "on", i.e. sending the switching voltage to the thermostat.

The TP4000 is a programmable stat - although there still is the possibility of another programmer somewhere?

 

[DevonDragon]

More likely to be a zone valve issue. Are you competent to take voltage readings ?

Yes I think so; but where are I taking them from?

 

[DevonDragon]

No. Joining the wires has the same effect as setting the programmer to "on", i.e. sending the switching voltage to the thermostat.

Do you mean Yes ?!

 

[Murdochcat]

does the boiler have seperate controls and if so is it set to have the heating on?

 

[DevonDragon]

does the boiler have seperate controls and if so is it set to have the heating on?

Not for the heating no; there are settings in there (Daikan system) but its all water temperature etc.
We havent activated the heating for many months - I guess a lot of people are similar; turning it on before the colder months hit us...

 

[DevonDragon]

Well that little test produced no heat; I guess that means its NOT the thermostat and the problem is ???? Any advice on whats the next logical thing to test would be greatly appreciated.

 

[terryplumb]

Giving us more information on your system,pictures of control gear,wiring centre, motorised valves etc would be helpful

 

[RandomGrinch]

Any advice on whats the next logical thing to test would be greatly appreciated.

As @terryplumb suggested earlier, it is likely to be a zone valve problem, or voltage isn't reaching the stat to begin with.
The zone valve is the logical thing to check next.
Having a multimeter, would also help greatly at this stage.

Sorry, didn't notice the above reply when I posted.