Problems after swapping T6360B for TP5000si thermostat

[Kieran42]

Hello,

Apologies first if this has already been asked but I couldn't find the answer or help I was looking for

I have a conventional boiler and I recently swapped out my mechanical Honeywell T6360B room thermostat for the digital battery powered Danfoss TP5000si. After completing set up (as per the user guide), I tested the tp5000si by raising the desired temperature above the displayed room temperature and as expected the central heating came on. However when I lowered the desired temperature to below the room temperature the central heating rather than turning off remained on!... I even went to the separate CH & HW programmer and switched the CH off from there but the boiler kept on running and wouldn't switch off!...

So the question I have is have I wired it wrong or is the tp5000si faulty?

The original wiring set up for the Honeywell T6360B (see photos) was as follows:

T1 -- Live-IN (Brown cable)
T2 -- Neutral (Blue cable)
T3 -- Switched Live-OUT (Yellow/Green Cable)


For the TP5000si the new wiring set up (see photos) is as follows:

1(OFF) -- (No cable Connected)
2(COM) -- Live-IN (Brown Cable)
3(ON) -- Switched Live (Yellow/Green Cable)

(The Neutral blue cable is left disconnected via an insulated terminal block)


As far as I am aware the wiring all looks fine... so I am puzzled why the central heating keeps coming on and going off on it's own accord even when the desired temperature is set below the room temperature???

Your thoughts on this would be much appreciated.

Thanks

 

[Phill Peck]

Swap wire from t3 to t1.
The tp5000 is designed to do both heating and cooling

 

[Phill Peck]

Swap wire from t3 to t1.
The tp5000 is designed to do both heating and cooling

Although iirc t3 is correct. Your programmer should also turn it off
Somethings not right with your wiring.

 

[MrTherm]

@ Kieran42,

The new TP5000si you have is a programmable room thermostat, it has a digital clock incorporated into it.

You still have an existing functional programmer installed in your system - so you really need to choose which one you need then disable the other because you cannot run a clock off a clock.

 

[stem]

Swap wire from t3 to t1.
The tp5000 is designed to do both heating and cooling

It was right as it was. T2 (Common) and T3 (On) are the correct terminals to use.



But as Mr Therm says, the Danfoss TP5000si is a programmable thermostat, so if you have some existing time control for your central heating that is still wired in circuit, it should be set to be permanently 'on' 24/7, otherwise it will keep cutting off the power to the new programmable thermostat.

 

[Phill Peck]

It was right as it was. T2 (Common) and T3 (On) are the correct terminals to use.

View attachment 132931

But as Mr Therm says, the Danfoss TP5000si is a programmable thermostat, so if you have some existing time control for your central heating that is still wired in circuit, it should be set to be permanently 'on' 24/7, otherwise it will keep cutting off the power to the new programmable thermostat.

That wouldn’t make the heating come on when set below the target point though.

 

[stem]

Correct, it wouldn't. Neither would anything the OP has done that is shown in the photos, it if was working before hand of course. I'm not convinced that really is the case that the heating comes on when set below the target point though.........

I tested the tp5000si by raising the desired temperature above the displayed room temperature and as expected the central heating came on.

 

[Kieran42]

Just so you know the boiler is a Glowworm Micron 60FF, and the boiler, programmer & t6360B mechanical thermostat were all fitted about 15years ago by a Corgi Registered heating engineer. I still have the Installation Log Book with the chaps Corgi Registration details.... but he's retired now.

Having used a Corgi registered heating engineer you'd think it should have all been wired correctly?

Also the central heating on the Honeywell Programmer is always set to 24/7 so permanently on, it's only the HW that comes on twice a day.

I have put the old thermostat back, wired as it was originally, and it's all working fine again ie I can control the CH coming on and off using the mechanical thermostat, and also if the boiler is on and I turn CH on the Programmer to OFF position the boiler will go off.... so can't also be a stuck motorised valve as someone else suggested to me.

I would like to get the digital tp5000si working as I find the old mechanical one inaccurate by at least 2-3 degrees.

So just to clarify one thing... is the wiring on the TP5000si as shown in the photo correct or should I swap the Yellow/Green cable for the Blue cable for the Switched Live "3(ON"?

 

[Kieran42]

...just to emphasis with the old thermostat there is no scenario where the boiler remains on when the thermostat is turned down below the room temperature

 

[stem]

The thermostat is just a switch, when it's 'on' the brown & green/yellow wires are joined together, and when it's 'off' they are separate. That applies to both this instance where terminal 1 (Live) and terminal 3 (switched Live) are joined together, when heating is required.



And in this instance where terminal 2 (Live) and terminal 3 (switched Live) are joined together, when heating is required.

should I swap the Yellow/Green cable for the Blue cable for the Switched Live "3(ON"?

The blue wire is a neutral and must not under any circumstances be joined to the live wires! It's purpose at the old thermostat was to operate a small accelerator heater in conjunction with the switched live, to improve the accuracy of the old mechanical technology. The new thermostat does not need it and is should be isolated and kept well out of the way.

 

[Kieran42]

Stem... that was my understanding too... just got confused what was meant by "Swap wire from t3 to t1" in an earlier message

 

[Kieran42]

Still none the wiser why things aren't working as expected... may get someone in to look at the wiring set up to see if it was wired properly originally

 

[stem]

If it's working now, it should have worked before. Like I said, nothing actually changes. In both cases the thermostat simply connects the brown & green/yellow wires together.

Are you sure that it was the heating calling for heat and that it wasn't just simply that the 'hot water' was calling for heat and was firing up the boiler?

 

[Kieran42]

Stem... my HW normally set on "Twice" ie comes on two times a day, once early in the morning and once in late afternoon before we get in. However to rule it out completely I turned it off... so basically the CH & HW on the programmer were set to the "OFF" position the thermostat was turned right down to the lowest target temperature setting ie 15degrees even though the displayed room temperature was howing as 21degrees , yet the boiler was till firing!...

As I mentioned I've now gone back to using my old thermostat and all is working as expected... so I've run out of ideas except to call someone in.

 

[Kieran42]

Stem... the tp5000si wiring you think looks fine, so then it could just be a faulty tp5000si I guess?