Fitting a Honeywell DT92E - Have no Room Thermostat

[UkWildy]

Hi Everyone,

Currently i am at a house that doesn't have a room thermostat, reading the instructions it shows the diagram on how to set it up but later on says "Keep AC mains supply/load cables separate from signal wiring"

Current process is:

1. Live Neutral and Earth at Boiler only.
2. Disconnected and Rerouted above cables to DT92E receiver Box
3. Installed new three core back to Boiler.
4. Terminated live and neutral into DT92E L and N
5. Joint neutral back to boiler, connected (3core) Live back to boiler then terminated into B

Do i now link L to L then L to A? as with above i am unsure.

Any help would be greatly appreciated! Thank you

 

[omega015]

What make/model boiler do you have?

 

[UkWildy]

Valiant don't know the model as currently not on site. Maybe a combe?

 

[stem]

First of all, if you have simply re-routed the mains supply, so that it is switched via the thermostat, then you will also only be able to get hot water when the central heating thermostat is calling for heat. Boilers have special dedicated terminals for the installation of a room thermostat that allow the main supply to remain permanent.

Secondly, if the boiler has a pump overrun facility, when the thermostat removes the mains supply to the boiler this will not operate, the boiler will overheat and probably trip its safety circuit.

As regards the link, if you are switching 230v then yes you would need to make it, although it won't rectify the situation above. However, if your boiler has 24v control circuits then they must be kept separate and not linked to the mains. This is what "Keep AC mains supply/load cables separate from signal wiring" means. Otherwise you may find yourself investing in an expensive new boiler PCB.

For further assistance, you will need to provide details of the boiler, not just the name of the manufacturer, but also the model. Failing that, a photo of all of the external boiler wiring terminals may help. Also, is there some time control somewhere?

 

[UkWildy]

The Boiler is a Valiant Eco Tec 831.

At Present all the rads are controlled by thermostatic valves.

 

[stem]

I have sketched a wiring diagram for your installation below. The Earths are omitted for clarity. If there is a link between the boiler terminals 3 and 4, it should be removed.

As you didn't answer my previous question about any existing time control, so I have assumed there isn't any.

The TRV should be removed from the radiator in the room where the Room Thermostat part (not the receiver) is located



Boiler wiring terminals should look something like this.