Install Hive and Bypass the Room Thermostat. Which Wires do I Link?

[RichB0623]

Hi, hope you can help please. Opened up the Wiring Center and frustratingly the wiring does not match the guide on the cover. Any ideas what ones I need to link to be able to decommission the Old Room Thermostat please?

I have a HONEYWELL HOME DT90E DIGITAL ROOM THERMOSTAT & Drayton LP722 Heating/Water Controller. I am guessing the Hive Controller is a simple swop for the LP722, but it's the decommissioning of the Thermostat that is throwing me

 

[Deleted member 267285]

Where does that black cable go to? I can’t see any zone valve cable/wires in that wiring center - this is what you need to find.

 

[RichB0623]

Chris. The Black Cable goes to my Hold & Cold Water Pump (sorry should have moved that out of site). I have three white cables 1 going to another wiring center which in turn has a black cable to the motorised valve, 1 to the Thermostat on the hot water cylinder, and 1 to another pump (picture below)

 

[Mottie]

I had a DT90E thermostat and when I fitted hive, I initially just connected the two wires that went to the thermostat together and fitted the hive unit in the same position. (You can just leave the thermostat there set on maximum if you want). I later traced the thermostat wiring to the wiring centre and just bridged it out.

 

[Deleted member 267285]

Chris. The Black Cable goes to my Hold & Cold Water Pump (sorry should have moved that out of site). I have three white cables 1 going to another wiring center which in turn has a black cable to the motorised valve, 1 to the Thermostat on the hot water cylinder, and 1 to another pump (picture below)
View attachment 256345

Upload a photo of this wiring center or do as Mottie suggests, link the 2 wires/set existing stat to max.

 

[stem]

If you have a 3-Port* motorised valve, one of the room thermostat wires is usually connected to a white wire from the motorised valve. In most installations that allows identification of the cable going to the room thermostat. [In your case with two wiring centres it may be more complicated if the connections are fed through both]

Once the suspect cable has been identified a simple test with a multimeter can be carried out to confirm.

*If you have a 2-Port valve, you are looking for a brown wire.

 

[RichB0623]

Thanks Stem, CBW & Mottie so far....

So I opened up the 2nd Wiring Centre this morning and think I have found out more. So in Wire Centre 2, I have a Black wire with a knot in it, connected to a White wire going to the motorised valve (Image 1 with Wires Highlighted). I traced this back to Wiring Centre 1, the Black Wire has a knot in it also, this goes to a Yellow wire and when I trace that back, I think this is the thermostat wire. It has a Live wire connected in port 11, to a Live wire which looks like is the ring main (Image 2 of wires highlighted as explained in Wiring Centre 1)....hope this all makes sense

So, if I am correct with the wires, I am thinking that I need to link the live from the ring main, to the black wire with a knot in it that way then, the live and yellow in the wall thermostat become defunct...what do you think?


Wire Centre 2 Image (highlighted)


Wire Centre 1 Image (Highlighted)

 

[stem]

The DT90E will have two wires connected to terminals A & B

You are looking to find the two terminals that each of the wires in A & B originate from. Once you have determined the terminals correctly, the two wires that go to the thermostat are disconnected, and then a link wire is inserted to join together the two terminals where the wires have just been removed from.

 

[RichB0623]

thank you Stem... I think I have it now

so in my DT90E I have 4 wires (Live, Neutral, Earth and a Yellow). I trace these back to Wiring Central (done this bit), disconnect the Live and Yellow from the Wiring Central so that my room thermostat no longer has an active live and yellow, and then link together where I took the Live from and where I took the Yellow from, so as to have no break in any of the wiring to the motorised valve

 

[stem]

Don't take too much notice of the wire colours when it comes to heating systems. I've seen blue wires and green/yellow wires used as live wires! It's what the wires are connected to at each end that determines what they do, not the colour of their insulation.

Both of the wires in A and B will be live wires.

Your DT90E is double insulated and doesn't have an earth terminal, and as it's battery operated doesn't need a neutral either. It's the other end of the wires in A and B you are interested in. If the other wires are connected to anything, possibly because there was another thermostat installed before the DT90E, they can simply be disconnected.

If you're still unsure, post a photo of the DT90E terminals.

 

[RichB0623]

Stem, took your advice and opened up the back of the Room Stat (photo below). As you predicted, just a red in A and Yellow in B with no Neutral and Earth connected

I now know the 2 wires which have to link together in Wiring Centre

Can't thank you all enough for the help.....