Replacing thermostat with Hive receiver.

[jspur84]

Hey,

I bought Hive heating (Combi) without installation as I wrongly assumed I could replace the existing thermostat with the hive receiver easily enough.

I've just taken the existing thermostat off the wall and noted that there is only a blue and brown wire going to the existing setup (see picture attached if I've done it correctly...)

I'm thinking that my existing thermostat is a wireless one and I would need to wire the receiver into the boiler, is this the case? If so I think I'll have to get someone in as I'm not willing to start messing around with the boiler itself. Thanks.


p.s. I've seen there's so many threads over lots of forums about this but couldn't find one with the same configuration as my own...

 

[RandomGrinch]

Hi,

I'm afraid we may need a little more information than that, to be able to help!
For a start, what make and model is your existing thermostat and combi?

Without knowing, we could guess that the thermostat is wireless, but that would mean there is probably a separate receiver, and your Hive receiver would go there.
However, your thermostat may be battery powered. If so, those wires may be the 'call to heat' and some rewiring may be needed!

 

[jspur84]

The boiler is a Potterton Promax Ultra and the thermostat is a Baxi wireless programmer

'Without knowing, we could guess that the thermostat is wireless, but that would mean there is probably a separate receiver, and your Hive receiver would go there.
However, your thermostat may be battery powered. If so, those wires may be the 'call to heat' and some rewiring may be needed!'


I can't see anything else near the boiler which could be a receiver. The thermostat isn't battery powered so I was assuming that the blue and brown wires going into the thermostat were for power only and it was communicating with the boiler wirelessly.

 

[CBW]

Personally I’d just wire Hive receiver near to boiler in 5 core heat resistant flex cable and decommission the existing. Make sure your Hive is single channel.

 

[RandomGrinch]

Looking at the manuals for what I believe are your models - I may be very wrong, but I think you have the wired programmer connected to the low voltage terminals of the combi.

The programmer is powered by a (extra) low voltage feed from the combi, but also passes control signals through those wires.
My reasoning being that the terminals are marked 1, 2 and 3, rather than L, N and earth. The Blue and Brown wires could just be from a convenient cable and don't necessarily mean mains voltage.

I may also be wrong and @CBW, or others can correct me, but it may be that the mains voltage terminals to connect the Hive, are only accessible by removing the front cover of the combi; this may be part of the room sealing of the appliance and should only be done by an RGI.

The only other thing to mention; it seems your combi is capable of being controlled by OpenTherm and your existing programmer may be using this. Hive is a relatively rudimentary on/off programmer.
The Hive will work, but it might not give you the optimum performance of the boiler.

I hope that makes sense!

 

[jspur84]

Thanks for taking the time to look into that for me @RandomGrinch, I'll have to look for a RGI now