Wiring to replace Geo Cosy with Hive Active Heating

[Shaun Evans]

Hi all

Desperate to replace the pretty rubbish Geo Cosy system that we got for free a few years ago when we switched our electric supplier with a nice new Hive system. I’m in a better place than most for this as we had a Worcester wireless thermostat originally and the engineer had to disconnect this completely to install the Cosy system, so this should be relatively easy, however...

When I open up the Geo Cosy receiver connected to the boiler, while there are only four cables (straightforward single zone combi boiler setup) and two are the live and neutral, the other two cables go to a terminal marked TP1 with no indication of which cable is live or the on or off, so I’m not sure which terminals on the Hive backplate to connect them to, anyone have any idea?

I’m pretty handy with a multimeter, so could test the cables if I know what I am looking for..?

Any advice would be much appreciated!

Thanks

Shaun

 

[CBW]

Both wires go to tp1? Photo?

 

[Shaun Evans]

Thanks Chris, yes both wires go to terminal 1 - with two connections though apologies if that wasn’t clear...
Terminal is labelled T1 rather than TP1 sorry - I’m sure the online manuals labelled it TP1, anyway same difference - photo attached.
Thanks
Shaun
https://www.amazon.co.uk/photos/share/68p5GLLws8F8rQi2W5VeSZ0BzsOXwhFwWucSplnUoSM

 

[JohnD]

You can add pictures by copy and paste into your post.

Or by "upload a file."

 

[Shaun Evans]

Thanks for the tip John!

 

[CBW]

Hi Shaun,

It’s difficult for me to tell whether it’s low voltage switching, but it appears that someone has used the green/yellow (normally earth cpc) as a switch wire. Using your multimeter on Volts ac, test between neutral and both those terminals, if you pick up 230vac than it’s mains switching, if not then chances are it’s low voltage switching - not entirely sure how to test for this, could be volts dc. Once established then you can transfer the wiring over to Hive as Com and NO (live in and switching).

 

[ianmcd]

Both wires in T1 go to the hive ,one into terminal 1 and the other into terminal 3, the L&N from the geo to L&N in the hive

 

[Shaun Evans]

Thanks Ian, what I’m really concerned with is which way round those two cables go in to 1 and 3 on the Hive (and/or I guess whether I’ll destroy the boiler if I get it wrong! ).
Thanks
Shaun

 

[ianmcd]

Thanks Ian, what I’m really concerned with is which way round those two cables go in to 1 and 3 on the Hive (and/or I guess whether I’ll destroy the boiler if I get it wrong! ).
Thanks
Shaun

doesnt matter which way round, the hive is simply a switch,they can go either way round

 

[Shaun Evans]

Thanks for all the help guys, had a tinker with the multimeter and the first cable with the yellow/ green earth colours is 240V, the second grey cable gave no reading on DC or AC.

However, when I bridged the earth and grey cables the boiler fired up straight away, and when I opened the link it switched off again, so I’m thinking the earth cable goes to terminal 1 on the Hive backplate and the grey cable goes to the heating on terminal 3...?

What could possibly go wrong?

Shaun

 

[ianmcd]

Thanks for all the help guys, had a tinker with the multimeter and the first cable with the yellow/ green earth colours is 240V, the second grey cable gave no reading on DC or AC.

However, when I bridged the earth and grey cables the boiler fired up straight away, and when I opened the link it switched off again, so I’m thinking the earth cable goes to terminal 1 on the Hive backplate and the grey cable goes to the heating on terminal 3...?

What could possibly go wrong?

Shaun

I told you that, it is not an earth cable, wire colours in heating wiring mean absolutely nothing, wire it as I told you and it will be fine , would be a good idea to put brown sleeving on the green and yellow wire, or some red or brown tape to warn others that this is a live wire and not an earth wire

 

[Shaun Evans]

Just to close the loop on this it worked exactly as described - green yellow wire to 2 on the Hive backplate, grey to 3 and away you go after the boiler messed about in syphon mode for ten minutes or so.

Massive thanks to everyone who contributed!