Fitting a hive to baxi potterton promax combi 28he

[stem]

Then it's not the Hive that's switching the heating on. So ruling that out, it would appear that there is something wrong with the boiler.

Did you have a room thermostat fitted before the Hive? and if so, did it work correctly?

I can't see in the photo anything that could 'short' the two boiler terminals together and switch it on, but it might be worth checking for a stray whisker of wire somewhere.

 

[michaeldiy1234]

It never had a thermostat before this I will have a look when I get back home

 

[RandomGrinch]

Looking at the boilers wiring schematic..

The clock is on a different terminal block to the thermostat connections - so it would be unlikely for any modifications to be made behind it, that would effect the thermostat connections.

Edit:
Actually, a link on the back of the clock between terminals 1 and 3 would bypass the thermostat connections.

It could also be linked out at terminal X3 9, but that would be a bit strange...

 

[RandomGrinch]

... and looking at the boiler PCB and Clock connections:

there must be a live connection to X3 9. Without this, the clock couldn't control the boiler. Where that link (or short) is made is another matter.

Edit:
See previous post, the thermostat connection could also be linked out at the clock.

 

[Deleted member 267285]

Could be a diverter failure too

 

[RandomGrinch]

Could be a diverter failure too

I'll leave that to your realm of knowledge and experience!

However, the OP seems to suggest that the C/H is operating correctly by using the clock.
If that is the case, then terminal 3 of the clock must be receiving a live connection from somewhere!