Hive dual controller - hot water permanently on.

[RandomGrinch]

So either a wiring fault, or faulty Hive, so if it does not fire up with Hive removed, fault has to be with Hive.

Eric, the Hive has been removed, and the hot water still fires...

Turned everything off to let water cool down. Swapped T1 wire to L terminal and turned back on (without connecting the receiver front) and boiler immediately fired up. Guess this means we can take the Hive out of the equation?

 

[ericmark]

There is no T1 with Hive, Nest Gen 3 has a T1 and to connect that to the 230 volt supply would likely mess it up, as T1 and T2 are 12 volt.

Are we sure actually using Hive?

 

[RandomGrinch]

There is no T1 with Hive,

Terminal one

Are we sure actually using Hive?

Looks like it to me

See #5

 

[ericmark]

This is the normally line terminal used to put three port valve in fully over position if you set DWH off and CH on, with CH off it does not do a thing. Well it can hold the three port valve all the way across, but it will not fire boiler. This wire must be line for the boiler to fire up to supply DHW if central heating not running.

The issue is with hot water - it's always on and kicks the boiler in when temperature drops below thermostat temperature.

It does not say DHW comes on with CH, it says "always on" so nothing to do with terminal 3 or the motorised valve.

REALLY appreciate you walking me through steps to troubleshoot the problem. Turned water permanently on via Hive and water still piping hot. Turned everything off to let water cool down. Swapped T1 wire to L terminal and turned back on (without connecting the receiver front) and boiler immediately fired up. Guess this means we can take the Hive out of the equation?

This points to a wiring fault, not anything wrong with Hive or motorised valve. It would seem most likely some one has tried to by-pass the wall thermostat in the wiring centre. As shown here but in error they have bridged the wrong pair.

With a picture of wiring centre we may see error, these two wires should be bridged at wiring centre end, maybe we can work out what has been bridged in error. But it may need some one with test gear to work out what has been done.

 

[RandomGrinch]

It would seem most likely some one has tried to by-pass the wall thermostat in the wiring centre. As shown here but in error they have bridged the wrong pair.

That's what I was getting at, asking about who linked out the BDR91.
Apparently the plumber linked it out, after the electrician was involved...

Our plumber linked it out. I assume he’s done this correctly.

Although not fully clear, the issue was reported to have happened after the Hive was replaced and not after the BDR91 was linked out. Could @YorkColin clarify?

 

[ericmark]

Although not fully clear, the issue was reported to have happened after the Hive was replaced and not after the BDR91 was linked out. Could @YorkColin clarify?

Agreed, this post is now dead until @YorkColin clarifies, he needs to quote or name us with the @ symbol so we get an alert once answered.

 

[YorkColin]

Thanks @ericmark and @RandomGrinch - a lot of this is over my head. I'm going to replace the cylinder stat as it's a simple job and only £18. If that doesn't do the job I'm going to find someone else to look at it. Will report back - just so you're in the loop with what the problem is... if I ever find out what it is!

 

[RandomGrinch]

Thanks @ericmark and @RandomGrinch - a lot of this is over my head. I'm going to replace the cylinder stat as it's a simple job and only £18. If that doesn't do the job I'm going to find someone else to look at it. Will report back - just so you're in the loop with what the problem is... if I ever find out what it is!

Sorry we didn't get to the bottom of it, but this really should.be solvable by someone 'on the ground', with some test equipment.
If you would like to post a picture of the wiring in the wiring centre, we may be able to check it over.
Please let us know the outcome!

 

[ericmark]

I'm going to replace the cylinder stat

Unlikely to be the problem. From what you say expect to find link in the wrong place in the wiring centre.