Hive dual controller - hot water permanently on.

[YorkColin]

Hive dual controller fitted to replace Honeywell ST9400C programmer and BDR91 wireless thermostat. We have a Worcester Bosch boiler with separate hot water tank (not a Combi). Central heating seems to work perfectly in so far as can be boosted and programmed to come on and turn off via the Hive. The issue is with hot water - it's always on and kicks the boiler in when temperature drops below thermostat temperature. A plumber has looked at it and says that it might be the Honeywell valve motorhead.

Could it be this? Could it be something else? Seems strange that all was working fine with the old controller and the valve motorhead has failed at same time as when changed. Any advice appreciated.

 

[cross thread]

If only started since changing it’s probably a wiring issue or you have it on permanent on the app.

 

[YorkColin]

If only started since changing it’s probably a wiring issue or you have it on permanent on the app.

Definitely not on permanent on the app. We got an electrician to do the installation and he says it was essentially a straight swap.

 

[RandomGrinch]

Definitely not on permanent on the app. We got an electrician to do the installation and he says it was essentially a straight swap.

It should have been a straight swap, the Hive could even have sat on the existing backplate and worked - although some modification would have been required to link out the BDR91.
Could you send us a pic of the wiring behind the Hive so we could double check?

 

[YorkColin]

It should have been a straight swap, the Hive could even have sat on the existing backplate and worked - although some modification would have been required to link out the BDR91.
Could you send us a pic of the wiring behind the Hive so we could double check?

Thanks for jumping on this. Hive and BDR91 wiring photos attached. Any advice appreciated.

 

[RandomGrinch]

Thanks for jumping on this. Hive and BDR91 wiring photos attached. Any advice appreciated. View attachment 356218

Thanks for the photos, nothing looks obviously out of place - although you still appear to have the BDR91 in place?
That should have been a simple job for the electrician to decommission and remove.
However, it shouldn't cause an issue with the hot water.

My first troubleshooting step, would be to check that the hot water doesn't turn off, if you set the hot water to on by the Hive - ensuring the electrician hasn't simply transposed the wires.

Secondly, to rule out the Hive as an issue.
With the power off, I would move the brown wire in terminal one, to the L terminal of the backplate.
With the Hive receiver still removed, I would turn the power back on (carefully avoiding the backplate and the live terminals); if the hot water remains on, then it is more likely to be a valve head or wiring problem.

 

[YorkColin]

Thanks for the photos, nothing looks obviously out of place - although you still appear to have the BDR91 in place?
That should have been a simple job for the electrician to decommission and remove.
However, it shouldn't cause an issue with the hot water.

My first troubleshooting step, would be to check that the hot water doesn't turn off, if you set the hot water to on by the Hive - ensuring the electrician hasn't simply transposed the wires.

Secondly, to rule out the Hive as an issue.
With the power off, I would move the brown wire in terminal one, to the L terminal of the backplate.
With the Hive receiver still removed, I would turn the power back on (carefully avoiding the backplate and the live terminals); if the hot water remains on, then it is more likely to be a valve head or wiring problem.

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?

Given that everything was working fine for 6 year with the Honeywell controller can we assume that the wiring is fine and that it’s most likely the Honeywell 3 port valve motor head? If so, would you suggest replacing this to see?

Again, really appreciate your help. I feel like we’re narrowing down the issue.

 

[YorkColin]

So an update... if anyone is still listening and can offer advice. Plumber replaced 3 port valve motor head during the week and problem still remains - hot water still firing up even when water is off on Hive and staying on permanently. The only time it doesn't heat up is when the receiver is turned off at the mains. I'm struggling to understand what else it could be other than wiring issues but no wiring has been altered since the Hive was fitted. Any thoughts/advice appreciated - Any thoughts @RandomGrinch?

 

[Murdochcat]

If the hot water is always on , this suggests the supply to the tank thermostat is always live - which it shouldn't be - shouldn't be tricky for somebody competent to investigate

For clarity is the water on when the heating is set to be off?

 

[RandomGrinch]

I'm so sorry, I missed the notification for your last post.
As @Murdochcat suggests, the only other component in the hot water circuit is the tank stat. And I'm struggling to think of a logical way that it could receive a permanent supply, given the Hive backplate replacement was such a simple swap.
I'm still intrigued by the BDR91, did the electrician delve into the wiring centre to link it out?

 

[YorkColin]

If the hot water is always on , this suggests the supply to the tank thermostat is always live - which it shouldn't be - shouldn't be tricky for somebody competent to investigate

For clarity is the water on when the heating is set to be off?

Thanks for the reply. Yes, the water is on when the heating is set to off. The heating doesn’t come on when water is on and seems to be working normally on the timer although we’ve not yet had it on for any length of time to test.

 

[YorkColin]

I'm so sorry, I missed the notification for your last post.
As @Murdochcat suggests, the only other component in the hot water circuit is the tank stat. And I'm struggling to think of a logical way that it could receive a permanent supply, given the Hive backplate replacement was such a simple swap.
I'm still intrigued by the BDR91, did the electrician delve into the wiring centre to link it out?

Hi @RandomGrinch - in terms of the BDR91, the electrician didn’t know it was there (my fault as I didn’t know it was wired in). Our plumber linked it out. I assume he’s done this correctly. He’s happy to come back to look at it again now we know it wasn’t the Honeywell Powerhead. Are the questions I should ask to check all is correct?

Could it be the actual valve that’s stuck - he only replaced the powerhead.

 

[ericmark]

Note three wires into the programmer or hive, also three wires to cylinder stat, there is a hot water off wire used, this makes the three port valve travel all the way across when CH but not DHW is required. However when CH not in use, the three port valve is not used at all by the electrics, it default state is hot water, so it has nothing to do with switching boiler on to get DHW.

I would remove the Hive unit and see if you have no domestic hot water, clearly leaves open contacts which will be live, so tape a plastic bag over it for test, if boiler does not fire, then clearly down to Hive, if does fire then nothing to do with Hive.

Hive can be configured for C Plan, you are on Y Plan with three port valve. Not sure if it can be configured for any other plans, but clearly must be set to correct plan.

 

[RandomGrinch]

I would remove the Hive unit and see if you have no domestic hot water, clearly leaves open contacts which will be live, so tape a plastic bag over it for test, if boiler does not fire, then clearly down to Hive, if does fire then nothing to do with Hive.

We've already tried that Eric...

Secondly, to rule out the Hive as an issue.
With the power off, I would move the brown wire in terminal one, to the L terminal of the backplate.
With the Hive receiver still removed, I would turn the power back on (carefully avoiding the backplate and the live terminals)

Although, I did suggest connecting the terminal 1 wire directly to L.
It may be interesting to know if the hot water doesn't heat, with the Hive receiver removed and the terminal 1 wire back in its correct place.
Whichever way, this doesn't seem to be a Hive issue.

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

If your plumber has done that correctly then we could also rule the BDR91 out, and it suggests the electrician hasn't gone anywhere near the wiring centre?

Could it be the actual valve that’s stuck - he only replaced the powerhead.

Any respectable plumber would have checked that the valve itself was free to move, before replacing just the head.

The only time it doesn't heat up is when the receiver is turned off at the mains.

You say the hot water turns off when the receiver is turned off - does this also turn off the boiler, or do they have separate power feeds?
If it also turns off the boiler, the problem may be with the boiler itself - the 3 port valve would naturally be in its rest position, allowing flow to the tank.

As @Murdochcat says...

shouldn't be tricky for somebody competent to investigate

Which means, someone familiar with a Y plan system and has appropriate electrical test equipment.

 

[ericmark]

But the DHW is not switched by the three port valve, so valve being stuck would not cause the boiler to fire up, only the tank thermostat which is it seems OK and the Hive unit, should have any bearing on if boiler fires up. See diagram.

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

If fault is Hive, next is it programmed for that system, but first is it Hive at fault, and easy to simply remove Hive to test.