Wiring Dual Hive for New Valliant Combi

[JackRusselll]

Hello, I know this has been asked a few times prior, but I want to be sure for my specific scenario...

Just had a standard boiler swapped out for a new Vaillant Ecofit Pure 830. Old boiler was connected to a Hive heating and hot water thermostat. I was hoping to use this for the combi boiler rather than mess about changing for the single channel version.

Gas engineer ran out of time tonight so will be back in the morning, but seemed a bit stumped on the wiring. I want to make sure he does it correctly first time (as we currently have no heating).

I've attached a picture of how it's been left, if someone could advise on which wire where that would be great.

I'm thinking live to live, neutral to neutral, then one of the wires into channel 4. There is a black wire (currently in 1) and a grey wire (currently in 3), so which one would that be? And what happens to the spare wire?

Thank you!

 

[RandomGrinch]

I'm thinking live to live, neutral to neutral, then one of the wires into channel 4.

Terminal 4 of the dual channel Hive backplate would connect to RT on the boilers mains voltage terminal block.
As per the instructions, the 24V=RT link wire would also be removed.

And what happens to the spare wire?

The spare wire would be safely isolated and tucked out of the way.
The bare earth wire in the Hive backplate needs a green/yellow sleeve.

There is a black wire (currently in 1) and a grey wire (currently in 3

Just to clarify, has this new cable been installed along with the boiler?

 

[ericmark]

Hive now has OpenTherm

the two terminals at the bottom are for OpenTherm, I note BUS connections, but not sure if your boiler is OpenTherm or if it has its own special system.

The whole idea with a modern boiler is it is not switched on/off, but has analogue controls, so the boiler flame is turned up/down to suit requirements, the boiler will work on/off, but not as efficient as up/down. As to how much it costs to use the old digital on/off rather than analogue up/down, I have no idea.
We are shown diagrams

the idea is the smoother OpenTherm or other ebus control leaves one being able to set the temperature slightly lower. I have a feeling you have to use Valiants own thermostat, but some do offer converters, but your installer should know what is required. But there does not seem to be a 230 volt (low voltage) option, so you will need a 24 volt (extra low voltage) thermostat.

This thread goes into converters etc which to be frank is a bit over my head.

 

[RandomGrinch]

Hive now has OpenTherm

Yes, since 2025, Hive does support OpenTherm. But this is irrelevant to the OP.
They are using their old Hive dual channel (Definitely not OpenTherm compatible)...

Old boiler was connected to a Hive heating and hot water thermostat. I was hoping to use this for the combi boiler rather

On top of that, as you say...

I have a feeling you have to use Valiants own thermostat, but some do offer converters, but your installer should know what is required.

Vaillant use eBUS which is not compatible with OpenTherm. There is an OT adapter available from the continent, but I've seen mention that fitting one to a UK boiler may void the warranty.

But there does not seem to be a 230 volt (low voltage) option, so you will need a 24 volt (extra low voltage) thermostat.

Ummm - when connecting a control (230V)...

 

[JackRusselll]

Terminal 4 of the dual channel Hive backplate would connect to RT on the boilers mains voltage terminal block.
As per the instructions, the 24V=RT link wire would also be removed.


The spare wire would be safely isolated and tucked out of the way.
The bare earth wire in the Hive backplate needs a green/yellow sleeve.


Just to clarify, has this new cable been installed along with the boiler?

Thank you for your reply. So if I'm following correctly, only one cable wire from the RT runs to terminal 4 in the Hive block. This could be either the black or the grey wire depending on which end is connected to the RT on the main block. The other wire is then not used.

Is the link removed from 'burner off' position too or just 24v RT?

I believe this is a new cable, but I'm not sure. I was hoping the gas engineer would be able to figure all this out, but he seemed unsure as the dual hive is not intended for combi boilers, so I appreciate your help on this. Also, he blew a fuse when initially attempting to connect to the Hive before calling it a night. I wonder if that had to do with the 24v link?

 

[RandomGrinch]

So if I'm following correctly, only one cable wire from the RT runs to terminal 4 in the Hive block. This could be either the black or the grey wire depending on which end is connected to the RT on the main block. The other wire is then not used.

Yes, and make sure the spare wire isn't connected to any terminal on the boiler side either.

s the link removed from 'burner off' position too or just 24v RT?

No, the link is only removed from the 24V=RT connector.

Also, he blew a fuse when initially attempting to connect to the Hive before calling it a night.

That's a little concerning - he had the wiring set-up for a single channel Hive using terminals 1 and 3. Hopefully he hasn't connected the other end of the cable to the 24V=RT terminals, or there may be damage to the boiler PCB.

 

[ericmark]

Sorry, yes, page 21 of the manual it shows the 230 volt option. Unfortunately, I don't have the option of analogue control. So can't really say from first-hand experience if worth getting the proper thermostat. As long as also using the linked TRV heads, then likely there will not be a large difference.

If I look at my TRV it gives a patten like this because my boiler does not modulate, and can only switch on/off, can't see the point of having a modern modulating boiler, and then not use the better control offered.

That's a little concerning - he had the wiring set-up for a single channel Hive using terminals 1 and 3. Hopefully he hasn't connected the other end of the cable to the 24V=RT terminals, or there may be damage to the boiler PCB.

I would agree, that is worrying.

 

[JackRusselll]

Yes, and make sure the spare wire isn't connected to any terminal on the boiler side either.

No, the link is only removed from the 24V=RT connector.

That's a little concerning - he had the wiring set-up for a single channel Hive using terminals 1 and 3. Hopefully he hasn't connected the other end of the cable to the 24V=RT terminals, or there may be damage to the boiler PCB.

Thanks, how would I know if the PCB has been damaged? So annoying if it has, you pay lots of money for a professional...

 

[CountryFan]

Thanks, how would I know if the PCB has been damaged? So annoying if it has, you pay lots of money for a professional...

I would say the thermostat or even the boiler won’t work. If it’s damaged it would be up to them to sort it out. A new pcb is in the region of £250!

 

[JackRusselll]

I would say the thermostat or even the boiler won’t work. If it’s damaged it would be up to them to sort it out. A new pcb is in the region of £250!

Hot water and screen on boiler works at the moment so hopefully it's okay.

Fingers crossed the thermostat is fine too...

 

[RandomGrinch]

Thanks, how would I know if the PCB has been damaged? So annoying if it has, you pay lots of money for a professional...

Don't panic yet!
It all depends on whether he connected the stat wiring to the mains voltage RT terminal, or the 24V ones.
If he had used the 24V terminals, and powered up the Hive, there may be an issue. If the fuse blew at any other point, it may have been an accidental short and your boiler may be fine.

 

[JackRusselll]

Don't panic yet!
It all depends on whether he connected the stat wiring to the mains voltage RT terminal, or the 24V ones.
If he had used the 24V terminals, and powered up the Hive, there may be an issue. If the fuse blew at any other point, it may have been an accidental short and your boiler may be fine.

Thank you - it's all working now.

I do have a further more troubling issue with the promises made by the installer, but will post separately for opinions.