Boiler external control installation advice

Gadgie

Hello,

I'm looking to install an external controller to my boiler, a Vokera Mynute 24m. I'm trying to make sense of the electrical connections, which I suspect are wired badly (house was built in 2006/7, at the height of the boom).

Currently, the boiler has an internal time clock, which is of the volt-free type. This is used to fire the boiler, and operates independently of the rest of the heating system.

In the hot press there are two Horstmann F222m valves, one for the hot water and another for the radiators.

• The hot water valve is connected directly to the 3A fuse switch, so is always on (valve open) if the boiler supply is on (regardless of whether the boiler is fired or not).
• The radiator valve is connected to a 1-gang switch beside the fuse switch, so can be switched on and off if the boiler supply is on.

The wiring from the boiler to the hot press is 3-core, and the valves have a 5-core cable.

• Live has been connected to the brown wire of the valves (CH/HW ON)
• Neutral (blue) & earth (yellow/green) have been connected correctly
• The orange (boiler live) and grey (any permanent live) wires have been snipped and aren't connected to anything. :rolleyes:

Both valves are not opening when powered on, so I have them manually forced open. I'm not sure if this is because they have been wired incorrectly, or the motors have failed. The only way I know they are turning on and off is the indicator LED.

The external controller I have is the Hive Active Heating 2-channel receiver. I purchased this from Amazon, and I was going to self-install before I realised what a mess the connections were.
The 2-channel receiver on/off terminals are mains voltage, but the boiler requires a "voltage free" connection, which is only on the single-channel receiver. I'm thinking I need some sort of relay setup to isolate the boiler terminals, which closes when either the HW or CH relays (or both) are turned on. Does such a thing exist?
Or do I need two separate mains operated relays?

I called a local gas installation company (who usually service our boiler) and asked if they would fit this for me. They gave me the number of an electrician they use and advised me to contact him. I asked several times if he was allowed to open the boiler (which will need to be done to disconnect the internal timer and connect the external programmer) as I thought you had to be an RGI to do so, and they said it was OK as long as the gas connections were not touched [I'm not convinced of this, so can someone clarify?]
Anyway, the electrician called out to have a quick look at the electrical connections (did not touch the boiler) and was a bit stumped on how it could be done, so I said I'd think about it and get back to him.

Can anyone offer advice?

DGOBS

You need to be a RGI to work on the boiler, once a tool is taken to the appliance it is gas works and requires certification.
(Your electrician could do all the wiring up the boiler, and the RGI can connect if needed)

You have a couple of issues here other than that.

You are correct, this boiler is lots free contacts for SWL, but there was an axillary PCB you could get for it once upon a time to allow 240v switching, but essentially you'd be better (cheaper) being a 240v to volts free relay.

Both motorised valves, I would guess have their orange and grey wired cut away or not used, these will need to be wired into play by you electrician and you will need a 7 core cable between this and the hive controller (remember if valves are remote from the boiler, you can always have the electrician install the Hive receiver where the valves are, not beside the boiler!), and 4 cores to the boiler from the wiring centre (L-N-E-SWL, to the boiler and relay)

Show the electrician a 2 zone 'S-Plan' this is what he will have to do, with Hive Receiver inplace of the time/controller, and loop out the room stat as the Hive stat is wireless and where SWL goes to the boiler, this will go to the 240v-volts free relay.

Also while doing it make sure they fit a cylinder stat and a bypass on the plumbing.

To wire this without a relay, your electrician can also use the auxially switch on the motorised valves as volts free (orange and grey wires) as the boiler has a switched live OUT and IN that are volts free.

DGOBS

Show this to your electrician.
Do not attempt to wire this yourself

Gadgie

Thanks a million for the detailed response and wiring schematic - that's very helpful indeed. I will get the electrician to follow this.

DGOBS wrote: »

You need to be a RGI to work on the boiler, once a tool is taken to the appliance it is gas works and requires certification.
(Your electrician could do all the wiring up the boiler, and the RGI can connect if needed)

That's what I thought - thanks for confirming.
I'm very surprised that I was told otherwise by the gas installers. I did state multiple times that the boiler cover would need to be removed to gain access to the electrical connectors.
The boiler is due a service, so will get the electrician to do the wiring, and then have the RGI connect it inside the boiler while they have it open.

DGOBS wrote: »

To wire this without a relay, your electrician can also use the auxially switch on the motorised valves as volts free (orange and grey wires) as the boiler has a switched live OUT and IN that are volts free.

Thanks for the suggestion - I didn't realise that the orange and grey wires were electrically isolated from the supply voltage. I opened up the Horstmann switch to take a look, and it is simply a microswitch that is closed when the valve is opened.
I'll need to get these replaced anyway, as the motors have failed.