Heatmiser UH8 volt free with a 230v switch wire boiler

[raidingKilt]

I haven't had the chance to install an UH8 before and it looks a cracking piece of kit.

However I'm a little unsure on best place to get a Live from, to feed the Volt-free LS, with the LR going to boilers 230 switch.

Take the UH8's main live or take the boilers? There's no valves at the moment to take a live from. Or have I missed something?

Advice appreciated.

 

[Leesparkykent]

I haven't had the chance to install an UH8 before and it looks a cracking piece of kit.

However I'm a little unsure on best place to get a Live from, to feed the Volt-free LS, with the LR going to boilers 230 switch.

Take the UH8's main live or take the boilers? There's no valves at the moment to take a live from. Or have I missed something?

Advice appreciated.

What boiler are you connecting it to?

 

[raidingKilt]

What boiler are you connecting it to?

its a Grant Vortex Eco 12-21

 

[Leesparkykent]

its a Grant Vortex Eco 12-21

The boiler and UH8 are fed from the load side of same switched fused spur?

 

[raidingKilt]

The boiler and UH8 are fed from the load side of same switched fused spur?

Yes, the spur will feed both the boiler's L,N&E and UH8 Main's Supply L,N&E via a junction box.

 

[Leesparkykent]

Yes, the spur will feed both the boiler's L,N&E and UH8 Main's Supply L,N&E via a junction box.

I would just feed the relay/contact from a perm live from within the UH8...I would take it from something that’s on the load side of the UH8’s internal fuse.

 

[raidingKilt]

ok, makes sense, so say one of the zone thermostat Lives?
Thanks for replies

 

[Leesparkykent]

ok, makes sense, so say one of the zone thermostat Lives?
Thanks for replies

Yeah that would do.

 

[raidingKilt]

Yeah that would do.

Ok, to carry this on.

If combing this volt free output with the relay output of the Hot water valve, will the volt free contact activate off the HW live, or will it act only on the UH8? Be nice to not have to get into relays.

 

[raidingKilt]

Right I’m stumped.

When HW or CH are switched on separately, all works as it should.
Yet when HW and CH are on together, but then Ch goes off, the UH8’s (CH) remain active and calling for heat.

The UH8’s have LS from the switched live of the programmer clock and the LR then combines with the HW to enable the cyclinder stat and system pump.

The uh8’s will be losing their Ls signal when the call for CH goes off, how are they remaining on??

I have a 8a relay switch I can install between the UH8’s and the HW, but I feel the UH8’s should be dealing with this and I’ve done something wrong.

 

[Leesparkykent]

Right I’m stumped.

When HW or CH are switched on separately, all works as it should.
Yet when HW and CH are on together, but then Ch goes off, the UH8’s (CH) remain active and calling for heat.

The UH8’s have LS from the switched live of the programmer clock and the LR then combines with the HW to enable the cyclinder stat and system pump.

The uh8’s will be losing their Ls signal when the call for CH goes off, how are they remaining on??

I have a 8a relay switch I can install between the UH8’s and the HW, but I feel the UH8’s should be dealing with this and I’ve done something wrong.

I’m finding hard to follow what you mean. Post a pic of your wiring maybe.

 

[raidingKilt]

see if this helps.

 

[raidingKilt]

basically when the CH goes off, but HW is on, there’s is 230v on the CH circuit, which means it’s getting through the Volt free heat-enable of the UH8.

When only the HW circuit is on (first) just the HW circuit is active and the volt-free heat enable does it’s job.

 

[davesparks]

From the diagram you have posted the volt free output appears to be fed from the same terminal as the switched live input to the uh8, this will cause it to back feed from the HW.

The volt free relay should have a seperate permanent live feed.

 

[raidingKilt]

I have same issue when it’s on a permanent live.

When I take the Live from the clock programmer, rather than SL clock number 1, it still back feeds, but ONLY when the CH goes off when HW is on. Hence my confusion.
If it was wired wrongly, surely when HW is on it back feeds and switches heating on, but it doesn’t.

 

[raidingKilt]

 

[davesparks]

Why is there a nest and a room stat I The diagram?
and why have you linked the room stat to the HW on from the nest?

Use the permanent live to feed the volt free switch to be sure of not getting a back feed there.

 

[raidingKilt]

Why is there a nest and a room stat I The diagram?
and why have you linked the room stat to the HW on from the nest?

Use the permanent live to feed the volt free switch to be sure of not getting a back feed there.

The nest is the heating system clock/programmer I have just popped the names in rather than drawing.
The ‘room stat’ is just a label as per a s-plan wiring diagram.

Circuit 4 (room stat on a s-plan diagram) is the ‘heat enabled’ output of the UH8, effectively the “room stat”.
There’s is only ONE hot water storage and ONE pump. So at some point the CH circuit and the HW circuit must merge so the one system pump and boiler can fire.
There are no 2-port valves or relays.

I have found the issue and all working correctly.