Heatmiser UH8-RF advice

[carlosparky]

I have upgraded from UH1-W to UH8-RF.
The old UH1-W had five wires connecting DHW and DHW-Stat. I have connected the DHW-Stat cables to the UH8-RF HW port, but unaure what to do with L and N previously connected. Timer switches on, but the HW timer does not activate the boiler.

Any advice?

 

[Avo Mk8]

It looks like the old and new circuit arrangement is the same, but whereas the UH1 has terminals on the pcb for both the stat and the valve, the new UH8 has just terminals for the valve, and the diagram shows you connect the stat in series with the valve.
ie one wire to the stat that previously went in UH1 'stat' terminal now goes in UH8 H/W (L), the other wire from the stat (that previously went into the UH1 other 'stat' terminal is now connected directly to the (L) feed to the valve (that was previously in UH1 DHW live), eg using a Wago connector or terminal block, and the the valve neutral goes into UH8 H/W (N). Not forgetting the earth wires, and the orange and grey from the valve (if you have them) stay where they are.

If you connected the stat directly to the H/W terminals on the UH8, I think you've connected the stat switch directly across the mains, so a fuse may have gone somewhere (or possibly a relay failed - hopefully not!)

PS For hot water, the boiler is going to be turned on by the orange wire from the valve (assuming you have that arrangement), so if the valve is not being operated, the boiler will not come on.

 

[carlosparky]

It looks like the old and new circuit arrangement is the same, but whereas the UH1 has terminals on the pcb for both the stat and the valve, the new UH8 has just terminals for the valve, and the diagram shows you connect the stat in series with the valve.
ie one wire to the stat that previously went in UH1 'stat' terminal now goes in UH8 H/W (L), the other wire from the stat (that previously went into the UH1 other 'stat' terminal is now connected directly to the (L) feed to the valve (that was previously in UH1 DHW live), eg using a Wago connector or terminal block, and the the valve neutral goes into UH8 H/W (N). Not forgetting the earth wires, and the orange and grey from the valve (if you have them) stay where they are.

If you connected the stat directly to the H/W terminals on the UH8, I think you've connected the stat switch directly across the mains, so a fuse may have gone somewhere (or possibly a relay failed - hopefully not!)

Thanks for your reply, the UH8-RF board has C, NO, NC terminals for HW so I am a bit confused with UH8 H/W (L) and UH8 H/W (N). I understand I made a mistake connecting the stat to HW (C) and HW (NO).

If I follow the wiring diagram, it looks like I should connect:

• Mains live to HW (C)
• The first Stat cable to HW (NO)
• The second Stat cable to the HW Valve Live cable through Wago connector
• The HW Valve Neutral to Mains Neutral through Wago connector
• The HW Valve Earth to Mains Earth through Wago connector

Is this correct ?

Thanks and thanks !

 

[Avo Mk8]

Mains live to HW (C)

• The first Stat cable to HW (NO)
• The second Stat cable to the HW Valve Live cable through Wago connector
• The HW Valve Neutral to Mains Neutral through Wago connector
• The HW Valve Earth to Mains Earth through Wago connector

Is this correct ?

Yes.

Sorry to confuse you - I must have found the wrong diagram!
Because you just have relay connections on your board, not connected to power, your previous go hasn't caused a problem.

You have the right idea - go for it!

 

[carlosparky]

Yes.

Sorry to confuse you - I must have found the wrong diagram!
Because you just have relay connections on your board, not connected to power, your previous go hasn't caused a problem.

You have the right idea - go for it!

Great thank you !

 

[carlosparky]

Great thank you !

It did work !!! Thanks again