HW but no CH puzzler

[BrianA]

Hi experts!

I have a WB Greenstar Heatslave 18/25 boiler that has been installed - and run trouble free - for almost 5 years.

On Thursday morning, when the CH was due to timed start it didn't. Basically, we now have HW (no apparent problems at all with that), but no CH.

I assumed it was a faulty zone valve (Honeywell v4043H) and fitted a replacement head. I'm as sure as can be that I got the right wiring connections, replaced them 1 for 1. (The old unit was 5 wire the new one was 6 wire, I just taped off the white.) But still no CH.

It's a C plan layout. The control board seems visually OK (no burning on the PCB underside).

So, at this point I'm stumped. Anyone have any ideas what to check next ?

Cheers

Brian

 

[Gas2Air]

Are you getting 240v on brown/orange when CH demands?

 

[holty]

you obviously checked the external controls. or the internal programmer. which i find are crap on these

 

[BrianA]

Are you getting 240v on brown/orange when CH demands?

Yep

 

[BrianA]

you obviously checked the external controls. or the internal programmer. which i find are crap on these

It's an external programmer, should have said. yes, AFAICS it's OK.

 

[twgas]

C plan usually needs the white wire connected to work properly

 

[holty]

check the boiler ch stat. also check the dhw sensor. is not keeping the boiler in dhw mode. just unplug. this would have the symptoms of the boiler constantly firing though.

 

[BrianA]

C plan usually needs the white wire connected to work properly

Hmm, the unit that came off only had 5 wires and had - obviously - been working OK.

There's only 1 zone valve, from which I had assumed C plan. Could it be something else ?

WHere would the white go to ?

 

[BrianA]

check the boiler ch stat. also check the dhw sensor. is not keeping the boiler in dhw mode. just unplug. this would have the symptoms of the boiler constantly firing though.

The boiler isn't constantly firing, just as needed by HW demand. SO I guess it wouldn't be the dhw sensor ?

I'll check the stat, thanks.

 

[holty]

scrub that. actually dont think the burner fires on the greenstar. just moves the divertor when dhw is called for. and relys on the programmer to keep the store hot.