worcester greenstar boiler- no power, no lights

[Burnerman]

Hi Robbie
I'm looking at a wiring diagram for a Greenstar Utility...not your particular one unfortunately but one with a slightly higher output, so...
The front panel has a knob control on the left, and in the centre there are 2 resettable thermostats.
According to the diagram, the live entering the boiler (via an external 5 amp fuse) goes first into a manually resettable flue thermostat (front panel), then continues into an automatically resetting heating thermostat, (presumably hidden in the boiler casing somewhere) then into a manually resettable heating thermostat (front panel) before heading to the control thermostat (presumably the one with the knob, front panel).
After that, the live continues onto the burner connection.
It seems that all of the 3 thermostats must be conducting for anything to happen, so I think I'd be reaching for the multimeter and checking each one for continuity. There is no reference to a pcb but if there is one - which seems doubtful after all - it will be in the steel control box behind the main thermostat knob.
Cheers
John

 

[robbie77]

Hi John,

Top man thanks for that. I think that the 2 lives that I can get access to are buttons C and D (flue and Boiler Heating) and apparently can be reset.

I tried this but it was a feeble looking reset, a threaded bit of plastic on the back of a sensor with a small platic pin that I pressed inwards (no click or anything).

Can you think of anything that would prevent them from working considering the boiler hasn't fired in months?

Thanks again

 

[Burnerman]

Yes, those pop out resets don't have any positive feel in them, I agree....check for electrical continuity on each one...according to the diagram I have, the phials of these stats disappear into the depths of a recess in the boiler - and there are 3 of them, as I said. Each stat has a thin copper tube leading from the stat to the phial.
Each stat needs continuity for the boiler to start.
John

 

[robbie77]

Right I've done some quick continuity testing and it looks like there could be an issue with the Flue overheat thermostat. It has copper wire going from it that leads into a plastic sealed box that sits at the top of the boiler (luckily the most accessible).
So I guess I need to find out if its the switch or the copper wire that is at fault? I'm not sure where the copper wire is leading and what would cause the break in circuit?
It looks like the circuit going into it is ok but not going out.

Any advice on what to do next?

I feel like I have made some progress at least thanks to help from here!

 

[Burnerman]

If I understand you correctly, the bare copper wire is actually a very thin tube leading into the thermostat 'phial' - this is the thing that senses an overheat situation and switches everything off.
I suspect that this is the problem - according to the wiring diagram the flue stat has 2 electrical connections, and joining these together would bypass the stat altogether. In a normal situation there would be electrical continuity across the flue stat.
John

 

[robbie77]

If I understand you correctly, the bare copper wire is actually a very thin tube leading into the thermostat 'phial' - this is the thing that senses an overheat situation and switches everything off.
I suspect that this is the problem - according to the wiring diagram the flue stat has 2 electrical connections, and joining these together would bypass the stat altogether. In a normal situation there would be electrical continuity across the flue stat.
John

Yes John, there are 2 electrical connections, I think one is a live from the other thermostat and like you, I thought if I bridged the two connections to the switch it would bypass the flue thermostat. This would make sense as you said the burner would not run unless all the switches made a circuit.
So maybe there is problem with the phial in the flue? not sure but I will try and bypass first.

 

[Burnerman]

Yep, go for a temporary bypass, and good luck!
Have to vanish now, back Sunday!
Cheers John

 

[robbie77]

Well I fixed it by George!
Had a better day fault finding. It turns out that my initial testing was not as thorough as it should have been. I wasn't getting a good neutral reading it was around 190v so I tested back to the thermostat and opened up a rats nest of poorly installed wires that were loose and all over the place. Made good.
Now working like a dream. Heat! Heat! was the chant!

In case anyone reads this who has similar problems in starting their oil boiler I would recommend removing the burner box and testing the incoming connections there. On my boiler I only get a 240v to the live if the aforementioned thermostat sensors work, you also need a 240 neutral that I did not have. The back of the burner box has a diagram of which is which.

Sorry if I am telling grandma's to suck eggs!

Thanks to help and support. Much appreciated

 

[slapper]

Well I fixed it by George!
Had a better day fault finding. It turns out that my initial testing was not as thorough as it should have been. I wasn't getting a good neutral reading it was around 190v so I tested back to the thermostat and opened up a rats nest of poorly installed wires that were loose and all over the place. Made good.
Now working like a dream. Heat! Heat! was the chant!

In case anyone reads this who has similar problems in starting their oil boiler I would recommend removing the burner box and testing the incoming connections there. On my boiler I only get a 240v to the live if the aforementioned thermostat sensors work, you also need a 240 neutral that I did not have. The back of the burner box has a diagram of which is which.


Good for you,well done

Sorry if I am telling grandma's to suck eggs!

Thanks to help and support. Much appreciated

 

[Burnerman]

Yo Robbie
Good on yer mate and well done! Well pleased you're warm again
John

 

[robbie77]

Thanks guys.
Its amazing what a mood lift being warm is not to mention the removal of the pressure from her in doors!