Vokera boiler problem

[cbbr16]

Hi
I have a Vokera Excell 80SP boiler. The pilot was off two days ago ( the boiler had been working well since it was repaired just over a year ago, which costed me a few hundreds quids). I relighted the pilot, and it seemed working again when I tuned on hot water and central heating, but it just worked for 3 or 5 minutes, then stopped, then I tested it a few times, I found a few problems: no indication of temperature by the temperature guage, it dropped below the scale 0; just about 10 seconds, the hot water copper tube was very hot and the pressure gauge started rising, above the safety upper limit (1.5bar) just in few minutes. Can anybody tell me what’s wrong, and how to sort it out.
Many thanks

 

[bellairaphon]

overheat stat tripped out the boiler. is the flame lower on central heating than hotwater?

 

[cbbr16]

Just found out as soon as switch on the electricity supply, it starts firing up as if hot tap or radiator is open when hot tap and radiators all closed, then stops a few minutes later.

 

[glasgowgas]

could be you have a micro switch on dhw divertor valve stuck in "made" position, this would fire boiler, but because the pump is not running and no cold water is running through the heat ex, your boiler will heat up too quickly causing it to overheat,which kills the pilot light.

 

[cbbr16]

the pilot still lit, but the boiler won't fire up when turn on hot water tap. Switch off the electrical supply for a while ( about 5 minutes). it fires up at the moment the elecrical supply back on ( but it won't fire up if the switch-off back-on time is too short.

 

[glasgowgas]

if you don`t run a hot tap, does it run on central heating?

 

[DP]

If boiler runs on its own accord (no HW demand or timer not calling) switch indeed could be faulty BUT boiler will not fire if pump is cuffed.

Overheat would extinguish the pilot.

If temperature gauge fails to register. it is broken but boiler can still function without it.

What was done to the boiler for it to cost you few hundred quid?

Make sure power to the boiler stays on otherwise you will end up with an internal leak. Otherwise put out the pilot.

 

[cbbr16]

it runs both hot tap and central heating ok as soon as the power is swith on, the problems is the presure rises by 0.2 bar just in 5 min, and stops, won't fire up again, swith off power, cools down for few min, swith on power, it fires up .

 

[kevplumb]

the problems is the presure rises by 0.2 bar just in 5 min,

nothing unusual

 

[cbbr16]

did another test, turned the mode switch to hot water only with hot closed but central heating on, it run central heating when power back on.

 

[DP]

Could OP read the replies for answer to his last remarks. Reason for boiler running in CH mode (when HW only selected) has already been provided.

Can you post the reason for last repair costing what you mentioned in the first post?