Worcester bosch greenstar danesmoor utility.... strange lockout issue

[Mark DM]

Hi. I have this Worcester oil fired boiler. 4 years old. Yearly serviced. A week before my last recent service it locked out. Pressed the reset and it started up and ran fine. However, over the 3 days prior to last Wednesday's service it locked out every day. The engineer checked it over during servicing and couldn't see any obvious issues. Cleaned the oil tank filter thinking maybe some oil starvation. Since he left its got steadily worse and locks out very often. The only way I can keep it running is to move the honeywell portable room stat to a small room, shut the door and keep it set low, about 17deg. It seems that as soon as a higher temperature is demanded and the requirement is to run for an extended period, it locks out. Wont reset until left for at least an hour. Same happens if there's a demand for hot water. Locks out after a few minutes. It's as if it can't cope with any higher heat demand over any extended period. Boiler stat is set at about 65deg. Pump runs normally. Hoping to get an engineer out under its apparent 7 year warranty but interested to hear of any suggestions of what could be going on. Did wonder if there's some kind of stat probe that may be faulty. Thanks for any input

 

[Bob Rathbone]

aper from the obvious issues of oil starvation, ignition failure and control unit, the capacitor on the fan/oil pump unit ages, slowly losing it's capacitance to such an extent that the motor will not start. However this is usually an issue with a cold boiler when the grease in the motor bearings is cold and thick.

 

[Mark DM]

Thanks for taking the time to reply Bob. It will start and run from cold. Temporarily overcoming the issue by ensuring it only has to switch on and run for a few minutes at a time by keeping portable room stat at 18 and shut in a very small space. It won't run for anything more than about 10 mins continuously without locking out. Limiting running time to a few minutes at a time has kept it going for about 36 hrs so far

 

[Bob Rathbone]

Thanks for taking the time to reply Bob. It will start and run from cold. Temporarily overcoming the issue by ensuring it only has to switch on and run for a few minutes at a time by keeping portable room stat at 18 and shut in a very small space. It won't run for anything more than about 10 mins continuously without locking out. Limiting running time to a few minutes at a time has kept it going for about 36 hrs so far

It does sound like fuel starvation, could it be that water has got into the fuel and frozen either uin the filter or in the pipeline. Another possible cause may be air being drawn into the fuel line by the suction of the fuel pump on the burner. This could be caused by a poor seal on the oil filter housing, if the 'O' ring was not changed with the filter. Is their any sign of a fuel leak from the filter bowl?

 

[BuildingMad]

Solenoid coil is my first check as they are a very common failure.
Always keep a spare; cheap & a five minute job to change

 

[Mark DM]

It does sound like fuel starvation, could it be that water has got into the fuel and frozen either uin the filter or in the pipeline. Another possible cause may be air being drawn into the fuel line by the suction of the fuel pump on the burner. This could be caused by a poor seal on the oil filter housing, if the 'O' ring was not changed with the filter. Is their any sign of a fuel leak from the filter bowl?

The engineer who did the service cleaned and blew out the filter with my airline. No leaks from the filter....and the issue was there prior to the filter clean out.

 

[Mark DM]

Thanks Bob and building mad for the suggestions.. the service guy is calling in this afternoon to further investigate and I hope, connect up on the phone with the manufacturer. I will pass on both of your suggestions .

 

[Mark DM]

Solenoid coil is my first check as they are a very common failure.
Always keep a spare; cheap & a five minute job to change

Hi building mad, just to update that the bosch engineer did as you suggested and replaced the coil, also a solenoid and the pump for good measure . He did also think it was the coil as they can break down and produce the symptoms I was experiencing. Good call!
Regards