Kidd VHE will not fire and locks out for no obvious reason

[cjcoffin]

We have a Kidd VHE boiler with EDGB Inter 2011 burner, Satronic control box and Danfoss BFP21L3 oil pump.

This morning the c.h. did not come on and I found the boiler had locked out. On pressing the reset button the motor runs for 14 secs without firing and then locks out again.

After various checks showed nothing obviously wrong I checked the start up sequence with the burner off, motor disconnected and a bleed pipe on the pump bleed nipple, and the following happens:

1. On pressing the reset button the ignition transformer buzzes and a heathly-looking blue-purple spark appears across the electrodes

2. After 6 secs the solenoid valve clicks and oil runs out of the bleed valve

3. After a further 8 secs the control box locks out and everything stops.

It cannot be the photocell as the boiler never fires in the first place. I have also checked the filter (which was clean), and with the stop tap turned back on there is a plentiful flow of clean oil with no bubbles from the filter housing. I have also cleaned the ignition electrode insulators and changed the nozzle for the one left at the previous service all to no avail.

With the pump running and the bleed valve open the flow is not much greater than the flow under gravity which suggests some kind of pump failure - what could have caused the pump to pack up suddenly overnight?

I should perhaps say that we had 500 litres of oil added to a nearly empty tank last week but after this the boiler has been running fine until this morning.

Any suggestions as to what might be wrong or what other tests I can do would be much appreciated

 

[cjcoffin]

Have just found this post which suggests a worn/failed oil pump drive dog could be the problem.

How easy is this to replace?

 

[oilhead]

It sounds as though the oil pump has failed. There is asmall possibiltty that the drive dog has failed. Best to call in a professional who can assess and repair what is necessary

 

[cjcoffin]

Thanks for replying. It was the drive dog so I am glad I checked it before calling anyone out over a holiday weekend. It had split in two places, which I have held together with a binding of monel seizing wire until the new dog arrives in the post (all £1-70 worth!).

 

[Agile]

Well that was a clever and perhaps novel way to keep it going.

I would probably have tried to turn up a bezel to hold it together but that sounds far quicker and easier.

Tony

 

[simond]

I take it the oil pump turned OK when you dismantled the burner?

The oil pumps on Kidd Boilers get a hard life because Mr Kidd runs them at higher pressures than typically used.

 

[cjcoffin]

Well that was a clever and perhaps novel way to keep it going.

I would probably have tried to turn up a bezel to hold it together but that sounds far quicker and easier.

Tony

Your bezel would probably have lasted longer! The temporary repair has now packed up but at least we had heat over the holiday cold snap and it confirms the pump itself is OK. The new dogs should arrive in tomorrow's post and with the sunny weather I am getting free hot water from the solar panels in the mean time.

I take it the oil pump turned OK when you dismantled the burner?

Yes, it turns quite nicely by hand, and subject to what I find when I fit the new dog I am hopeful this is all it will need.

The oil pumps on Kidd Boilers get a hard life because Mr Kidd runs them at higher pressures than typically used.

That might explain why the previous owner of the house left us with the instructions for two other pumps, so it appears to be on the third one since it was installed in 1995. Compared with the rest of the boiler it certainly looks very new and shiny.

How long do they usually last and what are the usual symptoms/failure mode - do the internals just wear so the clearances increase to the point it ceases to provide enough pressure, or is there something more subtle to watch out for?

Thanks everyone for your useful replies.