Heating Engineers!

Hi, you wonderful people!

Woke up this morning to discover no electric. Turned out the main breaker had tripped. Narrowed down the fault to the spur for the boiler. Funny thing is that the fault must have occurred between midnight and 7 in the morning. During these times, the boiler is effectively off at the time switch and not cold enough to trigger the frost stat.

Any idea what might cause what is presumably an earth fault in a "dormant" boiler (Worcester Danesmoor oil fired)?

I'll get a closer look at it when I've moved the bus out of the way - currently charging the battery!

 

The first thing you need to check for is water leaks inside the boiler casing or in the wiring at the spur

 

It’s is a Danesmoor, a Danesmoor Heatslave or a Greenstar Danesmoor?

Does it use a Worcester plug in timer or external controls?

 

This ^^^

The boiler, via a fused spur, will have a permanent live feed waiting for the timer/stat inputs to fire up. Must either be water tracking to earth, or a loose cable that has overheated and is now tracking to earth.

 

Obvious question, but have you tried standing in front of it, sucking your teeth?

 

Probably when he was cold..

 

Arms crossed?

 

"That'll all have to come out"

 

He's told himself he won't be able to get round to it till at least a week on Tuesday

 

Got another job on in the kitchen?

 

Good call!
When I finally got the bus out of the way and took the front panel off, there was a small leak from the water pump top connection. By the amount of scale around it, its been like that for some time. It's possible that a drip might have landed in something electrical. Strangely, disconnecting the frost stat stopped it tripping. Gave everything a good dust down, had a fan heater blowing at it for a while, put it all back together and it's working fine now.

 

Must be at least 25 years old. Not sure of the model just now as I left the instructions in the garage. It is controlled externally by a Honeywell thingy. Here's the circuit, using a Dunsley Baker system:

 

Must have been something like that but, touch wood, seems to be working ok now.

 

Many thanks for the suggestions. Maybe it was peeing in the cistern that cured it, or was it the chocolate Hobnobs with the tea?

How much should I bill myself for sorting lt?

 

£80 callout, plus biscuits.

 

Probably needs a strip down when its warmer as the damp trail that tripped the breaker may now be a path of crusty metal salts thats just waiting for humidity to increase a bit again.. you probably havent had the last failure for the year... like when the weather warms up boiler cycles less frequently and cools down more between firing cycles..

 

I’d just like to point out that if it’s a std danesmoor then it won’t have a P/Live. Those boilers don’t have a pump over run unless they have the on board plug in controls. In which case they have a separate “post purge board”.
As this one has external water pump and controls it will be switched live only. This is why I asked what model it is.

Up there for thinking and down there for dancing.

 

You've most likely found your source of the tripping - something to do with the frost stat.
Where is the frost stat installed? You mentioned that it trips sometime between midnight and 7am, that is probably the most likely time period for a frost stat to activate?

 

Total for the job £125 then not including tea money.

 

It's a Danesmoor 15/19 and does have a permanent live and a post purge unit. It has an internal water pump to circulate hot water into the system when the boiler is on. The c/h is circulated by a separate pump by the Dunsley Baker unit.