On Mon, 03 Dec 2012 09:19:32 +0000 (GMT), "Dave Liquorice"
wrote:

On Mon, 03 Dec 2012 07:58:35 +0000, MM wrote:

No/insufficient oil.

There is plenty in the tank.

But is there a big enough hole down the supply pipe? If it's been well
below freezing for a while I'd suggest slush in a low point of line, that
can stop enough oil getting to the boiler. Has the line been cleaned? By
that I mean disconnected at both ends and a wodge of cloth on a wire
pulled through in the same direction a few times. Just flushing through
with oil won't get suffcient flow to purge water or muck from a low
point. BTDTGTTS...

Filters clean, no blocked orfices in filter housing, same with the fire
valve? Doesn't take a very big flake of paint or insect carapace to act
as a butterfly valve over/in a small hole. Such a little bit can take a
while to be drawn to the place where it causes problems then fall away
again once the flow stops.

Engineer has checked the above exhaustively over the past month and
cleaned whatever components needed cleaning. New transformer, control
box, solenoid and photocell fitted in the last two weeks. The pump was
replaced in 2010 because it was diagnosed "noisy".

New jet?

No fan can be heard to start. There is NO noise of ANY kind when the
LED comes on. I have had the boiler cover off and stood in front of it
listening intently for any signs of life. Zilch.

So it looks like it is powering up in "lock out". Fairly that state is
remembered across complete power downs, that would be the safe thing to
do.

Spark

Would one hear that sparking?

Possibly, the noise of the fan can mask it.

There IS no fan noise! There is *no* noise of any kind. The LED on the
DKO970 comes on. That's all.

When the boiler starts successfully (on its own), the LED does not
come on at all. There are a few seconds which elapse since the Danfoss
timer triggered its ON event, then the fan starts, then a few seconds
later the burner starts and everything is hunky dory.

But it's when the boiler *does not* start, that's when there is NO fan
noise, no other noise, no other signs of life -- and then the LED
comes on and stays on. It's as if you had an LED wired across a
battery through a resistor and simply completed the circuit. The
entire boiler is otherwise dead.

Should start about 10s after
the fan and last about 5s before it decides that there is no flame and
locks out. Flame detection turns off the spark.

Yes, that is how it happens (approximately) when it starts
automatically. I do hear the fan noise. I hear it even from outside
the garage with the boiler cover in place. Hearing the fan start is
always indication to me that the burner itself will fire in the next
few seconds, and it *always* does. It's when the fan doesn't start and
the LED comes on, that's the mystery.


Fuel valve(s) open

Ditto?

Doubt it, never heard it on ours, to much other noise. An acoustic probe
on the right bit might pick it up.

When the LED first lights up, it's as if the sequence you describe
isn't even starting at all -- as if there is an "OK" box waiting for
a click in Windows to acknowledge something!

Or the previous shutdown was a lock out and is remembering that state. As
almost everything else has been changed recently I'd be looking at a
complete strip down and check for free flow of oil through of every
component in the fuel line and all sections of the line itself are clear
of muck/water. Any flexible hoses, has that been changed?

Dunno about a *complete* strip down, but he has had the whole caboodle
in bits at least once. He checked for no water in the tank, but the
actual line itself has not been removed/blasted through. Perhaps it
should? The distance between the boiler and the tank is approximately
12 metres. The boiler is mounted on/in the outside garage wall, the
pump being approximately 190cm above the base of the garage.

The hose has been replaced.

The motor, however, hasn't been changed. Allan Mac just now mentioned
a possible problem with a 'tight' spot on the motor bearings.'


As the boiler starts and behaves everytime the lockout is cleared I don't
think there is anything fundemental wrong with boiler. It looks as if
it's going into lockout at some random/indeterminate period after running
for a while. This could be a fault in the shutdown procedure, does the
boiler have a permenant live or just a single "call for heat" live? I
don't find that very likely TBH.

I don't understand that last question. Don't have the technical
knowledge.


I suspect fuel starvation hence the full dismantling and checking of the
complete fuel line. Sorry about the thoughts being a bit random, sure you
can sort 'em out though.

Yes, many thanks, I'll put all of the above points to the heating
engineer.

I just did a test start (manual override on the Danfoss) and the
boiler started fine. I'll leave it on for 15 minutes, then wait a
couple of hours and repeat the test.

MM