On Fri, 20 Dec 2013 08:00:48 -0600, philo* wrote:
On 12/20/2013 07:51 AM, micky wrote:
On Fri, 20 Dec 2013 06:26:29 -0600, philo wrote:
On 12/19/2013 09:43 PM, micky wrote:
On Thu, 19 Dec 2013 21:51:05 -0500, wrote:
As I said, I was looking for a problem that would let it run for 2 or
6 hours, but then fail, and I'm wondering if perhaps the ignition
TRANSFORMER could fail when it gets hot enough?
P&M
I was thinking, assuming the furnace works fine now, about whether to
save the old transformer, and it suddenly dawned on me.
How come the transformer failed at the same time I replaced the
nozzle? And the answer is almost obvious, even if it took me 2 days
to think of it. For the last several years, the furnace has probably
never run more than 20 minutes at a time, because I turn it on in the
fall when it's cold but not that cold out, and from then on the house
is 68 or 70.
It's only because the nozzle failed that the furnace was off for 16
hours or more and the house got down to 62 degrees that it took so
long to warm back up, 80 minutes, plus soon after that 20 more
minutes, almost 2 hours of running, enough to get the transformer hot.
And again after it failed, it was off for -- I forget -- 16 or even 20
hours, and the next day I started it up and it ran for maybe 3 hours
with breaks or maybe 6 hours, and by that time it was hot and it
failed again.
The "new" transformer is better than the old, but I could put the old
back in now and it would work too, because the house is 68 degrees and
the furnace only has to run for a few minutes to keep it that way, not
enough time for it to get hot enough to fail.
So what I should have done is clean the furnace in the fall so it
woudn't have to go without running on a 32 degree day like Tuesday
was.
And if this transformer fully fails in the winter, and the house is
cold, I can go back to the first xformoer by letting it warm the house
4 degrees, then letting the xformer cool for 4 or 5 hours, then
warming the house another 4 degrees. etc.
It's almost as important to me to solve these questions as it is to
have heat, and I think this one is solved.
Twice I've taken 2 month** working vacations, November and December,
drained the pipes and turned the thermostat down to 50 or 45. It had
no trouble warming the house up when I got back because the
transformer was fine then.
**I take few vacations, not even one a year, but when I do they are
usually long.
The problem could be caused by a faulty transformer /or/ insulators that
have broken down. I gave you what I thought was the most likely cause
and certainly a very inexpensive option.
I wasn't complaining. I'm grateful for your help, and to all who
replied.
Part of normal maintenance on an oil burned is replacing the
insulators...but a transformer replacement is not part of a normal PM.
Of course not. But I think it accounts for the problem If I had
set the thermostat for 64, and then 12 hours after that, 68, it might
have worked. If it didn't, I could start over by setting it to 63,
then in 16 hours to 66, then in 16 hours to 68.
I'd actually enjoy the chance to try that some time. (but I know
myself and I won't unless I'm forced to.)
The transformer is in a sealed metal box, so I can't look at it. I
can measure the resistance of the secondary, about 20K ohms, but
measuring the primary is more work and the transformer would be
cooling off while I did it. Well, it's only 5 or 10 minutes and I
should have done it. If it were open, I would have known the problem
right away. Next time I'll do better.
(The transformer is probably easier and less dirty to change than the
nozzle. And no chance of spilling fuel oil. Loosen one bolt on the
right side, move the piece of metal that holds it shut, lift the
xformer on the right side so the chamber underneath is uncovered,
disconnect its two wires which are attached, each to two other wires,
by wire nuts, slide out the electric eye/flame detector from its slot
on the transformer base, Put the transformer back. Take out two
more bolts on the left side that hold the hinges, and lift the whole
thing out. Reverse to install. )
This also means it was a good choice to salvage the burner my neighbor
took out.
Anyway, if the furnace runs normally for the next few days I'd say you
should be OK...but as a precaution I'd still replace the insulators next
time you work on the unit.
If you read to the bottom of the last post, I said I would, and I
will. :-)