On Fri, 9 Sep 2016 15:37:02 -0400, Ralph Mowery
wrote:

Jeff I think you are mixing up the AC and DC power formulas.

Oops. Y'er right.
Big rush - No time - No brain - No excuse.

A quick check of the Goyen catalog shows they draw about .05 to .07 Amps
depending on the coil at 240 volts.

Ok, that's better and less than the 5A fusing current for #34 awg.

That is around 10 to 16 watts. The DC resistance of the coils was not
given. The coils on many of the valves can be changed to several
voltages.

10 - 16 watts might get the coil quite warm if energized continuously.
Probably not enough to melt solder, but certainly will add a few
degrees to the heat from the furnace.

I don't think it's overheating from the furnace or the warm coil. It
will get hot, but not enough to melt solder. Since various other
solenoids have failed in the same manner, I don't think the failures
are caused by some kind of soldering defect. The long time that it
takes to fail might be the copper wire slowly dissolving in the
solder. However, my limited experience indicates that most of the
damage occurs immediately during soldering, not many months later.
With a 5A fusing current and the rather large inductance of the
solenoid, I don't see a high current "surge" fusing the #34 wire.

Offhand, I was thinking something else might be happening here.
Something like a sharp edge on the solenoid terminal slowly cutting
its way through the copper wire every time the solenoid is energized.
It might be 50 Hz vibration work hardening of the wire causing
embrittlement. However, these are unlikely to have also occurred in
the other replacement solenoids, that also failed. It might be the
difference in coefficient of thermal expansion between the epoxy and
the copper wire. Usually, some paper or tape wrapping will provide
room to expand, but again it would be an amazing coincidence if the
same problem appeared in a competetors solenoid.

That leaves external influences, such as line voltage glitches and
surges. Get your Dranetz power quality monitor/logger back, borrow
something, or just setup a data logger on the AC line.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558