aquastat problem

dan g

Dec 4, 2006

From the testing and examination of my aquastat in my
Bryant boiler, gravity, dual supply/return system with
large iron piping (1968 vintage) I have concluded that
the bulb no longer expands and contracts properly to
close/open microswitch. Viewing the
brass/bronze/copper bulb, it appears to me that it should
be a bulletproof component. However, I have been
unable to affect any switch function with
application/removal of temperature to bulb. Microswith appears to function fine and elect circuit opens and closes with dial adjustment.

Question:

Does this component periodically fail after extended
service?

Is it critical that the immersion well (I think that
is proper terminolgy for the horizontal orifice that
retains the bulb on the upper part of boiler) contain
some type of thermal conductor such as a special
grease or ??? to conduct heat exchanger temperature to
the bulb of the aquastat? My well is dry and shows no
evidence of any residual fluid/grease.

The aquastat is Honeywell part # L 4080X 1005 1

Is this a good part # and are they still available?

It spooks me when my wife gets the itchy hand (cold
feet) to dial in a few extra degrees in our drafty old
house and the boiler sends (slowly) hot water
throughout the system and the burner does not shut off
until the original Honeywell thermostat on the main
floor sees sufficient heat and shuts off the .5 volt
current to the burner valve. By this time the entire
system has developed so much thermal inertia that the
house temp will rise well beyond the originally
desired temp. I can only toss and worry on those
sleepless nights wondering and envisioning the results
of cast iron radiators filled with water exceeding 212
degrees when the boiler is in the "I think I can"
operating plan.

I guess that's why a functioning aquastat has so much
logic associated with it's place in the system.

Appreciate your advice.

realolman

If it don't work

I'd git a new one.