On Oct 31, 10:26 pm, "Zyp" wrote:
wrote:
I have a 14 year old Rudd hot air gas furnace in a basement with a
--lines deleted
to eliminate that as an issue, which I will.
He says if that's not the problem the next thing they will have to do
is replace the blower motor.

Do you agree with this diagnosis?
Is it safe to leave the pilot funnel removed with the furnace
operating?

Thanks much

You have a damaged or ruptured fire box [heat exchanger.] Call your local
HVAC guy and have him pull the blower housing and inspect the heat exchanger
from there. If he can't find anything, there is a new product on the market
that can be "sprayed" into the firebox chamber and detected using a halon
[freon] detector in the area I just mentioned.

The problem occurs after the heater has been on for a bit, and the rupture
opens, letting in blower air. When the inducer stops, the blower creates a
positive pressure in the heat exchanger and blows the pilot out.

Generally, on a furance that has air conditioning, and a standing pilot,
there exists excessive condensation around the pilot area and, as a result,
the heat exchanger fails [rusts through]. This is on older furnaces. Newer
furances will not have this problem because there is not a burning pilot.

Replacing the furance will reduce your utility cost of operation saving you
money. Probably paying for the change out in less than 10 years depending
on the cost of fuel in your area.

--
Zyp- Hide quoted text -

- Show quoted text -

All:
Thanks everyone for your responses.
FYI 1. The furnace is in a large undisturbed basement with no drafts,
only one door (almost always closed), closed windows, and nothing near
or covering the vents in the furnace housing. 2. The pilot orifice
appears clean.

Zyp
You are correct, the furnaces are also used for air conditioning.
There is a condensate pump, not sure if it is working.
There is no external visible sign of rust near the pilot or anywhere
else on the furnace, except on two of the three bolt heads securing
the inducer blower to the heat exchanger.

Below are some other symptoms and additional tests I performed after
reading your response.
Do these symptoms confirm your diagnosis?
If so I'll skip the $180 flue cleaning and have the heat exchanger
inspected.

- I hear a "puff" sound when the power is cut (and inducer blower and
main blower turns off).
- When I put a lighted butane lighter in three gas jets I tested (even
ones several inchces from the pilot) and cut the power, the flame on
the lighter goes out instantly with the "puff" sound. This occurs if
the furnace has been heated only for 10+seconds.
Also, when covering the hole on the inducer blower where the funnel
tube above the pilot normally connects, there is no significant
sensation of back pressure coming from the inducer when the power is
cut.

Thanks for your kind input
Mike


PS There are no signs of external rust in the pilot/gas jet area
(except two of the three draft inducer/blower screw heads are rusted)
or on the external surfaces of the furnace. However, there is rust on
the ground below the condensate pump which was replaced a few years
ago, and rust is possible in the water coming out of the condensate
pump (there's a clear plastic flexible tube but its discolored brown
from age so it's hard to tell what's brown and what's rust).