My house has a basic HVAC system. We have a gas fired furnace in the
basement and central air installed with the furnace. The evaporator A
coil sits in the warm air plenum above the furnace. The Condenser sits
outside by the back door. The whole setup of furnace and air conditioner
is Lennox and about 5 years old - installed in the summer of 2016. The
previous furnace was Lennox and was installed when the house was new in
1981. The AC was added later in the summer of 1984. It worked fine and
was still working fine when we replaced it, primarily to get a higher
efficiency furnace.
The furnace sits near the south wall of the basement and there is a
rectangular duct above the plenum on the unit to feed warmed or cooled
air across the basement from which smaller round ducts carry the air to
the rooms on the 1st and 2nd floors - 2 storey house. There is also a
rectangular duct that provides a cold air return to the vertical duct
that feeds air through the filter at the floor level to the blower in
the bottom of the furnace.
All very common - nothing unusual.
The current system appears to be working fine. The house is cool and the
compressor turns on and off like it should.
However, we are experiencing an issue that we have not seen previously.
The cold air return duct extends from the furnace north across the
basement ceiling. It also extends south but only for a couple of feet
and there are round ducts off of it to pick up air from upstairs. The
issue is that we have water dripping out of the rectangular cold air
return duct on the short side of the furnace. We do not believe we have
ever experienced this before. The electric hot water tank is below the
duct and we have a rectangular plastic wash basin about the size that
fits in a double kitchen sink sitting on top of the hot water tank. I am
emptying it 2 or 3 times each day with and inch or two of water in it.
That means it is a fairly significant drip. I can install a drain on the
duct to take the water down to the floor level and over to the sump pit
but I would like to confirm the source of the water. I have to assume it
is just condensation forming on the inside of the ducting.
I have looked all over above the cold air return duct and there are no
leaking water pipes or drain pipes that I can identify. I drilled a hole
into the cold air return duct near where it drips and fed a boroscope
(sp?) into it to have a look and I see a little moisture but no puddle
and no frost or ice forming on the metal ducting.
Water does not appear to be flowing down the cold air return duct to the
bottom of the furnace, or at least not significantly. The filter is not
wet except for maybe 3/4" on the one lower corner. I have pulled the
cover off of the furnace and see no evidence of water infiltration.
I may drill a couple more holes so that I can look into the plenum above
the furnace to see what the evaporator looks like.
We have had hot weather (for us anyway). Today it is 30C which is about
86F. It is humid today as we have had some rain in the past few days. It
has been warm throughout most of July but it was very dry as we had not
had much rain. We were experiencing the water dripping when it was dry
outside as this has existed for all of July.
We also run a dehumidifier in the basement to keep the moisture level down.
We have been in this house since 1981 and have never had this issue
before to our knowledge. Certainly not to the extent we have it right
now in any event. I don't go back behind the furnace all that often so
it might have dripped before but if it had done so at the level it is
doing now, it would have flowed out to where it was obvious.
Anyone have any thoughts on the issue?
Randy
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