Remove the furnace humidifier that's not working
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Photo 1: Disconnect and remove the furnace humidifier that doesn't work
Remove the screws from the bottom of the old
humidifier. Then unscrew the fasteners at the top. Tilt
the top out and lift it off the duct or plenum.
Furnace humidifiers are pretty simple gadgets. When they
Stop working, the cause is usually a clogged or burned-out solenoid
water valve or a bad drum motor. You can replace those
parts yourself—if you can find them at an affordable price.
The price of the parts for a humidifier that’s 20 years old or
older can be shocking. In that case, you may be better off
replacing the entire unit with a newer and more efficient
model. Many of the newer models
come with a digital humidistat and
automatic outdoor temperature compensation
(such as the Honeywell No.
HE 225 DG 115; about $153 from discounthumidifiers.com). The compensation feature
automatically dials down
humidifier output as outdoor temps
drop. That reduces any condensation
on your windows.
If you can operate tin snips and read
a wiring diagram, you can do the entire
job yourself in about two hours.
Turn off the power to the furnace
and humidifier. Next, disconnect the
round bypass duct (if equipped) coming
into the old unit. Then turn off the
water valve and disconnect the old
water line. Disconnect the wiring to
the solenoid valve and humidistat and
remove the old furnace humidifier (photo 1).
Install the new furnace humidifier
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Photo 2: Cut the new opening
Slice an opening into the new metal by
hammering the narrow edge of a screwdriver into it.
Then jam tin snips into the “slice” and cut out and
along the edges of the trace. Leave the corners for
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Photo 3: Install the bypass
Install the summer/winter
damper (provided with the new furnace humidifier)
and insert the bypass duct. Secure it
with sheet metal screws.
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Photo 4: Install the outdoor temperature sensor
Connect the thermostat cable to the
outdoor sensor. Then push the extra wire
back into the hold and caulk the hole.
Mount the sensor to your house.
Refer to the installation manual and
compare the new opening size to the old
opening. If the new humidifier requires a
smaller opening (most do), you’ll have to
make an adapter plate. Cut a piece of
sheet metal to completely cover the old
opening. Attach it with No. 6 x 1/2-in. self-drilling
sheet metal screws. Then trace
the new opening onto the plate, making
sure your lines are level. Cut the new
opening (photo 2). Use caution to avoid
damaging the A/C coil. Hook the bottom
edge of the new humidifier onto the
opening and tilt the top toward the duct.
Level the unit and secure with self-drilling
sheet metal screws. Then attach the
bypass duct (photo 3).
Locate the new humidistat on the return
air duct. Then run 18-2 thermostat cable
to a shady non-south-facing side of the
house for the outdoor temperature sensor.
Mount the outdoor sensor (photo 4).
Connect the water line to the solenoid
valve and hook up the humidistat wiring.
Turn the power back on and test the