Aprilaire 4655 Setup guide

English 1
Humidier
SAFETY AND INSTALLATION INSTRUCTIONS
Model 4655
Manual Humidier Control
THESE INSTALLATION INSTRUCTIONS
ARE FOR THE APRILAIRE® MANUAL
HUMIDIFIER CONTROL ONLY.
For AprilAire® Humidier installation, follow
AprilAire Humidier Installation Instructions.
B2204275B • 10007235 • 6.22
Product Info &
Digital Manual

2English
WARNING
ATTENTION INSTALLER: This product must be
installed by a qualied heating and air conditioning
contractor. Failure to do so could result in serious
injury from electrical shock.
1. 120 volts may cause serious injury from electrical
shock. Disconnect electrical power to the furnace
before starting installation.
2. Sharp edges may cause serious injury from cuts.
Use care when cutting plenum openings and
handling ductwork.
CAUTION
1. Do not set humidity higher than recommended.
Condensation damage may result.
2. Do not set humidity up to recommended levels
if there is condensation on the inside of windows
of any unheated living space. Condensation
damage may result.
3. Do not mount the Manual Humidier Control
on the supply plenum or duct. The unit cannot
withstand supply temperatures and will
malfunction.
4. Do not mount the Manual Humidier Control
downstream of the bypass outlet. False humidity
conditions will cause the humidier to operate
incorrectly.

English 3
TABLE OF CONTENTS
INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
LOCATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
GENERAL INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
INSTALLING AND WIRING. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
INSTALLATION TEMPLATE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
INTRODUCTION
The Manual Humidier Control (Part 4655) is designed
for low voltage service to control humidication
equipment. An increase in relative humidity (RH)
expands the nylon ribbon which opens the control
switch to stop operation of the humidier. A decrease in
RH reverses the process and closes the control switch.
SPECIFICATIONS
RANGE 15% to 50%
OPERATIONAL DIFFERENTIAL 8% RH NOMINAL
DIMENSIONS (inches)
Length: 5-1/8”
Height: 3-3/8”
Depth: 1-15/16”
ELECTRICAL DATA
• SPST Switch
• 2 wires
• 24 volts A.C.
• Maximum load
(contacts) 5.2 amps

4English
LOCATION
The Control can be mounted on wall in living space or on
return duct.
WALL MOUNT
• Locate on an inside wall of living area approximately
5 feet above the oor.
• Do not locate control in the direct path of drafts from
open doors and windows.
• Do not install where operation might be affected
by lamps, sunlight, replace, registers, radiators,
concealed air ducts and pipes, or room occupants.
• The basic rules for location of thermostats also apply to
humidier controls.
DUCT MOUNT
Locate on the furnace return air plenum or duct, at least
6” upstream of the humidier, humidier bypass ductwork
(if applicable) or fresh air intake ductwork (if applicable).
GENERAL INSTRUCTIONS
• Do not mount the Humidier Control on counter ow
furnace. Furnace malfunction will result in improper
humidier operation.
• Be sure the Humidier Control is installed on a 24 VAC
circuit only.
• Make sure no bare wires are exposed or insulation
damaged.
• Make sure all splices are mechanically and electrically
secure.
• To remove dirt or other foreign matter from the nylon
ribbon and control interior, dust lightly with a ne soft brush.

English 5
INSTALLING AND WIRING
WALL INSTALLATION
1. Select location for the Humidier Control on an inside
wall. Mount the Humidier Control in a location where
low voltage wires from the furnace area are already
in place, or can be easily run.
2. Drill a 1/2” hole into the wall at the selected Humidier
Control location.
3. Pull low voltage wires from the furnace area and
through the hole in the wall. Before mounting the
Humidier Control, the hole in wall should be plugged
to prevent drafts affecting the Humidier Control
reading. All wiring should conform to the National
Electrical Code and local regulations.
4. (See FIGURE 1) Gently pull knob A from Humidier
Control cover B. Cover is held in place by snap clips.
Remove cover by pulling carefully. Do not touch the
sensing element.
5. Pull low voltage leads through opening in base
plate D.
6. Attach wires to terminal screws on Humidier Control.
(NOTE: If wires are “bunched” between Humidier
Control and wall, base plate may become warped or
cracked and calibration may be affected.)
7. Remove the gasket (not required for wall mount).
Attach base plate with humidistat switch to the
wall using two screws E and two wall anchors F, if
necessary.
8. Reassemble Humidier Control cover by snapping
back in place. Press on knob.

6English
ANCHOR F(x2)
SCREW E(x2)
BASE PLATE D
HUMIDISTAT SWITCH C
COVER B
KNOB A
BASE PLATE D
FIGURE 1 – WALL MOUNT
90-1228

English 7
DUCT (SHEET METAL) INSTALLATION
1. Select Humidier Control location on furnace return
air duct.
2. Use the attached template to mark the duct
opening.
3. Carefully cut the opening in the duct.
4. (See FIGURE 2) Gently pull knob A from Humidier
Control cover B. Cover is held in place by snap clips.
Remove cover by pulling carefully. Do not touch the
sensing element.
5. Run low voltage leads to control location. All wiring
should conform to the National Electrical Code and
local regulations.
6. Attach low voltage wires.
7. Make sure that the gasket G is in place. Use four
sheet metal screws H (not provided) to mount the
Humidier Control in the duct opening.
8. Reassemble Humidier Control cover, guiding the
low voltage wires through the cover side opening.
Press on knob.

8English
SCREW H
(x4)
INSIDE OF
RETURN
DUCT
GASKET G
BASE PLATE D
HUMIDISTAT SWITCH
C
COVER B
KNOB
A
RETURN DUCT
FIGURE 2 – SHEET METAL DUCT MOUNT
90-1229

English 9
DUCT (FIBER BOARD) INSTALLATION
1. Select Humidier Control location on furnace return
air duct.
2. Cut a rectangular hole in the duct board, no smaller
than 5-3/4 inches long by 3-3/4 inches wide.
3. Cut a rectangular piece of sheet metal to t behind
the hole in duct board for mounting the Humidier
Control.
4. Use the attached template to mark the sheet metal
opening for the Humidier Control.
5. Carefully cut the opening in the sheet metal.
6. (See FIGURE 3) Gently pull knob A from Humidier
Control cover B. Cover is held in place by snap clips.
Remove cover by pulling carefully. Do not touch the
sensing element.
7. Run low voltage leads to control location. All wiring
should conform to the National Electrical Code and
local regulations.
8. Attach low voltage wires.
9. Make sure that the gasket G is in place. Use four
sheet metal screws H (not provided) to mount the
Humidier Control in the sheet metal opening.
10. Reassemble Humidier Control cover, guiding the
low voltage wires through the cover side opening.
Press on knob.
11. Secure the sheet metal plate inside the duct.

10 English
KNOB A
SHEET METAL
PLATE
CUT OPENING IN
RETURN DUCT
RETURN
DUCT SHEET METAL
PLATE
RETURN DUCT
BASE PLATE D
COVER B
HUMIDISTAT SWITCH C
GASKET G
SCREW H
(x4)
INSIDE OF
RETURN
DUCT
FIGURE 3 – FIBER BOARD DUCT MOUNT
90-1230