Aprilaire 220 Service Manual page 14

INDIVIDUAL UNIT SERVICE—MODELS 760, 760A, 768 & 700
WARNING: 1. 120 VOLTS may cause serious injury from electrical shock. Disconnect
power and shut off water supply before servicing or troubleshooting
this unit.
2. Rotating or electrical components may cause serious injury from con-
tact. Keep hands and face clear when checking operation.
I. LACK OF HUMIDITY
● Check The Home — See Pages 2 and 3.
● Check Furnace Operation — See Page 3.
● Check The Humidity Control — See Page 4.
● General Maintenance — See Pages 4 and 5.
1. AIR FLOW/ELECTRICAL COMPONENTS — To check the fan, disconnect power and
remove cover assembly from the base assembly. The fan blade should be tight on the
shaft and 1/3 through the orifice plate toward the motorboard. If not, reposition the fan
and tighten set screw to flat on the motor shaft.
Aprilaire Humidifier Control
APRILAIRE HUMIDIFIER
TRANSFORMER
(2 VA MINIMUM)
24 VAC
FURNACE
BLOWER
MODEL
50
120 VAC
HUMIDISTAT
FAN
24 VAC
SOLENOID
POWER
CORD & PLUG
TO 120VAC
FAN
60Hz POWER
MOTO
SUPPLY
NORTH, EAST
OR WEST SIDE
OF HOME
OUTDOOR
TEMPERATURE
SENSOR & SHIELD
*
OUTDOOR
TEMPERATURE
ABOVE EXPECTED
SENSOR & LEADS
SNOW LINE
Note: for installation in manual mode, replace
*
outdoor temperature sensor with plastic resistor
case and attach manual face plate. See form
#DP10005402 for complete wiring instructions,
included with each humidifier.
LEADS
DO NOT WIRE
TO APRILAIRE
SOLENOID
TERMINALS
LEADS TO
EXTERNAL
24 VAC
SOURCE
SOLENOID
4 PIN
Manual Humidistat
HUMIDISTAT
FAN
SOLENOID
POWER
CORD & PLUG
TO 120VAC
FAN
60Hz POWER
MOTO
SUPPLY
NOTE
SOME FURNACES ARE EQUIPPED
WITH ACCESSORY TERMINALS THAT
CAN BE USED FOR THE HUMIDIFIER.
THE RP MODEL 50 RELAY MAY NOT BE
NECESSARY IN THIS CASE. CONSULT
THE FURNACE MANFACTURER'S REC-
OMMENDATIONS FOR WIRING.
- 13 -
SOLENOID
4 PIN
24 VAC
24 VAC
VALVE
CURRENT SENSING
RELAY
COMMON
LEAD
FURNACE
BLOWER MOTOR
IMPORTANT
USE 120 VAC POWER SOURCE
OTHER THAN FURNACE
MOTOR CIRCUIT.
HUMIDISTAT