Aprilaire 220 Service Manual page 4

Listed below is the square footage that each unit is designed to handle:
Chart A
Square Feet Capacity *
Loose House
Average House
Tight House
Chart B
Square Feet Capacity *
Loose House
Average House
Tight House
*Based on 8' ceiling height.
Models 220, 224, 400, 440, 445, 445A, 448, 550, 550A, 558, 560, 560A, 568 and 600
Total Static Pressure Drop Across Supply & Return Plenum ....................................0.2"
(1) Calculations are based on:
a. 120ºF Plenum Temperature
b. 70ºF and 35% R.H. Indoor Air
c. 20ºF and 70% R.H. Outdoor Air
d. Internal Moisture Gain = 1 lb/hr.
e. 70% Blower Operation
f. 55ºF Service Water Temperature
Recommended Settings — It is recommended that the temperature-humidity table noted below
be followed. Square feet capacities are based on these settings
OUTSIDE TEMPERATURE
+40ºF.....................................................................45%
+30ºF.....................................................................40%
+20ºF.....................................................................35%
+10ºF.....................................................................30%
–10ºF.....................................................................20%
–20ºF.....................................................................15%
Excess humidity may result in condensation on doors, windows, inside of outer walls, and on
other exposed surfaces. If this exists, reduce the setting on the Control.
Furnace Operation — Plenum mounted humidifiers are dependent upon heat for evaporation
and normally extract this heat directly from the hot air in the supply plenum. With self-contained
units or power units applied to the return air plenum, heat required for the evaporation process
can be obtained directly from service hot water.
Lack of humidity complaints can often times be traced to oversized furnaces where the burner is
on only for a short period of time. With installations such as these, it is our recommendation that
the furnace blower be adjusted for longer operation or the blower be operated continually off the
manual setting so the humidifier can function over a longer period of time to satisfy the humidistat.
In many installations, the water supply may be switched from cold water to service hot water to
supply the necessary heat required in the evaporation process. This has also been a suggestion
when the sizing for the humidifier is marginal.
Multi-Speed Furnace Blower Motors — Furnaces with a multi-speed blower may damage the
humidifier. Premature component failure may result when interfacing Aprilaire Humidifiers with fur-
naces having multi-speed direct drive motors or having other than 120VAC. Use the RP Model 50
Current Sensing Relay.
Low Voltage — Disconnect electrical power. Check for low voltage in the house and at the unit
itself.
Model
760 (1) /760A (1) /768 (1) /700 (1)
1,050
2,100
4,200
Model
220 (1)
600
1,250
2,500
0ºF.....................................................................25%
Model Model
110 (1) 112 (1)
800 1,150
1,600 2,350
3,250 4,750
Model Model
224 (1) 440 (1)
1,000 1,000
2,100 2,100
4,200 4,200
(2) Calculations are based on:
a. 70ºF and 35% R.H. Indoor Air
b. 20ºF and 70% R.H. Outdoor Air
c. Internal Moisture Gain = 1 lb/hr.
d. 140ºF Service Water Temp. @ 6 GPH
e. Continuous Operation at 150 CFM
RECOMMENDED HUMIDITY
- 3 -
Model Model
350 (2) /360 (2) 400 (1) /560 (1) /560A
1,100 1,000
2,250 2,100
4,500 4,200
Model Model
445 (1) /445A/448 550 (1) /550A
1,000 750
2,100 1,500
4,200 3,000
(1) /568 (1) /600 (1)
(1) /558 (1)