Aprilaire 448 owner manual Figure B

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(Table 3) Outdoor-Indoor Relative Humidity

Outside Temperature

Recommended RH

 

 

+40°

45%

+30°

40%

+20°

35%

+10°

30%

25%

–10°

20%

–20°

15%

 

 

The humidistat is a precision instrument that can be used to determine the RH accurately in your home during the winter. Turn the dial to the lower setting, then reverse the dial direction slowly until you hear the solenoid valve “click on”. At this point, read the RH on the dial. This will be very close to the actual RH in your home. (See Figure B)

(Figure B)

MANUAL MODE

To check the humidifier operation, set the knob to “test”, make sure that the water saddle valve is open and that there is electricity to the unit. Generally, the furnace blower motor must be operating for the Aprilaire Humidifier to function. After the humidifier has oper- ated for one minute and water is entering the unit and coming out at the drain, reduce the humidistat setting to the recommended inside relative humidity, depending on the outside temperature. DO NOT LEAVE IN TEST MODE AS HUMIDIFIER WILL NOT OPERATE. Follow the suggested settings prior to a drop in the outside temperature.

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Contents Automatic Humidifier Introduction Principle of Operation Page Automatic Mode Manual Mode-see pg Operation GuideFigure a Outdoor Temperature ºF Setting Dial % Relative Humidity GuideFigure B III. Effect of Water Characteristics IV. Annual Maintenance Inspection and Service Instructions Model ForMaintenance Instructions For Models Reservoir Pump Sections Models Model Model Limited Warranty Aprilaire Zone Control Systems Aprilaire Fresh Air Exchangers Electronic ThermostatsService and Water Panel Replacement Record DP #10005406