Aprilaire 400 Troubleshooting Guide download pdf (Page 3)

STEP 12: Humidifier Wiring

Strip the wires used for all the Humidifier Control

terminal connections 1/4 inch.

• If FURNACE ACCESSORY TERMINALS are used, wire the solenoid

valve in series with the “H” terminals on the Humidifier Control

without using a Model 50 Relay. See furnace manual for operation

of accessory terminals. (Figure H)

• If an EXTERNAL TRANSFORMER is used, a Model 50 Current

Sensing Relay must be connected to the solenoid valve and the

“H” terminals on the Humidifier Control to allow the humidifier to

operate only when the blower is on. (Figure I)

Wire the Model 50 Relay into the “H” circuit only.

Bypass and Power units are wired to the AHC in the same fashion.

System Checkout

1. For system Test/Reset, be sure that 24 VAC is applied to the “R” and “C”

terminals of Humidifier Control.

2. Snap the door back onto the Humidifier Control Base.

3. Activate furnace blower and be sure thermostat is calling for heat.

4. Rotate the control knob of Humidifier Control clockwise to the “Test/Reset”

position. When the knob is set in the “Test/Reset” position, the green

“Change Water Panel” light will blink. Make sure the knob is not left in the

“Test/Reset” position when the installation is done. Rotating knob to test

position resets the water panel change timer to zero. The Control must be

energized to reset the Water Panel Indicator.

5. If all is set up properly, you should be able to hear the solenoid valve click

open. In “Test/Reset” mode, the Aprilaire Humidifier will operate for 1 minute.

6. If the humidifier does not activate with the Humidifier Control in

the “Test/Reset” position, refer to troubleshooting guide.

7. Setting the Humidifier Control:

• If home is occupied, set Humidifier Control to “Normal”

(For Manual Operation, set to 35%)

• If home is vacant, set Humidifier Control to “Off”

8. Inform homeowner to refer to the Aprilaire Owner’s Manual for the initial

adjustment period.

9. Make sure the Red Diagnostic Light is not lit. If the Red Diagnostic Light is

lit, re-check your wiring. If the Red Diagnostic Light does not go off, replace

the Humidifier Control with a new unit.

Humidifier Control Troubleshooting Guide

Applies to both Automatic and Manual Operation unless indicated otherwise.

SYMPTOM

Humidifier does not

operate in “Test” mode

TROUBLESHOOTING PROCEDURE

• Make sure furnace blower is operating and thermostat is calling for heat.

• Make sure the Outdoor Temperature Sensor is connected to the “ODT” terminals of the control. (For Manual Operation,

make sure Manual Mode Resistor Case is in place of the Sensor).

• Check main wiring diagram for correct Humidifier Control installation.

• If connected to a Model 400 Humidifier, make sure both floats in the bottom of the scale control insert are in the down

position. If necessary, dump out water to lower floats.

• Check voltage at Humidifier Control “R” and “C” terminals. Voltage should be 22 VAC minimum – 30 VAC maximum.

• Check Model 50 Current Sensing Relay (if used) for correct installation (see Model 50 instructions). Do not use Model 50

Relay in transformer circuit or “R” and “C” circuit of Humidifier Control. Model 50 relay is to be used in the “H” circuit only.

• In “Test” mode, humidifier will operate for 1 minute only. DO NOT LEAVE IN TEST MODE AS HUMIDIFIER WILL NOT OPERATE

• Make sure saddle valve is open.

WARNING

Sharp edges on the opening may cause cuts. Use care when cutting the plenum opening

and installing the Humidifier Control.

CAUTION

• Do not mount Humidifier Control on supply plenum or duct. The unit will not withstand

supply temperatures and will malfunction!

• When installing Humidifier Control on counterflow furnaces, ensure blower continues

to run after a heat call is satisfied to eliminate high temperatures from damaging the

Humidifier Control.

• Do not mount Humidifier Control downstream of the bypass outlet. False humidity

conditions will cause humidifier to operate incorrectly.

1. TEAR OUT TEMPLATE ALONG PERFORATED EDGES.

2. PLACE THIS TEMPLATE ON THE RETURN PLENUM UPSTREAM OF (BEFORE) THE

HUMIDIFIER CONNECTION.

3. TRACE THE OUTSIDE EDGES OF THIS TEMPLATE.

4. REMOVE TEMPLATE AND ACCURATELY CUT THE PLENUM OPENING.

5. USING 4 SHEET METAL SCREWS, INSTALL HUMIDIFIER CONTROL IN PLENUM OPENING.

PERFORATED

HUMIDIFIER

CONTROL

TEMPLATE

FURNACE

ACCESSORY

TERMINALS

(10 VA MINIMUM)

Figure H

Furnace

Accessory

Terminal

TRANSFORMER

(10 VA MINIMUM)

FURNACE BLOWER

Figure I

Constant

Power with

External

Transformer

• Call your installer to have your Water Panel changed, or visit your installer to purchase a

new Aprilaire Water Panel. Follow the instructions on the Water Panel box.

“Change Water Panel”

Indicator is lit.

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