RH-D AND RH-W ELECTRIC DUCT HEATERS
21
1.800.627.4499
INSTALLATION, OPERATION AND MAINTENANCE MANUAL
RENEWAIRE.COM
MAINTENANCE
7.3 RH-D TROUBLE SHOOTING
7.1 RH-D ANNUAL MAINTENANCE
7.2 RH-W ANNUAL MAINTENANCE
7.0 MAINTENANCE
RISK OF BURNS
This device is an electric heater and produces very high temperatures, capable of causing severe
burns. Use caution when working on the heater and wear appropriate Personal Protective Equipment
(PPE) whenever working on the unit.
CAUTION
7.3.1 Testing AFS and S1 Sensors
7.3.2 Testing Control Modules D21-T and D22-T
Remove AFS and/or S1 sensor from D21-T/D22-T board and measure the ohms across the Thermistor:
The reading should be 10KΩ at 77 F. If the temperature is higher, the resistance will go down and if the
temperature is lower, the resistance will go up. If the sensor reads OPEN LINE, replace sensor.
A D22-T is essentially a D21-T with 2 power outputs instead of one. Here are the steps to follow to test
and troubleshoot these 2 boards:
The first step in testing the D21-T/D22-T controllers is to confirm that there is 24 VAC powering the
board. (Top left connections on the board). The airflow sensor is a device that protects the heater
element section from overheating. If there is a lack of proper airflow, the controller and the airflow
sensor will make the unit modulate proportionally with the airflow. This simply means that, if the
element section is getting half of the needed airflow, the heater will work at half the capacity. This
prevents overheating of the elements which would damage them. For testing purposes, remove the
Airflow sensor (AFS) from the terminals A and A. When that airflow sensor is removed, the heater will
still operate normally but without element protection (this is only for testing). Make sure you reconnect
the airflow sensor after testing.
If there is a built-in duct temperature sensor connected to S and S, you can simply dial your set point
on the blue potentiometer on the controller. If the red light never turns on, temporarily disconnect wires
connected on S and S. The board can still operate but only in an ON/OFF mode. The heater/red light
should turn ON, if the potentiometer is set anywhere between 0 and 18 and OFF anywhere else. Again,
if the red light never turns on, the controller is defective and replacement is required. If the heater is
controlled remotely with a room or duct thermostat, simply set the potentiometer to position “R” (R for
Remote control). Note that these controllers have power outputs. It is possible after many switching
cycles that the built-in triacs will stay stuck in a closed or open position. The control side of the board
might still be good, but the power side will not operate. If the triacs are stuck closed, the thermal cut-
outs will cut power to the unit. If the triacs are stuck open, the unit will not put out any heat even if
there is a demand.
There is no required annual maintenance for any RH-D heater.
RH-W heaters have a fault indicator LED. RenewAire suggests that the LED be checked annually for
indication of detected problems.
