18
(b)
If no voltage to contactor coil, check continuity of wires from PC board to contactor.
If continuity is OK, PC board is likely defective.
5. Check voltage signal to power module. The voltage across EC1-10 and EC1-18 (low
voltage signal to power module) should be 11-12 Vdc.
(a) If no or low voltage, the PC board is likely defective.
(b) If voltage is OK, but green “LOAD” LED on the power module is not on, power
module is defective.
6. If green “LOAD” LED on power module is on, check voltage drops across power module.
Humidifier overfills with water on initial fill.
1. Check electrode canister (float canister for DI units) and level electrodes for debris or scale build up.
Clean as needed. See Page 16 for cleaning procedure for electrodes. On DI Units, the high water
float switch may be defective or “hung up”. Check continuity across wires to the switch. Make sure
switch axis is vertical so float lever arm swings freely.
2. The fill valve may be stuck open. Turn off power to the humidifier. If fill valve does not
close, clean or replace valve.
3. If the high water circuit is closed and the fill valve shuts off when the power is turned off,
the PC board is defective.
Humidifier runs continuously, %RH is well over set-point.
1. Verify humidistat is wired correctly and stat selector jumpers (S3 & J3, See Fig. 9-1
and 22-1) on the PC board are set correctly for the humidistat signal.
2. Disconnect humidistat wiring to humidifier. If humidifier shuts off, the problem is with the
humidistat. Consult humidistat manufacturer or Armstrong for proper troubleshooting/
calibration procedures.
3. If humidifier generates steam with the humidistat disconnected.
(a) Check for power at the contactor coil. If 24-28 VAC, PC board is defective.
(b) Check voltage drop across contactor. If voltage drop is low (it should be line
voltage), remove, disassemble and inspect contactor.
(c) Check green “LOAD” LED on power module. If it is On or blinking, PC board is
likely defective.
(d) Check voltage drop across power module. If voltage drop is low (it should be line
voltage), power module triacs may be failed closed. Shut off main power and
perform continuity check across high voltage input and output terminals. Continuity
indicates a shorted triac. Note: Some power modules have two triacs rather than
three. Check schematic on power module to verify.
Humidifier runs continuously, %RH is well under set-point.
1. Verify humidistat is wired correctly and stat selector jumpers (S3 & J3, See Fig. 9-1
and 22-1) on the PC board are set correctly for the humidistat signal.
