TRoUbleSHooTInG GUIDe
Table 5 – Troubleshooting Guide
Problem Possible cause action
Humidifier does
not energize; steam
canister does not
heat up, display
lights not on
No power to humidifier • Check main power supply.
• Check main line safety switch.
• Verify terminal block electrical connections.
• Verify humidifier is turned on.
No power to low voltage
control circuit • Check for proper supply voltage.
• Verify terminal block electrical connections.
• Check for control circuit voltage, 24 VAC.
Control terminals
are open • Check if auxiliary limit controls are not allowing system to operate, e.g., high limit
humidistat, airflow proving switch, etc. Reset, replace, or calibrate as needed.
ADHC faults:
• Open, shorted,
or incorrect wiring
of control
• Check terminals for 24 VAC.
• Check control circuit wiring.
Steam canister failure Improper wiring • Verify proper electrical connections.
Mineral buildup
on steam canister
electrodes
• Inspect steam canister for severe mineral buildup on or around electrodes. If severe
mineral buildup is present, replace steam canister.
Steam canister electrode
corrosion • Inspect electrodes for surface corrosion or pitting. This is usually caused by a high
chloride level in the supply water. Replace steam canister.
Unit does not fill
with water No water supply to
fill valve • Verify that manual water supply valve is open and that pressure exists.
• Check if in-line strainer in inlet port of fill valve is plugged. Clean strainer or replace.
Unit control is not on • Press On/Off switch.
Malfunctioning fill valve • If fill valve does not open:
– Check for obstruction in valve.
– Verify fill valve electrical connections.
– Verify proper 24 VAC to fill valve. If voltage is present and valve does not open,
replace valve.
Drain valve is open • Check for obstruction in drain valve.
Fill valve does
not close Malfunctioning level
control system • Check that high water sensor electrical plug is fully engaged.
Fill valve is stuck • Check if there is an obstruction that does not allow valve to seat properly. Clean or
replace valve as needed.
Drain valve is open • Clean or replace drain valve if an obstruction in the valve does not allow complete
closure.
If a problem arises with the Aprilaire Model 800 Steam Humidifier, please review the following troubleshooting guide for possible causes and
solutions. If the problem persists, call Aprilaire Tech Support toll-free at 1-800-334-6011. Please be prepared to describe the exact nature of
the problem.
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