Aprilaire 1150 Installation, Operation And Maintenance Manual page 41

Problem Possible Cause
Heater burnout Improper wiring
Water level is too low .
Mineral buildup on heaters
Heater corrosion
Unit does not fill
No water supply to fill valve • V erify that manual water supply valve is open and that pressure exists.
with water
Unit control is not on
Malfunctioning fill valve
Malfunctioning level
control system
Humidifier is in auto drain
mode .
fill valve does
Malfunctioning level
not close control system
Fill valve is stuck open .
Drain valve is open .
fill valve cycles on Malfunctioning level
and off frequently control system
(several times per
minute)
Drain valve not fully closed
Unit does not perform No power to automatic
autodrain sequence drain valve
Drain fault, plugged drain
valve, or plugged drain pipe
Defective automatic drain
valve
Unit does not perform Input signal always has a
end-of-season drain demand
Drain valve
Action
• V erify proper voltage applied to heater.
• V erify proper electrical connections.
• R eplace probe assembly.
• I f heaters are on continuously and therefore not expanding and contracting with on-off cycles
to shed mineral buildup, the humidifier may be undersized . Replace with a larger unit or add an
additional humidifier .
• I nspect chamber for severe mineral buildup on or around heater. If present, increase cleaning
frequency or use softened supply water .
• I nspect heater for surface corrosion or pitting. This is usually caused by a high chloride level in
the supply water .
• C heck if water supply line strainer is plugged. Clean strainer or replace.
• V erify fill valve electrical plug is fully engaged.
• P ress On/Off switch on display panel.
• V erify transformer electrical plug is fully engaged.
• U nplug probe head. Fill valve should open. If fill valve does not open:
– Verify fill valve electrical plug is fully engaged .
– Verify proper 24 VAC (terminals 33 and C) to fill valve . If voltage is present and valve does not
open, replace valve .
• C heck terminals 3, 4, 5, and C on the internal controller board terminal block for correct wiring.
• N ormal operation. Chamber will fill after completing auto drain sequence.
• C heck that probe electrical plug is fully engaged.
• V erify that probe is wired per wiring diagram.
• V erify the green and yellow ground wire is connected to the C terminal and the subpanel.
• I f the internal control board relay output is shorted to fill valve coil, replace board.
• I f needed, clean probe rods.
• C heck water conductivity. Water conductivity must be at least 100 μS/cm. Add salt to increase.
• C heck for control voltage across fill valve coil (terminals 33 and C on control terminal strip).
• C heck if fill valve is installed backwards. If yes, repipe.
• C heck if there is an obstruction that does not allow valve to seat properly. Clean or replace valve
as needed .
• I f automatic drain valve is locked in manual open position, reset to automatic.
• R eplace valve if there is a broken return spring on the drain valve.
• C lean or replace drain valve if an obstruction in the valve does not allow complete closure.
• I f needed, clean probes.
• V erify that probe wiring is correct.
• C heck water conductivity. Water conductivity must be at least 100 μS/cm. Add salt to increase.
• I f an obstruction does not allow drain valve to fully close, clean valve.
• V erify drain valve electrical plug is fully engaged.
• C heck if 24 VAC is present at the internal controller board terminals 32 and C for drain valve.
• C heck drain valve piping.
• I f voltage is present at valve and it still does not open, replace valve.
• R educe demand signal at the humidistat.
• V erify drain valve electrical plug is fully engaged.
• V erify drain valve is wired correctly to control board.
• C heck 24 VAC across valve coil during test cycle (terminals 32 and C on control terminal strip).
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