TRoUbleSHooTInG GUIDe
The following troubleshooting guide is intended to help diagnose and resolve general operational problems with the Steam Humidifier and
optional Fan Pack . If a problem persists, call Aprilaire Tech Support toll-free at 1-800-334-6011 . Please be prepared to describe the exact nature
of the problem . For general operational problems, check to make sure humidifier is installed correctly .
CaUTIon
Contact with electrical circuits can cause property damage, personal injury or death. Service and Troubleshooting must be
performed by qualified electrician.
Table 6 – Humidifier Troubleshooting Guide
Problem
Possible Cause
action
General operating
problems . Humidifier
will not turn on or
turn off .
Field-wired terminal
connections .
Verify L1, N/L2 and ground connections are properly wired and appropriate voltage is present .
Check HUMIDISTAT and (if used) FAN PACK terminal connections are tight and properly wired .
HUMIDISTAT terminals must be connected to an on/off device .
Check wiring connections and settings on Accessory items such as high limit switch and airflow
proving switch .
Internal connections .
Check electrode and high water probe connections on the top of the canister .
Make sure ribbon cable from membrane switch is securely plugged into control circuit board .
Make sure black/white wire is attached to terminal that matches input voltage .
No power to humidifier .
Check main power supply and switch .
Ensure breaker is sized appropriately for the amperage draw .
Check for proper voltage across L1 and N/L2 terminals .
Humidifier not turned on .
Make sure front cover is attached to engage safety interlock switch . Press On/Off button .
Make sure ribbon cable from membrane switch is not damaged and is securely plugged into the
control circuit board .
No power to 24 volt control
circuit .
Check fuse on PCB (replace with 5 amp slow burn fuse if necessary) .
With humidifier energized, check that LED light D8 is energized on the circuit board . If the LED is lit,
replace the membrane switch, if not, replace the circuit board .
Steam Light does not
turn on .
Call for humidity not being
received .
Check humidistat wiring and setting . (Do not leave ADHC in TEST mode .)
Check wiring and settings of high RH limit switch and airflow proving switch .
Water is leaking from
humidifier .
Loose plumbing
connections .
Check water supply connection at fill valve inlet . Tighten as needed .
Check internal hose clamp connections . Reposition clamps and tighten as needed .
Check steam hose connection on top of canister . Tighten clamp as needed .
Hoses are blocked .
Check internal hoses and eliminate kinks or blockage .
Drain hose is blocked .
Make sure drain hose has constant downward slope and is not blocked .
Water constantly runs
down drain .
Debris in drain valve
preventing it from closing .
Remove canister and clean debris from drain valve .
O-ring in drain valve is not
properly seated in groove .
Remove canister and check O-ring for damage . Replace O-ring as necessary . Ensure O-ring is properly
seated in its groove .
Water is flowing from fill
cup overflow port .
Check internal hoses and eliminate kinks or blockage .
High static pressure in duct
is causing back pressure in
canister .
Make sure dispersion tube is not discharging into duct with greater than 2 .0 in .wg static pressure .
Make sure dispersion tube tubelets are pointed up .
Humidifier is filling
and water is flowing
down drain but drain
light is not on .
High static pressure in
steam line is causing back
pressure in canister .
Install a tee and drain trap in any low points in the steam line . See
figure 9
.
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