HM750A1000
33-00289—01
24
TROUBLESHOOTING
CAUTION
High Voltage Hazard.
Be aware, when troubleshooting, that the
humidifier is powered by high voltage and
familiarity with both good practices and wiring of
the humidifier is recommended. Any
troubleshooting that requires opening the cabinet
should be done by qualified personnel.
CAUTION
Burn and Scalding Hazard.
Hot water or steam with a temperature above
120 °F (49 °C) can cause burns from scalding.
NOTE:
Most humidifier faults are not caused by faulty
equipment but rather by improper installation. A
complete fault diagnosis always involves a
thorough examination of the entire system. Often,
the steam hose connection has not been properly
executed, or the fault lies with the humidity
control system.
TROUBLESHOOTING REQUIREMENTS
• Ensure the installation meets the installation
requirements outlined in these instructions.
• Familiarize yourself with the operation of the humidifier
by reading these instructions in their entirety.
• The wiring diagram for your specific humidifier is
installed on the inside of the humidifier door. A generic
copy of the HM750 wiring diagram is also included at
the end of this chapter for reference purposes.
• When contacting your local representative or
Honeywell for troubleshooting assistance, please
ensure the serial number and manufacturing date on
the label at the left side of the housing has been
obtained for reference purposes (Fig. 1).
Table 6. General troubleshooting.
Symptom
Cause
Corrective Action(s)
Humidifier appears to have no
power, even when the
Power/Drain button is pressed
on.
Fuse blown
Check on-board fuse located beside transformer.
Incorrect voltage
Check voltage against specification label and correct.
Step down transformer not
outputting 24 VAC
Replace the circuit board.
Incorrect primary power
jumper
Check that the on-board voltage selection jumper is
installed correctly. If 240 VAC power was supplied to a
unit where the voltage selection jumper was set to
120 VAC, the circuit board will need to be replaced.
Humidifier will not humidify or
not reaching humidification
(RH%) setpoint
Humidistat terminals not
closed.
Check voltage.
Low conductivity water
If operated on low conductivity water, it may take
several hours for the HM750 to reach full capacity.
This is normal. During this time, the humidifier will not
perform any drains and the conductivity of the water
in the cylinder will increase.
The unit will not operate on reverse osmosis or
deionized water. Ensure that tap water is used.
Note: New humidifier cylinders are supplied with a
salt tablet inside.
No airflow in duct
Check that the AP terminals on the control board are
wired correctly, and closing the 24 VAC chain.
Humidifier has faulted and red
Fault
LED is flashing.
Software has detected an
abnormal condition
Review fault-code label on the inside cover of the
HM750 or see Table 7 on page 25.
Distributor spitting out water
into duct
DUCT INSTALLATION: fill valve
failed open
Check that the fill valve has not failed in the open
state. This would make water flow inside the cylinder
above the level of the high water sensor, to a
maximum of the fill cup overflow level. At this point,
water may carry over into the distributor nozzle and
“spit” into the duct.
REMOTE INSTALLATION:
condensate generation
Ensure the nozzle is oriented correctly and the steam
line is sloped correctly, as per the guidelines in these
installation instructions.
