HM750A1000
33-00289—01
16
OPERATION
LED Status Lights
The HM750 user interface includes a series of LEDs that
provide information about the humidifier status.
Fig. 25. Humidifier User Interface.
Status
Idle
This green LED will illuminate if there is power to the
humidifier, it has been turned on, but there is no
demand from the humidistat.
If there is demand, but the
AP
terminals on the control
board are not closed, the
Idle
LED will flash.
The
Idle
LED will also illuminate during a 72-hour no-
demand drain, which is an automatic drain that occurs
if there is no demand for humidification after 72 hours
– for hygiene purposes.
Filling
This green LED will illuminate immediately after there
is a demand for steam. This LED will turn off once the
humidifier determines that there is steam being
generated.
Humidifying
This green LED will illuminate once the humidifier
determines that there is steam being generated. See
Filling
description.
Draining
This green LED will illuminate during a 72-hour no-
demand drain (see
Idle
description).
This LED also illuminates when the user presses the
Power/Drain
button, since the humidifier will drain
before turning off.
SERVICE
Cylinder
This yellow LED will illuminate when the humidifier has
determined that the cylinder is nearing the end of its
life, due to scale accumulation on the electrodes. The
LED will flash on and off, during which time the
humidifier will continue to operate as normal. After 7
days of flashing, the LED will remain on solid, and the
humidifier will not generate steam. The cylinder must
be replaced. See “Cylinder Replacement KIT” on
page 19.
Fault
This red LED will flash if the humidifier has detected an
error:
• 1 flash: Excess Current fault
• 2 flashes: Fill/Drain fault
• 3 flashes: Insufficient Current fault
• 4 flashes: PCB fault
• 5 flashes: Wrong Voltage Selector fault
See the Troubleshooting section for more information.
MAIN BUTTON
Power/Drain
When primary power has been wired to the humidifier,
the
Power/Drain
button must be pressed in order to
enable steam generation.
When the user so decides, the humidifier may be turned
off by pressing this button. Honeywell does not recom-
mend turning the humidifier off at any time during
normal operation. If there is no demand for humidifica-
tion, the humidifier will not draw power to the
electrodes.
The
Power/Drain
button is also used to reset a fault.
The button is pressed and held down for 5 seconds to
reset the unit from a fault.
Selecting a Relative Humidity
Setpoint
The optimum humidity setpoint depends on the reasons
that a space is being humidified. The “ASHRAE Handbook
HVAC Applications” recommends the specific design
relative humidity for specific applications.
AHRI recommended humidity is shown in Table 3 on
page 4.
Recommended Set-point
– The benefit of humidity is
most pronounced in the 40-60% RH range. A humidity
setting of 40-45% RH is recommended for this purpose to
prevent over humidifying.
Temperature Setback
– In cold climates, it is often
necessary to reduce the humidity level in a conditioned
environment to prevent build-up of condensation on the
inside of exterior walls, windows, and trim. It is highly
recommended that any humidity setback functions from
humidistats or other control devices be used under these
conditions to prevent damage from condensation. The
digital control with an outdoor temperature sensor
installed will automatically setback the humidity setpoint
to correspond with outdoor temperature.
M36945
HM750
Status
Idle
Filling
Humidifying
Draining
Service
Cylinder
Fault
Power
Drain
Fault Codes In Front Cover
