Honeywell Home HM750 User manual

INSTALLATION INSTRUCTIONS
33-00289EF-03
IMPORTANT
Read and save these instructions. This guide should be kept by the installer.
HM750A1000
ADVANCED ELECTRODE STEAM HUMIDIFIER
INTRODUCTION
The HM750 is the most advanced residential steam
humidifier available and provides steady and reliable
humidification for a home. The humidifier is designed for
connection directly to a supply air duct for humidity on
demand. The humidifier may be directly mounted to the air
duct, or remotely from the air duct, with a steam hose
connecting the humidifier to a distributor nozzle installed
at the air duct.
Included in the Box
— HM750 steam humidifier
— H6062 HumidiPRO
— Steam distributor nozzle
— Rubber drain hose
— LDPE water hose
— Baffle (duct mount only)
— Foam gasket (duct mount only)
— Steam hose (wall mount only)
— Fittings, hardware, and mounting template
— Installation Instructions, 33-00289EF (this document)
— Annual Operation and Maintenance Reminder
Tools Needed
— Flat-head screwdriver
— Phillips screwdriver
—Wrench
— Copper pipe (optional)
— Level
—Holesaw
Humidifier Configuration
The HM750 is configured at the factory to operate under
most conditions without the need to change its
configuration.
NOTE: Because the humidifier is factory configured for
optimal performance, Resideo strongly
discourages changes to the configuration of the
humidifier not described in these instructions.
Before Installation
1. Ensure that available voltage and phase
corresponds with humidifier voltage and phase as
indicated on humidifier’s specification label.
2. Ensure that the dedicated external fuse disconnect
is of sufficient size to handle the rated amps as
indicated on the specification label. Refer to local
codes.
3. Ensure sufficient clearances will be available as
described in the Location section on page 6.
4. If the humidifier will be wall mounted, ensure steam
lines can be routed to duct as described in the Steam
Line Instructions on page 7.

HM750A1000
33-00289EF—03 2
Table 1. Specifications.
Fig. 1. Specification label location.
CAUTION
Servicing
Disconnect main power before any servicing.
• The plumbing and electrical compartments
contain high voltage components and wiring.
Access should be limited to authorized
personnel only.
• During and following operation of the
humidifier, the steam and components in
contact with the steam such as the steam lines,
steam distributors, and condensate lines can
become hot and can burn if touched.
• Resideo does not accept any liability for
installations of humidity equipment installed by
unqualified personnel or the use of
parts/components/equipment that are not
authorized or approved by Resideo.
• To maintain warranty, only Resideo approved
parts and cylinders may be used in the
operation of the product.
CAUTION
Electrical
All electrical work should be done according to
local and national electrical code.
Electrical connection to be performed by a licensed
electrician.
Unit recommended to be powered by a dedicated
GFCI circuit.
CAUTION
Plumbing
Plumbing to be performed by a licensed plumber.
Drain water from humidifier can be very hot. Drain
water to floor drain. Do not drain to public sink.
All plumbing work should be done according to
local plumbing code.
CAUTION
Installation
Do not mount on surfaces hotter than 176 ºF
(80 ºC).
Do not mount in area where freezing can occur.
Do not mount on vibrating surface.
Do not mount on floor.
The HM750 produces steam at atmospheric
pressure. No devices which could block steam
output should be connected to the steam outlet.
Steam lines must be installed so that no restriction
can produce backpressure in the humidifier.
Do not mount outdoors without protection against
rain, snow, condensation or equivalent.
CAUTION
Water quality
The HM750 requires a cold water connection from
your home's main water supply between 15-
100 PSIG. A throttle valve may be necessary, and
a water shut-off valve is recommended for
safety. Reverse Osmosis (RO) and Deionized
(DI) water must not be used. Water conductivity
is important to ensure the electrode humidifier
operates effectively. Resideo recommends
125-1200 μS/cm (microsiemens/cm).
Volts
Steam Output
GPD KW Amps Phase
Max Ext.
Fuse
(Amps)
Standard
Cylinder
Net/Full
Weight
lbs. (kg)
Dimensions
W x H x D
110/120 11 1.5 12 1 15
HM750ACYL
10.5 / 18.5
(4.8 / 8.4) 10x18x7in. 254 x 457 x 178 mm
220/240 22 3.0
MODEL: HM750A1000
1
PHASE: 1HZ:60
Countryoforigin:Canada
Paysd’origine:Canada
Auto-Adaptive
Professionallyservicedonly.
Entretienpar desprofessionnels seulement.
S/NDATECODE
205X
HUMIDIFIER
VOLT 110-120220-240
AMP1212
GPD1122
KW1.
53.0
HM750
Status
Service
Power
Idle
Filling
Humidifying
Draining
Cylinder
Fault
Drain
FaultCodesIn Front Cover
MODEL: HM750A1000
1
PHASE: 1HZ: 60
Country of origin: Canada
Pays d’origine : Canada
Auto-Adaptive
Professionally serviced only.
Entretien par des professionnels seulement.
S/N DATECODE
205X
HUMIDIFIER
VOLT 110-120 220-240
AMP 12 12
GPD 11 22
KW 1.5 3.0
M37184
MODEL:HM750A1000
1
PHASE:1HZ:60
Countryoforigin:Canada
Paysd’origine:Canada
Auto-Adaptive
Professionallyservicedonly.
Entretienpardesprofessionnelsseulement.
S/NDATECODE
205X
HUMIDIFIER
VOL
T1
10-120220-240
AMP 1212
GPD1122
KW 1.53.0

HM750A1000
333-00289EF—03
Parts and Accessories
The following parts and accessories are available and may have been included with your HM750 humidifier. The cylinder
is the only item that will need periodic replacement to maintain proper humidifier operation.
Table 2. Parts and accessories.
How the Humidifier Works
The HM750 is an atmospheric steam generator that uses
heat generated by electrical current flowing between
submerged electrodes to generate steam. The HM750 is
designed for on-demand air humidification via a steam
distributor nozzle.
STEAM GENERATION
• Once the humidistat terminals and the air proving
terminals are closed (AP on the control board), the
humidifier closes the power relay and measures the
electrical current.
• If current is lower than full load amperage, after a brief
delay the water fill valve will be activated and water will
flow into the fill cup. Water from the fill cup flows into
the bottom of the cylinder through a hose connected to
the drain valve housing.
NOTE: The cylinder is gravity fed from the fill cup. If
backpressure from the steam line is too high it
will cause water to back up in the fill cup and flow
down the overflow line to the drain.
• As soon as the water in the cylinder comes in contact
with the energized electrodes, current flows through
the water. The resistance of the water to the electrical
current generates heat and in turn steam. The electrical
current (and steam output) increases as the level of
water increases, as more of the electrode becomes
submerged. The unit continues to fill until the current
reaches full load amperage, or the high water sensor
detects a high water level.
• The water level and current draw in the cylinder
decreases from evaporation (through steam
generation).
• If the high water sensor was activated before full load
amperage is achieved, the water will boil down until the
high water sensor is no longer activated. If full load
amperage was achieved, the water will boil down to a
predefined amperage.
• The HM750 repeats the fill and boil down cycle
repeatedly to provide a constant steam output.
• Over time, minerals in the water will adhere to the
cylinder electrodes. The humidifier will automatically
fill to a higher water level to maintain full capacity
during the life of the cylinder. Eventually, because of
scale formation, it will no longer be possible for the
humidifier to reach its full capacity. The HM750
software monitors this condition and, when detected,
will stop operating and the Cylinder LED will be
illuminated.
DRAINS
• As steam is produced, minerals are left behind,
increasing the conductivity of the water. The HM750
auto-adaptive cycle will monitor the water conductivity
and perform drains to maintain the water at optimal
conductivity for peak performance.
• The auto-adaptive cycle ensures cylinder life is
maximized. It does this by keeping the tightest control
and most efficient use of water during the entire
cylinder life.
STEAM DISTRIBUTION
Steam generated by the humidifier may be introduced into
the air in two different ways. The humidifier may be
mounted directly onto the duct, to allow the steam
distributor nozzle to enter into the supply air duct.
Alternatively, the humidifier may be located remotely from
the air supply duct. It may be connected to the distributor
nozzle at the duct using a steam hose.
STEAM LINE
The steam line between the cylinder steam outlet and the
distributor nozzle serves two purposes: it is used as a
conduit to transfer the atmospheric steam from the
humidifier to the distributor nozzle, as well as providing a
means to remove condensate. See “Steam Line
Instructions” on page 7 for information on selecting steam
lines.
Whenever steam is distributed, condensate is formed in
the distribution system. Insulating steam lines is one
important way to reduce the amount of condensate
formed. Steam lines must also be sloped so that
condensate does not collect in the lines and create a
restriction to steam flow. As shown in the Plumbing
section, steam lines should maintain a slope back to the
humidifier of, as a minimum, 4 in. (10 cm) RISE per 12 in.
(30 cm) of RUN.
Part/Accessory Part Number
Replacement Cylinder HM750ACYL
HumidiPRO Humidistat H6062A1000
Drain and Fill Valve Kit HM750AVKIT
Remote and Duct Nozzle Kit HM750ANKIT
Replacement PC Board HM750APCB
15 ft. Steam Hose Kit HM750AHOSEKIT
Differential Pressure Switch for Air Proving 50027910-001

HM750A1000
33-00289EF—03 4
SIZING
IMPORTANT
The HM750 should only be installed if it has been
sized properly. Do not use square feet when sizing
a humidifier installation. Instead, cubic feet must
be used, since the humidity is filling a volume of
space (width x length x height). Also, take into
consideration the “tightness” of a home’s
construction.
The HM750 produces 11 gallons per day (GPD) when run
on 120 V and 22 GPD when run on 240 V. See Figure 20
for details on configuring the HM750 to run on a different
voltage.
Table 3 contains AHRI recommendations for humidity
requirements and Table 4 shows what humidifiers and
output configuration will satisfy the humidification
requirements.
Table 3. AHRI Recommended Humidity (in US gallons per day).
Table 4. Steam humidifier(s) necessary for application.a
aIn the table above, 11 GPD indicates a steam humidifier configured to run on 120 V and 22 GPD indicates a steam
humidifier configured to run on 240 V.
Construction
Type 8,000 ft312,000 ft316,000 ft320,000 ft324,000 ft332,000 ft340,000 ft3
Tight 3.3 5.0 6.7 8.3 10.0 13.4 16.7
Average 6.7 10.0 13.4 16.7 20.0 26.7 33.4
Loose 10.0 15.0 20.0 25.0 30.1 40.1 50.1
Construction
Type 8,000 ft312,000 ft316,000 ft320,000 ft324,000 ft332,000 ft340,000 ft3
Tight 11 GPD 11 GPD 11 GPD 11 GPD 11 GPD 11 GPD (x2) or
22 GPD (x1)
11 GPD (x2)
or
22 GPD (x1)
Average 11 GPD 11 GPD 22 GPD 22 GPD 22 GPD 11 GPD (x4) or
22 GPD (x2)
11 GPD (x4)
or
22 GPD (x2)
Loose 11 GPD 22 GPD 22 GPD 11 GPD (x4) or
22 GPD (x2)
11 GPD (x4)
or
22 GPD (x2)
11 GPD (x4)
or
22 GPD (x2)
11 GPD (x5)
or
22 GPD (x3)

HM750A1000
533-00289EF—03
Fig. 2. Typical HM750 Installation.
Measurements in inches (mm).
240 VAC
M37185
36 (914)
MINIMUM
2 (51) SCREWS
MOUNTING
STEAM
DISTRIBUTION
CONTROLS
PLUMBING
ELECTRICAL
4 (102)
12 (305)
MAIN SUPPLY
L1
L2/N
GND
(OPTIONAL)
HOT
NEUTRAL
GROUND
MAIN SUPPLY
L1
L2/N
GND
(OPTIONAL)
OFF ON
HOT
HOT
GROUND
OFF ON
120 VAC
4 (102)
1 (25) 1 (25)
4 (102)
1 (25) IF WIRED BEFORE MOUNTING.
36 INCHES (914) FOR WIRING ACCESSIBILITY
240VAC
120VAC
HUMIDIPRO
H6062
AIR PROVING
(OR JUMPER)
24VAC
COM
HUM
HUM
AP
AP
Air Proving
Humidistat
1
1
THERMOSTAT OR HUMIDISTAT
3/4 (19) OD
1/4 LDPE
OR COPPER
WATER LINE
ALWAYS INSTALL
A WATER
SHUT-OFF VALVE.
USE 1/2 IN. OD COPPER
TO WITHIN 4 FT (1.2 M)
OF HUMIDIFIER.
AIR PROVING JUMPER COMES
PRE-INSTALLED. REMOVE JUMPER
IF AIR PROVING IS UTILIZED.

HM750A1000
33-00289EF—03 6
LOCATION
Mount on a suitable wall or vertical surface. Do not sit the
unit on the floor. Allow clearances required for plumbing
and electrical connections. Clearance dimensions shown
are for reference only and are the minimum required for
maintenance of the humidifier.
Fig. 3. Clearances for the HM750.
Consult local and national codes before final location and
installation. Resideo does not accept responsibility for
installation code violations.
• Install only in areas with ambient temperature 41 to
104 °F (5 to 40 °C) and relative humidity 5 to 95 %,
non-condensing.
• Humidifier must be installed below the steam
distributor nozzle. Take care to provide proper steam
line routing.
• DO NOT locate the humidifier any further than
absolutely necessary from the steam distributor nozzle
location as net output will be reduced as a result of heat
loss through the steam line.
• When possible, mount the HM750 humidifier at a
height convenient for servicing.
NOTE: Do not mount on surfaces above 176 °F (80 °C),
where freezing can occur, vibrating surface, or floor.
Fig. 4. Distributor nozzle installed vertically
in a horizontal duct. (Remote mount)
Steam Nozzle Location
Whether the humidifier is being installed directly on the
air duct or remotely, the location of the distributor nozzle
in the air duct should follow the subsequent rules:
Fig. 5. Distributor installed horizontally (side mount)
in a horizontal duct. (Remote mount)
Measurements in inches (mm).
Fig. 6. Distributor nozzle installed horizontally
in a vertical duct. (Remote mount)
24 INCHES (610 MM)
4 INCHES (102 MM)
1 INCH
(25 MM)
41˚ - 104˚ F
(5˚ - 40˚ C)
0-95%
NON CONDENSING
M36860A
1 INCH (25 MM) IF WIRED BEFORE MOUNTING.
36 INCHES (914 MM) FOR WIRING ACCESSIBILITY.
1
1
AIR FLOW
1/2 DUCT WIDTH
M37234
AIR FLOW
8 (204)
MINIMUM
4.5 (114)
M37232
MINIMUM CLEARANCE TO TOP OF DUCT.
1
1
AIR FLOW
1/2 DUCT
WIDTH
M37233

HM750A1000
733-00289EF—03
Steam Line Instructions
The following instructions must be followed for installation of steam lines for the HM750. Failure to use recommended
material (see Table 5), or failure to follow any other steam line installation instructions will result in improper operation
and could void the warranty.
Table 5. Recommended Steam Line Material for HM750 Duct.
* The use of steam line other than Resideo supplied steam hose line will void the warranty and may adversely affect the
operation of the humidifier.
NOTE: Condensate is not returned to the humidifier using a separate condensate line. Rather, the condensate is
returned to the humidifier via the steam line. Ensure proper sloping.
If a condensate pump is preferred, ensure the pump is rated for hot water.
Main Rules for Atmospheric Steam Lines
• Steam lines must not have any restrictions which could
result in back pressure.
• Maximum recommended steam line length: 15 ft. (4.6 m)
• Use only Resideo supplied hose and follow
recommended lengths.
• Install steam line in a vertical (upwards) fashion from
the HM750 to the distribution nozzle, with a minimum
slope of 4 in. (10 cm) RISE for every 12 in. (30 cm) RUN.
• Insulate with 1.5 in. (3.8 cm) pipe insulation on steam
hose (recommended).
• Do not over tighten hose clamp at cylinder steam outlet.
• If the 15 ft. steam hose is used, support the hose to
maintain proper slope and avoid excess weight on the
humidifier and nozzle.
Steam Distributor Nozzle
Remote-Mount — The HM750 must be connected with a
steam hose to a steam distributor nozzle installed in the
supply-side of ductwork. As shipped, the HM750 is
configured with a steam guide for remote mounting. The
steam outlet points upwards and is only used when the
humidifier is installed remote to the air supply duct.
The steam distributor nozzle should be installed as close
as possible to the humidifier – to a maximum of 15 ft.
(4.6 m). The HM750 is supplied with a 5 ft steam hose. A
15 ft hose is available as an accessory. Short steam
distribution lines minimize condensate loss and the
possibility of generating backpressure in the steam
distribution line. It is important that the steam line have a
constant slope of, as a minimum, 4 in. (10 cm) RISE for
every 12 in. (30cm) of RUN. See Fig. 8.
Fig. 7. Molded steam guide.
Fig. 8. Minimum slope requirements for steam line.
Measurements in inches (mm).
Voltage
Steam Output Material*
Steam Line
Length
Possible Losses Minimum
Airflow
CFM
Max
Static
Pressure
lbs/hr
(kg/hr) GPD
Steam
Hose lbs/hr GPD
110/120V 3.8
(1.7) 11
1in.dia.
Recommended:
5 ft. (1.5 m)
Maximum:
15 ft. (4.6 m)
0.4 1.1 115
2.0 in. w.c.
220/240V 7.7
(3.5) 22 0.4 1.1 230
M37216
STEAM
CYLINDER
HOSE
CLAMPS
STEAM
HOSE
MOLDED
HOSE
GUIDE
WARNING
ElectricShock Hazard
Cancause severe injury
or death.
Aseparate groundwire
must be used.
AVERTISSEMENT
Fire Hazard
Cancause severe injury,
death, or substantial
property damage.
Replace only with same type
of 1.0 amp fast-acting fuse.
32332376-001Rev.A
Risque de chocélectrique
Peut causer des blessures
graves oula mort.
Unfil de mise à la terre
séparéest nécessaire.
Risque d’incendie
Peut causerdesblessures
graves, la mort oudes
dégâts matérielsimportants.
Remplacer seulement avec
le même type defusible à
action rapide de1.0 amp.
AIR SUPPLY DUCT
STEAM DISTRIBUTOR
NOZZLE
STEAM HOSE
HUMIDIFIER
4
(105)
12 (305)

HM750A1000
33-00289EF—03 8
Steam Line Installation Examples
Fig. 9. Steam distributor above humidifier (hose).
Measurements in inches (mm).
Fig. 10. Steam distributor below humidifier with
obstruction (hose). Measurements in inches (mm).
Fig. 11. Common steam line installation errors.
M37200
12 (305)
MINIMUM
RADIUS
SUPPORT
BRACKETS
12 (305)
4 (102)
MINIMUM
HM750
Status
Service
Power
Idle
Filling
Humidifying
Draining
Cylinder
Fault
Drain
FaultCodes In FrontCover
CONNECT
STEAM
HOSE TO
CYLINDER
M37204
TO DRAIN
OBSTRUCTION
12 (305)
MINIMUM
RADIUS
SUPPORT
BRACKETS
USE FULL SIZE CONDENSATE
TEE AT LOW POINT. SLOPE
LINES UP TO “T” AND
IMMEDIATELY AFTER IT.
HOSE WILL SOFTEN OVER TIME. PROPER SUPPORT IS NECESSARY.
1
4 (102)
MINIMUM
12
(305)
MINIMUM
1
HM750
Status
Service
Power
Idle
Filling
Humidifying
Draining
Cylinder
Fault
Drain
FaultCodesIn Front Cover
12 (305)
MINIMUM
M37205
NO
CONDENSATE
TRAP AT
VERTICAL
TRANSITION
STEAM LINE
NOT SLOPED
HM750
Status
Service
Power
Idle
Filling
Humidifying
Draining
Cylinder
Fault
Drain
FaultCodes In FrontCover
INSUFFICIENT
BEND RADIUS
INSUFFICIENT
BEND RADIUS

HM750A1000
933-00289EF—03
MOUNTING THE HUMIDIFIER
The HM750 can be mounted either directly on a supply air
duct or remotely mounted on a wall. When remotely
mounted the steam nozzle is mounted on a duct and
connected to the HM750 with a steam hose.
The HM750 has a keyhole and three additional mounting
holes as shown in Fig. 12.
Fig. 12. Mounting locations. (Rear view)
Mounting to a Wall
The HM750 comes in wall-mount configuration. In this
configuration, the humidifier can be mounted to a 2x4
stud and the steam distributor nozzle, located at the end
of a 5 ft. (1.5 m) steam hose, is inserted through the air
supply duct (Fig. 13).
NOTE: Use #8 screws at least 2 in. (5 cm) in length
(included) to mount directly to a 2x4 stud. Use
longer screws if the stud is behind a drywall or
other spacer.
NOTE: The steam distributor nozzle MUST be installed
higher than the humidifier (see Fig. 13). The
steam hose should maintain an inclination of at
least 4 inches (10 cm) of rise for every 12 inches
(30 cm) of run.
CAUTION
Do not remove the cover when the humidifier
powered.
1. Remove the humidifier cover and pull out the
cylinder. Insert the top screw until 1/4 in. (6 mm) is
exposed. Hang the humidifier via its keyhole on the
screw head (see Fig. 12).
2. After making sure the humidifier is level, affix it to
the stud with another screw at the lower stud-mount
location (Fig. 12).
3. Drill a 1-3/4” hole in the duct for the steam
distributor nozzle. Attach the steam hose to the
distributor nozzle and the remote adapter on the
humidifier. Then insert the steam distributor nozzle
and secure it with screws.
Fig. 13. Wall mount.
Fig. 14. Mounting with keyholes.
M36932
KEYHOLE
STUD
MOUNT
DUCT
MOUNT
DUCT
MOUNT
M36946
AIR FLOW
INSERT SCREW LEAVING
1/4 IN. (6 MM) EXPOSED.
HANG UNIT, THEN
TIGHTEN SCREW.
INSTALL SECOND
SCREW AFTER
HANGING
HUMIDIFIER
2X4 OR OTHER
STRUCTURAL
MEMBER
NUMBER 8 x 2
INCHES (5 CM)
WOOD SCREW
M37235A

HM750A1000
33-00289EF—03 10
Mounting to the Supply Duct
The HM750 can also be mounted directly onto the supply
duct. In this case, the steam guide must be removed and
replaced with the steam nozzle and baffle as follows:
REMOVE THE STEAM GUIDE
CAUTION
Do not remove the cover when the humidifier
powered.
1. Remove the humidifier front cover.
2. Remove the cylinder plugs and high water sensor
plug from the cylinder pins by pulling vertically.
3. Loosen the hose clamp furthest from the cylinder
steam outlet (the one attached to the plastic steam
guide). Remove the cylinder with the short steam
hose still attached. See Fig. 15.
4. Remove the hose adapter by pressing on the release
tab toward the back of the humidifier and sliding the
hose adapter down.
Fig. 15. Changing to duct mount configuration.
PREPARE THE STEAM NOZZLE
1. Locate the supplied steam nozzle and baffle.
2. Insert the baffle into the duct-mount nozzle.
NOTE: There is a keying feature on the baffle that
ensures proper orientation of the baffle in the
nozzle.
Fig. 16. Insert baffle into the duct-mount nozzle.
Key ensures proper alignment.
INSTALL THE STEAM NOZZLE
1. Install the nozzle with baffle directly onto the
humidifier at the location where the hose adapter
was removed. It clicks into place.
2. Insert cylinder base into drain valve. Press down on
the cylinder to ensure it is properly seated in the
drain valve, otherwise it could leak
3. Rotate the cylinder back in place while guiding the
short steam hose attached to the cylinder onto the
duct mount nozzle.
4. Secure the steam hose to the duct mount nozzle with
the hose clamp. Do NOT overtighten, or the duct
mount nozzle could be damaged.
5. Reconnect the cylinder plugs and high water sensor
plug to the cylinder pins.
MOUNT HUMIDIFIER ON DUCT
1. Using the duct mount template supplied with the
humidifier, locate the template on the side of the
duct where the humidifier will not interfere with the
operation or maintenance of the furnace.
2. Following the template, drill a 1-3/4” hole in the
duct to insert the duct mount nozzle.
3. Insert the top screw until 1/4 in. (6 mm) is exposed.
Hang the humidifier via its keyhole on the screw
head (see Fig. 17).
NOTE: The donut-shaped foam gasket must be installed
between the humidifier and the duct.
4. After making sure the humidifier is level, secure it to
the duct using two screws at the duct-mount
locations (Fig. 12), and then replace the cover.
Fig. 17. Duct mount. Install foam gasket between
humidifier and air supply duct.
M37218
2. TILT OUT TO
REMOVE CYLINDER
1. REMOVE WIRE PLUGS
LOOSEN HOSE CLAMP
4. SLIDE DOWN
HOSE GUIDE
WARNING
ElectricShockHazard
Cancause severe injury
or death.
Aseparate groundwire
must be used.
AVERTISSEMENT
Fire Hazard
Cancause severe injury,
death, or substantial
property damage.
Replace only withsame type
of 1.0 amp fast-acting fuse.
32332376-001Rev.A
Risque de chocélectrique
Peut causer des blessures
graves oulamort.
Unfil de mise à la terre
séparéest nécessaire.
Risque d’incendie
Peut causerdes blessures
graves, la mortoudes
dégâts matérielsimportants.
Remplacer seulement avec
le même type defusible à
action rapide de1.0 amp.
3. PRESS ON
RELEASE TAB
M37197
AIR FLOW
FOAM
GASKET
AIR DUCT
MOUNTING
SCREWS

HM750A1000
11 33-00289EF—03
PLUMBING
Fig. 18. Water supply and drain connection.
IMPORTANT
— Use potable water.
— All water supply and drain line connections should
be installed in accordance with local plumbing
codes.
— Drain water is automatically cooled to 160 °F
(71 °C) when HM750 cycles a drain. When an
emergency drain occurs, temperature may be
higher. The drain material (tube and drain) must
be rated for 200 °F (93 °C).
• Supply water should be between 30 and 100 PSIG. A
PRV may be used, if necessary.
•Do not use reverse osmosis or deionized water.
Supply water must be between 125-1200 μS/cm
(microsiemens/cm) for optimal performance.
•Supply water should be cold; 39.2 to 86 °F (4 to 30 °C).
• Install water shut off valve before humidifier to
facilitate servicing.
• The drain line should not end in a sink used frequently
by personnel for safety reasons, or where plumbing
codes prohibit it. Route to a floor drain or connect
directly to building drain system.
• Ensure drain line is adequately sized to provide free
and easy draining. A restricted drain can cause cylinder
water to over concentrate and result in poor operation.
• Drain line must be continuously sloped down from unit.
• If a drain is not located near the humidifier, use a
condensate pump rated for hot drain water.
Connecting the Water Supply Line
Connect water supply line (Copper or LDPE, supplied with
equipment) to the supply connection (Fig. 18). This is done
by pushing the water pipe into the quick-connect fitting.
NOTE: To remove the water supply line, the floating tip of
the fill connection is pushed in slightly, which will
release the grip on the water supply line. The
water supply line is then free to be removed.
Connecting the Drain Line
Connect drain hose (supplied with equipment) to the drain
connection (Fig. 18). Note that there is an internal air gap
in the drain, so no air gap is required external of the
humidifier. The drain line may be connected directly to the
red drain spigot using a gear clamp or similar.
Fig. 19. Proper drain hose routing (anchors not included).
3/4 (19) OD
1/4 LDPE
OR COPPER
WATER LINE
USE 1/2 IN. OD COPPER TO
WITHIN 4 FT (1.2 M) OF HUMIDIFIER.
M37187
ALWAYS INSTALL
A WATER
SHUT-OFF VALVE.
M35855

HM750A1000
33-00289EF—03 12
ELECTRICAL
CAUTION
Wiring to be performed by a licensed electrician.
Installation on a GFCI circuit is recommended.
Do not remove the cover when the humidifier
powered.
CAUTION
Equipment Damage Hazard
Failure to wire the humidifier in accordance with
the wiring instructions may cause permanent
damage to the product and will void the warranty.
Voltage Selection
To select the correct voltage (120 VAC or 240 VAC), ensure
that the jumper is properly placed between the
appropriate terminals of the humidifier control board. The
HM750 is factory-configured for 240 VAC. If the
humidifier will run on a 120 VAC circuit, move the jumper
to the 120 VAC terminals as seen in Fig. 20.
Fig. 20. Voltage selection jumper on
humidifier control board.
Connecting Power
Requirements
• 12 AWG or 14 AWG wire
•Dedicated 15 amp, 120/240-volt circuit (a GFCI circuit
is recommended)
• Disconnect switch (optional. The use of a disconnect
switch between the humidifier and the circuit breaker is
recommended and will be useful for future servicing.).
WARNING
To comply with UL product listing, the HM750
must be hardwired to a dedicated 15 amp circuit.
All wiring must be done per governing electrical
codes. Failure to do so will void the product
warranty.
The use of electric cord plugs can cause
overheating and result in risk of damage to
property and/or personal injury.
Wiring Procedure
1. Install a disconnect switch between the humidifier
and the circuit breaker as shown in Fig. 21 and Fig.
22 (optional).
2. Route the power supply wire through the strain relief
located at the top of the red electrical box.
3. Connect the power wires to MAIN SUPPLY
terminals (L1, L2/N, and GND) on the humidifier
control board.
Fig. 21. 120 VAC (1 Phase) primary power connection.
Fig. 22. 240 VAC (1 Phase) primary power connection.
NOTES:
— Resideo recommends the use of a GFCI circuit
on this device to protect the homeowner from
electrical shock.
— Ensure that adequate power is available to
carry full humidifier amp draw as indicated on
the specification label.
— Do not use neutral wire as a ground; connect a
dedicated ground to ground termination.
— All wiring to be in accordance with national
and local electrical codes.
240VAC
120VAC
M36944
M37206
HM750
Status
Service
Power
Idle
Filling
Humidifying
Draining
Cylinder
Fault
Drain
FaultCodesIn Front Cover
MAIN SUPPLY
L1
L2/N
GND
(OPTIONAL)
OFF ON
M36861A
HOT
NEUTRAL
GROUND
MAIN SUPPLY
L1
L2/N
GND
(OPTIONAL)
OFF ON
M36862A
HOT
HOT
GROUND

HM750A1000
13 33-00289EF—03
Low-voltage Controls
Requirements
• 18 AWG solid wire or greater.
• Low voltage wiring must be routed through the hole
that is to the left of the high voltage strain relief.
• Keep control wires as short as possible.
Wiring Procedure
The humidifier can be connected to the following three
devices (Fig. 23):
1. Humidistat or thermostat
2. Air Proving device (recommended)
3. External fan (required when used with a humidistat).
Humidistat or Thermostat Connection
Connect a humidistat or thermostat to the HUM terminals
of the humidifier. The humidifier provides a 24-VAC source
to power the humidistat or thermostat if needed (5 VA max.).
NOTE: It is acceptable, but not recommended to install
the HumidiPRO in the furnace area (on duct). If
possible, locate the HumidiPRO in a high traffic
area inside the home.
Air Proving Device
Resideo recommends the use of an Air Proving device
such as Resideo Differential Pressure Switch (50027910-
001) to ensure steam is distributed only when there is air
circulation. Connect the air proving device to the AP
terminals. If you do not install an air proving device, place
a jumper between the AP terminals.
Fan Interlock
Connect an external fan (optional) to the EXTERNAL
terminals. The fan will turn on whenever there is a call for
humidity.
Fig. 23. Wiring the steam humidifier with a digital thermostat.
Fan Interlock Wiring with HumidiPRO
When distributing steam into a duct, there could be a call
for humidity when there is no air flow. The HM750 with
HumidiPRO control or some other thermostat can be
used to enable a fan on a call for humidity. If using another
thermostat, consult that control’s manual for wiring
instructions to enable the fan with a powered
humidification device.
NOTE: Humidifier will stop producing steam if the air
proving switch is open or the air proving terminals
AP are not jumped.
This information is relevant to all controls, factory
supplied or otherwise. For wiring use minimum 18 AWG
solid wire and keep as short as possible.
Humidity Control
• Can be located either in return air duct (preferred) or in
room being humidified.
• Avoid placing near discharge diffuser of humidified air.
• Mount in area representative of room humidity (drafts,
doorways, sunlight, or an overhang such as a shelf can
affect reading).
Optional Outdoor Temperature Sensor (included with
HumidiPRO)
• Mount outside in area representing air temperature.
AIR PROVING
(OR JUMPER)
THERMOSTAT, HUMIDISTAT, OR EQUIPMENT INTERFACE MODULE (EIM)
24VAC
COM
HUM
HUM
AIR PROVING JUMPER COMES PRE-INSTALLED.
REMOVE JUMPER IF AIR PROVING IS UTILIZED.
M36863C
AP
AP
GT
RF
GF
Main Supply
Air Proving
Humidistat
External
L1 L2/N GND
2
1
1
WIRING FOR FAN INTERLOCK EQUIPMENT (REQUIRED WHEN USED WITH
A HUMIDISTAT)
2
J14J13
Equipment Interface Module (EIM)

HM750A1000
33-00289EF—03 14
Fig. 24. Wiring the steam humidifier with a mechanical thermostat.
NOTE: If a Prestige, VisionPRO, Round Smart (or similar) is used to control humidity, wire the two U contacts from
thermostat to HUM and HUM on the HM750. With the jumper in place between AP terminals on the HM750, only
these two wires are necessary to control humidity. Be sure to configure the thermostat to force fan on with a call
for humidity if the RF, GT, and GF wiring is not used.
HVAC
THERMOSTAT
R
C
U
U
S
S
GYWR
Rc GYW
R
C
M37760
OUTDOOR
SENSOR
AIR PROVING
OR JUMPER
24VAC
COM
HUM
HUM
AP
AP
GT
RF
GF
Air Proving
Humidistat
External
H6062
HUMIDIPRO
HM750

HM750A1000
15 33-00289EF—03
START UP
Installation Check
Before turning on power to the HM750, inspect the
installation to ensure that it was carried out correctly, as
per these installation instructions.
On/Off
The HM750 is factory-configured to operate as an On/Off
humidifier. It will run when 24 VAC from one HUM terminal
is fed back into the other HUM terminal through an
On/Off humidistat.
WARNING
Personal Injury Hazard.
Damaged or improperly installed units must not be
operated. Damaged or improperly installed units
may present a danger to persons and property.
Start Up Procedure
1. Make sure the voltage selection jumper on the
main circuit board is correctly configured to match
the mains supply voltage (120 VAC or 240 VAC).
2. If a disconnect switch is installed, turn it to the “ON”
position.
3. Ensure the water supply valve is open.
4. Press the Power/Drain button on the front of the
humidifier. This will turn the device on.
• The humidifier will perform a self-diagnostic
sequence during which the LED’s and internal
components will be momentarily activated. See
“LED Status Lights” on page 16 for an
explanation of the LEDs and sequences.
• If an error is detected during the self-diagnostic
sequence the humidifier will not start. The
yellow Fault LED will flash in sequence to
indicate the detected fault. See Tables 6 and 7
for information on diagnosing and correcting
faults.
• After the system test the humidifier is in normal
operation mode.
5. Check and adjust the control set point on the control
humidistat, and if applicable, the high limit
humidistat. This will enable a call for humidity.
6. If the fan enable relay on the control board is used,
the green LED will continue to flash until the air
proving closes. Once the air closes, the flashing
green LED will become solid and the humidifier will
start steam production.
7. When the external humidistat calls for humidity, and
the air proving terminals are closed, the Filling LED
on the front of the humidifier will light up, the power
relay on the control board will engage, the water fill
valve will activate (after a delay), and the cylinder will
slowly fill with water.
NOTE: While the cylinder is filling with water there
should be no water flowing down the drain. If
water is flowing down the drain it can indicate
excessive backpressure or a leaking drain valve.
See Troubleshooting.
8. It can take up to 20 minutes for the water to be
heated up by the submerged electrodes and for
steam to be produced.
NOTE: The humidifier is shipped with a salt tablet
already inserted inside the steam cylinder. The
first start-up will provide a first boil in
5-20 minutes, depending on the water supply
conductivity.
NOTE: If the humidifier is being restarted after it has
been drained, and it has already gone through
several boil down cycles, it may take a longer
period of time for the HM750 to reach full output
capacity. It may take several hours with low
conductivity water. During this time, the
humidifier will not perform any drains and the
conductivity of the water in the cylinder will
increase.
NOTE: The humidifier performs drains intermittently as
part of its normal process of optimizing the
conductivity of the water in the cylinder. During
these drains, the Drain LED will not illuminate.

HM750A1000
33-00289EF—03 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. Resideo 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

HM750A1000
17 33-00289EF—03
Fig. 26. Humidifier components.
HM750
Status
Service
Power
Idle
Filling
Humidifying
Draining
Cylinder
Fault
Drain
Fault Codes In Front Cover
M37211
STEAM
OUTLET
HIGH
WATER
SENSOR
USER
INTERFACE
POWER/DRAIN
BUTTON
FILL
VALVE
QUICK
CONNECTOR DRAIN
OUTLET
DRAIN
VALVE
STEAM
CYLINDER
CYLINDER
PLUGS
FILL
CUP
Component Function
Cylinder plugs Power connectors to electrodes in cylinder.
Drain outlet Connection to drain hose, used to remove water from the humidifier.
Drain valve Drains water from humidifier.
Fill cup Provides an air gap for backflow prevention.
Fill valve Controls flow of water into humidifier.
High water sensor Used to detect maximum water level in cylinder.
Power/Drain button Used to turn the humidifier on or off. Note that before the humidifier turns off, the water in the
cylinder is drained.
CAUTION
The unit will still be powered internally even after being shut down.
Steam cylinder Steam generating vessel that holds electrodes in water. Current between electrodes generates
heat used to generate steam.
Steam outlet Connects to steam guide with short piece of steam hose.
Supply water
connection Connection for supply water.
User interface Used to indicate the status of the humidifier to the user.

HM750A1000
33-00289EF—03 18
MAINTENANCE AND SERVICING
Required Maintenance
The HM750 humidifier has been designed to require
minimal maintenance. Regular maintenance consists of
checking the humidifier to ensure it is in good condition,
replacing the cylinder when the software advises that the
cylinder is spent and cleaning out the drain valve
whenever the cylinder is replaced.
CYLINDER
The cylinder LED will indicate when to replace the device
cylinder (see page 16). Approximate frequency of
replacement is once per year.
NOTE: It is normal to hear a rattle in a new cylinder
because it is shipped with a salt tablet to boost
conductivity.
FILL VALVE
The inlet to the fill valve is equiped with a strainer that
prevents debris in low quality supply water from entering
the system. Accumulation of debris on the strainer can
lead to reduced inlet water flow or complete blockage.
Thus, the fill valve strainer should be cleaned periodically,
depending on the water quality, or at the end of each
season.
DRAIN VALVE
Inspect annually.
Remove and clean scale/debris at the end of each season,
or as needed.
Running on highly conductive water can generate high
amount of scale leading to blockage of the valve plunger,
potentially causing a continuous leak. This could be
detected by the control system indicating a drain fault or
triggering GFCI if electric current leak is detected.
In all cases, proper cleaning of the drain valve is
recommended.
HOSE CONNECTIONS
Inspect annually, clean as necessary.
NOZZLE (DUCT OR REMOTE)
Inspect annually, clean as necessary.
Extended Shutdown
Should it be required to disconnect power to the
humidifier for a period of extended shut-down, the
following procedure shall be followed:
1. Press the Power/Drain button.
2. Wait until the humidifier is completely drained
(usually takes less than 10 minutes). During the
drain cycle the fill valve will be activated to temper
the drain water.
3. Shut off the power to the humidifier with the external
disconnect.
4. Close the supply water shut-off valve.
NOTE: As long as the HM750 is powered, it will
automatically drain the cylinder when there has
not been a call for humidity for an extended
period of time (3 days). This feature will reduce or
prevent the possibility of corrosion and the
accumulation of algae and bacteria growing in
the cylinder. The cylinder will remain empty until
there is a call for humidity at which time the fill
valve will open and refill the cylinder. The unit will
go through its normal process for optimum
operation.
STARTING AFTER EXTENDED SHUTDOWN
1. Check to see the humidifier has not been damaged
and the installation has not been altered. See “Start
Up Procedure” on page 15.
2. Turn on the power to the humidifier with the external
disconnect and open the supply water shut-off valve.
3. Press the Power/Drain button.
4. Ensure there is no water flowing to drain.
5. Follow the start up procedure on page 15.

HM750A1000
19 33-00289EF—03
REPLACEMENT PARTS
CAUTION
Before Servicing
1. Disconnect main power source before accessing
internal compartments.
2. The plumbing and electrical compartments
contain high voltage components and wiring.
Access should be limited to licensed HVAC
professionals only.
3. During and following operation of the humidifier,
the steam components in contact with the steam
such as the cylinder, steam lines, steam
distributors, and condensate lines can become
hot and burn if touched.
4. Installations of humidity equipment installed by
unqualified personnel or the use of non-Resideo
parts and components will void warranty.
Cylinder Spent Fault
The yellow cylinder 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 cylinder LED will flash on and off, during which time
the humidifier will continue to operate as normal. After 7
days of flashing, and if the cylinder is not replaced, the
humidifier will shut down and the cylinder LED will be
on constantly (no flashing). At this point, the cylinder
must be replaced.
The steam cylinder is disposable and must be replaced at
end of cylinder life. Cylinder life is dependent on water
supply conditions and humidifier use.
Always clean the drain valve before installing a new
cylinder. Scale from the spent cylinder may have fallen
into the drain valve and could prevent its proper operation.
To properly clean the drain valve, it must be removed and
disassembled.
CAUTION
Equipment Damage
Failure to replace the cylinder at the end of cylinder
life will result in improper operation and may result
in damage to the humidifier. Resideo is not
responsible for any damages resulting from, or
attributed to, the failure to replace a spent cylinder.
NOTE: Resideo recommends keeping a replacement cyl-
inder in stock throughout the humidification sea-
son. This will prevent possible downtime when the
humidifier reaches cylinder end of life.
CYLINDER REPLACEMENT KIT
Product Number: HM750ACYL
Dimensions: See Fig. 27
Included in the Box
• Replacement Cylinder
Tools Needed
• Screwdriver
• Adjustable Wrench
•Pliers
Fig. 27. Measurements in inches (mm).
M37222
WATER INLET
AND DRAIN
12-51/64
(325)
Ø 5-45/64
(145)
STEAM OUTLET
1 (25)

HM750A1000
33-00289EF—03 20
Removing the Cylinder
WARNING
Disconnect main power source before accessing
internal compartments.
The inside of the humidifier cabinet contains high
voltage components and wiring. Access should be
limited to authorized personnel.
1. Drain the existing cylinder by pressing the
Power/Drain button on the front of the humidifier for
1 second. Let the humidifier drain until no more
water is flowing out to drain (usually not more than
10 minutes). Following the drain cycle, the
humidifier will switch off.
2. Close the supply water shut off valve.
3. Turn off power to the humidifier with the external
disconnect.
4. Using a flat screwdriver, turn the lock on the
humidifier’s front cover 90° counterclockwise to
release. Rotate the base of the cover outwards
6 inches, then lift upwards to remove.
Fig. 28. Removing the cover.
5. Remove the high level water sensor connections.
6. Remove the cylinder plugs from the cylinder pins by
pulling vertically.
7. Using a flat screwdriver or 5/16 in. nut driver, loosen
the hose clamp closest to the cylinder.
8. Pull the cylinder away from the steam hose to
disengage. When free of steam hose, lift the cylinder
out.
9. Some water may remain in the cylinder, even after
fully draining. Have a cloth available to absorb any
water.
Fig. 29. Removing the cylinder.
IMPORTANT
Always clean the drain valve before installing a
new cylinder. Scale from the spent cylinder may
have fallen into the drain valve and could prevent
proper operation. See page 21 for instructions.
10. Install the new cylinder by following the above
instructions in reverse order ensuring;
a. Cylinder is fully seated in drain valve;
b. Hose clamp is tightened to 12 in/lb.;
c. Cylinder plugs are securely reconnected.
1. TURN LOCK
90˚ COUNTER
CLOCKWISE.
3. LIFT COVER.
2. TILT BASE
OUT 6 INCHES.
MCR37236
1. LOOSEN
HOSE CLAMP
3. PULL
CYLINDER
AWAY FROM
HOSE BY
TILTING
CYLINDER.
2. REMOVE
CYLINDER
PLUGS BY
PULLING
VERTICALLY.
4. LIFT
CYLINDER
OUT FROM
DRAIN VALVE.
MCR37237