MHU 80
OPERATING INSTRUCTIONS
Model #
AND OWNER’S MANUAL
READ INSTRUCTIONS CAREFULLY: Read and follow all instructions. Place instructions in a safe
place for future reference. Do not allow anyone who has not read these instructions to assemble,
light, adjust or operate the heater.
For model serial numbers,
see page E16.
LANGUAGES
ENGLISH
Pages E1 — E16
SPANISH
Pages S1 — S16
COMPACT UNIT HEATER FOR COMMERCIAL USE
COMPACT UTILITY HEATER FOR RESIDENTIAL USE
FRENCH
Pages F1 — F16
MHU 50
MHU 80
WARNING: Improper installation, adjustment, alteration, service or maintenance
can cause injury or property damage. Refer to this manual. For assistance or
additional information consult a qualified installer, service agency or the gas supplier.
—
WHAT TO DO IF YOU SMELL GAS
• Open Windows
• DO NOT try to light any appliance.
• DO NOT use electrical switches.
• DO NOT use any telephone in your house. Immediately call your local gas supplier from a
neighbor’s telephone. Follow the gas supplier’s instructions.
• Do not touch any electrical switch; do not use any phone in your building.
• Installation and service must be performed by a qualified installer, service agency or the gas
supplier.
• If you cannot reach your gas supplier, call the Fire Department.
FOR YOUR SAFETY:
Do not store or use gasoline or other flammable vapors and liquids in the vicinity of this or any other appliance.
WARNING: If the information in these instructions are not followed exactly, a fire or
explosion may result causing property damage, personal injury or loss of life.
02/12 Rev. 12A #60185MR. HEATER, INC., 4560 W. 160TH ST., CLEVELAND, OHIO 44135 •800-251-0001
WARNING:
YOUR SAFETY IS IMPORTANT TO YOU AND TO OTHERS,
SO PLEASE READ THESE INSTRUCTIONS BEFORE YOU
OPERATE THIS HEATER.
GENERAL HAZARD WARNING:
FAILURE TO COMPLY WITH THE PRECAUTIONS AND
INSTRUCTIONS PROVIDED WITH THIS HEATER, CAN
RESULT IN DEATH, SERIOUS BODILY INJURY AND
PROPERTY LOSS OR DAMAGE FROM HAZARDS OF
FIRE, EXPLOSION, BURN, ASPHYXIATION, CARBON
MONOXIDE POISONING, AND/OR ELECTRICAL SHOCK.
ONLY PERSONS WHO CAN UNDERSTAND AND FOLLOW
THE INSTRUCTIONS SHOULD USE OR SERVICE THIS
HEATER.
IF YOU NEED ASSISTANCE OR HEATER INFORMATION
SUCH AS AN INSTRUCTION MANUAL, LABELS, ETC.
CONTACT THE MANUFACTURER.
THE STATE OF CALIFORNIA REQUIRES THE FOLLOWING WARNINGS:
WARNING:
FIRE, BURN, INHALATION, AND EXPLOSION HAZARD.
KEEP SOLID COMBUSTIBLES, SUCH AS BUILDING
MATERIALS, PAPER OR CARDBOARD, A SAFE DISTANCE
AWAY FROM THE HEATER AS RECOMMENDED BY THE
INSTRUCTIONS NEVER USE THE HEATER IN SPACES
WHICH DO OR MAY CONTAIN VOLATILE OR AIRBORNE
COMBUSTIBLES, OR PRODUCTS SUCH AS GASOLINE,
SOLVENTS, PAINT THINNER, DUST PARTICLES OR
UNKNOWN CHEMICALS.
WARNING: Combustion by-products produced when using this product contain carbon monoxide, a chemical
known to the State of California to cause cancer and birth defects (or other reproductive harm).
WARNING: This product contains chemicals, including lead, known to the State of California to cause cancer and
birth defects or other reproductive harm. Wash your hands after handling.
CONTENTS
UNIT DIMENSIONS ................................................................E-4
SHIPPING ...............................................................................E-5
REQUIREMENTS .....................................................................E-5
UNIT HEATER INSTALLATION..................................................E-6
COMBUSTION & VENTILATION AIR ........................................E-6
VENTING .......................................................................... E-6-10
ELECTRICAL CONNECTIONS ................................................. E-10
GAS CONNECTION ...............................................................E-11
LEAK CHECK .........................................................................E-11
START-UP OPERATION ...........................................................E-11
HEATING SEQUENCE OF OPERATION ................................... E-12
IGNITION CONTROL LED ...................................................... E-12
ADJUSTMENTS..................................................................... E-12
SERVICE ............................................................................... E-13
WIRING DIAGRAM ............................................................... E-13
PARTS LIST ........................................................................... E-14
WARRANTY ......................................................................... E-16
Compact Unit / Utility Heater Operating Instructions and Owner’s Manual
E-2
AIR
FLOW
HEAT EXCHANGER
(ALUMINIZED STEEL)
HANGING
BRACKETS
MHU 50/MHU 80 UNIT DIMENSIONS
(N-NATURAL GAS, P-PROPANE)
MOUNTING SLOTS (Typical)
5/16 x 3 Inches (8 x 76 mm)
DIMENSION 50 80
A 12 (305) 17 (432)
B 5-1/2 (140) 6-1/2 (165)
C 4-1/4 (108) 6-3/4 (171)
TOP VIEW
START–UP AND PERFORMANCE CHECK LIST
Job Name: __________________________________________
Job Location: ________________________________________
Installer: ____________________________________________
Unit Model No.: ______________________________________
Electrical Connections Tight? _______________________________________________
Supply Voltage ___________________________________________________________
Gas Piping Connections Tight & Leak-Tested? __________________________________
Motor Amps _____________________________________________________________
Furnace Btu Input ________________________________________________________
Line Pressure ____________________________________________________________
Manifold Pressure w.c. ____________________________________________________
Job No.: ______________________________________
City: _________________________________________
City: _________________________________________
Serial No.:_____________________________________
HANGING
BRACKETS (2)
ADJUSTABLE
SERVICE
ACCESS PANEL
LOUVERS
SIDE VIEW
Date: _______________________________________
State/Province: _______________________________
State/Province: _______________________________
Service Technician: ____________________________
Flue Connections Tight? __________________________________________________
Fan Timer Operation Checked? _____________________________________________
THERMOSTAT
Calibrated? _____________________________________________________________
Heat Anticipator Properly Set?
Level? _________________________________________________________________
E-3
Operating Instructions and Owner’s ManualCompact Unit / Utility Heater
SHIPPING
The heater is completely assembled. Installation instructions,
two mounting brackets (shipped loose), and a flue transition are
included. Check the unit for shipping damage. The receiving party
should contact the last carrier immediately if any shipping damage
is found.
REQUIREMENTS – CSA IN THE USA
Installation of gas unit heaters must conform with local building
codes or, in the absence of local codes, with the current National
Fuel Gas Code ANSI Z223.1.
Installation in aircraft hangers must be in accordance with the
current Standard for Aircraft Hangers ANSI/NFPA No. 409.
Installation in parking structures must be in accordance with the
current Standard for Parking Structures ANSI/NFPA No. 88A.
Installation in repair garages must be in accordance with the
current Standard for Repair Garages ANSI/NFPA No. 88B.
These units are approved for residential applications. For
installation in a residential garage these units must be installed
so that the bottom of the heater is located no less than 8 feet
(2.438m) above floor. Heater must be located or protected to
avoid physical damage by vehicles. Refer to the National Fuel Gas
Code, ANSI Z223.1, current edition.
Authorities having jurisdiction should be consulted before NFPA
installation. Air for combustion and ventilation must conform
to the methods outlined in ANSI Z223.1, section 5.3, Air for
Combustion and Ventilation, or applicable provisions of local
building codes. The National Fuel Gas Code is available from:
American National Standard Institute Inc.
11 West 42nd Street
New York, NY 10036
These units are CSA International design certified. These unit
heaters are certified for installation to combustible material
as listed in table 1 and on unit rating plate. Accessibility and
service clearances must be observed in addition to fire protection
clearances.
All electrical wiring and ground for unit must be in accordance
with the regulations of the current National Electric Code ANSI/
No. 70.
The National Electric Code is available from:
National Fire Protection Association
1 Batterymarch Park
PO Box 9101
Quincy, MA 02269-9101
TABLE 1
UNIT CLEARANCES
Top Sides Access Panel
in mm in mm in mm
1 25 1 25 18 457
Bottom Rear Single Wall Vent*
in mm in mm in mm
0 0 18 456 6 152
*Except for listed clearance thimbles.
REQUIREMENTS – CSA IN CANADA
The instructions are intended only as a general guide and do not
supersede local codes in any way. Authorities having jurisdiction
should be consulted before installation. The installation must
conform with local building codes or in the absence of local
codes, with the current CSA B149.1, Natural Gas and Propane
Installation Code. All electrical wiring and grounding for the unit
must also comply with the Canadian Electrical Code CSA C22.1,
current edition.
These heaters are CSA International certified for the clearances to
combustible material listed on the rating plate and table1. Provide
adequate clearance around air openings into the combustion
chamber, clearances from combustible material, and provisions
for accessibility and for combustion and ventilation air supply.
Provision shall be made for service accessibility to the heater.
Note that fire protection clearances may be exceeded to provide
additional space for service and accessibility.
GARAGE INSTALLATIONS:
Installation in parking structures must be in accordance with the
current Standard for Parking Structures ANSI/NFPA No. 88A.
Installation in repair garages must be in accordance with the
current Standard for Repair Garages ANSI/NFPA No. 88B.
1. In a storage area, clearance from heaters to combustible
materials must be such that the material shall not attain a
temperature above 160°F by continuous operation of the unit.
2. Eight foot minimum clearance from the floor to the bottom
of the heater must be maintained. Refer to the CSA B149.1,
Natural Gas and Propane Installation Code
AIRCRAFT HANGER:
Installation of gas unit heaters must conform with local building
codes or, in the absence of local codes, with the current National
Fuel Gas Code ANSI Z223.1.
1. In an area where aircraft are housed or serviced, 10’
minimum clearance from highest surface of aircraft to bottom
of the heater must be maintained.
2. In other areas, 8’ minimum clearance from the floor to
bottom of heater must be maintained.
3. Heaters should be located so as to be protected from
damage from aircraft or other appliances needed for
servicing of aircraft. Refer to requirements of the enforcing
authorities.
Compact Unit / Utility Heater Operating Instructions and Owner’s Manual
E-4
These units are certified for residential applications. For installation
in a residential garage, these units must be installed so that
burners and ignition source are located no less than 18” (457mm)
above floor. Heater must be located or protected to avoid physical
damage by vehicles. Refer to CSA B149.1, Natural Gas and Propane
Installation Code current edition.
In a confined area, the heater must be installed in accordance
with the CSA B149.1, Natural Gas and Propane Installation Code.
Be sure to check with local codes and ordinances for additional
requirements.
UNIT HEATER INSTALLATION
Unit is shipped ready for installation. Unit may be installed as
shown in figure 1 or inverted 180
as governed by clearances, vent connection, air direction, gas
supply, electrical supply and service accessibility.
1. If installing unit in an inverted position: Remove and retain
screws securing door and rotate door 180
retained screws. Rotate louvers directing airflow as desired.
2. Choose location for mounting brackets.
3. Remove and retain three screws along top edge (bottom
edge when inverted) of front of unit.
4. Align screw holes on mounting bracket with holes along
top edge (either upright or inverted) of unit. Secure one
mounting bracket to front of unit with retained screws.
Secure other mounting bracket to back of unit with screws
provided in bag assembly containing flue transition.
5. To support unit, secure mounting bracket to ceiling joist or
truss. Unit may also hang on rods as shown in figure 1.
INSTALL UNIT / UTILITY HEATER
MOUNTING
BRACKETS (2)
o
depending on desired location
o
. Secure with
FIGURE 1
SUPPORT
RODS
Gas Code, ANSI Z223.1, in the U.S.A., CSA B149.1 Natural Gas
and Propane Installation Code, or applicable provisions of local
building codes.
All gas fired appliances require air to be used for the combustion
process. In many buildings today, there is a negative indoor air
pressure caused by exhaust fans, etc. If sufficient quantities of
combustion air are not available, the heater or another appliance
will operate in an inefficient manner, resulting in incomplete
combustion which can result in the production of excessive carbon
monoxide.
CAUTION Insufficient combustion air can cause headaches,
nausea, dizziness, asphyxiation or death.
If indoor air is to be used for combustion, it must be free of the
following substances or the life of the heat exchanger will be
adversely affected: chlorine, carbon tetrachloride, cleaning solvent,
halogen refrigerants, acids, cements and glues, printing inks,
fluorides, paint removers, varnishes, or any other corrosives.
VENTING
A – GENERAL RECOMMENDATIONS AND
REQUIREMENTS
NOTE: The vent is a passageway, vertical or nearly so, used to
convey flue gases from an appliance, or its vent connector, to the
outside atmosphere. The vent connector is the pipe or duct that
connects a fuel-gas burning appliance to a vent or chimney.
Unit heaters must be vented in compliance with all local codes
or requirements of the local utility, the current standards of the
(American) National Fuel Gas Code, ANSI Z223.1 or (Canada)
CSA B149.1 Natural Gas and Propane Installation Code, and the
following instructions.
A metal stamped/extruded transition is supplied with this certified
unit. It must not be modified or altered and must be installed
on the outlet of the induced draft blower assembly prior to the
installation of the vent or vent connector. Failure to comply with
this requirement will void the certification of the unit by the
approval agencies. All joints shall be secured with at least two
corrosion resistant screws. All joints must be checked for gas
tightness after installation.
COMBUSTION AND VENTILATION AIR
Adequate facilities for supplying air for combustion and ventilation
must be provided in accordance with the latest edition of section
5.3, Air for Combustion and Ventilation, of the National Fuel
TABLE 2
MAXIMUM VENT LENGTHS
HORIZONTAL VENTS
No. of ft m
Elbows
1 25 7.6
2 20 6.1
3 15 4.6
4 10 3.0
5 5 1.5
Maximum length of vent connector not to exceed 30 ft. (9.1m).
Operating Instructions and Owner’s ManualCompact Unit / Utility Heater
E-5
B – VERTICAL VENTS USING METAL VENT
VENT TERMINATION ON SINGLE WALL VENT
SINGLE WALL TERMINATION
DOUBLE WALL (TYPE B-1) TERMINATION
ROOF FLASHING
ROOF PITCHED
FROM 0” TO 45”
SHALL NOT BE A
CONCEALED SPACE
2” CLEARANCE
THIMBLE
ROOF FLASHING
ROOF PITCHED
FROM 0” TO 45”
12” MAX
CLEARANCE TO BE AS
SPECIFIED ON TYPE “B”
VENT PIPE
SEAL JOINT BETWEEN SINGLE WALL VENT
AND “B”VENT AND THE ANNUL AR SPACE OF THE “B” VENT
PIPE – COMMERCIAL AND RESIDENTIAL
INSTALLATIONS
HSU compact unit heaters are listed as Category I appliances for
vertical vent installations.
1. HSU unit heaters are to be used with NFPA- or ANSI-approved
chimneys, U.L. listed type B-1 gas vents, single wall metal
pipe, or listed chimney lining system for gas venting where
applicable, as well as the modifications and limitations listed
in figure 2. Seal single wall vent material according to the
section A - General Recommendations and Requirements.
2. The vent connector shall be 3” (76mm) diameter on 50 units.
In all cases, a flue transition piece (supplied) is required to
fit over the outlet of the induced draft assembly on the
appliance.
3. Keep the vent connector runs as short as possible with
a minimum number of elbows. Refer to the (American)
National Fuel Gas Code ANSI Z223.1 or (Canada) CSA B149.1
Natural Gas and Propane Installation Code for maximum
vent and vent connector lengths. Horizontal run of the vent
connector from the induced draft blower to the chimney/vent
cannot exceed the values in table 2.
4. When the length of a single wall vent, including elbows,
exceeds 5 feet (1.5m), the vent shall be insulated along
its entire length with a minimum of 1/2” thick foil faced
fiberglass 1-1/2# density insulation. If a single wall vent is
used in an unheated area it shall be insulated. Failure to do
so will result in condensation of flue gases.
5. The unit may be vented vertically as a single appliance or as
a common vent with other gas-fired appliances. In common
venting situations, vent connectors for other appliances
must maintain a 4” (100mm) vertical separation between
the vent connectors. Refer to common venting tables in the
(American) National Fuel Gas Code ANSI Z223.1 or (Canada)
CSA B149.1 Natural Gas and Propane Installation Code for
proper vent size.
6. Clearance to combustible material is 6” (152mm) for single
wall vent material except where a listed clearance thimble is
used. Clearance to combustible material for type B-1 vent or
factory-built chimney is per manufacturer’s instructions.
7. The vent connector shall be supported without any dips or
sags. Vertical vents shall be supported in accordance with
their listing and manufacturers’ instructions. All horizontal
vent connector runs shall have a slope up to the vertical vent
of at least 1/4” per foot (1mm per 50mm).
8. All vertical type B-1 vents, single wall vents, or listed chimney
lining system must be terminated with a listed vent cap or
listed roof assembly.
9. The vent must extend at least 3’ (1m) above the highest point
where it passes through a roof of a building and at least 2’
(0.6m) higher than any part of a building within a horizontal
distance of 10’ (3.05m) unless otherwise specified by the
(American) National Fuel Gas Code, ANSI Z223.1 or (Canada)
CAN/CGA-B149 Installation Code. The vent must extend at
least 5’ (1.6m) above the highest connected equipment flue
collar.
Compact Unit / Utility Heater Operating Instructions and Owner’s Manual
FIGURE 2
C – HORIZONTAL VENTING – GENERAL
Due to changes to Z83-8 2009 CSA2.6-2009, the use of single
wall B-Vent is no longer permitted as an acceptable material
when venting horizontally, this change covers both residential
and commercial installations. All horizontally vented units
manufactured after July of 2011 must be vented as a Caterory
III Unit/Utility Heater in compliance with UL 1738 & ULS636.
Common venting is not allowed when horizontally venting the unit
heater.
The minimum horizontal vent length is three feet (914mm).
1. If possible, do not terminate the horizontal vent through a
wall that is exposed to prevailing wind. Exposure to excessive
winds can affect unit performance.
2. Vent termination must be free from obstructions and at least
12” (306mm) above grade level and maximum snow height.
3. Do not terminate vent directly below roof eaves or above
a walkway, or any other area where condensate dripping
may be troublesome and may cause some staining. Avoid
windows where steam may cause fogging or ice buildup.
4. When horizontally vented, minimum clearance for termination
from any door, window, gravity air inlet, gas or electric
meter, regulators, and relief equipment is 4 ft. (1.2m) for U.S.
installations. Refer to NFPA 54/ANSI Z223.1 in the U.S.A. and
CSA B149.1 Natural Gas and Propane Installation Code and
.2 in Canada or with authorities having local jurisdiction. In
Canada, vent termination must have a minimum 6 ft. (1.8
m) horizontal clearance from gas and electric meters and
relief devices as specified in the Canadian B149.1, Natural Gas
Installation Code.
E-6
5. Vent termination must be a minimum of 4’ (1.2m) below or
4’ (1.2m) horizontally from any soffit vent or under-eave vent.
6. Vent must be a minimum of 6’ from an inside corner formed
by two exterior walls. If possible, leave a 10’ clearance.
7. Vent termination must be a minimum of 10’ (3m) from any
forced air inlet (includes fresh air inlet for other appliances,
such as a dryer).
8. When termination is routed through an exterior combustible
wall the vent must be supported using a listed clearance
thimble. Seal the connection between the single wall and
double wall pipes and the annular space of the double wall
pipe as shown in figure 2. Inside edge of vent termination
tee must be at least 12 inches from outside wall as shown in
figure 3.
9. For horizontal venting, the vent pipe shall be supported with
hangers no more than 3ft. (1m) apart to prevent movement
after installation.
D – HORIZONTAL VENTING – COMMERCIAL
1. Horizontal commercial installations are for buildings which
are not attached to living spaces. The vent may be single wall
vent material installed according to the sections
Venting A - General Recommendations and
Requirements and C - Horizontal Venting General and D -
Horizontal Venting - Commercial. Refer to figure 3.
2. The vent pipe diameter for horizontal commercial installations
shall be 4” (76mm) on 50 units. In all cases, a flue transition
piece (supplied) is required to fit over the outlet of the
induced draft assembly on the appliance.
3. Refer to table 2 for maximum vent connector lengths.
4. Select a wall termination point that will maintain ¼” rise per
foot slope of horizontal run of vent pipe.
5. For upward sloped vent a condensate tee and drain must
be installed within the first 5’ (1.5m) from the unit heater
to protect the appliance. If a flexible condensate drain line
is used, the drain line must include a loop entering the
structure. If the unit is shut down for an extended period of
time and will be exposed to sub-freezing temperatures, the
condensate may freeze.
E – HORIZONTAL VENTING – RESIDENTIAL
1. For horizontal residential installations these units are
certified as Category III appliances. Venting A - General
Recommendations and Requirements and C - Horizontal
Venting General and E - Horizontal Venting - Residential.
Refer to figure 6.
2. The vent pipe diameter for horizontal residential installations
shall be 4” (100mm) on 50 and 80 units. A standard vent
transition is required at unit in addition to the transition
supplied with the unit.
3. The maximum vent length is 5’ (1.5m) plus one 90-degree
elbow. The minimum length is 3’(.91m).
4. The vent must maintain a ¼” rise per foot of slope upwards
toward the termination.
CONDENSATE DRAIN THROUGH TEE PIPE AND DRAIN LOOP
UPWARD SLOPE ON HORIZONTAL VENT-COMMERCIAL INSTALLATION
CATEGORY III VENT ACCORDING TO THESE INSTALLATION INSTRUCTIONS.
SLOPE: + 1/4 INCH FOR 1 FOOT RUN MINIMUM.
INDUCED DRAFT BLOWER
NOTE - MINIMUM HORIZONTAL LENGTH 3 FT. (914MM),
NOT INCLUDING CAP FOR TERMINATION. REFER TO TABLE
2 FOR MAXIMUM LENGTH AND NUMBER OF ELBOWS.
COMMON VENTING NOT ALLOWED WHEN HORIZONTALLY VENTING THE UNIT / UTILITY HEATER
FLUE TRANSITION
(PROVIDED)
LISTED THIMBLE
THROUGH COMBUSTIBLE
WALL
DRAIN LOOP WITH WATER
TRAP (TO CONDENSATE DRAIN)
FIGURE 3
12 INCHES MIN.
(30.5 CM)
EXHAUST VENT
TERMINATION TEE
12” (30.5 CM)
MINIMUM ABOVE ALL
HIGHEST SNOWFALL
E-7
Operating Instructions and Owner’s ManualCompact Unit / Utility Heater
INDUCED DRAFT BLOWER
CATEGORY III VENT ACCORDING TO THESE INSTALLATION
INSTRUCTIONS.
SLOPED: + 1/4 INCH FOR 1 FOOT RUN MINIMUM.
NOTE - MINIMUM HORIZONTAL LENGTH 3FT. (914MM), NOT
INCLUDING CAP FOR TERMINATION.
MAXIMUM HORIZONTAL LENGTH 5FT. (1.5M) PLUS ONE
90-DEGREE ELBOW.
COMMON VENTING NOT ALLOWED WHEN HORIZONTALLY VENTING THE UNIT / UTILITY HEATER.
HORIZONTAL VENTING - RESIDENTIAL INSTALLATION
FLUE TRANSITION
(PROVIDED)
UPWARD SLOPE
12 INCHES
MIN. (30.5CM)
VENT TERMINATION CAP
LISTED THIMBLE THROUGH
COMBUSTION WALL
FIGURE 6
F – VENTING USING A MASONRY CHIMNEY
The following additional requirements apply when a lined masonry
chimney is being used to vent the compact unit / utility heater.
1. Masonry chimneys used to vent Category I units heaters
must be either tile-lined or lined with a listed metal lining
system or dedicated gas vent. Unlined masonry chimneys are
prohibited. A category I appliance must never be connected
to a chimney that is servicing a solid fuel appliance. If a
fireplace chimney flue is used to vent this appliance, the
fireplace opening must be permanently sealed.
2. A fan assisted unit heater may be commonly vented into an
existing lined masonry chimney provided:
• The chimney is currently serving at least one draft-hood
equipped appliance.
• The vent connector and chimney are sized in accordance
with venting tables in the (American) National Fuel Gas
Code ANSI Z223.1 or (Canada) CSA B149.1 Natural Gas
and Propane Installation Code.
IMPORTANT Single appliance venting of a fan assisted unit
heater into a tile lined masonry chimney (interior or outside wall)
is prohibited. The chimney must first be lined with either type B-1
vent or an insulated single wall flexible vent lining system, sized
in accordance with venting tables in the (American) National Fuel
Gas Code ANSI Z223.1 or (Canada) CSA B149.1 Natural Gas and
Propane Installation Code.
3. A type B-1 vent or masonry chimney liner shall terminate
above the roof surface with a listed cap or a listed roof
assembly in accordance with the terms of their respective
listings and the vent manufacturer’s instructions.
4. Do not install a manual damper, barometric draft regulator, or
flue restrictor between the unit heater and the chimney.
5. If type B-1 double-wall vent is used inside a chimney, no other
appliance can be vented into the chimney. Outer wall of type
B-1 vent pipe must not be exposed to flue products.
6. Insulation for the flexible vent pipe must be an encapsulated
fiberglass sleeve recommended by the flexible vent pipe
manufacturer.
7. The space between liner and chimney wall should NOT
be insulated with puffed mica or any other loose granular
insulating material.
8. If type B-1 vent or an insulated flexible vent pipe cannot be
used as liners, the chimney must be rebuilt to accommodate
one of these methods or some alternate approved method
must be found to vent the appliance. When inspection
reveals that an existing chimney is not safe for the intended
purpose, it shall be rebuilt to conform to nationally
recognized standards, lined or relined with suitable materials
or replaced with a gas vent or chimney suitable for venting
unit heaters. The chimney passageway must be checked
periodically to ensure that it is clear and free of obstructions.
G – REMOVAL OF UNIT FROM COMMON VENT
In the event that an existing unit heater is removed from a venting
system commonly run with separate gas appliances, the venting
system is likely to be too large to properly vent the remaining
attached appliances. The following test should be conducted while
each appliance is in operation and the other appliances are not in
operation, yet remain connected to the common venting system.
If the venting system has been installed improperly, the system
must be corrected.
1. Seal any unused openings in the common venting system.
2. Visually inspect the venting system for proper size and
horizontal pitch. Determine there is no blockage or
restriction, leakage, corrosion, or other deficiencies which
could cause an unsafe condition.
3. If practical close all building doors and windows and all
doors between the space in which the appliances remaining
connected to the common venting system are located and
other spaces of the building. Turn on clothes dryers and any
appliances not connected to the common venting system.
Turn on any exhaust fans, such as range hoods and bathroom
exhausts, so they will operate at maximum speed. Do not
operate a summer exhaust fan. Close fireplace dampers.
4. Follow the lighting instructions. Place the appliance being
inspected in operation. Adjust thermostat so appliance will
operate continuously.
Compact Unit / Utility Heater Operating Instructions and Owner’s Manual
E-8
LINE VOLTAGE FIELD WIRING
L1
N
EQUIPMENT
GROUND
BLACK WIRE WITH WHITE TAPE OR
WHITE WIRE WITHOUT TAPE
FIGURE 7
GAS SUPPLY CONNECTION
GROUNDED
JOINT UNION
DRIP LEG
FIGURE 8
GAS SUPPLY TO UNIT HEATER
MANUAL MAIN SHUT-OFF VALVE
WILL NOT HOLD NORMAL TEST
PRESSURE
UNIT
BLACK
BLACK
WHITE
WHITE
MANUAL
MAIN SHUT-OFF VALVE
(FURNISHED BY INSTALLER)
GAS FLOW
ISOLATE
GAS VALVE
5. Test for spillage at the draft hood relief opening after five
minutes of main burner operation. Use the flame of a match
or candle, or smoke from a cigarette, cigar, or pipe.
6. After it has been determined that each appliance remaining
connected to the common venting system properly vents
when tested as outlined above, return doors, windows,
exhaust fans, fireplace dampers and any other gas-burning
appliance to their previous condition of use.
7. If improper venting is observed during any of the above
tests, the common venting system must be corrected. The
common venting system should be resized to approach the
minimum size as determined by using the appropriate tables
in Appendix G in the current standards of the National Fuel
Gas Code, ANSI Z223-1 in the U.S.A. and the appropriate
Category I Natural Gas and Propane appliances venting sizing
tables in the current standards of the CSA B149.1 Natural Gas
and Propane Installation Code in Canada.
NOTE Local codes may supersede any of the above provisions.
ELECTRICAL CONNECTIONS
NOTE The MHU series unit heaters use a direct spark ignition
NOTE: The MHU/HSU series unit/utility heaters use a direct spark
system. There is no pilot necessary as the spark lights the
ignition system. There is no pilot necessary as the spark lights
main burner as the gas valve is turned on. The direct spark
the main burner as the gas valve is turned on. The direct spark
ignition control board emits radio noise during burner ignition.
The level of energy may be enough to disturb a logic circuit in a
microprocessor controlled thermostat. It is recommended that
an isolation relay be used when connecting the unit heater to a
microprocessor controlled thermostat. Select circuit protection
and wire size according to the unit rating plate. Install a separate
disconnect switch (protected by either fuse or circuit breaker) near
the unit so that power can be turned off for servicing. Remove
electrical junction box cover and connect wiring through knockout
on the junction box located on the side of the heater. Refer to
heater wiring diagram for connection information. Use 18 gauge
wire or larger for line power connections. Make sure to connect
line power to wires located in the external electrical junction box
behind junction box cover. DO NOT CONNECT LINE POWER TO
THERMOSTAT TERMINAL STRIP ON OUTSIDE OF HEATER.
Electrically ground the unit in accordance with local codes or
in the absence of local codes, in accordance with the current
National Electrical Code (ANSI/NFPA No. 70) in the USA, and in
Canada with the current Canadian Electrical Code, Part 1 CSA
C22.1
NOTE: Un-insulated ground wire must be warped in electrical tape
to avoid damage to the electrical system.
Make line voltage connections as shown in figure 7. Connect field
wiring as shown on wiring diagram on unit. Also, refer to typical
diagram in this manual.
An additional thermostat wire must be run to terminal g on
heater when continuous blower is desired. Thermostat (optional).
See wiring schematic on pager E-13.
CAP
UNIT HEATER
FIGURE 9
E-9
Operating Instructions and Owner’s ManualCompact Unit / Utility Heater
ignition control board emits radio noise as the sparking process
WARNING
is underway. The level of energy may be sufficient to disturb
a logic circuit in a microprocessor controlled thermostat. It is
recommended that an isolation relay be used when connecting
the unit heaters to a microprocessor controlled thermostat.
Install the thermostat according to instructions provided. Select
circuit protection and wire size according to the unit rating plate.
Install a separate disconnect switch (protected by either fuse or
WARNING
circuit breaker) near the unit so that power can be turned off
for servicing. Connect wiring through knockout on the junction
box located on the side of the unit heater. Refer to heater wiring
diagram for connection information. Use 18 gauge wire or larger
for thermostat connections.
Electrically ground unit in accordance with local codes or, in the
WARNING
absence of local codes, in accordance with the current National
Electrical Code (ANSI/NFPA No. 70) in the U.S.A., and in Canada
with the current Canadian Electrical Code, Part 1 CSA C22.1.
NOTE Un-insulated ground wires must be wrapped in electrical
tape to avoid damage to the electrical system.
WARNING
Make line voltage connections as shown in figure 7. Connect field
wiring as shown on wiring diagram on unit. Also refer to typical
diagram in this manual. An additional thermostat wire must be
run to terminal “G” on heater when continuous blower is desired.
Electric shock hazard. Can cause injury or
death. Do not use this heater if any part has
been under water. Immediately call a qualified
service technician to inspect the furnace and
to replace any part of the control system and
any gas control which has been under water.
Danger of explosion. Can cause injury or
product or property damage. If over-heating
occurs or if gas supply fails to shut off, shut
off the manual gas valve to the appliance
before shutting off electrical supply.
Electric shock hazard. Can cause injury or
death. Before attempting to perform any
service or maintenance, turn the electrical
power to unit OFF at disconnect switch(es).
Unit may have multiple power supplies.
Danger of explosion and fire. Can cause
injury or product or property damage. You
must follow these instructions exactly.
GAS CONNECTION
GAS CONNECTION
When connecting gas supply lines, the length of the piping run
from the meter to must be considered in determining the pipe size
When connecting gas supply, the length of the run from the
to avoid excessive pressure drop. A line pressure of 7” WC (178mm
meter must be considered in determining the pipe size to avoid
WC) for natural gas should be maintained when sizing the piping.
excessive pressure drop. A line pressure of 7” w.c. (178mm w.c.)
A line pressure of 13” WC (330mm WC) should be maintained
for natural gas should be maintained when sizing piping. A line
for propane (LP) gas. For correct sizing of piping, refer to the
pressure of 13” w.c. (330mm w.c.) should be maintained for
(American) National Fuel Gas Code ANSI Z223.1, or (Canada) CSA
liquefied petroleum (LP) gas. For correct sizing of piping, refer to
B149.1, National Gas and Propane Installation Code or consult the
the (American) National Fuel Gas Code ANSI Z223.1 or (Canada)
utility having jurisdiction.
CSA B149.1, Natural Gas and Propane Installation Code or consult
WARNING: TO PREVENT HEATER DAMAGE.
the utility having jurisdiction.
WHEN USING A PROPANE TANK TO SUPPLY
A drip leg should be installed in the vertical pipe run to the unit.
HEATER, A MINIMUM 11”W.C. LOW PRESSURE
In some localities, codes may require that a manual main shutoff
REGULATOR TO A MAXIMUM 14”W.C. LOW PRESSURE
valve and union (furnished by installer) be installed external to the
REGULATOR IS REQUIRED. THIS REGULATOR MUST BE
unit. Union must be of the ground joint type. A drip leg should be
INSTALLED BETWEEN THE TANK AND THE HEATER.
readily accessible to permit cleaning and emptying. See figure 8.
Regulator not supplied with heater.
NOTE If a switch box is mounted over electrical knockouts on
A drip leg should be installed in the vertical pipe run to the unit.
back of unit, leave a minimum of 4” (102mm) clearance between
In some localities, codes may require that a manual main shutoff
switch box and drip leg.
valve and union (furnished by installer) be installed external to the
unit. Union must be of the ground joint type. A drip leg should be
A 1/8” NPT plugged tap shall be installed immediately upstream
readily accessible to permit cleaning and empting. See figure 8.
of the gas supply connection to the heater.
NOTE If a switch box is mounted over electrical knockouts on back
NOTE Compounds used on threaded joints of gas piping must be
of unit, leave a minimum of 4” (102mm) clearance between switch
resistant to the actions of liquefied petroleum gases.
box and drip leg.
A 1/8” NPT plugged tap shall be installed immediately upstream of
the gas supply connection to the heater.
NOTE Compounds used on threaded joints or gas piping must be
resistant to the actions of Liquefied petroleum gasses.
LEAK CHECK
After gas piping is completed, carefully check all piping
connections, (field and factory), for gas leaks. Use a soap solution
or other preferred means.
Due to the natural heating cycles and vibration of this unit it is
recommended, as part of its annual maintenance, to check these
connections for proper tightness and leak-check with a soap
solution or other preferred means prior to putting into service.
CAUTION DO NOT use matches, candles, flame or other sources
of ignition to check for gas leaks.
IMPORTANT The heater and its individual shut off valve must
be disconnected from the gas supply piping system during any
pressure testing of that system at test pressures in excess of 1/2
psig (3.45kPa).
The appliance must be isolated from the gas supply piping system
by closing its individual manual gas shutoff valve during any
pressure testing of the gas supply system at test pressures equal
to or less than 1/2 psig (3.45kPa). See figure 9.
NOTE In case emergency shutdown is required, shut down main
gas valve and disconnect main power to unit. These devices
should be properly labeled by the installer.
START – UP AND OPERATION
UNIT START–UP
FOR YOUR SAFETY READ BEFORE LIGHTING
BEFORE LIGHTING smell all around the appliance area for gas.
Be sure to smell next to the floor because some gas is heavier
than air and will settle on the floor.
Use only your hand to move the gas control switch to the on
position. Never use tools. Do not use excessive force to switch
valve from off to on position. Force or attempted repair may result
in a fire or explosion.
MHU 50/80 unit heaters are equipped with an automatic spark
ignition system. There is no pilot. In case of a safety shutdown,
move thermostat switch to OFF, then return the thermostat switch
to HEAT position.
Should overheating occur, or the gas supply fail to shut off, shut
off the manual gas valve to the appliance before shutting off the
electrical supply.
GAS VALVE OPERATION FOR HONEYWELL
VR8205M SERIES VALVE (FIGURE 10)
1. STOP! Read the safety information at the beginning of this
section.
2. Set the thermostat to lowest setting.
3. Turn off all electrical power to appliance.
4. This appliance is equipped with an ignition device which
automatically lights burner. DO NOT attempt to light the
burners manually.
5. There is a black rotary switch knob that can be moved
between the on and off position. Rotate the switch knob to
the off position. (See Figure 10)
6. Wait five minutes to clear out any gas. If you then smell gas,
STOP! Immediately call your gas supplier from a neighbor’s
phone. Follow the gas supplier’s instructions. If you do not
smell gas go to next step.
7. Rotate the black switch knob to ON.
8. Turn on electrical power to unit.
9. Set the thermostat to desired setting.
10. The combustion air blower will start. The burners will light
within 40 seconds.
Compact Unit / Utility Heater Operating Instructions and Owner’s Manual
E-10
11. If unit does not light first time (gas line not fully purged) it
will attempt up to two more ignitions before locking out.
12. If lockout occurs, repeat steps 1 through 9.
13. If appliance still will not operate, follow the instructions “TO
TURN OFF GAS TO UNIT” and call your service technician or
gas supplier.
HONEYWELL VR8205M GAS VALVE
GAS VALVE KNOB SHOWN
IN OFF POSITION
MANIFOLD
PRESSURE TAP
flashback or burning within the burner. The flames shall
be predominantly blue in color and shall be approximately
centered in the tubes with no apparent impingement taking
place.
7. The ignition control will energize the fan approximately 45
seconds after ignition is established.
8. After the thermostat demand is satisfied the gas valve
is closed; 5 seconds after the demand is satisfied the
combustion air blower is shut off.
9. The control center shall shut off the system fan approximately
150 seconds after the gas valve is de-energized.
IGNITION CONTROL LED
The ignition control board contains a green LED which indicates
the following:
LED UNIT OPERATION
Slow Flash* Normal Operation - No call for heat
Fast Flash Normal Operation - Call for heat
Current signal at FLAME terminal 0.6 to 1.0 microamps
INLET PRESSURE TAP
MANIFOLD PRESSURE ADJUSTMENT
SCREW UNDER CAP
GAS VALVE
ROTARY SWITCH
FIGURE 10
TO TURN OFF GAS TO UNIT
1. Set thermostat to lowest level.
2. Turn off all electrical power to unit if service is to be
performed.
3. Rotate black knob
to OFF position.
HEATING SEQUENCE OF OPERATION
1. When the thermostat calls for heat, the combustion air
blower starts immediately.
2. Combustion air pressure switch proves blower operation
before allowing power to the ignition controller. This switch is
factory set and no adjustment is necessary.
3. After pre-purge of approximately 30 seconds, the spark
ignition is energized and the solenoid valves open in the gas
valve.
4. The spark then ignites the gas, the ignition sensor proves the
flame and the combustion process continues.
5. In the event that the flame is not detected after the first
10-second trial for ignition, the controller will repeat steps
3 and 4 an additional two times before locking out the gas
valve. Ignition control will then automatically repeat steps 3,
4, and 5 after 60 minutes.
To interrupt the 60-minute lockout period, move thermostat
from “Heat” to “OFF” then back to “HEAT.” Heating sequence
then restarts at step 1.
6. The burners shall light without noticeable crossover delay.
There shall be no flame lifting from the burner heads,
2 Flashes System lockout - failed to detect or sustain flame
Current signal at FLAME terminal <0.6 microamps
3 Flashes Pressure switch failed closed before CAB is energized
or failed open after CAB is energized
4 Flashes High limit or rollout switch open
5 Flashes Flame sensed and gas valve not energized
Steady Off Loss of power
Steady On Ignition control failure
*When thermostat is placed in continuous fan mode LED will slowly flash.
TABLE 3
IGNITION CONTROL LED
ADJUSTMENTS
HIGH ALTITUDE
Units may be fired at full input up to 2000 ft. (610m) above sea
level. Above 2000 ft. (610m), manifold pressure must be adjusted
on some units. Adjust pressure regulator to pressure shown in
table 4 for natural gas and table 5 for LP/propane gas.
GAS FLOW
To check for proper gas flow to the combustion chamber,
determine the Btu input from the appliance rating plate. Divide
this input rating by the Btu per cubic feet of available gas. Result is
the required number of cubic feet per hour. Determine the flow of
gas through the gas meter for two minutes and multiply by 30 to
get the hourly flow of gas.
E-11
Operating Instructions and Owner’s ManualCompact Unit / Utility Heater
GAS PRESSURE
1. Check gas line pressure with unit firing at maximum rate. A
minimum of 5.0” w.c. for natural gas or 10.9” w.c. for LP/
propane gas should be maintained for proper unit operation.
2. After line pressure has been checked and adjusted, check
manifold pressure. Correct manifold pressure is shown on the
unit rating plate. See figure 10 for gas pressure adjustment
screw location. A natural gas to LP/propane gas changeover
kit is required to convert unit. Refer to installation instructions
provided with changeover kit for conversion procedure.
TABLE 4
NATURAL GAS MANIFOLD PRESSURES - IN.WG. (KPA)
ALTITUDE FT. (M)
MHU 50/80 0-2000 2000-4500
(0-610) (610-1370)
50/80 4.0”WC (0.99 kPa)*
3.6”WC (0.89 kPa)
*No adjustment required.
TABLE 5
LP/PROPANE GAS MANIFOLD PRESSURES - IN.WG. (KPA)
ALTITUDE FT. (M)
MHU 50/80 0-2000 2000-4500
(0-610) (610-1370)
50/80 10.5”WC (2.62 kPa)*
8.5”WC (2.12 kPa)
*No adjustment required.
LIMIT CONTROL
The limit control switch is factory set and not field adjustable.
LOUVER VANE ADJUSTMENTS
Rotate louver vanes to direct airflow upward, downward, straight,
or any combination of these directions. When unit is installed
in an inverted position, louvers may be positioned in the same
manner.
COMBUSTION AIR PRESSURE SWITCH
This pressure switch checks for proper combustion air blower
operation before allowing an ignition trial. The switch is factory set
and no field adjustment is necessary.
FLAME ROLLOUT SWITCH
The flame rollout switch(es) are located on the burner box top,
behind the ignition control board. This normally closed switch
opens on a temperature rise. Check for adequate combustion air
before manually resetting switch.
SERVICE
CAUTION Turn off gas and electrical power to unit before
performing any maintenance or service operations on this unit.
Remember to follow lighting instructions when putting unit back
into operation after service or maintenance.
If any of the original wire as supplied with the appliance must
be replaced, it must be replaced with wiring material having a
temperature rating of at least 105°C.
Do not use this appliance if any part has been under water.
Immediately call a qualified service technician to inspect the
appliance and replace any gas control which has been under
water.
BURNERS
1. Periodically examine burner flames for proper appearance
during the heating season.
2. Before each heating season examine the burners for any
deposits or blockage that may have occurred.
3. Clean burners as follows:
• Turn off both electrical and gas supplies to unit.
• Disconnect gas supply piping, high tension and sensor
leads. Remove gas manifold. Remove burner tray.
• Clean burners as necessary. Make sure that burner
heads line up properly to ensure flame crossover. Check
spark gap on electrode and adjust if required. The gap
should be between 0.110 inch and 0.140 inch (2.79mm
to 3.56mm). The gap may be checked with appropriately
sized twist drills or feeler gauges.
• Reinstall burner tray, gas manifold, high tension and
sensor leads. Reconnect gas supply piping.
• Restore electrical power and gas supply. Follow lighting
instructions to light unit. Check burner flame.
4. Clean burner filter screen as follows:
• Turn off both electrical and gas supply to unit.
• Remove the filter screen from the inlet to the burner
housing by squeezing and pulling out.
• With screen out of the heater, clean with light soap and
water or blow out with compressed air (blowing away
from you).
• Dry screen thoroughly with air and make sure all air
passages in the screen are fully opened.
• Replace screen into burner housing opening.
• Restore electrical and gas supply.
• Follow lighting instructions to light the heater. Check
burner flame.
FLUE PASSAGEWAY AND FLUE BOX
The flue passages and flue box should be inspected and cleaned
prior to each heating season. The sequence of operation should
be as follows:
1. Turn off both electrical and gas supply to unit.
2. Disconnect combustion air blower wiring.
3. Remove screws securing flue box to unit. Remove flue box. If
necessary, remove blower assembly from flue box. Clean flue
box with wire brush.
4. Remove turbulator retention bracket and turbulators. Clean
turbulators with wire brush.
5. Remove burners as described in section “BURNERS” section.
6. Clean tubes with a wire brush.
7. Reassemble unit. The combustion air and flue box gaskets
should also be replaced during reassembly.
8. Restore electrical power and gas supply. Follow lighting
instructions to light unit. Check operation of unit.
COMBUSTION AIR BLOWER
Under normal operating conditions, the combustion air blower
should be checked and cleaned prior to the heating season with
the power supply disconnected. Use a small brush to clean blower
wheel.
Compact Unit / Utility Heater Operating Instructions and Owner’s Manual
E-12
LADDER DIAGRAM
Red
White
OPTIONAL THERMOSTAT
INSTALLATION
IT IS RECOMMENDED TO USE
18AWG WIRE WHEN INSTALLING
THE THERMOSTAT. CONNECT
THERMOSTAT WIRING TO
TERMINALS ‘R’ AND ‘W’ AS
ILLUSTRATED ON THE SCHEMATIC
DIAGRAM.
NOTE: THERMOSTAT TERMINAL
CONNECTIONS ARE MOUNTED ON
THE BACK PANEL OF THE HEATER.
EXTERNAL THERMOSTAT
TERMINAL STRIP WARNING: DO
NOT CONNECT LINE POWER TO
THE THERMOSTAT TERMINAL
STRIP.
E-13
Operating Instructions and Owner’s ManualCompact Unit / Utility Heater
ELECTRICAL
1. Check all wiring for loose connections.
2. Check for correct voltage at unit (unit operating).
3. Check amperage draw.
FLUE AND CHIMNEY
Check all vent and vent connector joints for tightness. Ensure that
connections are sealed and that there are no blockages.
2. Is main disconnect closed?
3. Is there a breaker tripped or a fuse blown?
4. Is gas turned on at meter?
5. Is manual shutoff valve open?
6. Is unit ignition system in lock out? If unit locks out again, call
service technician to inspect unit.
7. Is pressure switch closed? Obstructed flue will cause unit to
shut off at pressure switch. Check flue passage and outlet.
FAILURE TO OPERATE
If unit fails to operate check the following:
1. Is thermostat calling for heat?
HeatStar • Compact Unit / Utility Heater • Model # MHU 50/80
REPAIR PARTS
When ordering repair parts include the complete unit model
number listed on the unit rating plate. For example: HSU50/80.
38
40
39
36
35
37
Compact Unit / Utility Heater Operating Instructions and Owner’s Manual
E-14
PARTS LIST:
SEE BACK PAGE FOR PARTS ORDERING INFORMATION
REF #. DESCRIPTION 50 ITEM # QUANTITY 80 ITEM # QUANTITY
1.................CIRCUIT BOARD .................................................... 60105 .......................1 ....................................S/A .......................1
2.................LIMIT SENSOR ....................................................... 60022 ......................1 ....................................60021 ...................2
3.................ELECTRODE IGNITER .............................................. 60139 .......................1 ....................................S/A .......................1
4.................ELECTRODE SENSOR .............................................. 60141 .......................1 ....................................S/A ....................... 1
5.................BURNER ................................................................60155 .......................3 ....................................60191 ....................5
6.................IGNITION LEAD ..................................................... 60045 ......................1 ....................................S/A .......................1
7.................SENSOR LEAD .......................................................60046 ......................1 ....................................S/A .......................1
8.................ORIFICE (NAT) ....................................................... 60049 ......................3 ....................................S/A ....................... 5
9.................ORIFICE (LP) .......................................................... 60156 .......................3 ....................................S/A .......................5
10 ...............GAS VALVE (NAT) .................................................. 60128 .......................1 ....................................S/A .......................1
11 ...............GAS VALVE (LP) ..................................................... 60129 .......................1 ....................................S/A .......................1
12 ...............TRANSFORMER .....................................................60025 ......................1 ....................................S/A .......................1
13 ...............PRESSURE SWITCH ................................................ 60147 .......................1 ....................................60146 ...................1
14 ...............HI LIMIT SENSOR HEAT EXCH. ...............................60015 .......................1 ....................................S/A .......................1
15 ...............PRESSURE SWITCH TUBE ....................................... 60031 .......................1 ....................................S/A .......................1
16 ...............INDUCED DRAFT MOTOR ...................................... 60020 ......................1 ....................................S/A .......................1
17 ...............VENT ADAPTER ..................................................... 60130 .......................1 ....................................60140 ...................1
18 ...............INDUCED DRAFT MOTOR GASKET .........................60157 .......................1 ....................................S/A .......................1
19 ...............BACK BRACKET ....................................................60075 ......................1 ....................................S/A .......................1
20 ............... FRONT BRACKET ..................................................60080 ......................1 ....................................S/A .......................1
21 ...............LOUVERS .............................................................. 60100 .......................5 ....................................S/A ....................... 7
22 ............... LOUVER SPRING ................................................... 60103 .......................5 ....................................S/A ....................... 7
23 ............... FLUE BOX ..............................................................60189 .......................1 ....................................60190 ...................1
24 ...............FLUE BOX GASKET ................................................. 60090 ......................1 ....................................60092 ................... 1
25 ............... HEAT EXCHANGER ................................................60065 ......................1 ....................................60068 ...................1
26 ............... ACCESS DOOR ..................................................... 60070.......................1 ....................................60072 ...................1
27 ...............FRONT ..................................................................60095 ......................1 ....................................60097 ................... 1
28 ............... SIDE DOOR ..........................................................60110 .......................1 ....................................60112 ....................1
29 ............... WRAPPER .............................................................60115 ........................3 ....................................60117 ....................3
30 ............... FAN MOTOR .......................................................... 60055 ......................1 ....................................60054 ................... 1
31 ...............FAN GUARD .........................................................60120 .......................1 ....................................60122 ....................1
32 ............... FAN ASSEMBLY ..................................................... 60125 .......................1 ....................................60127 ....................1
33* ............. CAPACITOR STARTER .....................................................................................................................28788 ...................1
34 ............... MANIFOLD ............................................................60062 ......................1 ....................................60064 ...................1
35 ............... INLET PIPE ............................................................. 60132 .......................1 ....................................S/A .......................1
36 ............... INLET FITTING ....................................................... 60131 .......................1 ....................................S/A .......................1
37 ...............BURNER SCREEN ...................................................60142 .......................1 ....................................S/A .......................1
38 ............... THERMOSTAT TERMINAL .......................................60144 .......................1 ....................................S/A ....................... 1
39 ............... WIRING JUNCTION BOX ........................................ 60159 .......................1 ....................................S/A ....................... 1
40...............COVER, WIRING JUNCTION BOX ........................... 60160 .......................1 ....................................S/A .......................1
Not Shown . GAS VALVE BRACKET ............................................. 60158 .......................1 ....................................S/A .......................1
*Not Shown
Optional Installation Components
24V THERMOSTAT ..................................................................................F210359
4” VERTICAL VENT KIT (80) ....................................................................F102848
3” VERTICAL VENT KIT (50) ....................................................................F102840
4” HORIZONTAL STAINLESS STEEL VENT KIT (80) ...................................F102860
Gas Conversion Kits
Natural Gas to Liquid Propane
MHU 50/80 50,000 and 80,000 BTU ....................................F260163
Liquid Propane to Natural Gas
MHU 50/80 50,000 and 80,000 BTU ....................................F260164
Operating Instructions and Owner’s ManualCompact Unit / Utility Heater
E-15
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