MrHeater MHU200NG Operating Instructions And Owner'S Manual Download Page 17

Large Unit Heater

17

Operating Instructions and Owner’s Manual

Line Voltage Field Wiring

FIGURE 12

 

WARNING: 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.

 

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.

FIELD WIRING SUPPLY VOLTAGE

Before proceeding with electrical connections, ensure that the supply 
voltage, frequency, phase, and current capacity meet the requirements 
specified on the rating plate. A dedicated line voltage supply with 
properly sized wire should run directly from the main electrical panel to 
the heater.

 

CAUTION: The power supply to the heater must be within 

+/- 5% of the voltage rating as indicated on the rating 
plate of the appliance. If input power does not meet these 
specifications, contact your utility company.

• 

An electrical service disconnect must be provided at the furnace 
location. A 2 x 4 junction box can be mounted directly to the unit 
panel utilizing the provided 1/2” knock-out. If conditions do not 
allow for this, locate the service disconnect not more than 5 feet 
away from the service access panel.

• 

The main electrical supply enters at the rear of the heater utilizing 
1/2” electrical knock-out. When routing the electrical supply 
conduit to the unit, ensure that it does not interfere or obstruct 
the heater’s service access panel.

• 

Unit comes with three wire leads to connect the main power 
supply. Connect the hot, neutral, and ground wires as shown 
in the field wiring diagram. When routing wires through the 
knockout, use a UL Listed bushing or chase nipple to prevent 
damage to the wire insulation. When operating this unit as a 
sealed combustion appliance, the cabinet opening to the junction 
box must be sealed air tight using either a UL approved bushing 
or a non-reactive UL approved sealant to bushing.

 

WARNING: Edges of sheet metal holes may be sharp. Use 

gloves as a precaution when routing wires.

• 

Connect wires together with UL approved wire connectors.

NOTICE:

 A UL Listed switch may be installed in the 2x4 junction box 

for use as a service disconnect.

 

CAUTION: Route the field supplied power wires so that 

they do not come in contact with the flue wrapper or 
venter housing. These hot surfaces may damage the wire’s 
insulation, resulting in damage to the unit.

THERMOSTAT LOCATION

The location of the thermostat should be determined by the desired 
heating requirements and be mounted on an inside wall five (5) feet 
above the finished floor. Locate the thermostat in a conspicuous 
location, away from where it could be influenced by heat from the unit 
or other sources, as this may cause the unit to short cycle. Care should 
be given to locate the thermostat away from drafts or frequently 
opened doors. To prevent drafts inside the wall from affecting the 
thermostat’s performance, plug hole for the wire with insulation 
or suitable caulk. For further information, see the accompanying 
instructions with the thermostat.

START-UP OPERATION

UNIT START–UP

 

WARNING: Improper installation, adjustment, alteration, 

service, or maintenance can cause property damage, serious 
injury, or death. This heater must be installed and serviced 
by a trained gas installation and service personnel only. 
During heater startup ensure that building is well ventilated.

 

CAUTION: Shock Hazard. Before attempting to perform any 

service or maintenance, turn electrical power to unit OFF at 
disconnect switch.

 

During the first unit startup, an odor and, perhaps, 
some vapor will come from the heater. This is the gasket 
binding material emitting this odor and/ or vapor. After 
approximately 20 minutes, this odor will disappear and not 
occur again.

 

During these 20 minutes it is recommended to ventilate the 
room as much as possible (open doors, windows, turn on 
any fans).

Pre-Start Up Checks

Verify that the installation conforms to all of the specifications of the 
manual, as well as with local, state, national, and provincial codes. In 
absence of local codes, the unit heater must be installed according to 
the current National Fuel Gas Code ANSI Z223.1 (NFPA 54). In Canada, 
the installation must conform to the current National Standard of 
Canada CSA-B149 Sections 1 & 2.

Prior to starting up the unit, verify that:

• 

The gas type listed on the rating label matches that of your 
application.

• 

The gas connections have been purged of air and properly leak 
tested.

• 

The voltage type and frequency listed on the rating label matches 
that of your application.

• 

The unit is properly grounded as per the National Electrical Code, 
ANSI/NFPA 70 or Canadian Electrical code CSA C22.1 Part 1.

• 

The unit is properly mounted to a permanent structure able to 
bear the weight of the unit.

Summary of Contents for MHU200NG

Page 1: ...o this manual For assistance or additional information consult a qualified installer service agency or the gas supplier WHAT TO DO IF YOU SMELL GAS DO NOT try to light appliance DO NOT touch any elect...

Page 2: ...E INSTRUCTIONS BEFORE YOU OPERATE THIS HEATER WARNING FIRE OR EXPLOSION HAZARD Failure to follow safety warnings exactly could result in serious injury death or property damage Be sure to read and und...

Page 3: ...perly Set ________________________________ Furnace BTU input _____________________________________ Level ___________________________________________________ Line Pressure _____________________________...

Page 4: ...al 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 i...

Page 5: ...nual is to provide information regarding safety design guidelines installation operation and maintenance of the this gas fired unit heater You must read and understand the instructions and all safety...

Page 6: ...tion of these units must comply with the National Fuel Gas Code ANSI Z223 1 NFPA 54 latest edition and other applicable local building codes In Canada the installation of these units must comply with...

Page 7: ...ontal pitch as directed in these instructions and the latest edition of the National Fuel Gas Code ANSI Z223 1 NFPA 54 or CSA B149 1 Installation Code Determine that there is not blockage restriction...

Page 8: ...h a diameter 4 inches greater than the vent pipe diameter must be used If there is 6 feet or more of vent pipe prior to passing through the combustible wall or floor then the metal thimble need only b...

Page 9: ...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 mu...

Page 10: ...ombustion which can result in the production of excessive carbon monoxide Follow these guidelines and all applicable codes for all models prior to installing the combustion air duct work WARNING Suffi...

Page 11: ...drip leg should be installed in the vertical pipe run to the unit In some localities codes may require that a manual main shutoff valve and union furnished by installer be installed external to the un...

Page 12: ...putting into service For leak testing on pressures below 20 inches W C Before leak testing close the field installed manual shut off valve shown on Figure 9 on the supply line to isolate the gas valve...

Page 13: ...ssure Input Rating W C kPa BTU Hr W W C kPa BTU Hr W MHU200NG 7 23 1 8 200 000 58 614 6 66 1 66 192 000 56 269 MHU250NG 7 23 1 8 250 000 73 268 6 66 1 66 240 000 70 337 MHU300NG 3 81 0 95 300 000 87 9...

Page 14: ...the side access control compartment of the unit The low voltage thermostat and accessory control devices can be wired to the terminals in the side access control compartment Refer to the wiring diagra...

Page 15: ...Large Unit Heater 15 Operating Instructions and Owner s Manual Main Components FIGURE 10 Line Voltage Thermostat Wiring Connector on Heater S1 S4 M1 VG MC FS S2 S3 S2 CB SE T1 RFC CFC...

Page 16: ...Large Unit Heater 16 Operating Instructions and Owner s Manual Internal Wiring Diagram FIGURE 11...

Page 17: ...field supplied power wires so that they do not come in contact with the flue wrapper or venter housing These hot surfaces may damage the wire s insulation resulting in damage to the unit THERMOSTAT LO...

Page 18: ...puts set it to the maximum rating 7 Observe the pressure rating on the pressure gauge Verify maximum inlet gas supply pressure 8 Turn off all other gas appliances on the same supply line 9 Observe the...

Page 19: ...manifold pressure hose connector using a soap solution or equivalent method as described in ANSI Z223 1 NFPA 54 Prior to Leaving Job Site Prior to leaving the job site verify that Service access door...

Page 20: ...hts burner DO NOT attempt to light the burners manually 5 There is a main shut off valve upstream of the unit Open it See Figure 9 on Page 11 6 Wait five minutes to clear out any gas If you then smell...

Page 21: ...upply Follow lighting instructions to light unit 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 sequenc...

Page 22: ...old Screws FUEL CONVERSION INSTRUCTIONS FIGURE 15 Rotation of the Valve Manifold Assembly ROTATE valve manifold assembly The heater is standard manufactured for operation with natural gas In case of u...

Page 23: ...NOT FOLLOWED EXACTLY A FIRE EXPLOSION OR PRODUCTION OF CARBON MONOXIDE MAY RESULT CAUSING PROPERTY DAMAGE PERSONAL INJURY OR LOSS OF LIFE THE QUALIFIED SERVICE AGENCY PERFORMING THIS WORK ASSUMES RES...

Page 24: ...space tightly sealed building 1 Remove obstruction or correct vent lengths 2 Replace wiring or hose connections 3 Replace pressure switch The control board does not send spark to the electrode 1 The e...

Page 25: ...ontrol board does not send 120 VAC to the air movement fan after approx 30 seconds after ignition and if contact relay fan control is open and there isn t 24VAC on relay fan control 3 The control boar...

Page 26: ...er listed on the unit rating plate Mr Heater Large Unit Heater Model MHU200NG MHU250NG MHU300NG MHU400NG Liquid Propane to Natural Gas Conversion Kit MHU200NG F260165 MHU250NG F260166 MHU300NG F260167...

Page 27: ...60291 60291 60291 60291 20 BLOWER DRIVE RELAY 60292 60292 60292 60292 21 PRESSURE SWITCH 60293 60294 60294 60294 22 DETECTION ELECTRODE 60295 60295 60295 60295 23 MANUAL RESET SAFETY THERMOSTAT 140 C...

Page 28: ...001 Address any Warranty Claims to the Service Department Mr Heater Inc 4560 W 160TH ST CLEVELAND OHIO 44135 Include your name address and telephone number and include de tails concerning the claim Al...

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