MrHeater MHU200NG Operating Instructions And Owner'S Manual Download Page 6

Large Unit Heater

6

Operating Instructions and Owner’s Manual

Heater Subcomponents

FIGURE 3

Flame Sensor

Pressure 
Switch

Control 
Board

Spark Electrode

Gas Valve

Manual Reset 
Safety Gas 
Switchers

Control Transformer

Draft Inducer

High Limit Switch

INITIAL INSTALLATION CONSIDERATIONS AND 
PRE-CHECKS

 

WARNING: Improper installation, adjustment, alteration, 

service, or maintenance can cause property damage, serious 
injury, or death. Read and understand the installation, 
operating, and maintenance instructions thoroughly before 
installing or servicing this equipment. 
This manual should be kept for future use for servicing or 
service diagnostics. Leave manual with the owner. Do not 
discard any literature shipped with this unit. Only a trained, 
qualified installation or service personnel may install or 
service this equipment. 
Do not attach ductwork, air filters, or polytubes to any 
propeller unit heater.

Placement of the heater is influenced by many factors. Aside from 
safety factors, considerations for the general space and heating 
requirements, availability of gas and electrical supply, and proximity of 
possible vent locations are a few examples of factors that should all be 
considered.

Inspect and evaluate the location of the heater to ensure that the 
structural support is adequate to support the unit’s weight. The unit 
must be installed in a horizontally level position to ensure proper 
operation. To reduce noise attenuation along the structure caused by 
vibration of the unit, the heater should be installed within 15 feet of 
a primary building support. In the cases where this installation is not 
practical or feasible, the use of spring vibration isolators may be used, 
so long as they are rated for use of the unit’s weight.

Adequate space around the heater must also be considered in order 
to maintain the published minimum clearance to combustibles and 
recommended service clearances (see 

Table 3

).

 

WARNING: Do not locate any gas-fired units in area where 

chlorinated, halogenated, or acid vapors are present in the 
atmosphere. These substances can cause premature heat 
exchanger failure due to corrosion which can cause property 
damage, serious injury, or death.

In the U.S., the installation 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 local plumbing or waste water codes 
and other applicable codes and with the current code CSA-B149.1.

All installation and service of these units must be performed by a 
qualified installation and service agency only as defined in ANSI Z223.1 
(NFPA 54) - latest edition or in Canada by a licensed gas fitter.

This unit is certified with the controls furnished. For replacements 
parts, please order according to the replacement parts list on rating 
plate. Always know your model and serial numbers, we reserves the 
right to substitute other authorized controls as replacements.

Unit is balanced for correct performance. Do not alter fan or operate 
motors at speeds below what is shown in this manual.

Information on controls is supplied separately. The same burner is used 
for natural and propane gas.

INSTALLATION

NOTICE:

 High humidity or saltwater atmospheres will accelerate heater 

corrosion and reduce useful life. Do not install the heater in locations 
where water (in the form of rain, drips, or spray) could fall onto the 
gas ignition components.

 

WARNING: Improper suspension of the unit heater may 

result in collapse and being crushed. 
Always suspend from a permanent part of the building 
structure that can evenly support the total force and weight 
of the heater. 
Failure to maintain minimum clearance to combustibles may 
result in fire and/ or explosion, property damage, serious 
injury, or death. Always maintain minimum clearances.

The units are designed to be hung with threaded bolts via the four (4) 
threaded inserts on the top panel of the heater:

Hanging Points

FIGURE 4

HANGING 

  POINTS: 

For the anchorage 

of the unit heater 

use 3/8”-16 bolts 

or eyebolts

18.86 inch 

(479mm)

1.63 inch 

(41.5mm)

7.89 inch 

(200.5mm)

9.16 inch

 

(233mm)

9.73 inch

 

(247mm)

22.13 inch

 

(562mm)

The suspension of the heater must conform to all applicable codes 
referenced in the STANDARDS section.

To ensure proper operation, the heater must be installed in a level 
horizontal position  depending on desired location as governed by 
clearances, vent connection, air direction, gas supply, electrical supply 
and service accessibility.

Be sure the means of suspension is adequate to support the 
weight of the unit (see 

Table 1

 for unit weights).

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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