MrHeater MHU200NG Operating Instructions And Owner'S Manual Download Page 10

Large Unit Heater

10

Operating Instructions and Owner’s Manual

Additional requirements for horizontal venting:

• 

Category III venting systems may NOT be common vented, and no 
other gas units are allowed to be vented into it.

• 

Vent must terminate a minimum of 3 feet (914mm) above any 
forced air inlet that is located within 10 feet.

• 

The bottom of the vent terminate must be located a minimum 
of 12 inches above grade level and must extend beyond any 
combustible overhang.

• 

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.

• 

Never join two sections of double wall vent pipe within one 
horizontal vent system, as it is impossible to verify that inner pipes 
are completely sealed.

• 

For a vent termination located under an eave, the distance of the 
overhang must be at least 24”. The clearance to combustibles 
above the exterior vent must be maintained at a minimum of 12”. 
Consult the National Fuel Gas Code for additional requirements 
for eaves that have ventilation openings.

• 

For horizontal venting, the vent pipe shall be supported with 
hangers no more than 3ft.(1m) apart to prevent movement after 
installation.

The Horizontal Run 

of Vent Pipe Shall 

be Pitched Upward 

1/ 4 IN. to the FT. 

(21 MM to the M).

Power 

Exhauster 

Outlet

5 ft. 

Min.

12” 

Min.

Terminal

Tee with Drip Leg and 

Cleanout Cap at Low 
Point of Vent System

Horizontal Venting

FIGURE 8

COMBUSTION AIR REQUIREMENTS

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 Gas Code, 
ANSI Z223.1, in the U.S.A., CSA B149.1 Natural Gas and Propane Instal-
lation Code,  the National Standards of Canada 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 in-
efficient manner, resulting in incomplete combustion 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: Sufficient combustion air must be supplied 

to the appliance at all times. Lack of combustion air may 
result in property damage, headaches, nausea, dizziness, 
asphyxiation, serious injury, or death.

GAS CONNECTIONS

 

WARNING: Danger of explosion and fire. Improperly 

connected gas lines may result in serious injury and death, 
explosion, poisonous fumes, toxic gases, or asphyxiation. 
Connect gas lines in accordance to national, state, provincial, 
and local codes. 
This heater burns natural gas or liquefied petroleum (LP) gas 
and is equipped with a regulator. The regulator is built into 
the gas valve. The maximum inlet pressure to this regulator 
is 20 in. W.C.. If gas line pressure exceeds 20 in. W.C., then 
an additional regulator must be installed before the heater/
regulator to step down the pressure to a maximum of 20 in. 
W.C.. 
All field gas piping must be pressure/leak tested prior to 
operation. Never use an open flame. Use a soap solution or 
equivalent for testing. 
You must follow these instructions exactly. 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.

 

CAUTION: Gas lines should be purged of air as described 

in ANSI Z223.1 (NFPA 54) or CSA-B149.1– latest version. 
Installation of the piping must also conform with the local 
building codes, or in the absence of local codes, with the 
latest edition of the National Fuel Gas Code (NFPA 54). In 
Canada, installation must be in accordance with CSA-B149.1. 
 
When leak testing the gas supply piping system, the 
appliance and its combination gas control must be isolated 
during any pressure testing in excess of 14” W.C. (1/2 psi). 
The unit should be isolated from the gas supply piping 
system by closing its field installed manual shut-off valve. 
This manual shut-off valve should be located within 6’ of the 
heater. 
Turn off all gas before installing appliance

NOTICE:

 The total input to the appliance must fall /- 5% of 

the rated input as indicated on the rating plate. Otherwise the heat 
exchanger may prematurely fail.

All piping installed must comply with local codes and ordinances or 
with National Fuel Gas Code, ANSI Z223.1 (NFPA 54), whichever takes 
precedence. When installing piping, the following requirements must 
be taken into consideration: Canadian installations must comply with 
the B149.1.2 Gas Code.

• 

Use new properly reamed black pipe free from chips.

• 

Apply a good quality pipe compound to all male threads prior 
to assembly. If LP gas is the fuel, ensure that pipe compound is 
resistant to LP gas. 

Do not use Teflon™ tape.

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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