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5

Installation Instructions and Owner’s Manual

Unvented Natural Gas Fired Room Heater

space such as, Vent–free heater, Gas water heater, Gas 

furnace, Vented gas heater, Gas fireplace logs, and Other 
gas appliances*

*Do not include direct-vent gas appliances. Direct-vent 

draws combustion air from the outdoors and vents to 
the outdoors.
Example:
Gas water heater 

40,000 Btu/hr

Vent Free   20,000 Btu/hr
Total 

 

=60,000 Btu/hr

4.  Compare the maximum Btu/hr the space can support 

with the actual amount of Btu/hr used.

Example: 51,800 Btu/hr (maximum Btu/hr the    
 

space can support)

 

60,000 Btu/hr (Actual amount of Btu/hr used)

The space in the above example is a confined space 
because the actual Btu/hr used is more than the 
maximum Btu/hr the space can support.

You must provide additional fresh air. Your options are 
as follows:

A. Rework worksheet, and the space of an adjoining room. 

If the extra space provides an unconfined space, remove 
door to adjoining room or add ventilation grills between 

the rooms. See Ventilation From Inside Building (Fig. 2)

B.  Vent room directly to the outdoors. See Ventilation From 

Outdoors (Fig. 3). 

C. Install a lower Btu/hr heater if lower Btu/hr size makes 

room unconfined. 

If actual Btu/hr used is less than the maximum Btu/
hr the space can support, the space is an unconfined 
space. You will need no additional fresh air ventilation.

VENTILATION AIR

Ventilation from Inside Building

This fresh air would come from an adjoining unconfined 
space. When ventilation to an adjoining unconfined space, 

you must provide two permanent openings: one within 12” 
of the ceiling and one within 12” of the floor on the wall 
connecting the two spaces (see options 1 & 2 of figure 2). 

You can also remove door into adjoining room (see option3, 

fig 2). Follow the National Fuel Gas Code NFPA 54/ ANSI 
Z223.1, Section 5.3, Air for Combustion and Ventilation for 

required size of ventilation grills or ducts.

WARNING:

 Rework worksheet, adding the space of 

the adjoining unconfined space. The combined space 
must have enough fresh air to supply all appliance in 
both spaces. 

Ventilation from Outdoors

If necessary provide extra fresh air by using ventilation grills 
or ducts. Connect these items directly to the outdoors or 
spaces open to the outdoors. These include attics* and 
crawl spaces. Follow the National Fuel Gas Code NFPA 

54/ ANSI Z223.1, Section 5.3, Air for Combustion and 

Ventilation for required size of ventilation grills or ducts.

Ventilation 
Gills into 
Adjoining 
Room - 
Option 1

Ventilation Gills into 
Adjoining Room - Option 2

(30.5 cm)12”

12” (30.5 cm)

Or remove 
door into 
Adjoining 
Room - 
Option 3

Figure 2

INLET 
AIR

OUTLET 
AIR

VENTILATION CRAWL SPACE

TO CRAWL 
SPACE

TO ATTIC

VENTILATION AIR

VENTILATED 
ATTIC

OUTLET AIR

Figure 3.

*IMPORTANT:

 Do not provide openings for inlet or 

outlet into attic. If attic has a thermostat-controlled power 

vent, heated air entering the attic will activate the power 
vent.

IMPORTANT:

 Vent-free heaters add moisture to the 

air. Although this is beneficial, installing heater in rooms 
without enough ventilation air may cause mildew to form 
from too much moisture. See Fresh Air for Combustion 
and Ventilation, pages 4 through 5. 

INSTALLATION

WARNING: 

Any change to this heater or its controls 

can be dangerous.

NOTICE: This heater is intended for the use as 
supplemental heat.

 Use this heater along with your 

primary heating system. Do not install this heater as your 
primary heat source. If you have a central heating system, 

you may run system’s circulating blower while using heater. 

This will help circulate the heat throughout the house. In 
the event of a power outage, you can use this heater as 
your primary heat source for the duration of the outage. 

WARNING:

 A qualified service person must install 

heater. Follow all local codes. 

Summary of Contents for MHVFB10NG

Page 1: ...Do not store or use gasoline or other flammable vapors and liquids in the vicinity of this or any other appliance WHAT TO DO IF YOU SMELL GAS Do not try to light any appliance Do not touch any electr...

Page 2: ...d of high surface temperature and should stay away to avoid burns or clothing ignition Young children should be carefully supervised when they are in the same room with heater A barrier designed to re...

Page 3: ...ou provide fresh outside air If heater keeps shutting off it requires servicing 5 Turn off and let cool before servicing Only a qualified service person should service and repair heater 6 Do not run h...

Page 4: ...l Fuel Gas Code or applicable local codes 3 Add the Btu hr of all the fuel burning appliances in the SAFETY DEVICE This heater has a pilot with an Oxygen Depletion Sensor ODS safety shut off system Th...

Page 5: ...Code NFPA 54 ANSI Z223 1 Section 5 3 Air for Combustion and Ventilation for required size of ventilation grills or ducts WARNING Rework worksheet adding the space of the adjoining unconfined space The...

Page 6: ...e 4 For convenience and efficiency install the heater Where there is easy access for operation inspection and service In the coldest part of the room CAUTION If you install the heater in a home garage...

Page 7: ...acket onto wall Line up holes on each end of bracket with hole drilled in wall 3 Insert mounting screws through bracket and into wall studs 4 Tighten screws until mounting bracket is firmly fastened t...

Page 8: ...n to the pressure regulator Use of floor mounting feet will require you to use a 3 8 NPT street elbow to make gas connection CAUTION Never connect heater to private non utility gas well This gas is co...

Page 9: ...gas meter 4 Check all connections and joints in gas supply piping system Apply mixture of liquid soap and water to gas joints Bubbles forming show a leak 5 Correct all leaks at once 6 Depressurize an...

Page 10: ...rol know slightly and turn counterclockwise to PILOT IGN and depress for five 5 seconds Note The first time that the heater is operated after connecting the gas supply the control knob should be depre...

Page 11: ...to keep the primary air opening s of the burner s clean may result in sooting and property damage CLEANING ODS PILOT AND BURNER Use as vacuum cleaner pressurized air or small soft bristled brush to cl...

Page 12: ...hutoff valve not fully open Fully open equipment shutoff valve Thermocouple connection loose at control valve Hand tighten thermocouple nut until snug and then tighten 1 4 turn more Pilot flame not to...

Page 13: ...sing odor causing products while heater is running Gas leak See WARNING statement at top of page 12 Locate and correct all leaks see Checking Gas Connections page 9 Heater shuts off in use ODS operate...

Page 14: ...1 9 80084 Regulator 1 10 80055 Regulator Mounting Bracket 1 ITEM P N PART DESCRIPTION QTY 1 1 80058 Floor Moutning Feet 1 12 NA Regulator Connection 1 13 80052 Back Panel 1 14 80036 Wall Mounting Bra...

Page 15: ...55 Regulator Mounting Bracket 1 8 80058 Floor Mounting Feet 1 9 NA Regulator Connection 1 10 80036 Wall Mounting Bracket 1 ITEM P N PART DESCRIPTION QTY 1 1 80052 Back Panel 1 12 80005 Valve Bracket 1...

Page 16: ...Y A QUALIFIED SERVICE AGENCY REPLACEMENT PARTS ORDERING INFORMATION PURCHASING Accessories may be purchased at any Mr Heater local dealer or direct from the factory FOR INFORMATION REGARDING SERVICE P...

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