Heat Controller MGD75-E3A User Manual

MGD Series Gas Furnace                                                                                        Installation Instructions 

Heat Controller, Inc. Jackson, MI 49203                                              MGD Installation Instructions     4 

The furnace may be installed free standing or in an 
alcove with a free flow of air back to the furnace. A 
minimum of 18” shall be provided at the front for 
return air and service access. 

 

Note: If return air is through a side wall, there must 
be a minimum of 6-in. clearance from side wall to 
furnace in addition to 6-in. minimum clearance from 
inside of closet door to front of furnace. 

 

If a louvered door complying with the minimum air 
requirements is used, the front clearance my be reduced to 
1”. 

 

Concerning under floor or ceiling return air systems, 
the following item (1 – 10) must be adhered to: 

 

1.  The return-air opening into the closet, regardless 

of location, is to be sized not less than specified 
on the appliance rating plate. 

 

2.  If the return-air opening is located in the floor of 

the closet (versus the vertical front or side wall), 
the opening is to be provided with means to 
prevent its inadvertent closure by a flat object 
placed over the opening. 

 

3.  The cross-sectional area of the return system 

(when located in the floor or ceiling of the 
manufactured home) leading into the closet is to 
be not less than that of the opening specified on 
the appliances rating plate. 

 

4.  The total free area of openings in the floor or 

ceiling registers serving the return-air duct 
system is to be not less than 150% of the size 
opening specified on the appliance rating plate. 
At least one such register is to be located where 
the likelihood of its being covered by carpeting, 
boxes, and other objects is minimized. 

 

5.  Materials located in the return duct system have 

a flame spread classification of 200 or less. 

 
6.  Non-combustible pans having one-inch upturned 

flanges are located beneath openings in the floor 
return duct system. 

 
7.  Wiring materials located in the return duct system 

conform to Article 300-22 (B&C) of the National 
Electric Code, ANSI / NFPA-70. 

 
8.  Gas piping is not run in or through the return duct 

system. 

 
9.  The negative pressure in the closet, as determined by 

test with the air-circulating fan operating at high 
heating speed and the closet door closed, is to be not 
more negative than minus 0.05-inch water column. 

 
10.  For floor return systems, the manufactured home 

manufacturer or installer shall affix a prominent 
warning where it is easily read when the closet door 
is open. 

 

The marking shall read: