MG3P Installation Manual

7
Manufactured Homes
Recreational Vehicles, Park Models
Manufactured Buildings
Modular Homes / Buildings
Air openings on top of the furnace and openings in closet doors
or walls must never be restricted. If the furnace is operated
without adequate air for combustion, the flame roll-out switch
will open, turning off the gas supply to the burners.
IMPORTANT NOTE
This safety device is a manually reset switch. DO NOT
install jumper wires across these switches to defeat their
function or reset a switch without identifying and correcting
the fault condition. If a switch must be replaced, use only
the correct sized part specified in the Replacement Parts
List provided online.
CAUTION:
Exhaust fans, clothes dryers, fireplaces and
other appliances that force air from the house
to the outdoors can create a negative pressure
inside the house, resulting in improper furnace
operation or unsafe conditions such as flame roll
out. It is imperative that sufficient air exchange
with the outdoors is provided to prevent
depressurization. Additional information about
how to test for negative pressure problems can
be found in the NFGC.
Direct Vent Installation
The MG3 furnace is listed as a Direct Vent (2-pipe) forced air
furnace (type FSP) for use with both natural and propane (LP)
gases. NOTE: Direct vent appliances draw combustion air
from the outdoors and vent combustion products back outside,
isolating the entire system from the indoor space. It is important
to make sure that the whole system is sealed and clearances
to combustibles are maintained regardless of the installation
being in a confined or unconfined space.
Installation in Confined Spaces
A confined space is an area with volume less than 50 cubic feet
per 1,000 Btuh of the combined input rates of all appliances
drawing combustion air from that space. Furnace closets, small
equipment rooms and garages are confined spaces. Furnaces
installed in a confined space which supply heated air to areas
outside the space must draw return air from outside the space
and must have the return air ducts tightly sealed to the furnace.
Ducts must have a cross-sectional area at least as large as the
free area of their respective openings to the furnace space. Attics
or crawl spaces must connect freely with the outdoors if they
are the source of air for combustion and ventilation.
The required sizing of these openings is determined by whether
inside or outside air is used to support combustion, the method
by which the air is brought to the space, and by the total input
rate of all appliances in the space. In all cases, the minimum
dimension of any combustion air opening is 3 inches.
Air From Inside
If combustion air is taken from the heated space, the two
openings must each have a free area of at least one square inch
per 1,000 Btuh of total input of all appliances in the confined
space, but not less than 100 square inches of free area. See
Example and Figure 2.
IMPORTANT INFORMATION
• This furnace must be vented in compliance with
the current revision of the National Fuel Gas Code
(ANSI-Z223.1/NFPA54). Instructions for determining the
adequacy of an installation can be found in the current
revision of the NFGC (ANSI Z223.1 / NFPA54). Consult
local codes for special requirements. These requirements
are for US installations as found in the NFGC.
• Furnace installation using methods other than those
described in the following sections must comply with
the National Fuel Gas Code (NFGC) and all applicable
local codes.
• Requirements in Canada (B149.1) are structured
differently. In Canada, venting shall conform to the
requirements of the current (CAN/CGA B149.1 or .2)
installation codes. Consult local codes for special
requirements.
• Provisions must be made during the installation of
this furnace that provide an adequate supply of air for
combustion. The combustion air from the outside needs
to be clear of chemicals that can cause corrosion. The
inlet pipe should not be placed near corrosive chemicals
such as those listed on page 4.
WARNING:
Upon completion of the furnace installation,
carefully inspect the entire flue system both inside
and outside the furnace to assure it is properly
sealed. Leaks in the flue system can result in
serious personal injury or death due to exposure
of flue products, including carbon monoxide.
WARNING:
This furnace must not be vented with other
appliances, even if that appliance is of the
condensing type. Common venting can result
in severe corrosion of other appliances or their
venting and can allow combustion gases to
escape through such appliances or vents. Do
not vent the furnace to a fireplace chimney or
building chase.
This condensing furnace is certified for installation either as a
Direct Vent (2-pipe) or Conventional (1-pipe) appliance. Direct
Vent appliances draw combustion air from the outdoors and vent
combustion products back outside. Installation with air taken
from around the furnace is often referred to as Conventional
installation - i.e. only the vent (exhaust) pipe is provided.
Another important consideration when selecting one or two pipe
installation is the quality of the Indoor air which can sometimes
be contaminated with various household chemicals . These
chemicals can cause severe corrosion in the furnace combustion
system. A 2-pipe installation has the additional advantage that
it isolates the system from the effects of negative pressure in
the house.
• The MG3 series gas furnace has been certified for use in
manufactured homes in the United States to the UL 307B
standard and to ANSI Z21.47 CAN/CGA-2.3 in Canada and
the United States. These furnaces may be installed in: