MG3P Installation Manual

ManualsBrandsRevolv ManualsFurnacesMG3P - 54k BTU - Gas Furnace - Manufactured Home - 92% AFUE

Example:

A space with a water heater rated at 45,000 Btuh input and a

furnace rated at 75,000 Btuh requires a volume of 6,000 cubic

feet [50 x (45 + 75) = 6,000] to be considered unconﬁned. If

the space has an 8 foot ceiling, the ﬂoor area of the space

must be 750 square feet (6,000 / 8 = 750).

TOTAL INPUT

RATING (BTUH)

MINIMUM FREE AREA

(EACH OPENING)

ROUND DUCT

DIAMETER

40,000 10 sq. In 4 inches

60,000 15 sq. In 5 inches

80,000 20 sq. In 5 inches

100,000 25 sq. In 6 inches

120,000 30 sq. In 6 inches

140,000 35 sq. In 7 inches

160,000 40 sq. In 8 inches

NOTE:

Each opening to outside

must be at least 1 sq. in. per

4,000 Btuh of total input rating.

12" Max.

Furnace

Water

Heater

Vent or

Chimney

12"

Max

See

Note

See

Note

Figure 6. Combustion Air Drawn from Outside

Through an Exterior Wall

Air Directly Through An Exterior Wall

If combustion air is provided directly through an exterior wall,

the two openings must each have free area of at least one

square inch per 4,000 Btuh of total appliance input. See Figure

6 (page 9).

Alternate Method of Providing Air from Outside

If acceptable under local Codes, it is permitted to provide outside

air using one opening (See NFGC).

Generally, conﬁned spaces must have two openings in the space

for combustion air. One opening must be within 12 inches of

the ceiling, and the other must be within 12 inches of the ﬂoor.

However, an alternative method recently adopted by the NFGC

uses one opening within 12 inches of the top of the space. This

method may be used if it is acceptable to the local codes.

THE FOLLOWING CONDITIONS MUST BE MET:

1. The opening must start within 12” of the top of the structure

and connect with the out of doors through vertical or horizontal

ducts or be ducted to a crawl or attic space that connects

with the out of doors.

2. The opening must have a minimum free area of 1 sq. in. per

3,000 Btu per hour of the total input rating of all equipment

located in the enclosure.

3. The free area must not be less than the sum of all the areas

of the vent connectors in the enclosure.

Installation in Unconﬁned Spaces

An unconﬁned space is an area including all rooms not separated

by doors with a volume greater than 50 cubic feet per 1,000

Btuh of the combined input rates of all appliances which draw

combustion air from that space.

In general, a furnace installed in an unconﬁned space will not

require outside air for combustion. However, in homes built for

energy efﬁciency (low air change rates), it may be necessary

to provide outside air to ensure adequate combustion and

venting, even though the furnace is located in an unconﬁned

space. See example.

Category IV Venting

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.

This furnace is classiﬁed as a “Category IV” appliance, which

requires special venting materials and installation procedures.

This section speciﬁes installation requirements for direct vent

(2-pipe) piping.

This type of appliance operates with positive vent pressure and

therefore requires the furnace to be vented to the outdoors and

thoroughly sealed. They also produce liquid condensate, which

is slightly acidic and can cause severe corrosion of ordinary

venting materials. Furnace operation can be adversely affected

by restrictive vent and combustion air piping.

The inducer assembly on this furnace can be rotated to vent the

ﬂue products out of the top, left or right side. This increases the

ﬂexibility of which direction the vent pipe can exit the furnace.

Vent Pipe Material

Vent and combustion air pipe and ﬁttings must be one of the

following materials in the list and must conform to the indicated

ANSI/ASTM standards.

MATERIALS STANDARDS

Schedule 40PVC ......................................................D1785

CPVC ........................................................................D1784

PVC-DWV .................................................................D2665

SDR-21 & SDR-26 ....................................................D2241

ABS-DWV .................................................................D2661

Schedule 40 ABS .....................................................F628

Foam / Cellular Core PVC ........................................ F891

*PolyPro

by DuraVent .............................................ULC-S636

*When using PolyPro

, all venting and ﬁttings must be from the same

manufacturer with no interchanging of other materials. Refer to speciﬁc

instructions supplied with the PolyPro vent kits

When joining PVC to PVC, use cement that conforms to ASTM

standard D2564. PVC primer must meet standard ASTM F656.

When joining ABS to ABS, use cement that conforms to ASTM

standard D2235. When joining PVC to ABS, use cement as

speciﬁed in procedure from ASTM standard D3138.

In Canada, all plastic vent pipes and ﬁttings including any cement,

cleaners, or primers must be certiﬁed as a system to ULC S636.

However, this requirement does not apply to the ﬁnish ﬂanges

or piping internal to the furnace.