Lennox G61MPVT-36B-070 Installation Instructions Manual page 43

When ducts are used, they shall be of the same cross−sec-
tional area as the free area of the openings to which they
connect. The minimum dimension of rectangular air ducts
shall be no less than 75mm (3 inches). In calculating free
area, the blocking effect of louvers, grilles, or screens
must be considered. If the design and free area of protec-
tive covering is not known for calculating the size opening
required, it may be assumed that wood louvers will have
20 to 25 percent free area and metal louvers and grilles
will have 60 to 75 percent free area. Louvers and grilles
must be fixed in the open position or interlocked with the
equipment so that they are opened automatically during
equipment operation.
EQUIPMENT IN CONFINED SPACE − ALL AIR FROM OUTSIDE
(Inlet Air from Crawl Space and Outlet Air to Ventilated Attic)
ROOF TERMINATED
EXHAUST PIPE
SIDE WALL
TERMINATED
EXHAUST PIPE
(ALTERNATE
G61MPV
T
LOCATION)
NOTE−The inlet and outlet air openings shall each have a free area
2
of at least 645mm per 1.17kW (one square inch per 4,000 Btu) per
hour of the total input rating of all equipment in the enclosure.
FIGURE 36
VENTILATION LOUVERS
(Each end of attic)
OUTLET
AIR
VENTILATION
LOUVERS
INLET
(For unheated
AIR crawl space)
EQUIPMENT IN CONFINED SPACE − ALL AIR FROM OUTSIDE
(All Air Through Ventilated Attic)
ROOF TERMINATED
EXHAUST PIPE
SIDE WALL
TERMINATED
EXHAUST PIPE
(ALTERNATE
LOCATION)
NOTE−The inlet and outlet air openings shall each have a free area
of at least 645mm
hour of the total input rating of all equipment in the enclosure.
EQUIPMENT IN CONFINED SPACE −
ROOF TERMINATED
EXHAUST PIPE
SIDE WALL
TERMINATED
EXHAUST PIPE
(ALTERNATE
LOCATION)
NOTE−Each air duct opening shall have a free area of at least
2
645mm per .59kW (one square inch per 2,000 Btu) per hour of the
total input rating of all equipment in the enclosure. If the equipment
room is located against an outside wall and the air openings com-
municate directly with the outdoors, each opening shall have a free
area of at least 645mm
Btu) per hour of the total input rating of all other equipment in the
enclosure.
Page 43
VENTILATION LOUVERS
(Each end of attic)
OUTLET
AIR
(Ends 12" above
G61MPVT
2
per 1.17kW (one square inch per 4,000 Btu) per
FIGURE 37
ALL AIR FROM OUTSIDE
OUTLET AIR
G61MPVT
INLET AIR
2
per 1.17kW (one square inch per 4,000
FIGURE 38
INLET AIR
bottom)