Single Stage Multi Position Furnace
Service Manual
13
440 08 2001 02
Table 3
APPROXIMATE OPERATING PRESSURES (
²²²²
OF W.C.)
Model
Vent Length
@Blower
@ Transition
50 Mbtu
Short -- (5
¢
No. Elbows)
--1.80
--2.60
50 Mbtu
Long -- (40
¢
+ 5 90
°
Elbows)
--1.30
--2.30
75 Mbtu
Short -- (5
¢
No. Elbows)
--1.80
--2.60
75 Mbtu
Long -- (40
¢
+ 5 90
°
Elbows)
--1.30
--2.30
100 Mbtu
Short -- (5
¢
No. Elbows)
--1.80
--2.60
100 Mbtu
Long -- (40
¢
+ 5 90
°
Elbows)
--1.70
--2.50
125 Mbtu
Short -- (5
¢
No. Elbows)
--1.80
--2.60
125 Mbtu
Long -- (40
¢
+ 5 90
°
Elbows)
--1.70
--2.50
Lower (Lesser) Negative Pressures
Lower than normal
negative pressures measured at the
Combustion Blower
may be caused by:
1. Restriction on the
Outlet
side of the combustion blow-
er. (I.E. Blocked Flue, Vent too long, Heat Exchanger
leak, etc.)
2. Leak (lack of restriction) on the
Inlet
side of the com-
bustion blower.
Higher (Greater) Negative Pressures
Higher than normal
negative pressures measured at the
Combustion Blower
may be caused by:
1. Restriction on the
Inlet
side of the combustion blower.
(I.E. Plugged Heat Exchanger, air inlet orifice too
small)
Inlet Pipe
(not used on
Single Pipe
models)
Vent Pipes MUST be
supported Horizontal-
ly and Vertically
*8
²²²²
Min.
20
¢¢¢¢
Max.
in same
atmospheric zone
Figure 14
*8
²²²²
Min.
20
¢¢¢¢
Max.
in same atmospheric zone
Coupling on ends of ex-
haust pipe. Total pipe &
coupling outside struc-
ture = 8
²²²²
Typical Vent/Combustion Air Piping Installation
Aluminum or non--rusting shield recommended.
(See Vent Termination Shielding for dimensions).
*
Increase minimum from 8
²²²²
to 18
²²²²
for cold climates (sustained temperatures below
0
°°°°
F).
DISCHARG
E
AIR
25--23--33
Inlet Pipe
(not used
on
Single Pipe
models)
UPFLOW
*8
²²²²
Min.
20
¢¢¢¢
Max.
in same
atmospheric
zone
Vent Pipes MUST
be supported
Horizontally
and
Vertically
*
Increase minimum from 8
²²²²
to 18
²²²²
for cold climates (sustained temperatures
below 0
°°°°
F).
See Vent Termination Shielding
in Vent Section.
*8
²²²²
Min.
20
¢¢¢¢
Max.
in
same
atmospheric zone
8
²
Min.
Coupling on inside
and outside of wall to
restrain vent pipe
25--23--33a
DOWNFLOW
