Lennox G61MPV Service Manual page 52

Use the following steps to correctly size vent pipe diameter.
1 − Determine the vent termination and its corresponding
equivalent feet value according to table 35.
2 − Determine the number of 90° elbows required for both
indoor and outdoor (e.g. snow riser) use. Calculate the
corresponding equivalent feet of vent pipe.
3 − Determine the number of 45° elbows required for both
indoor and outdoor use. Calculate the corresponding
equivalent feet of vent pipe.
4 − Determine the length of straight pipe required.
5 − Add the total equivalent feet calculated in steps 1
through 4 and compare that length to the maximum
values given in table 37 for the proposed vent pipe di-
ameter. If the total equivalent length required exceeds
the maximum equivalent length listed in the appropri-
ate table, evaluate the next larger size pipe.
IMPORTANT
Do not use screens or perforated metal in exhaust
terminations. Doing so will cause freeze−ups and
may block the terminations.
TABLE 36
MINIMUM VENT PIPE LENGTHS
G61MPV MIN. EQUIV.
MODEL VENT LENGTH
045, 070,
071, 090,
091
15 ft.*
110, 111**
135***
*Any approved termination may be added to the minimum equivalent length
listed.
**G61MPV−60C−110 must have 90° street ell (supplied) installed directly into
unit flue collar.
***G61MPV−60D−135 must have 3" to 2" reducing ell (supplied) installed direct-
ly into unit flue collar.
EXAMPLE
5 ft. plus 2 elbows of 2", 2−1/2", 3"
or 4" diameter pipe
5 ft. plus 2 elbows of 2−1/2" 3" or 4"
diameter pipe
5 ft. plus 2 elbows of 3" or 4"
diameter pipe
MAXIMUM VENT PIPE LENGTHS
G61MPV
ALTITUDE
MODEL
045
070
071
090
0 − 4500
(0 − 1371 m)
091
110*
111
135**
045
070
0701
090
4501−7500
(1372−2286 m)
091
110*
111
135**
045
070
071
7501 − 10000
090
(2287 − 3048
091
m)
110*
111
135**
n/a −− Not allowed.
*G61MPV−60C−110 must have 90° street ell (supplied) installed directly into
unit flue collar.
**G61MPV−60D−135 must have 3" to 2" reducing ell (supplied) installed directly
into unit flue collar.
†On G61MPV−071, −091 and −111 units, sweep elbows must be used for all
90° elbows in the venting system when 2", 2−1/2" or 3" vent pipe is used.
Sweep elbows are recommended for use in vent systems of other
G61MPV units.
‡ On G61MPV−60D−135 units, sweep elbows must be used for all 90°
elbows in the vent system when 3" pipe is used.
B−PVC Joint Cementing Procedure
All cementing of joints should be done according to the
specifications outlined in ASTM D 2855.
WARNING
DANGER OF EXPLOSION!
Fumes from PVC glue may ignite during system
check. Allow fumes to dissipate for at least 5 minutes
before placing unit into operation.
1 − Measure and cut vent pipe to desired length.
2 − Debur and chamfer end of pipe, removing any ridges
or rough edges. If end is not chamfered, edge of pipe
may remove cement from fitting socket and result in a
leaking joint.
3 − Clean and dry surfaces to be joined.
4 − Test fit joint and mark depth of fitting on outside of pipe.
5 − Uniformly apply a liberal coat of PVC primer for PVC or
use a clean dry cloth for ABS to clean inside socket
surface of fitting and male end of pipe to depth of fitting
socket.
Page 52
TABLE 37
MAXIMUM EQUIVALENT VENT
LENGTH FEET
2" dia. 2−1/2" dia. 3" dia.
59 65 77
59 65 78
†
59 65 78
26 42 72
†
26 42 72
n/a 32 72
†
n/a 32 72
‡
n/a n/a 61
59 65 77
59 65 78
†
59 65 78
26 42 72
†
26 42 72
n/a 32 72
†
n/a 32 72
‡
n/a n/a 46
59 65 77
59 65 78
†
59 65 78
26 42 72
†
26 42 72
n/a 32 72
†
n/a 32 72
‡
n/a n/a 46
4" dia.
234
214
214
204
204
179
179
160
234
214
214
204
204
179
179
160
234
214
214
204
204
179
179
160