Calculating Equivalent Feet - John Wood POWER VENTED GAS FIRED WATER HEATER Installation And Operating Instructions Manual

Calculating Equivalent Feet

WATER HEATER
HEATER INPUT
MODEL (Btu/hr)
40 & 50 gal. 40,000
60 gal. 42,000
40 & 50 gal. 50,000
40 & 50 gal. 40,000
60 gal. 42,000
40 & 50 gal. 50,000
50 gal. (short) 62,000
75 gal. 72,000
40 & 50 gal. 40,000
60 gal. 42,000
40 & 50 gal. 50,000
50 gal. (short) 62,000
75 gal. 72,000
Equivalent lengths of straight pipe for various elbows using Schedule 40 PVC, CPVC and polypropylene.
Vent Pipe
Size
2"
3"
4"
2"
3"
4"
Table 1
TERMINATION
ELBOW
RODENT
SCREEN
(INSTALL
INTO
ELBOW)
305mm (12 in.)
MIN. OR ABOVE
ANTICIPATED
SNOW LEVEL.
GROUND LEVEL
Figure 16
VENT SIZE PRESSURE
(Inside SWITCH
Diam) SETTING
- 0.27 in. w.c.
2" (50mm) - 0.27 in. w.c.
- 0.37 in. w.c
- 0.27 in. w.c.
3" (76mm) - 0.27 in. w.c.
- 0.37 in. w.c.
- 0.99 in. w.c.
3" (76mm)
- 0.99 in. w.c.
- 0.27 in. w.c.
4" (102mm) - 0.27 in. w.c.
- 0.37 in. w.c.
- 0.99 in. w.c.
4" (102mm)
- 0.99 in. w.c.
Elbow Short Sweep/
Type Short Radius
90° 8 ft. (2.44m)
45° 4 ft. (1.22m)
Note: The vent pipe must be supported every 1.2m (4 ft.). To prevent vibration it is recommended to use isolation
pads when attaching straps to fl oor joists, walls or ceilings. The vent pipe should be sloped upwards away from
the blower assembly at a pitch of 3mm (1/8 in.) rise per 1.2m (4 ft).
Example for calculating equivalent feet.
Section "A" 0.5 ft. (0.15m)
90° elbow 5.0 ft. (1.52m)
Section B 1.0 ft. (0.31m)
45° elbow 2.5 ft. (0.76m)
Section C 1.5 ft. (0.46m)
45° elbow 2.5 ft. (0.76m)
Section D 15.0 ft. (4.57m)
Total Equivalent 28.0 ft. (8.53m)
Based on this example use the (fully open) rodent
screen for vent length greater than 20 equivalent ft.
(6.1 equivalent metres) (see Figures 14 & 15).
MAXIMUM EQUIVALENT
VENT LENGTH
50 ft. (15.2m) +
termination elbow
125 ft. (38.1m) +
termination elbow
50 ft. (15.2m) +
termination elbow
180 ft. (54.9m) +
termination elbow
125 ft. (38.1m) +
termination elbow
Long Sweep/ Notes:
Long Radius 1. Use long radius elbows where
possible. Minimum distance between
90º elbows should be 6" (150mm)
5 ft. (1.52m)
wherever possible.
2. Venting systems may use a maximum
of fi ve (5) 90° elbows.
2.5 ft. (0.76m)
3. Use proper screen termination (see
Figures 14 & 15).
STRAP
– 13 –
MINIMUM EQUIVALENT
VENT LENGTH
7 ft. (2.1m) +
termination elbow
60 ft. (18.3m) +
termination elbow
7 ft. (2.1m) +
termination elbow
125 ft. (38.1m) +
termination elbow
60 ft. (18.3m) +
termination elbow
45°ELBOW
90°ELBOW