Calculating Equivalent Feet - Smith BTF-80 SERIES 210 Installation And Operating Manual

Calculating Equivalent Feet

WATER HEATER VENT SIZE
HEATER INPUT
MODEL (Btu/hr)
75 gal. 76,000
* see Figure 26, "Venting terminations and sizing" and "Vent screen installation".
Equivalent lengths of straight pipe for various elbows using Schedule 40 PVC, CPVC and polypropylene.
Size Type
3"
90° elbow
4"
3"
45° elbow
4"
Note: Use only Schedule 40 CPVC piping and fi ttings for the fi rst linear 1.5m (5 ft.) of the outlet vent system.
COVER PLATE
(OPTIONAL)
TERMINATION
ELBOW
RODENT
SCREEN
(INSTALL INTO
ELBOW)
305mm (12 in.)
MIN. OR ABOVE
Example for calculating equivalent feet.
ANTICIPATED SNOW
Section "A"
LEVEL.
90° elbow
Section B
45° elbow
Section C
45° elbow
Section D
Total Equivalent 10.7m
Based on this example use the (fully open) rodent
screen for vent length greater than 6 equivalent
GROUND LEVEL
metres (20 equivalent ft.) (see Figure 26).
331432-001
PRESSURE
(Inside SWITCH
Diam.) SETTING
3"
-0.90 in. w.c.
4"
Short Sweep/ Long Sweep/
Short Radius Long Radius
8' (2.44m)
4' (1.22m) 2.5' (0.76m)
Note: The vent pipe must be supported every 1.2m (4 ft.). To prevent vibration and sagging, it is recommended
to use isolation pads when attaching straps to fl oor joists, walls or ceilings. PVC and CPVC 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.). Polypropylene
vent systems require a 6.5mm (1/4 in.) per 305mm (1 ft.) upward slope to ensure proper drainage.
305mm (0.5 ft.)
2.4m (8.0 ft.)
610mm (1.0 ft.)
1.2m (4.0 ft.)
450mm (1.5 ft.)
1.2m (4.0 ft.)
4.5m (15.0 ft.)
(34.0 ft.)
MAXIMUM EQUIVALENT
VENT LENGTH
50' (15m) + termination
elbow and screen*
125' (38m) + termination
elbow and screen*
Notes:
1. Use long radius elbows where possible. Minimum
distance between 90º elbows should be 150mm
5' (1.5m)
(6 in.) wherever possible.
2. Venting systems may use a maximum of fi ve (5)
90° elbows.
3. Use proper screen termination (see Figure 26).
Table 2
STRAP
Figure 28
MINIMUM EQUIVALENT VENT
LENGTH
7' (2m) + termination elbow and
screen*
50' (15m) + termination elbow
and screen*
45° SHORT
ELBOW
90° SHORT
ELBOW
27