John Wood Superflue Power Vent (75 Gallon) - Manual (Page 13)

Venting terminations and sizing
• Refer to Figure 8 and Table 2 for vent pipe materials
and sizing and Figure 11 for vent termination clear-
ances. Examples of the vent terminations are shown in
Figures 9 and 10. If the installation requires a vent riser,
suitable drainage must be provided to ensure conden-
sation does not accumulate. Termination through a roof
is shown Figure 12.
• G/JW75 gallon models are supplied with a 76mm (3 in.)
termination elbow that includes a steel mesh rodent
screen and a 76mm (3 in.) plastic screen.
• The screen is required to keep foreign objects, rodents
and small birds from entering the venting system and
only one (1) screen is to be installed in the termination
elbow. These screens have been sized to ensure maxi-
mum energy efficiency of the venting system based on
the "equivalent length" of the vent piping. How to deter-
mine the equivalent length is shown in Figure 8. The
appropriate screen is to be installed into the end of the
termination elbow and secured with a small amount of
silicone sealant. This will allow for easy removal for
inspection and cleaning.
Venting instructions
1. Plan the venting layout starting at the vent termination
and work back toward the heater. Take into considera-
tion the style and position of the vent termination, the
vent pipe routing, elbows and connectors required and
the necessary support hangers.
2. G/JW75 gallon heaters use 76mm (3 in.) schedule 40
venting material. Allowable venting length is determined
using the “Equivalent vent length” method described in
Table 2. See also section on “Vent pipe connection to
blower”.
3. Venting should be as direct as possible with the fewest
number of fittings. Use long radius 45-degree and long
radius 90-degree elbows wherever possible.
4. Do not use 90-degree elbows "back to back" and do not
use street elbows. Maintain a minimum 150mm (6 in.)
straight section between elbows. Closely coupled and
short radius elbows reduce the venting capacity. Figure
6 shows examples of vent pipe connections.
5. DO NOT USE AN ELBOW AS A SUPPORT POINT.
Elbows are not designed to carry the weight of the vent-
ing system.
– 13 –
Example for calculating equivalent feet.
Section “A” . . . . . . 0.15m . . (0.5 ft.)
90° elbow . . . . . . . 2.44m . . (8.0 ft.)
Section B . . . . . . . 0.31m . . (1.0 ft.)
45° elbow . . . . . . . 1.22m . . (4.0 ft.)
Section C . . . . . . . 0.46m . . (1.5 ft.)
45° elbow . . . . . . . 1.22m . . (4.0 ft.)
Section D . . . . . . . 4.57m . (15.0 ft.)
Total Equivalent . 10.37m . (34.0 ft.)
Based on this example use the (fully open) rodent
screen for vent length greater than 6.1 equivalent
metres (20 equivalent ft.) (see Figure 7).
NOTE: VENT PIPE MUST BE SUPPORTED EVERY 1.2m (4 ft.). TO PREVENT VIBRATION, USE ISOLATION
PADS WHEN ATTACHING STRAPS TO FLOOR JOISTS, WALLS OR CEILINGS.
PVC ADAPTER
(SUPPLIED)
STRAP
150mm
(6 in.)
MIN.
45°
ELBOW
90°
ELBOW RODENT SCREEN
(INSTALL INTO
ELBOW)
Figure 8 General Venting Layout
TERMINATION
ELBOW
GROUND LEVEL OR
MAXIMUM SNOW
LINE*
WATER
HEATER
MODEL
SUFFIX
VENT PIPE
SIZE
PRESSURE
SWITCH
SETTING
* VENT
MATERIAL
(SCHEDULE 40)
MAXIMUM EQUIVALENT
VENT LENGTH
MINIMUM EQUIVALENT
VENT LENGTH
G/JW75
SNV,
SPV
76mm (3 in.)
- 0.50 in. w.c.
(-.124 kPa)
PVC**, CPVC
15.2m (50 ft.) +
termination elbow with
steel mesh screen 0.91m (3 ft.) + one 90°
elbow + termination elbow
with plastic screen
Notes:
1. Each 76mm (3 in.), 90° elbow is equivalent to 2.44m (8 ft.) of vent length.
2. Each 76mm (3 in.), 45° elbow is equivalent to 1.22m (4 ft.) of vent length.
3. Use long radius elbows. Minimum distance between elbows is 150mm (6 in.).
4. Do not mismatch venting materials. *Check local codes to determine which materials are allowed in your area.
5. **Pipe assembly adapter must be used with PVC venting material (see Figure 13).
Table 2 Allowable Vent Lengths and Materials (Vert. and Horiz.).