Gas Piping - A.O. Smith 650A, 740A Installation & Operation Manual

5. Attach a properly sized length of Selkirk Metalbestos model
PS or model G venting to the exhaust vent adapter using the
inner vee bands, see Figures 7 and 7B on page 10.
6. Fill the grooves in both inner vee bands with high-temp
silicone sealant, Dow Corning 736 or equivalent.
7. Position the inner vee bands around the inner pipe flanges
and tighten the screws securing the bands.
8. Align the outer channel band with the outer pipe grooves
and tighten the screws securing the bands.
9. Repeat steps 6-8 for each successive pipe length until the
venting reaches the heater.
10. Follow the manufacturer's instructions for proper support
and guide spacing for horizontal runs of pipe, see Table 6.
Vent Diameter
8" - BTPV -540A, 650A & 740A
S = Maximum spacing between two guides or a support
and a guide in either a vertical or horizontal direction.
F = Maximum height above a guide or support for free
standing system above a roof or parapet wall.
11. Use an expansion joint between any two fixed points in the
exhaust venting system wherever the expansion may exceed
1/4". Selkirk Metalbestos model PS and model G venting
will expand by one inch per 100°F in gas temperature per
100 feet of vent length. The expansion can be calculated by
the following formula:
Expansion, Vent length between
=
Inches two fixed points, feet
If the expansion calculated is greater than 1/4", an expansion
joint must be used between the two fixed points.
12. Attach the flue reducer included in the exhaust vent hood
package to the flue collar on the heater.
13. Attach the flue reducer to the vent system using a seal ring.
Attach this ring to the venting using the inner vee bands as
outlined in Steps 5-7.
14. Attach 8" air-intake connector to intake vent hood collar. It
may be necessary to use a slip-slip coupling to fit the pipe
to the intake vent hood.
15. Attach 8" air-intake connector back to the 6" burner air inlet
with 8" x 6" reducer. Prime and cement each joint to assure
gas-tight construction.
16. Seal all joints at the vent hoods with silicone sealant. Also
seal the joints at the flue collar and air inlet adapter. Joint on
the exhaust side must be sealed with high-temp silicone
sealant, Dow Corning 736 or equivalent.
TABLE 6.
S F
15' 3" 7' 6"
x
100
PRIMERS AND CEMENTS ARE EXTREMELY FLAMMABLE, AND
MUST NOT BE STORED OR USED NEAR HEAT OR OPEN FLAME.
ALLOW ADEQUATE CURING TIME BEFORE OPERATING HEATER.
DRAIN VALVE AND ACCESS PANELS
The heaters are equipped with a 3/4" NPT drain valves mounted
above and to the left of the burner.
An access panel is located above and to the right of the burner,
see Figure 8. This panel covers the cleanout opening in the tank
which is sealed by a gasket and cover. Another cleanout access
panel is located towards the back of the heater.
Contact your local gas service company to ensure that adequate
gas service is available and to review applicable installation
codes for your area.
Size the main gas line in accordance with Table 9 and 9A.
5
Minimum required gas supply pipe size is 1 1/4". The figures
shown are for straight lengths of pipe at 0.5 in. w.c. pressure
drop, which is considered normal for low pressure systems.
Note that fittings such as elbows and tees will add to the pipe
pressure drop.
MAXIMUM CAPACITY OF PIPE IN CUBIC FEET OF GAS PER HOUR
(Based upon a Pressure Drop of 0.5 inch Water Column
and 0.5 Specific Gravity Gas and max. gas press. of .5 psig)
LENGTH
IN
FEET 1/2" 3/4"
10 175 360
20 120 250
30 97 200
40 82 170
50 73 151
60 66 138
70 61 125
80 57 118
90 53 110
100 50 103
125 44
150 40
175 37
200 35
11
WARNING
FIGURE 8.

GAS PIPING

TABLE 9
Nominal Iron Pipe Sizes, Inches
1" 1 1/4" 1 1/2" 2"
680 1400 2100 3960
485 950 1460 2750
375 770 1180 2200
320 660 990 1900
285 580 900 1680
260 530 810 1520
240 490 750 1400
220 460 690 1300
205 430 650 1220
195 400 620 1150
93 175 360 550 1020
84 160 325 500 950
77 145 300 460 850
72 135 280 430 800
2 1/2" 3" 4"
6300 11000 23000
4360 7700 15800
3520 6250 12800
3000 5300 10900
2650 4750 9700
2400 4300 8800
2250 3900 8100
2050 3700 7500
1950 3450 7200
1850 3250 6700
1650 2950 6000
1500 2650 5500
1370 2450 5000
1280 2280 4600