12
LOW GAS PRESSURE SWITCH
(SEE FIGURE 13)
The Low Gas Switch (LGS) is a single-pole, normally open pressure switch
that will close its contacts when a rising pressure of 5.0 in. (1.25 kPa) W.C.
is encountered. The contacts will open when the pressure falls below the
fixed set point of 5.0 in. (1.25 kPa) W.C. The LGS monitors the gas supply
pressure to the heater. If the gas supply falls below 5.0 in. (1.25 kPa) W.C.,
the main burner is
extinguished (if heater is running) or the heater will not
start up.
Size the main gas line in accordance with Table 3. The figures shown are
for straight lengths of pipe at 0.5 in. (125 kPa) 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.
CAUTION
DO NOT USE FLEXIBLE GAS PIPING.
WARNING
THE HEATER IS NOT INTENDED FOR OPERATION AT HIGHER THAN 14.0"
WATER COLUMN (1/2 POUND or 3.45 kPa PER SQUARE INCH) SUPPLY
GAS PRESSURE. HIGHER GAS SUPPLY PRESSURES REQUIRE
SUPPLEMENTAL REDUCING SERVICE REGULATION. EXPOSURE TO HIGHER
GAS SUPPLY PRESSURE MAY CAUSE DAMAGE TO THE GAS CONTROLS
WHICH COULD RESULT IN FIRE OR EXPLOSION. IF OVERPRESSURE HAS
OCCURRED SUCH AS THROUGH IMPROPER TESTING OF GAS LINES OR
EMERGENCY MALFUNCTION OF THE SUPPLY SYSTEM THE GAS VALVE
MUST BE CHECKED FOR SAFE OPERATION. MAKE SURE THAT THE OUTSIDE
VENTS ON THE SUPPLY REGULATORS AND THE SAFETY VENT VALVES
ARE PROTECTED AGAINST BLOCKAGE. THESE ARE PARTS OF THE GAS
SUPPLY SYSTEM, NOT THE HEATER. VENT BLOCKAGE MAY OCCUR
DURING ICE STORMS.
IT IS IMPORTANT TO GUARD AGAINST GAS VALVE FOULING FROM
CONTAMINANTS IN THE GAS WAYS. SUCH FOULING MAY CAUSE
IMPROPER OPERATION, FIRE OR EXPLOSION.
IF COPPER SUPPLY LINES ARE USED THEY MUST BE INTERNALLY TINNED
AND CERTIFIED FOR GAS SERVICE.
BEFORE ATTACHING THE GAS LINE BE SURE THAT ALL GAS PIPE IS CLEAN
ON THE INSIDE.
TO TRAP ANY DIRT OR FOREIGN MATERIAL IN THE GAS SUPPLY LINE, A
DIRT LEG (SOMETIMES CALLED A SEDIMENT TRAP OR DRIP LEG) MUST BE
INCORPORATED IN THE PIPING (SEE FIG. 14). THE DIRT LEG MUST BE
READILY ACCESSIBLE AND NOT SUBJECT TO FREEZING CONDITIONS.
INSTALL IN ACCORDANCE WITH RECOMMENDATIONS OF SERVING GAS
SUPPLIERS. REFER TO THE NATIONAL FUEL GAS CODE.
LENGTH
NORMAL IRON PIPE SIZES (INCHES)
IN
INPUT IN THOUSANDS BTU/HR
FEET
1/2"
3/4"
1"
1 1/4" 1 1/2"
2"
2 1/2"
3"
4"
10
175
360
680
1400
2100
3960
6300
11000 23000
20
120
250
485
950
1460
2750
4360
7700
15800
30
97
200
375
770
1180
2200
3520
6250
12800
40
82
170
320
660
990
1900
3000
5300
10900
50
73
151
285
580
900
1680
2650
4750
9700
60
66
138
260
530
810
1520
2400
4300
8800
70
61
125
240
490
750
1400
2250
3900
8100
80
57
118
220
460
690
1300
2050
3700
7500
90
53
110
205
430
650
1220
1950
3450
7200
100
50
103
195
400
620
1150
1850
3250
6700
125
44
93
175
360
550
1020
1650
2950
6000
150
40
84
160
325
500
950
1500
2650
5500
175
37
77
145
300
460
850
1370
2450
5000
200
35
72
135
280
430
800
1280
2280
4600
NOTE: LOW GAS IS
LOCATED ON INLET
SIDE OF GAS VALVE.
FIGURE 13
ON/OFF SWITCH
The ON/OFF Switch is a single-pole, single-throw rocker switch. This switch
provides 120V from the line source to the heater.
CAUTION
THE WATER HEATER IS POLARITY SENSITIVE. BEFORE APPLYING
ELECTRICITY TO THIS HEATER BE CERTAIN THAT SUPPLY NEUTRAL WIRE
TO GROUND CHECK INDICATES ZERO VOLTAGE.
HOT SURFACE IGNITER
The Hot Surface Igniter is a device that ignites the main burner by high
temperature (>1800°F or >982°C). When 120VAC is applied to the igniter,
sufficient heat is generated to ignite the main burner. Although improvements
have been made to strengthen the igniter, it is still fragile and care must be
taken when handling the igniter to prevent breakage.
GAS PIPING
Contact your local gas service company to ensure that adequate gas service
is available and to review applicable installation codes for your area.
TABLE 3
MAXIMUM CAPACITY OF PIPE IN CUBIC FEET OF GAS PER HOUR
(Based upon a Pressure Drop of 0.5 inch Water Column and 0.6 Specific Gravity Gas and max. gas pressure of 0.5 psig)
LENGTH
NORMAL IRON PIPE SIZES (INCHES)
IN
INPUT IN KW
METERS 1/2"
3/4"
1"
1 1/4" 1 1/2"
2"
2 1/2"
3"
4"
3.0
51
105
199
410
615
1160
1845
3221
6735
6.1
35
73
142
278
428
805
1277
2255
4626
9.1
28
59
110
225
346
644
1031
1830
3748
12.2
24
50
94
193
290
556
878
1552
3192
15.2
21
44
83
170
264
492
776
1391
2840
18.3
19
40
76
155
237
445
703
1259
2577
21.3
18
37
70
143
220
410
659
1142
2372
24.4
17
35
64
135
202
381
600
1083
2196
27.4
16
32
60
126
190
357
571
1010
2108
30.5
15
30
57
117
182
337
542
952
1962
38.1
13
27
51
105
161
299
483
864
1757
45.7
12
25
47
95
146
278
439
776
1610
53.3
11
23
42
88
135
249
401
717
1464
61.0
10
21
40
82
126
234
375
688
1347
FIGURE 14
Summary of Contents for SUF 100 150NE
Page 31: ...31...
