12
BLOCKED OUTLET PROVER SWITCH
(SEE FIGURE 13)
The Blocked Outlet Prover Switch is set up to shut the unit off when a build-
up of positive pressure in the exhaust vent pipe occurs. This switch is a
positive pressure switch that requires an increase in pressure to change
the electrical contacts from normally closed to open. When this switch
prevents the unit from igniting, most likely the exhaust is blocked by some
means Check to see if the condensate is allowed to flow freely from the
exhaust elbow and for obstructions in the exhaust venting and exhaust
vent terminal. Also verify that there is no more than fifty equivalent feet
(15.2 m) of three inch PVC vent pipe on the exhaust.
BLOCKED INLET PROVER SWITCH
(SEE FIGURE 13)
The Blocked Inlet Prover Switch is set up to shut the unit off when a build-
up of negative pressure in the intake vent pipe occurs. This switch is a
negative pressure switch that requires an increase in negative pressure
to change the electrical contacts from normally closed to open. The switch
is connected to the pressure tap on the PVC flange connected to the inlet
of the blower. When this switch prevents the unit from igniting, most likely
the intake is blocked by some means. Check to see if there is no more than
fifty equivalent feet (15.2 m) of three inch PVC vent pipe on the intake. Also
verify that the intake and intake vent terminal is free of obstructions that
may prevent air from entering the unit.
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. (1.25Kpa) W.C.
is encountered. The contacts will open when the pressure falls below the
fixed set point of 5.0 in. (1.25Kpa) W.C. The LGS monitors the gas supply
pressure to the heater. If the gas supply falls below 5.0 in. (1.25Kpa) W.C.,
the main burner is extinguished (if heater is running) or the heater will not
start up.
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.
Size the main gas line in accordance with Table 3. The figures shown are
for straight lengths of pipe at 0.5 in. (125Pa) 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.
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)
WARNING
THE HEATER IS NOT INTENDED FOR OPERATION AT HIGHER THAN 14.0"
WATER COLUMN (1/2 POUND or 3.45Kpa 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.
FIGURE 14
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
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