Controls and Switches, GAS Piping | Ferguson JWSH100150, JWSH100250

CONTROLS AND SWITCHES

All models are provided with four pressure switches. These switches are essential to the safe and proper operation of the unit. All switches are wired in series. The controller is set up to shut the unit down whenever there is a failure of any of the switches. It is important to understand the purpose of each switch.

FIGURE 12.

BLOWER PROVER SWITCH

(SEE FIGURE 12)

The Blower Prover Switch is provided on the heater to verify that the fan is operating. It is a positive pressure switch whose electrical contacts are normally open. When the fan increases the pressure in the burner, the pressure switch will allow the electrical contacts to close. The pressure switch is connected to the burner tap by a piece of tygon tubing. This tubing must be connected in order for the switch to change the electrical contacts. The

controller requires that the electrical contacts on this air flow switch be open

before it will allow the blower to come on.

BLOCKED OUTLET PROVER SWITCH

(SEE FIGURE 12)

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 12)

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 12)

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 4.8"WC (1.18Kpa) for natural gas models and 8.5"WC (2.08Kpa) for propane models. 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" (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") 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 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