Bradford-White Corp CX, D)W275T*(BN, C(S service manual Determine Water Heater Tank Temperature

	SERVICE PROCEDURE AG-III
	Honeywell Thermowell Testing and
	Replacement
DETERMINE WATER HEATER TANK TEMPERATURE
NOTE:	WARNING
It is important to understand once the resistance	Stored water may be HOT when
for the thermowell is determined, water flow	performing the following steps in this
through the water heater should not occur. Prior	procedure. Take necessary precaution to
to performing the steps below turn off cold water	prevent personal injury
supply to the water heater. This will prevent cold
water flow into the tank affecting the resistance	CAUTION
value of the thermowell.	DO NOT use standard multimeter
	probes to test. Doing so will damage
	connector. Use special pin type
Step 1. Turn the gas control to the “OFF” position and	electronic probes or small diameter
disconnect the thermowell harness from the gas control. wire pins inserted into connector

Step 2. Using a multimeter set to measure Ohms determine the resistance of the thermowell sensor (See caution on this page).

Step 3. Hold one probe in the center pin and measure the outside positions pins (see figure 29 & 30, page 16).

Step 4. Draw approximately 1 quart of water from the drain valve and immediately measure the water temperature using an accurate thermometer. It may be necessary to open a hot water faucet to allow the heater to drain.

Step 5. Refer to Table 1 below to determine the correct resistance value for the water heater tank temperature.

Example: If the temperature of the water is 84°F, then the resistance through the sensor would be 8449 (see shaded area). NOTE: Sensor resistance increases as the temperature falls.

Sensor Resistance at Various Temperatures

(Table 1)

In Degrees F

°F	0	1	2	3	4	5	6	7	8	9
40	26109	25400	24712	24045	23399	22771	22163	21573	21000	20445
50	19906	19383	18876	18383	17905	17440	16990	16553	16128	15715
60	15314	14925	14548	14180	13823	13477	13140	12812	12494	12185
70	11884	11592	11308	11032	10763	10502	10248	1000	9760	9526
80	9299	9078	8862	8653	8449	8250	8057	7869	7685	7507
90	7333	7165	7000	6839	6683	6531	6383	6238	6098	5961
100	5827	5697	5570	5446	5326	5208	5094	4982	4873	4767
110	4663	4562	4464	4368	4274	4183	4094	4006	3922	3839
120	3758	3679	3602	3527	3453	3382	3312	3244	3177	3112
130	3048	2986	2925	2866	2808	2752	2697	2643	2590	2538
140	2488	2439	2391	2344	2298	2253	2209	2166	2124	2083
150	2043	2004	1966	1928	1891	1856	1820	1786	1753	1720
160	1688	1656	1625	1595	1566	1537	1509	1481	1454	1427
170	1402	1376	1351	1327	1303	1280	1257	1235	1213	1191
180	1170	1150	1129	1110	1090	1071	1953	1035	1017	999
190	982	965	949	933	917	901	886	871	857	842
200	828	814	801	788	775	762	749	737	725	713

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