Honeywell PDX250T*F(BN,SX,CX) service manual Determine Water Temperature Inside Tank, PDX Series

PDX Series

PDX SERVICE PROCEDURE VI

Gas Control/Thermal Well Testing and

Replacement

WARNING

Stored water may be HOT when performing the following steps in this procedure.

Take necessary precaution to prevent personal injury.

Determine Water Temperature Inside Tank

Note: It is important to understand once the resistance for the thermal well is determined from page 25, water flow through the heater should not occur. Prior to performing the steps below, turn off the cold water supply to the water heater. This will prevent cold water flow into the tank affecting the resistance value of thermal well.

Step 1. Position gas control power switch to “OFF” position.

Step 2. Draw approximately 4 gallons of water from drain valve into a container and discard. Draw an additional gallon and immediately measure water temperature using an accurate thermometer. It may be necessary to open a hot water faucet to allow heater to drain.

Step 3. Using the chart below, determine correct resistance value for the water temperature from step 2.

Example:		If temperature of 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
						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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