Lochinvar 1.3 Checking temperature sensors, Troubleshooting continued, Service Manual

Service Manual

3 Troubleshooting (continued)

Checking temperature sensors

The boiler temperature sensors (inlet water, outlet water, system water, flue, and outdoor air) are all resistance type devices. The following tables show the correct values for the sensors at various temperatures. Use an ohmmeter to read the resistance of the sensor at a known temperature. If the resistance of the sensor does not closely match its corresponding table, replace the sensor.

Table 3B - Inlet/Outlet System Sensor Resistance vs. Temperature

	Temperature		Resistance	Temperature		Resistance
	50	18,780		158	1,990
	68	12,263		176	1,458
	86	8,194		194	1,084
	104	5,592		212	817
	122	3,893		--	--
	140	2,760		--	--
Table 3C - Flue Temperature Sensor Resistance vs. Temperature
	Temperature		Resistance	Temperature		Resistance
	68	14,773		176	1,707
	86	9,804		194	1,266
	104	6,652		212	952
	122	4,607		230	726
	140	3,252		248	560
	158	2,337		--	--
Table 3D - Outdoor Air Sensor Resistance vs. Temperature
	Temperature		Resistance	Temperature		Resistance
	-50		490,813	20		46,218
	-40		336,606	30		34,558
	-30		234,196	40		26,099
	-20		165,180	50		19,900
	10		118,018	60		15,311
	0		85,362	70		11,883
	10		62,465	80		9,299

45