Honeywell PDX450S*F(BN,SX) Blower Temperature Switch Testing, PDX Series, Pdx Service Procedure

PDX Series

PDX SERVICE PROCEDURE V

Blower Temperature Switch Testing

and Replacement

Blower Temperature Switch

Testing.

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

WARNING

120 volt potential exposure. Use caution

to avoid personal injury.

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Step 2. Remove tubing from inlet pressure tap.

Step 3. Remove the three screws (Phillips screw driver) from control access cover on blower and remove cover (see photo 15).

Step 4. Locate blower temperature switch (see photo 16)

Switch Setting

Opens on rise @ approximately 155°F

Auto resets on fall @ approximately 128°F

Cool switch to

below 125°F

Disconnect wire leads to		N
switch. Using a multi-meter			Replace switch
set to the ohms setting, is
			(see page 24)
there continuity between the
switch terminals?
	Y
				N
Reconnect wire leads and
		Y	Do switch contacts Y
observe heater operation. Do
exhaust gas temperatures rise			open?
to or above 175°F?
	N
Do switch contacts Y			Replace switch
open?			(see page 23)

16

Blower temperature

switch location

Air mixing inlet

			Common causes for
		high exhaust temperature
Exhaust	1. Vent length is below minimum allowable.
temperature is too	2. Vent diameter not to specification.
hot.	3. Restricted dilution air inlet.
	4. Missing or deteriorated flue baffle.
	5. Gas pressure is out of specification.
	6. Excessively high ambient temperatures.

N

Switch OK

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