Bradford-White Corp U4TW60T*FRN, U4TW50T*FRN, U4TW40T*FRN Pressure Switch Testing cont’d, Page

Pressure Switch Testing

Pressure Switch Testing (cont’d)

Pressure switch

With steps 1,2 & 3 complete, discon- nect wire leads from pressure switch.

wire leads

Use a multi-meter

set to the ohms

setting. With

blower off, check across the pres- sure switch termi- nals. Are the switch contacts open (no electrical continuity)?

Y

Position the gas

control power

switch to the “ON” position and adjust the thermostat to call for heat. This will start the blower. Check with the multi-meter. Do the pressure switch contacts close with the blower running?

Y

The switch contacts are OK. See safety circuit trace (page 40).

N	Check the tubing and	N
	pressure tap on switch	Replace switch
	for blockage. Is there	(see page 27).
	a blockage?

	Y	Clear blockage
		Y
Check the tub-
N ing and pressure N		Is the vent
tap on switch for		system
blockage. Is		blocked?
there a block-
age?		N

	Y
Is vent system
length within the Y	See blower
vent table specifi-	testing (page
cations listed on	28). Is the
pages 9 & 10?	Blower OK?

N	N
Reconfigure vent	Correct the
system to be	blower prob-
compliant with	lem.
vent tables.

Page 26

26