Bradford White U-TW4-75S-76R-3N - Manual (Page 22)

U TTW SERVICE PROCEDURE V
Blower Testing and Replacement
WARNING
115 volt potential exposure. Use caution when
making voltage checks to avoid personal injury.
Blower Testing
Is there 115VAC across
terminals shown in
photo 15?
Incorrect supply
voltage polarity
Determine
power source
problem and
correct.
Does blower energize Within 2
minutes?
Y
Disconnect cord set
shown in photo 12. Is
there 115VAC across
terminals shown in photo
14?
N
See pressure switch
testing
Page 20.
Is there 115 VAC at
wall outlet?
Check power cord
for damage.
Y
N
Disconnect
pressure switch
tubing from blower
(see photo 11).
Connect
manometer to
pressure tap of
blower
(see photo 11).
With blower running, and exhaust
adapter removed from top of blower,
is there a negative pressure of -2.15"
to -2.30" W.C.?
Step 1. Position gas control power switch
to “ON” position and adjust control to call for heat.
Step 2. Remove the three screws (Phillips Screw driver)
from control access cover on blower assembly and
remove cover (see photos 9 and 10).
Reconnect cord set shown
in photo 12, is there
115VAC between blue wire
and green ground wire
(see photo 16).
Replace blower
Does cord set
have electrical
continuity?
Disconnect vent
system from top of
blower and remove
vent adapter
(see photo 13).
Does blower energize after 2
minutes, run for 30 seconds
and shut down?
N
Is there 115vac across blue
and green wires
(see photo 16)?
Blower OK
Y
Repair or replace
power cord
Replace blower
Y
N
N
N
N
Y
Y
Y
Y
N
Pressure switch
tubing
Pressure tap
Remove exhaust
adapter
Shown with pressure
switch removed.
Green ground
wire
Blue wire
Replace blower
Y Determine voltage
problem and correct.
N
Page 22
10
11 12
14 15
16
13
Replace gas
control
Y
Replace
cord set
N
Control
Access
Cover
Screws
9
R
22