Bradford White EF120T4003NA3 Service Manual page 36

Blocked Vent Pressure Switch Testing and Replacement
Check Exhaust Tube Pressure
With manometer, take a
reading at the exhaust tube
pressure tap location. Is
value .4" or less? (see
image below).
Y
With ohmmeter check
pressure switch for
continuity. Contacts
should be closed.
Y
Pressure switch is O.K.
Exhaust tube pressure tap located behind
serivce panel access doors at bottom of heater
36
Service Procedure VI:
Is exhaust venting
system blocked or
N
obstructed? Also
check condensate
elbow and drain.
N
Is vent system total
length compliant with
vent tables in the
instruction manual?
Y
Replace blocked exhaust vent switch
(see Blocked Exhaust Vent Switch
Testing and Replacement, pg 32).
Is pressure in exhaust tube near 2.7" W.C. or more? If so, correct
blockage (below). If exhaust pressure is low (0.40" or less), replace
N
pressure switch. Is pressure in intake tube near 2.3" W.C. or more? If
so, correct blockage (below). Replace blocked exhaust vent switch
(see Blocked Exhaust Vent Switch Testing and Replacement, pg 32).
Clear obstruction.
Y
Determine cause
and correct.
Reconfigure vent
system to be
N
compliant with vent
tables (see
Specifications, pg 5).
36
Exhaust tube pressure
tap location