LAARS U.H.E. - Service Manual - Manual (Page 28)

LAARS Heating Systems Page 28
Check Exhaust Tube Pressure
Exhaust Pressure Switch Testing and Replacement
Exhaust Tube
pressure tap location
Exhaust tube
at bottom of heater
N
Replace
blocked vent switch.
(see page 29)
Is exhaust venting
system blocked or
obstructed? Also
check condensate
elbow and drain.
Clear obstruction.
Determine cause
and correct.
Y
Is vent system total
length compliant with
vent tables in the
instruction manual?
Reconfigure vent
system to be
compliant with
vent tables (see
“Specifications”).
Y
N
With monometer, take a
reading at the exhaust
tube pressure tap location.
Is value negative (-) or
slightly postitive
(see illustration below).
Y
N
With ohmmeter check
pressure switch for
continuity. Contacts should
be closed.
Y
N
Pressure switch O.K.
28
Is pressure in exhaust tube near 2.7" w.c. or more? If so, correct
blockage (above). If exhaust pressure is low (0.40" or less), replace
pressure switch.