Service Manual

With ohmmeter check

pressure switch for continuity.

Contacts should be closed.

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.

Pressure switch O.K.

Service Procedure VI

Blocked Vent Pressure Switch Testing and Replacement (Continued)

Check Exhaust Tube Pressure

With manometer, take a

reading at the exhaust tube pressure

tap location. Is value negative (-) or

slightly positive (see image below).

Is exhaust venting system

blocked or obstructed? Check

condensate elbow and drain.

Clear obstruction.

Determine cause

and correct.

Is vent system total length

compliant with vent tables in

the instruction manual?

Replace blocked vent switch (see

Blocked Vent Switch Testing and

Replacement, pg 85).

Reconfigure vent system

to be compliant with vent

tables (see

Specifications, pg 53).