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AOS WPC - Tech Training 55 of 72 Ashland City, TN © 2007
Servicing should only be performed by a Qualified Service Agent
VF BOILER SERVICE MANUAL
ERROR MESSAGES (CONT)
DISPLAYED MESSAGE
CONDITION/INDICATES
CHECK/REPAIR
“Blower Prov Stg1”
Blower Is Starting
(If the blower is not starting go to the “Blower Prov
Stg1” Blower Is Not Starting
tables)
Three conditions can cause this error message
when the blower is starting:
Normally Open Low Blower Prover or High Blower
Prover pressure switch contacts are not closing
during the pre or post purge operating states - or
within 5 minutes of call for heat being activated.
OR
Normally Open High Blower Prover pressure switch
contacts did not re-open after pre purge operating
state was completed. The High Blower Prover switch
is used to prove adequate purging of the combustion
chamber during pre and post purge cycles only. The
blower runs at approximately 5000 rpm during pre
and post purge operating states and at lower speeds
during all other operating states. High blower prover
switch contacts must close during the pre and post
purge states ONLY and open during all other
operating states.
OR
Normally Open Low Blower Prover pressure switch
contacts have opened during any operating state
when the blower should be running. IE: This can be
caused due to blower failure during the heating cycle
or if the pressure sensed by the switch rises above
the switches activation pressure for any reason. The
normally open contacts on both Blower Prover
switches close on a fall in pressure - the pressure
sensed must be in a vacuum.
Operational Note:
See blower prover switch information on page 24
and the Sequence of Operation on page 15.
Pressure Reading Test
• Take a manifold gas pressure reading. See
page 23 for how to perform this test. Allow the
boiler to operate until the Pre purge cycle com-
pletes and the blower speed reduces for igni-
tion. Record the highest and lowest pressures
observed. This may require jumpering the BPS
switches as described on pages 53 and 54.
This pressure must be between -0.12" W.C. and
-4.8" W.C. (negative pressures - in a vacuum)
during all operating states or one of the two BPS
switches will trigger a the “Blower Prov Stg1”
fault condition and lock out will occur.
If the actual pressure readings maintain within
this range - at least one BPS is defective as
determined from the pressure readings here
and the tests on pages 53 & 54. Because the
sensing tubes are T fitted together it is not con-
clusive which BPS is at fault. IE: a leaking dia-
phragm on the Low BPS could prevent the High
BPS from closing its contacts. Therefore -
replace both the High and Low BPS.
If the actual pressure observed in the pressure
test above did not drop to at least -4.8" W.C.
during the pre purge period when the blower is
running at 5000 rpm - see page 13. Or did not
drop to at least -0.12" W.C.or lower at any time
while the blower was running during the test the
BPS switches are not defective. Continue:
• Closely inspect all fittings and flanges in the gas
train between the outlet of the boiler’s 24 VAC
gas valve and the Venturi assembly. See page
12. Reseal/repair any leaking connections -
ensure all gaskets are properly seating.
• Disassemble the Venturi from the inlet connec-
tion at the blower and the intake air connection -
ensure the large “O” ring gaskets are not dam-
aged and seating properly.
Closely inspect the cone shaped restrictor
inside the Venturi for any signs of damage or
wear. If the restrictor is damaged or worn -
replace the Venturi.