Poor Combustion - Ignition Problems - A.O. Smith VF VB 1000 Service Handbook

POOR COMBUSTION - IGNITION PROBLEMS

If the high and/or low fire CO
shown on page 19, the CO readings are high, or if the boiler is experiencing ignition failure
or rough starting perform the following procedures:
Adequate Combustion - Proper Venting
1. Ensure there is an adequate supply of fresh air for combustion and the boiler is vented
properly. DO NOT OVERLOOK THIS STEP. Lack of combustion air and improper
venting is often the root cause for poor combustion.
Direct Vent Installations: If the boiler is direct vented ensure the intake air or the vent
pipe is not restricted and neither has exceeded the maximum 70 equivalent feet. Ensure
the vent and intake air terminations are positioned correctly so that vent gases are not
recirculating to the intake air termination. Installation note: each 90° elbow is equivalent
to 10 linear feet of pipe on VF boilers. If the boiler is in an equipment room with a door to
the outdoors, temporarily disconnect the intake air pipe and prop open the equipment
room door. Take combustion readings again to see if this corrects the problem.
Conventional Vent Installations: If the boiler is using room air for combustion ensure
the vent pipe has not exceeded the 100' maximum equivalent feet. Installation note:
each 90° elbow is equivalent to 10 linear feet of pipe on VF boilers. Ensure the fresh air
openings in the equipment room are adequately sized for the combined input Btu/hr
rating of all conventionally vented gas fired appliances in the room. If the boiler is in an
equipment room with a door to the outdoors - prop open the equipment room door. Take
combustion readings again to see if this corrects the problem.
General venting guidelines are shown here. Refer to the Instruction Manual that came with
the boiler for complete combustion air and vent installation information.
Direct Vent
Configurations
Installation Note:
VF Boilers are classified as Category IV
appliances. AL29-4C vent material must
be used for the exhaust vent on all
installations.
Conventional Vent
Configurations
AOS WPC - Tech Training
VF BOILER SERVICE MANUAL
combustion readings are not in accordance with the tables
2
Servicing should only be performed by a Qualified Service Agent
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