A.O. Smith TC-099 - Manual (Page 23)

VF BOILER SERVICE MANUAL
AOS WPC - Tech Training 22 of 72 Ashland City, TN © 2007
Servicing should only be performed by a Qualified Service Agent
POOR COMBUSTION - IGNITION PROBLEMS (CONT)
VFD Operating Parameters
Approximate MCB/VFD operating parameters for natural gas models are shown in the first
table below. Parameters for propane models are shown in the second table.
When combustion is poor, the firing rate of the boiler or blower speed is in question, or the
boiler is experiencing rough starts or ignition failure compare the values given here to actual
readings taken during the various operating states shown. Actual readings will vary
somewhat but should be relatively close to what is shown here when the MCB and the VFD
are operating properly.
Approximate Values Natural Gas
Blower Speed Control VFD
VW/VB
500
VW/VB
750
VW/VB
1000
MCB Instruction Pre/Post Purge Mode Approx - VDC 8.6 8.6 8.9
MCB Instruction Ignitor Warm Up Period Approx - VDC 3.7 3.7 3.7
MCB Instruction Min Mode 25% Approx - VDC 1.3 2.1 2.1
MCB Instruction Max Mode 100% Approx - VDC 4.3 7.2 7.7
Blower Speed Pre/Post Purge Mode - Approx RPM 5000 5000 5000
Blower Speed Ignitor Warm Up Period - Approx RPM 2200 2200 2200
Blower Speed Min Mode 25% - Approx RPM 800 1200 1250
Blower Speed Max Mode 100% - Approx RPM 2500 4100 4500
Blower Power Freq Pre/Post Purge Mode - Approx Hz 172 Hz 172 Hz 179 Hz
Blower Power Frequency Ignitor Warm Up Period - Approx Hz 75 Hz 75 Hz 75 Hz
Blower Power Frequency Min Mode 25% - Approx Hz 26 Hz 41 Hz 43 Hz
Blower Power Frequency Max Mode 100% - Approx Hz 85 Hz 144 Hz 155 Hz
Approximate Values Propane Gas
Blower Speed Control VFD
VW/VB
500
VW/VB
750
VW/VB
1000
MCB Instruction Pre/Post Purge Mode Approx - VDC 8.6 8.6 8.9
MCB Instruction Ignitor Warm Up Period Approx - VDC 3.7 3.7 3.7
MCB Instruction Min Mode 25% Approx - VDC 1.4 2.1 2.4
MCB Instruction Max Mode 100% Approx - VDC 4.3 7.7 7.7
Blower Speed Pre/Post Purge Mode - Approx RPM 5000 5000 5000
Blower Speed Ignitor Warm Up Period - Approx RPM 2200 2200 2200
Blower Speed Min Mode 25% - Approx RPM 1000 1300 1400
Blower Speed Max Mode 100% - Approx RPM 2500 4500 4500
Blower Power Freq Pre/Post Purge Mode - Approx Hz 172 Hz 171 Hz 179 Hz
Blower Power Frequency Ignitor Warm Up Period - Approx Hz 74 Hz 75 Hz 75 Hz
Blower Power Frequency Min Mode 25% - Approx Hz 27 Hz 43 Hz 47 Hz
Blower Power Frequency Max Mode 100% - Approx Hz 85 Hz 155 Hz 155 Hz