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ULTRAFORCE COMMERCIAL GAS WATER HEATER
SUF 120 thru 400 SERVICE HANDBOOK
State Water Heaters – Technical Training Department 34 Ashland City, Tennessee © 2009
Servicing should only be performed by a Qualified Service Agent 198152-002
VARIABLE FREQUENCY DRIVE - BLOWER SPEED AND PRESSURE READINGS
The instructions for the VFD are sent from the CCB to in the form of a DC current. The chart
below lists the current readings, the frequency signal displayed by the VFD, and the pressure
switch settings needed for the CCB to let the burner operate. The frequency numbers
displayed may vary slightly with slight variations in the DC voltage generated by the CCB. If
the water heater exhibits poor run characteristics check the frequency display. If the
frequency is more than 5% out of range, check the DC volt signal at the terminals shown on
page 33.
Voltage – Frequency – Speed Instructions - VFD
Model SUF
400
Instruction Volts DC
Terminals 0V and AI1
0 – 10
VDC
Volts Frequency Pressure
W.C.”
Ignition (low speed) 7.53 150 Hz+/- 2 5.3”
Purge (high speed) 7.77 155 Hz+/- 2 5.85”
VFD Part Number 197500-000
Frequency is displayed
in the red LED. 155Hz
155