Filter
Top Products
RC RA 0V AI1 +5V DO LI1 LI2 LI3 LI4 +15V
ULTRAFORCE COMMERCIAL GAS WATER HEATER
SUF 120 thru 400 SERVICE HANDBOOK
State Water Heaters – Technical Training Department 33 Ashland City, Tennessee © 2009
Servicing should only be performed by a Qualified Service Agent 198152-002
VARIABLE FREQUENCY DRIVE – SUF 400
VARIABLE FREQUENCY DRIVE
1-10 VDC Speed Instruction Enable Disable Circuit
The Ultra Force SUF 400 model has a variable frequency drive (VFD) that controls the
rpm of the blower motor. The VFD receives a signal from the central control board that
instructs the VFD to transmit the proper frequency to the blower to produce the proper blower
speed and proper input.
Three conditions must be met for the frequency drive to start the blower:
1. 120VAC must be supplied to the VFD 120VAC input.
2. The ignition control board closes an enable circuit – terminals LI1 and +15V
3. The ignition control board sends a 1-10VDC instruction – terminals 0V and AI1. See table
on the next page for voltage and frequency information.
GROUND HOT NEUTRAL
R/L1 N
G
BLOWER MOTOR WIRES
BLACK WHITE RED
U/T1 V/T2 W/T3
NOTE: BE SURE TO MATCH WIRE
COLORS WHEN CONNECTING BLOWER
WIRES OR BLOWER MAY RUN
BACKWARD AND CAUSE A FAULT.
155