Variable Frequency Drive - Suf 400 - State Water Heaters SUF 130 300 Service Handbook

ULTRAFORCE COMMERCIAL GAS WATER HEATER
VARIABLE FREQUENCY DRIVE – SUF 400
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.
on the next page for voltage and frequency information.
GROUND HOT
R/L1
G
BLOWER MOTOR WIRES
BLACK WHITE
U/T1 V/T2
NOTE: BE SURE TO MATCH WIRE
COLORS WHEN CONNECTING BLOWER
WIRES OR BLOWER MAY RUN
BACKWARD AND CAUSE A FAULT.
RC RA
1-10 VDC Speed Instruction
State Water Heaters – Technical Training Department 33
SUF 120 thru 400 SERVICE HANDBOOK
NEUTRAL
N
RED
W/T3
0V AI1
Servicing should only be performed by a Qualified Service Agent
VARIABLE FREQUENCY DRIVE
+5V DO LI1
Enable Disable Circuit
See table
155
LI2 LI3 LI4
Ashland City, Tennessee © 2009
+15V
198152-002