State Industries SUF100199, SUF100150 Ground HOT Neutral, Blower Motor Wires Black White RED, AI1

ULTRAFORCE COMMERCIAL GAS WATER HEATER

SUF 120 thru 400 SERVICE HANDBOOK

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. See table on the next page for voltage and frequency information.

GROUND HOT NEUTRAL VARIABLE FREQUENCY DRIVE

G

R/L1

155

N

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.

RC	RA	0V	AI1	+5V	DO	LI1	LI2	LI3	LI4	+15V
1-10 VDC Speed Instruction						Enable Disable Circuit

State Water Heaters – Technical Training Department 33 Ashland City, Tennessee © 2009

Servicing should only be performed by a Qualified Service Agent 198152-002