Emerson Complete Guide to DSI Valves for Furnace Systems

►System Applications

Hot Surface Ignition (HSI)

The thermostat calls for heat and energizes the HSI control. If system is equipped with prepurge, the purge fan is energized and power will be delayed thirty seconds before application to the Hot Surface Ignitor. If prepurge is not selected, the ignitor is powered within one second. The ignitor heats up and at the end of the heating period, the redundant and main valves are opened. A flame must be detected within a fixed time period or both valves close, the ignitor is turned off and the HSI control locks out unless the system is equipped with retry. Retry indicates the ignition sequence will be repeated for a total of three tries if flame is undetected or lost within 30 seconds of ignition.

M

T

G

T

M

L

H

F

L

H

V

N

V

S

S

R

H

2

P

1

2

D

1

2

1

BURNER

BLUE

GROUND

HOT

RED

MV2

SURFACE

C

FLAME

ADAPTER

IGNITER

P

MV1

M

PROBE

GAS	External	LIMIT
VALVE	Jumper	CONTROLLER
		L1
		(HOT)
		L2

THERMOSTAT OR	ALTERNATE TRANSFORMER
CONTROLLER	LIMIT

Typical Wiring for Hot Surface Ignition System

Direct Spark Ignition (DSI)

The thermostat calls for heat and simultaneously energizes the DSI control module and gas valve solenoid. Sparks at the ignition electrodes ignite the gas at the main burner. Flame is sensed through the electrodes by the flame detection circuit and shuts off the sparking. If flame is not established within a fixed time period (lock-out time) main and redundant valves close, sparking ceases and the control module locks out.

MV	VAL	TR	TH	GND	FLY LEAD	SPARK
MV
(GND)					FLAME

SPARK PROBE

FLAME PROBE

External

Jumper

M P C

GAS

VALVE

	Burner Ground	LIMIT
		CONTROLLER
	(GND)	L1 (HOT)
		L2
THERMOSTAT OR	ALTERNATE TRANSFORMER
CONTROLLER	LIMIT

Typical Wiring for Direct Spark Ignition System

8Gas Valve Cross Reference