G76x Direct Spark Ignition Controls Product Bulletin

Heating Line Product Guide Ignition Controls Section Product Bulletin Issue Date

435.0

G76x 0600

G76x Direct Spark Ignition Controls

The G76x family of controls is designed for direct main burner ignition and supervision. The G76x is approved for ignition of natural gas, Liquefied Petroleum (LP) gas, manufactured gas, mixed gas, or LP gas-air mixtures.

Figure 1: G76x Direct Spark Ignition Controls

Features and Benefits

Microprocessor-based

Design

Multiple Trial for Ignition

and Prepurge Timings (Optional)

Multiple Trials (Optional) Automatic Recycle

(Optional)

Optional Light-Emitting

Diode (LED)

Provides precise timing and sequencing functions

Offers selectability of timing functions that will best suit the appliance

Increases opportunity for main burner ignition

Eliminates nuisance lockouts by restarting the ignition system (after a predetermined delay) if pilot flame is not proven within the trial-for-ignition time

Reduces troubleshooting time by visually informing service technicians of current status

? 2000 Johnson Controls, Inc. Code No. LIT-4350420

1



Application Requirements

Following are the application requirements of the G76x control.

? The G76x can be used on gas-fired equipment with a maximum firing rate of 117 kW (400,000 Btu/hr). Any application greater than 117 kW (400,000 Btu/hr) must have written approval in advance from the Johnson Controls Heating Products Engineering Department.

? All G76x applications must use a redundant gas valve system where the main valve seats are in series and open simultaneous for direct spark burner ignition.

Operating Mode Definitions

The following definitions describe operating conditions: G Prepurge: Initial time delay between thermostat

contact closure and trial for ignition. G Trial for Ignition: Period during which the main

valve and spark are energized in an attempt to ignite gas at the main burner. The control attempts to prove flame at the main burner within the trial-for-ignition time. G Run: Main gas valve remains energized and the spark is turned off after successful ignition. G 100% Shutoff: For controls with automatic recycle, main gas did not ignite within the trial-for-ignition time. The control de-energizes the spark circuit and main valve. G Automatic Recycle: If 100% shutoff occurs, the control delays for a specific recycle delay period before beginning another trial for ignition. (Models with recycle only.) G Interpurge: Period between trials for ignition when both the gas valve and spark are deactivated to allow unburned gas to escape before the next trial. Interpurge occurs between unsuccessful trials on a multi-trial control or after a loss of proven flame (flameout). G Ignition Lockout: Main gas did not ignite within the final trial-for-ignition time. Open the thermostat contacts for 30 seconds, then close to restart the sequence of operation. (Models with an optional LED will flash the LED to indicate ignition lockout.) G Flameout: Loss of proven flame. G Hard Lockout: The control detected a fault. Open the thermostat contacts for 30 seconds, then close to restart the sequence of operation. (Models with an optional LED will turn off the LED to indicate a hard lockout.)

Sequence of Operation

Figure 2 illustrates the sequence of operation of the G76x control.

The control is energized on a call for heat from the system thermostat. (Models with an optional LED will turn on the LED [steady on] until the call for heat is satisfied.) If the control is equipped with the optional prepurge, the control will delay for the time selected before initiating a trial for ignition. During the trial for ignition, the control attempts to light the main burner by simultaneously energizing the main gas valve and supplying a continuous spark at the igniter electrode. If the optional prepurge is not selected, then the trial for ignition begins within one second after the call for heat. The spark is deactivated immediately following the trial for ignition.

Under normal conditions, the main burner gas ignites within the trial-for-ignition time. If the control senses main burner flame by the end of the trial, the control proceeds to a run condition. During the run state, the control energizes the main valve until the call for heat ends, or until a flameout occurs. If main burner flame is not sensed by the end of the trial-for-ignition time, the control may:

? proceed to a 30-second interpurge followed by another trial (three trial models whose first two trials produced no flame)

? proceed to a lockout (no automatic recycle models whose final trial produced no flame)

? proceed to a recycle delay period followed by another trial (automatic recycle models whose final trial produced no flame)

If the main burner flame extinguishes during the run state, the control de-energizes the main gas valve for an interpurge of 30 seconds. After this period, another trial for ignition is initiated. If this flameout cycle repeats for a total of 16 times (main burner flame established, then lost), the control will:

? Enter the lockout mode if the control is a G760. The thermostat contacts must be opened for 30 seconds and then closed to escape the lockout condition.

? Enter the 100% shutoff mode and recycle period (5 minute recycle delay for the G765 and 60 minute recycle delay for the G766) before beginning another trial for ignition, starting with prepurge.

2 G76x Direct Spark Ignition Controls Product Bulletin

Start

Thermostat call for heat

Prepurge Trial for ignition

Flame present when not expected

Flame

No

present for

Yes

30 seconds?

Detected fault

Hard Lockout (optional LED

turns off)

Main valve Yes flame sensed?

No

Interpurge

No

Maximum number of trials Yes

attempted?

Run

Flameout? No

Yes

Thermostat calling for heat?

Yes

No

Ignition Lockout (optional LED

flashes)

Control No with ignition

recycle?

Yes

Yes

Sixteenth

flameout?

No

Recycle delay period

De-energize control and valves

End

Figure 2: Sequence of Operation

G76x Direct Spark Ignition Controls Product Bulletin 3

Mounting

Choose a location that provides the shortest, direct cable route to the spark igniter/flame sensor assembly. Easy access to the terminals is desired for wiring and servicing.

The control may be mounted in any position. Refer to Figure 3 for mounting dimensions and Figure 4 for wiring diagram.

8 0.31

56 2.22

1

6 0.22

58 2.28

6 0.25

Spade Terminals

78 3.06

34 1.33

GROUND 5

20 0.77

1

Add 13 mm (0.50 in.) for Rajah type connector.

108 4.25

THS 2

P.V. 1

M.V. 3 SENSE 4

116 4.57

Two Holes 4.1 for No. 8 Machine 0.162 or No. 6 Sheet Metal

Mounting Screws

120 4.70

6

67

0.22

2.63

51 2.00

Figure 3: Mounting Dimensions, mm (in.)

4 G76x Direct Spark Ignition Controls Product Bulletin

Wiring Diagram

Main Burner Ground

Spark Electrode/ Sensor Assembly

GROUND

5

LED THS 2

M.V. 3 SENSE 4

G76x Ignition Control

Main Main Valve Valve

Limits in Thermostat Line Only

Thermostat

Power Supply

Transformer

Figure 4: Wiring Diagram for G76x Ignition Control

G76x Direct Spark Ignition Controls Product Bulletin 5

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