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G77x Intermittent Pilot Ignition Controls
The G77x family of controls is designed for indirect ignition of natural
Description
gas, Liquefied Petroleum (LP) gas, manufactured gas, mixed gas, or
LP gas-air mixtures.
Following are the application requirements of the G77x control.
Application
Requirements
• The G77x can be used on gas-fired equipment with a maximum firing
• All G77x applications must use a redundant gas valve system where
© 2000 Johnson Controls, Inc.
Part No. 24-8143-588, Rev. A
Code No. LIT-121250
All manuals and user guides at all-guides.com
Gas Combustion Combination Controls and Systems G
Figure 1: G77x Intermittent Pilot Ignition Controls
rate of 117 kW (400,000 Btu/hr). Any application over 117 kW
(400,000 Btu/hr) must have written approval in advance from the
Johnson Controls Heating Products Engineering Department.
the pilot and main valve seats are in series and opened in sequence for
intermittent pilot ignition.
Installation Sheets Manual 121
Technical Bulletin G77x
Issue Date 0600
www.johnsoncontrols.com
1
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Table of Contents
Related Manuals for Johnson Controls G77 Series
Summary of Contents for Johnson Controls G77 Series
- Page 1 117 kW (400,000 Btu/hr). Any application over 117 kW (400,000 Btu/hr) must have written approval in advance from the Johnson Controls Heating Products Engineering Department. • All G77x applications must use a redundant gas valve system where the pilot and main valve seats are in series and opened in sequence for intermittent pilot ignition.
- Page 2 The performance specifications are nominal and conform to acceptable industry standards. For application at conditions beyond these specifications, consult the local Johnson Controls office. Johnson Controls, Inc. shall not be liable for damages resulting from misapplication or misuse of its products.
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Page 3: Operating Mode Definitions
All manuals and user guides at all-guides.com The following definitions describe operating conditions: Operating Mode • Prepurge--Initial time delay between thermostat contact closure and Definitions trial for ignition. • Trial for Ignition--Period during which the pilot valve and spark are activated, attempting to ignite gas at the pilot burner. -
Page 4: Sequence Of Operation
All manuals and user guides at all-guides.com Figure 2 illustrates the sequence of operation of the G77x control. Sequence of Operation 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.) The vent damper, if used, is energized and when fully opened, also energizes the ignition control. - Page 5 All manuals and user guides at all-guides.com Start Flame present when not expected Detected fault Thermostat call for heat Flame Hard Lockout present for (optional LED 30 seconds? turns off) Prepurge Trial for ignition Pilot Energize flame main valve sensed? Maximum Thermostat number of trials...
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Page 6: Installation And Wiring
These instructions are intended as a guide for Wiring qualified personnel installing or servicing Johnson Controls ignition controls. Carefully follow all instructions in this bulletin and all instructions on the appliance. Limit repairs, adjustments, and servicing to the operations listed in this bulletin or on the appliance. - Page 7 All manuals and user guides at all-guides.com Electrical Connections CAUTION: Equipment Damage Hazard. Connect the high voltage cable to the spark transformer terminal and spark electrode (pilot burner assembly) before applying power to the control. Be certain the ground wire is attached to the pilot burner and control ground terminal strip.
- Page 8 All manuals and user guides at all-guides.com Vent Damper System Pilot Burner Integral Assembly Igniter/Sensor Main Burner Ground Pilot Gas Supply Vent Damper GROUND Wiring Harness 24 V THS 2 Power PV 1 Main Pilot Supply Valve Valve MV 3 Thermostat Transformer Ignition Control...
- Page 9 All manuals and user guides at all-guides.com Vent Damper System Pilot Burner Flame Sensor Assembly Main Burner Ground Pilot Gas Supply Vent Damper Wiring Harness GROUND 24 V THS 2 Power PV 1 Pilot Main Supply Valve Valve MV 3 SENSE 4 Thermostat Transformer...
- Page 10 All manuals and user guides at all-guides.com Pilot Burner Flame Sensor Assembly Main Burner Ground Pilot Gas Supply GROUND Limits in Thermostat Line Only THS 2 R.O. SWH Power PV 1 Supply Pilot Main Valve Valve MV 3 SENSE 4 Thermostat Transformer Ignition Control...
- Page 11 All manuals and user guides at all-guides.com Pilot Instructions for installing the spark electrode and sensor assembly are Burner/Igniter- typically provided by the appliance manufacturer. It is important to follow Sensor those instructions. If such information is not included, use the following basic instructions.
- Page 12 All manuals and user guides at all-guides.com Checkout and WARNING: Fire or Explosion Hazard. Avoid personal injury or Startup property damage by making sure the control Procedure functions properly and there are no gas leaks. Follow this checkout and startup procedure before leaving the installation.
- Page 13 All manuals and user guides at all-guides.com The anticipator setting is normally equal to the ignition system current Thermostat draw, plus that of the pilot and main valve. Heat Anticipator Due to variations in appliance wiring and valves, it is advisable to measure Settings the actual current draw of the heating system at the thermostat location.
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Page 14: Replacement Procedure
All manuals and user guides at all-guides.com Replacement WARNING: Shock Hazard. Avoid electrical shock and Procedure equipment damage. Disconnect electrical power and turn off the gas before wiring the control into the circuit. CAUTION: Equipment Damage Hazard. Label all wires prior to disconnection when servicing controls. - Page 15 All manuals and user guides at all-guides.com Modifying All spark ignition controls have a spark transformer connected to a high Existing Ignition voltage cable. There are three types of connections for the high voltage Cable cable: Spike, Rajah, and 6.35 mm (1/4 in.) male spade (see Figure 9). The replacement G77x has a Spike transformer.
- Page 16 All manuals and user guides at all-guides.com Service WARNING: Fire or Explosion Hazard. Do not attempt servicing Checkout or troubleshooting when the LED is flashing (recycle Procedures mode or ignition lockout). The control automatically energizes the system and could cause personal injury or property damage.
- Page 17 All manuals and user guides at all-guides.com Start Is 24 VAC present between Check for defective transformer, Terminal 2 and thermostat, or faulty wiring ground? Open thermostat contacts for 30 seconds and then close System was in lockout, causes spark present include flameout or an internal fault now? pilot remain lit...
- Page 18 All manuals and user guides at all-guides.com Start Are pilot valve Connect pilot valve securely connections between Terminal 1 and ground correct and secure? Is 24 VAC Replace between Terminal 1 control and ground? Is inlet gas pressure Correct gas per manufacturer’s pressure specifications?
- Page 19 All manuals and user guides at all-guides.com Start Does spark stay on Is 24 VAC Replace after the pilot between Terminal 3 control lights? and ground? Make sure sensor cable Is gas and spark cable are inlet pressure separated and not per manufacturer’s Correct wrapped around any...
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Page 20: Repairs And Replacement
Use only an exact or factory recommended replacement control. All other accessories, such as flame sensors, electrode assemblies, pilot assemblies, and leads can be obtained through the original equipment manufacturer or a Johnson Controls distributor. Controls Group www.johnsoncontrols.com 507 E. Michigan Street FAN 121 P.O.