Johnson Controls G77 Series Service manual

Installation Sheets Manual 121
Gas Combustion Combination Controls and Systems G
Technical Bulletin G77x
Issue Date 0600
© 2000 Johnson Controls, Inc. 1
Part No. 24-8143-588, Rev. A www.johnsoncontrols.com
Code No. LIT-121250
Figure 1: G77x Intermittent Pilot Ignition Controls
The G77x family of controls is designed for indirect ignition of natural
gas, Liquefied Petroleum (LP) gas, manufactured gas, mixed gas, or
LP gas-air mixtures.
Following are the application requirements of the G77x control.
•The G77x can be used on gas-fired equipment with a maximum firing
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.
•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.
G77x Intermittent Pilot Ignition Controls
Description
Application
Requirements

2 GG77x Intermittent Pilot Ignition Controls Technical Bulletin
Table 1: Specifications
Ignition Type Indirect
Ignition Source High voltage spark, capacitive discharge
High Voltage Cable
Maximum Length
1,220 mm (48 in.)
Flame Sense Cable
Maximum Length
1,220 mm (48 in.)
Flame Detection Means Flame rectification
Flame Detection Types Integral and remote
Minimum Flame Current 0.15 microampere
Flame Failure Response
Time
0.8 second maximum
1.5 seconds maximum (G776_G models only)
Spark Gap 2.5 mm (0.1 in.) nominal
Ignition Trials 1 or 3
Ignition Trial Times 8, 25, 50, 85, or 120 seconds*
Prepurge Times 0, 4, 15, or 30 seconds*
Interpurge 0, 15, or 30 seconds*
Automatic Recycle Delay
Period
No recycle (G770, G777)
5 minutes* (G775, G779)
60 minutes* (G776, G778)
Power Requirements Control: 24 VAC, 60 Hz, nominal
Operation Current: 0.2A nominal + valves
Contact Rating Main Valve: 2A continuous, 5A inrush
Pilot Valve: 2A continuous, 5A inrush
Ambient Operating and
Storage Temperature
-40 to 70°C (-40 to 160°F) standard models
-40 to 80°C (-40 to 175°F) high temperature models
Humidity 95% RH non-condensing
Wiring Connections Spark: Spike, Rajah, or 6.35 mm (1/4 in.) male spade
Control: 6.35 mm (1/4 in.) male spade
4.76 mm (3/16 in.) male spade optional
Types of Gas Natural, Liquefied Petroleum (LP), manufactured, mixed, or
LP gas-air mixture
Packaging Bulk pack supplied to original equipment manufacturer
(individual pack optional).
Bulk Pack Quantity 50
Bulk Pack Weight 15 kg (33 lb)
Agency Listing CSA (AGA/CGA) Certificate Number 164933-1073441
Australian Gas Certificate Number 4524 (G770 models only)
Specification Standards ANSI Standard Z21.20, Z21.20a, Z21.20b
CAN/CSA-C22.2 No.199
*Timings listed are for 60 Hz operation. Timings increase 20% for 50 Hz operation.
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.
Refer to the G77x Series Product Bulletin (LIT-4350430) for necessary information on operating
and performance specifications of this product.

GG77x Intermittent Pilot Ignition Controls Technical Bulletin 3
The following definitions describe operating conditions:
•Prepurge--Initial time delay between thermostat contact closure and
trial for ignition.
•Trial for Ignition--Period during which the pilot valve and spark are
activated, attempting to ignite gas at the pilot burner. The control
attempts to prove flame at the pilot burner within the trial-for-ignition
time.
•Run--Pilot and main gas valves remain energized and spark is turned
off after successful ignition.
•Shutoff--Pilot gas did not ignite within the trial-for-ignition time. The
control de-energizes the spark circuit and pilot valve, and enters
automatic recycle period.
•Automatic Recycle--If shutoff occurs, the control delays for a specific
recycle delay period before beginning another trial for ignition (models
with recycle only).
•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 flameout (if the control has an interpurge).
•Ignition Lockout--Pilot gas did not ignite within the final
trial-for-ignition time. Open thermostat contacts for 30 seconds, then
close, to restart the sequence of operation. (Models with an optional
Light-Emitting Diode (LED) will flash the LED to indicate ignition
lockout.)
•Flameout--Loss of proven flame.
•Hard Lockout--The control detected a fault. Open 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.)
Operating
Mode
Definitions

4 GG77x Intermittent Pilot Ignition Controls Technical Bulletin
Figure 2 illustrates the sequence of operation of the G77x 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.) The vent damper, if used, is energized and when
fully opened, also energizes the ignition control. If the control is equipped
with the optional prepurge, the appliance prepurge fan or relay is also
energized through the thermostat contacts. In the prepurge mode, the
control will delay for the time selected (e.g., 15 seconds) before
simultaneously opening the pilot valve and supplying a continual spark at
the pilot burner. If prepurge is not selected, the pilot valve is opened and
spark initiated within one second after the call for heat.
Under normal conditions, the pilot burner gas ignites within the
trial-for-ignition time (e.g., 8 seconds), the pilot flame sensor detects pilot
flame, and signals the control to energize the main valve. The main gas
valve will not be energized until the flame sensor detects the presence of
pilot flame. The spark will continue until flame is sensed at the pilot
burner or the trial-for-ignition period has elapsed, whichever occurs first.
If the pilot flame is not sensed before the end of the trial-for-ignition
period, the control may:
•proceed to 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 pilot burner flame extinguishes during the run state (flameout), the
control de-energizes the pilot and main gas valve for the interpurge period.
After this period, another trial for ignition is initiated. If the flameout cycle
repeats for a total of 16 times (pilot burner flame established then lost), the
control will:
•Enter the lockout mode if the control is a G770/G777. The thermostat
contacts must be opened for 30 seconds and then closed to escape the
lockout condition.
•Enter the shutoff mode and recycle period (5 minute recycle for the
G775/G779 and 60 minute recycle for the G776/G778) before
beginning another trial for ignition, starting with prepurge.
Sequence of
Operation

GG77x Intermittent Pilot Ignition Controls Technical Bulletin 5
No Yes
Yes
No Maximum
number of trials
attempted?
Yes
No
Yes No
Yes
No
Yes
De-energize
control and valves
No
Sixteenth
flameout?
Control with
ignition
recycle?
Ignition lockout
(optional LED
flashes)
Yes
No
Recycle delay
period Shutoff
Flame present when
not expected
Hard Lockout
(optional LED
turns off)
Start
Thermostat
call for heat
Prepurge
Flame
present for
30 seconds?
Detected fault
Trial for
ignition
Pilot
flame
sensed?
Energize
main valve Run
Thermostat
calling for heat?
Flameout?
Interpurge
End
Figure 2: G77x Sequence of Operation

6 GG77x Intermittent Pilot Ignition Controls Technical Bulletin
IMPORTANT: These instructions are intended as a guide for
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.
!
WARNING: Fire or Explosion Hazard. Avoid serious injury by
carefully following precautions 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.
!
WARNING: Fire or Explosion Hazard. If the control is installed
in an area that is exposed to water (dripping,
spraying, rain, etc.), it must be protected. If the
control has been exposed to water in any way, do not
use it.
!
WARNING: Shock Hazard. Avoid electrical shock and
equipment damage. Disconnect electrical power and
turn off gas before wiring control into circuit.
!
CAUTION: Equipment Damage Hazard. Do not mount the
control where it will be exposed to direct infrared
radiation from the main burner or to temperatures in
excess of the maximum product temperature rating.
Choose a location that provides the shortest, direct cable route to the spark
electrode, pilot burner/igniter-sensor assembly. Easy access to the
terminals is desired for wiring and servicing. The control may be mounted
in any position. Mount the control on a grounded metal surface with metal
screws or bolts through the mounting holes provided in the enclosure.
Installation and
Wiring
Location and
Mounting

GG77x Intermittent Pilot Ignition Controls Technical Bulletin 7
!
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.
!
CAUTION: Equipment Damage Hazard. Locate all limit and
operating controls in series with the thermostat
terminal (THS 2) on the ignition control.
Check the voltage rating marked on the control and make sure it is suited
to the application. Use a National Electrical Code (NEC) Class 2
transformer to provide 24 VAC under maximum load, including valves.
A transformer having excessive primary impedance due to poor coupling
will affect the ignition potential.
Refer to Figures 3 through 7 for wiring diagrams. All wiring should be in
accordance with the NEC and all other local codes and regulations. The
high voltage spark transformer cable must not be in continuous contact
with a metal surface. Use standoff insulators. Ensure that the flame sensor
wire and the high voltage spark transformer cable are separated from
one another a minimum of 6.35 mm (1/4 in.) and not wrapped around any
pipe, other wiring, or accessories.
Electrical
Connections

8 GG77x Intermittent Pilot Ignition Controls Technical Bulletin
Vent Damper System
Thermostat
PLUG
GROUND
5
24 V
LED
THS 2
PV 1
MV 3
Transformer
Power
Supply
Vent Damper
Wiring Harness
Ignition Control Limits in Thermostat
Line Only
Pilot Burner
Assembly Integral
Igniter/Sensor
Main Burner
Ground
Pilot
Gas Supply
Pilot
Valve
Main
Valve
Figure 3: Wiring Diagram for Integral Spark/Sense
with Vent Damper
Thermostat
PLUG
GROUND
5
24 V
LED
THS 2
PV 1
MV 3
Transformer
Pilot Burner
Assembly Integral
Igniter/Sensor
Main Burner
Ground
Pilot
Gas Supply
Ignition Control Limits in Thermostat
Line Only
Pilot
Valve
Main
Valve
Figure 4: Wiring Diagram for Integral Spark/Sense
without Vent Damper

GG77x Intermittent Pilot Ignition Controls Technical Bulletin 9
Flame Sensor
Thermostat
Vent Damper System
Transformer
PLUG
5
24 V
LED
THS 2
PV 1
MV 3
SENSE 4
GROUND
Ignition Control Limits in Thermostat
Line Only
Power
Supply
Vent Damper
Wiring Harness
Pilot Burner
Assembly
Main Burner
Ground
Pilot
Gas Supply
Pilot
Valve
Main
Valve
Figure 5: Wiring Diagram for Separate Spark/Sense
with Vent Damper
Flame Sensor
Thermostat Transformer
PLUG
5
24 V
LED
THS 2
PV 1
MV 3
SENSE 4
GROUND
Ignition Control
Pilot
Valve
Main
Valve
Limits in Thermostat
Line Only
Power
Supply
Main Burner
Ground
Pilot
Gas Supply
Pilot Burner
Assembly
Figure 6: Wiring Diagram for Separate Spark/Sense
without Vent Damper

10 GG77x Intermittent Pilot Ignition Controls Technical Bulletin
Main Burner
Ground
Pilot
Gas Supply
Pilot Burner
Assembly Flame Sensor
Limits in Thermostat
Line Only
Thermostat Transformer
Power
Supply
Main
Valve
Pilot
Valve
Rollout
Switch
Ignition Control
SENSE 4
MV 3
PV 1
R1R.O. SWH
THS 2
5
GROUND
Figure 7: Wiring Diagram for G77x with Rollout Switch Terminal
The rollout switch is wired into the G77x ignition control at terminal R1
(see Figure 7). The rollout switch (a normally closed set of contacts) is
positioned to detect flames rolling out of the combustion chamber. If
rollout occurs, the switch contacts open and the G77x immediately goes
into a lockout condition, closing the main and pilot valves so that the
system is not allowed to function.
The thermostat contacts must be opened for 30 seconds, then closed to
escape the lockout condition. When the rollout switch contacts have
returned to the closed position, the G77x will start its operating sequence
when the thermostat contacts close.
Rollout Switch
Function

GG77x Intermittent Pilot Ignition Controls Technical Bulletin 11
Instructions for installing the spark electrode and sensor assembly are
typically provided by the appliance manufacturer. It is important to follow
those instructions. If such information is not included, use the following
basic instructions.
Location/Mounting
The pilot burner/igniter-sensor must be positioned for easy access and
securely mounted to the main burner to ensure that the pilot burner flame
remains properly positioned with respect to the main burner flame. The
pilot burner must be located such that the flame receives an ample supply
of air free from the products of combustion. The flame must not be
exposed to draft conditions, the full force of main burner ignition, or
falling scale, which could otherwise impede ignition of main burner flame.
The pilot burner/igniter-sensor should be securely mounted to the main
burner with metal screws at a distance approximately 9.52 mm (3/8 in.)
above and 6.35 mm (1/4 in.) away from center of the nearest main burner
port. Ensure that the main burner flames do not impinge on any part of the
pilot burner.
Make sure that the flame sensor wire and the high voltage spark
transformer cable are separated from one another by a minimum distance
of 6.35 mm (1/4 in.) and not wrapped around any pipe, other wiring, or
devices.
Pilot
Burner/Igniter-
Sensor

12 GG77x Intermittent Pilot Ignition Controls Technical Bulletin
!
WARNING: Fire or Explosion Hazard. Avoid personal injury or
property damage by making sure the control
functions properly and there are no gas leaks. Follow
this checkout and startup procedure before leaving
the installation.
!
WARNING: Fire or Explosion Hazard. Do not attempt to check
out this system by manually lighting the pilot. This
could energize the main valve.
Make sure all components function properly by performing the following
shutoff test.
1. With the gas and thermostat off, turn on power to the appliance.
2. Turn the thermostat to the highest setting and verify that the control
goes through the operating sequence to a shutoff condition.
Note: The burner will not light because the gas is off.
3. Turn off the thermostat.
4. Turn on the gas and purge gas lines of all air.
5. Check for gas leaks on all pipe joints upstream of the gas valve with a
soap solution.
6. Turn the thermostat to the highest setting and verify successful
ignition and a normal run condition for at least three minutes. If the
appliance fails to run, see the Service Checkout Procedures section.
7. Check for gas leaks on all pipe joints downstream of the gas valve
with a soap solution.
8. Turn the thermostat down for at least 30 seconds, and then back up
again. Verify successful ignition at least three times.
9. Return the thermostat to a normal temperature setting before leaving
the installation.
Checkout and
Startup
Procedure

GG77x Intermittent Pilot Ignition Controls Technical Bulletin 13
The anticipator setting is normally equal to the ignition system current
draw, plus that of the pilot and main valve.
Due to variations in appliance wiring and valves, it is advisable to measure
the actual current draw of the heating system at the thermostat location.
Measuring this current can be accomplished by opening the thermostat
contacts (lowering the setpoint) and installing an AC ammeter across the
terminals, or by using a clamp-on ammeter with a 10-turn multiplier
attached to the terminals. See Figure 8.
IMPORTANT: Measuring the current with an ammeter will energize
the system. Wait until the appliance is in the run
condition before taking a current draw measurement.
Ten Tu rns
WR
WR
AC Ammeter Low Scale Setting
To
Heating
System
To
Heating
System
Clamp-on Ammeter
(divide reading by ten.)
Figure 8: Measuring the Thermostat Current
Thermostat
Heat
Anticipator
Settings

14 GG77x Intermittent Pilot Ignition Controls Technical Bulletin
!
WARNING: Shock Hazard. Avoid electrical shock and
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. Wiring
errors can cause improper and dangerous operation.
Verify proper operation after servicing.
Perform the following procedure to replace the existing intermittent pilot
ignition control.
1. Shut off power to the appliance.
2. Turn off the gas at the manual shutoff valve adjacent to the appliance.
3. Label each wire with the correct terminal designation prior to
disconnection.
4. Disconnect the power supply (transformer) and the thermostat lead
wire at the ignition control.
5. Disconnect the sensing probe lead from Terminal 4 on the ignition
control (separate spark/sense models only).
6. Disconnect the high voltage cable from the spark transformer.
7. Disconnect the Pilot Valve 1 and Main Valve 3 leads from the ignition
control.
8. Disconnect any wires connected to the ground terminals.
9. Remove the screws holding the ignition control assembly in place.
10. Remove the ignition control and discard.
11. Using the same holes as the old ignition, mount the new control with
metal screws or bolts through the mounting holes in the enclosure.
12. Refer to the Installation and Wiring section for electrical connections
and wiring information. The replacement G77x control has a Spike
transformer connection. Refer to the Modifying Existing Ignition Cable
section for connection to a Spike transformer.
13. Perform the Checkout and Startup Procedure before leaving the
installation.
Replacement
Procedure

GG77x Intermittent Pilot Ignition Controls Technical Bulletin 15
All spark ignition controls have a spark transformer connected to a high
voltage cable. There are three types of connections for the high voltage
cable: Spike, Rajah, and 6.35 mm (1/4 in.) male spade (see Figure 9).
The replacement G77x has a Spike transformer. When replacing a control
that has a Rajah or male spade connection, the crimp-on connector must be
cut off and connected as follows.
1. Slide the rubber boot up the cable.
2. Cut the lead just above the connector (see Figure 10). Make a straight
cut perpendicular to the cable.
3. Center the exposed wire on the end of the lead over the spike in the
spark transformer and push the wire lead down firmly over the spike
(see Figure 11).
4. Ensure the lead is inserted all the way into the spark transformer.
Slide the boot back down the cable and over the spark transformer.
Spike Connection Rajah Connection 6.35 mm (1/4 in.)
Male Spade
Figure 9: High Voltage Cable Connectors
High Voltage Cable
Insulating Boot Crimp-on
Connector
Cut off connector here.
Figure 10: High Voltage Cable with Crimp-On Connector
High Voltage Cable
Spike must be in
contact with the
center wires.
Figure 11: Spark Transformer Connection
Modifying
Existing Ignition
Cable

16 GG77x Intermittent Pilot Ignition Controls Technical Bulletin
!
WARNING: Fire or Explosion Hazard. Do not attempt servicing
or troubleshooting when the LED is flashing (recycle
mode or ignition lockout). The control automatically
energizes the system and could cause personal injury
or property damage.
If the system does not function properly, determine the cause using the
procedures in this section.
Before proceeding with troubleshooting the system, check the following:
•Are all mechanical and electrical connections tight?
•Is the system wired correctly?
•Is gas inlet pressure per manufacturer’s specifications?
•Is the system powered?
•Is the thermostat calling for heat?
•Is the optional LED flashing? If so, the control is in recycle mode or it
has entered an ignition lockout.
•Is the optional LED off? If so, the control is not receiving power, or it
has detected a fault. Faults are:
- flame present for more than 30 seconds at call for heat
- a defective control
There are three potential system failure conditions:
•No spark present, and system does not work.
•Spark is present, but pilot does not light.
•Pilot lights, but main burner does not come on.
Determine the failure condition, then use the respective flowchart on the
following pages to troubleshoot the system. Perform the procedures in the
Checkout and Startup Procedure section after any servicing.
Service
Checkout
Procedures
Preliminary
Checks
Failure
Conditions and
Corrective
Action

GG77x Intermittent Pilot Ignition Controls Technical Bulletin 17
Start
Check for defective transformer,
thermostat, or faulty wiring
Is 24 VAC
present between
Terminal 2 and
ground?
Open thermostat contacts for
30 seconds and then close
Yes
Is
spark present
now?
Yes
No
System was in lockout, causes
include flameout or an internal fault
Did
pilot remain lit
from previous
cycle?
Replace
gas valve
Turn off
supply voltage
Yes
No
No
Is spark
cable securely
connected to ignition
control?
Is
spark cable
brittle, burnt, or
cracked?
Is spark
electrode ceramic
cracked?
Is spark
gap per manufacturer’s
specifications and
located in pilot gas
stream?
Replace
control
End
Yes
No
No
Correct or
replace pilot
burner
Yes Replace pilot
burner
No
Yes
Replace
cable
Yes
No
Correct
Figure 12: No Spark, and System Does Not Work

18 GG77x Intermittent Pilot Ignition Controls Technical Bulletin
Start
Connect pilot valve securely
between Terminal 1 and ground
Are pilot valve
connections
correct and
secure?
Yes
Is 24 VAC
between Terminal 1
and ground?
No Replace
control
Yes
No
No
End
Yes
No
Yes
Yes
No
Is inlet
gas pressure
per manufacturer’s
specifications?
Correct gas
pressure
Is gas at
pilot burner?
Make sure pilot line is
not obstructed. Check
for clean orifice.
If OK,
replace pilot
valve
Is spark gap
per manufacturer’s
specifications and
located in pilot
stream?
Correct or
replace pilot
burner
Shield from
drafts
Figure 13: Spark Present, but Pilot Does Not Light

GG77x Intermittent Pilot Ignition Controls Technical Bulletin 19
Start
Does
spark stay on
after the pilot
lights?
Yes
No
No
No
End
Yes
No
Yes
Yes
No
Is sensor
cable securely
connected to Terminal 4
and flame
sensor?
Is sensor
ceramic
cracked?
Is 24 VAC
between Terminal 3
and ground?
No Replace
control
Yes
Make sure sensor cable
and spark cable are
separated and not
wrapped around any
pipes or accessories.
Is gas
inlet pressure
per manufacturer’s
specifications? Correct
Correct
Yes
Is main valve
wiring securely
connected to
Terminal 3
and ground?
Correct
No
Yes
Replace
main valve
Replace
flame sensor
Yes Is
sensor cable
grounded
out?
Correct
Does
sensor cable lack
continuity or good
insulation?
No
Replace
cable
If system still fails, clean
the pilot assembly with
steel wool, or replace
flame sensor, orifice, or
control.
Figure 14: Pilot Lights, but Main Burner Does Not Come On

20 GG77x Intermittent Pilot Ignition Controls Technical Bulletin
!
CAUTION: Label all wires prior to disconnection when servicing
controls. Wiring errors can cause improper and
dangerous operation. Verify proper operation after
servicing.
The G77x controls are not field repairable. Do not attempt field repairs.
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.
Repairs and
Replacement
Controls Group www.johnsoncontrols.com
507 E. Michigan Street FAN 121
P.O. Box 423 Installation Sheets Manual
Milwaukee, WI 53201 Printed in U.S.A.