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