Johnson Controls G76 Series User manual

Installation Sheets Manual 121
Gas Combustion Combination Controls and Systems Section G
Technical Bulletin G76x
Issue Date 0400
© 2000 Johnson Controls, Inc. 1
Part No. 24-8143-561, Rev. A www.johnsoncontrols.com
Code No. LIT-121245
Figure 1: 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, or LP gas-air
mixtures.
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 over 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.
G76x Direct Spark Ignition Controls
Description
Application
Requirements

2 G—G76x Direct Spark Ignition Controls Technical Bulletin
Table 1: Specifications
Ignition Type Direct Spark
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 Remote sensing
Minimum Flame
Current
0.3 microampere
Flame Failure
Response Time
0.8 second maximum
Spark Gap 2.5 mm (0.1 in.) nominal
Ignition Trials 1 or 3
Ignition Trial Times 4, 6, 8, or 10 seconds*
Prepurge Times 0, 15, or 30 seconds*
Interpurge 30 seconds*
Automatic Recycle
Delay Period
No recycle (G760)
5 minutes* (G765)
60 minutes* (G766)
Power Requirements Control: 24 VAC, 50/60 Hz, nominal
Operation Current: 0.2A nominal + main valve
Contact Rating (MV) 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 164933-1079185
Australian Gas Certificate Number 4524 (G760 models
only)
Specification
Standards
ANSI Standard Z21.20, Z21.20a, Z21.20b
CAN/CSA-C22.2 No. 199
*Timings listed are for 60 Hz operations. 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 G76x Series Product Bulletin (LIT-4350420) for necessary information on operating
and performance specifications of this product.

G—G76x Direct Spark 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 main gas 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.
•Run--Main gas valve remains energized and spark is turned off after
successful ignition.
•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.
•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.)
•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).
•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 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 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.)
Operating
Mode
Definitions

4 G—G76x Direct Spark Ignition Controls Technical Bulletin
Figure 2 illustrates the sequence of operation of the G76x control.
The G76x 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 1 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 period. 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 period, 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 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.
Sequence of
Operation

G—G76x Direct Spark 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
Flame
present for
30 seconds?
Thermostat
call for heat
Hard Lockout
(optional LED
turns off)
Run
Thermostat
calling for heat?
Sixteenth
flameout?
Ignition Lockout
(optional LED
flashes)
Interpurge
Flameout?
End
Start
Flame present when
not expected
Main valve
flame sensed?
Prepurge
Control
with ignition
recycle?
Recycle delay
period
No
Yes
Detected Fault
Figure 2: G76x Sequence of Operation

6 G—G76x Direct Spark 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 the control into the 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
igniter/flame 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—G76x Direct Spark Ignition Controls Technical Bulletin 7
!
CAUTION: Equipment Damage Hazard. Connect the high
voltage cable to the spark transformer terminal and
spark electrode before applying power to the control.
Ensure that the ground wire is attached to the sensor
assembly and the ignition 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 Figure 3 for wiring diagram. 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
high voltage spark transformer cable are separated from one another by a
minimum of 6.35 mm (1/4 in.) and are not wrapped around any pipe, other
wiring, or accessory.
Transformer
Thermostat
G76x Ignition Control
SENSE 4
5
THS 2
M.V. 3
GROUND
LED
Limits in
Thermostat
Line Only
Power
Supply
Main Burner
Ground
Spark Electrode/
Sensor Assembly
Main
Valve
Main
Valve
Figure 3: Wiring Diagram for G76x Ignition Controls
Electrical
Connections

8 G—G76x Direct Spark Ignition Controls Technical Bulletin
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 spark electrode and sensor assembly must be positioned for easy
access and securely mounted to the main burner to ensure that the
assembly remains properly positioned with respect to the main burner
flame. The main burner flame must engulf at least 9.52 mm (3/8 in.) of the
flame sensor. If a separate flame sensor is used, keep the sensor wire as
short as possible and do not rest it against grounded metal surfaces.
Standoff insulators are recommended.
The spark electrode, flame sensor, and G76x must share a common ground
with the main burner to operate correctly. Thermoplastic insulated wire
with a minimum rating of 105°C (221°F) is recommended for the ground
wire. Ensure that the flame sensor wire and the high voltage spark
transformer wire are separated from one another by a minimum distance of
6.35 mm (1/4 in.) and are not wrapped around any pipe, other wiring, or
accessory.
Spark Electrode
and Sensor
Assembly

G—G76x Direct Spark Ignition Controls Technical Bulletin 9
!
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
main burner.
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

10 G—G76x Direct Spark Ignition Controls Technical Bulletin
The anticipator setting is normally equal to the ignition system current
draw, plus that of the 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 the current draw 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 4.
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 Turns
WR
WR
AC Ammeter Low Scale Setting
To
Heating
System
To
Heating
System
Clamp-on Ammeter
(divide reading by ten.)
Figure 4: Measuring the Thermostat Current
Thermostat
Heat
Anticipator
Settings