Johnson Controls G770BGJ User manual

Installation Sheets Manual 121
Gas Combustion Combination Controls and Systems G
Technical Bulletin G770
Issue Date 0498
© 1998 Johnson Controls, Inc. 1
Part No. 24-8143-596, Rev. 
Code No. LIT-121253
Figure 1: G770BGJ 100% Lockout,
Microprocessor-Based IPI Control
The G770BGJ is a member of the G700 series ignition control family.
This Intermittent Pilot Ignition (IPI) control is microprocessor-based and
provides two additional trials if the supervised pilot flame is not proven
within the initial trial for ignition period. A diagnostic LED (Light-
Emitting Diode) indicates operating status and assists in system
troubleshooting.
The microprocessor provides improved reliability and performance. All
function timings are independent of voltage and temperature variations.
The control is monitored on a cycle-by-cycle basis for maximum
operational integrity.
G770BGJ 100% Lockout, Microprocessor-Based
Intermittent Pilot Ignition Control
Description

2 G—G770BGJ 100% Lockout, Microprocessor-Based Intermittent Pilot Ignition Control
Table 1: Specifications
Ignition Type Indirect
Ignition Source High-voltage spark, capacitive discharge
Maximum High Voltage Cable
Length 914.4 mm (36 in.) recommended
Flame Detection Means Flame rectification
Flame Detection Types Remote
Minimum Flame Current 0.040 microampere
Flame Failure Response Time 0.8 second maximum @ twice the minimum flame
sensing threshold
Spark Gap 2.65 mm (0.10 in.) nominal
Ignition Trial Time 30 seconds*
Prepurge Time 0 second*
Interpurge Time 15 seconds*
Ignition Trials 3
Flameouts 15
Flame Establishing Period 2 seconds maximum
Automatic Recycle Delay Period No recycle allowed
Power Requirements 24 VAC, 60 Hz
Contact Rating Steady state: 2A total, maximum @ 24 VAC
Inrush: 5A maximum @ 24 VAC
Ambient Operating and Storage
Temperature -40 to 80°C (-40 to 176°F)
Humidity Rating 95% RH (non-condensing)
Types of Gas Natural, Liquefied Petroleum (LP), manufactured,
mixed, or LP gas-air mix
Packaging Bulk pack supplied to original equipment
manufacturer (individual pack optional).
Bulk Pack Quantity 50
Bulk Pack Weight 16 kg (33 lb)
Agency Listings IAS (AGA/CGA) Certificate Number C2154002
Specification Standards ANSI Standard Z21.20
CSA C22.2-No. 199
* Timings listed are for 60 Hz operations. Timings increase by 20% under 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.
Table 2: LED Flash Codes
Flash Code Flash Code Description
LED On Control energized and operating normally
LED Off Control not energized or fault detected

G—G770BGJ 100% Lockout, Microprocessor-Based Intermittent Pilot Ignition Control 3
The G770BGJ ignition control is designed to ignite gas at the pilot burner
through the use of a spark. An electrode is positioned in the pilot gas
stream and adjusted to provide a nominal spark gap of 2.54 mm (0.10 in.).
The pilot burner then ignites the main burner.
The G770BGJ control proves the presence of the pilot flame by flame
rectification, and automatically shuts off the gas supply to the pilot burner
and the main burner if the pilot flame does not prove.
All applications must use redundant gas valves. This control is suitable for
operation over a temperature range of -40 to 71°C (-40 to 160°F). Any
application over 117 kW (400,000 Btu/hr) must be approved by the
Johnson Controls Application Engineering Department.
The following definitions describe operating conditions:
•Prepurge--Initial time delay between thermostat contact closure and
activation of the spark circuit and pilot valve.
•Trial for Ignition--Total time pilot valve and spark circuit energize in
an attempt to light the pilot.
•Run--Main valve energizes and spark turns off after pilot flame is
proven. Main burner remains on until thermostat contacts open.
•Interpurge--Period between trials for ignition when both gas valve
and spark are deactivated to allow unburned gas to escape before the
next ignition sequence. Interpurge occurs only if ignition was not
successful during the previous trial or after a flameout.
•Flameout--Loss of proven flame.
•Lockout--An internal or external fault that causes the control to
de-energize the spark circuit and gas valves. The thermostat contacts
must be opened for 30 seconds and then closed to begin a trial for
ignition.
Application
Operating Mode
Definitions

4 G—G770BGJ 100% Lockout, Microprocessor-Based Intermittent Pilot Ignition Control
Figure 2 illustrates the sequence of operation of the G770BGJ control.
The G770BGJ Intermittent Pilot Ignition Control is energized on a call for
heat from the system thermostat. The control will wait 0.6 second and then
energize the LED and begin the trial for ignition. Prepurge will not occur
before the first trial.
The control will activate the spark and pilot valve for up to 30 seconds in
an attempt to light the pilot burner. When the pilot burner gas ignites, the
pilot flame sensor detects pilot flame and signals the control to energize
the main valve. The spark continues for 5 seconds after the main valve is
energized. The control remains in the “run” condition, with spark
de-energized and pilot and main valves energized, until the call for heat is
removed or the flame is lost.
If the control fails to detect pilot flame by the end of the 30-second trial,
the control will allow up to two more 30-second trials for ignition with a
15-second interpurge between trials. If the pilot burner flame is not
detected by the end of the third 30-second trial, the control will enter the
lockout state. The pilot valve, spark, and LED will de-energize. The
control will remain in the lockout state until the 24 VAC power to the
control is cycled.
If the pilot flame goes out (flame loss with thermostat calling for heat)
within 10 seconds of proving, the main valve will be de-energized and the
pilot valve will remain energized. The control will immediately begin a
30-second trial for ignition. During the first second of the trial, the spark
will remain energized regardless of the presence of flame. During the
remaining (up to) 29 seconds of the trial, the control will act in the normal
manner (energize the main valve when pilot burner flame is detected and
continue to spark for 5 seconds after pilot burner flame is detected).
If the pilot flame goes out (flame loss with thermostat calling for heat)
10 seconds or more after proving, the main valve and pilot valve will
immediately be de-energized and remain off for a 15-second interpurge
period. After 15 seconds, the control will energize the spark and pilot
valve and begin a normal 30-second trial for ignition.
A total of 15 flameouts may occur during any single heating cycle.
Whether the flameout occurs less than or greater than 10 seconds after
pilot flame is proven, the total number of re-ignitions after flameout
cannot exceed 15 during any one thermostat call for heat cycle. On the
sixteenth flameout, the control goes to lockout, the LED turns off, and the
control remains in lockout until 24 VAC power to the control is cycled.
If flame is detected when the thermostat calls for heat, it must extinguish
within 30 seconds for normal operation. If flame is still present after
30 seconds, the control goes into lockout state (gas valves and spark
de-energized) and the LED turns off.
Sequence of
Operation

G—G770BGJ 100% Lockout, Microprocessor-Based Intermittent Pilot Ignition Control 5
Start Thermostat
call for heat.
Flame
present for
30 seconds? Lockout End
Prepur
g
e
Trial for
i
g
nition
Flame
sensed? Run
Flameout?
Number of
trials = maximum
allowed?
Sixteenth
flameout? Interpur
g
e
Lockout
End
Yes
No
Yes
No
No
Yes
No
Yes
No
Thermostat
callin
g
for heat? Yes
No
Yes
Figure 2: G770BGJ Sequence of Operation

6 G—G770BGJ 100% Lockout, Microprocessor-Based Intermittent Pilot Ignition Control
IMPORTANT: These instructions are intended as a guide for qualified
personnel installing or servicing Johnson Controls
ignition controls. Carefully follow all instructions in this
sheet and all instructions on the appliance. Limit repairs,
adjustments, and servicing to the operations listed in this
sheet or on the appliance.
!
WARNING: Fire or Explosion Hazard. Avoid serious injury by
carefully following precautions in this sheet and all
instructions on the appliance. Limit repairs,
adjustments, and servicing to the operations listed in
this sheet 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.
Location/Mounting
!
CAUTION: Equipment Damage Hazard. Do not mount 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 G770BGJ may be
mounted in any position. Mount the control on a grounded metal surface
with No. 8 machine or No. 6 sheet metal screws.
Installation and
Wiring
Ignition Control

G—G770BGJ 100% Lockout, Microprocessor-Based Intermittent Pilot Ignition Control 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. Ensure that 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.
All wiring should be in accordance with the National Electrical Code
(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 distance of 6.35 mm (1/4 in.) and not wrapped around any pipe,
other wiring, or accessories.
Check the voltage rating marked on the control and make sure it is suited
to the application. Use an 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.
Transformer
Thermostat
Limits in
Thermostat
Line Onl
y
Main Burner
Ground
Power
Suppl
y
Pilot Burner/
I
g
niter-Sensor
Assembl
y
G770BGJ
I
g
nition Control
SENSE
THS
M.V.
P.V.
Pilot Gas
Suppl
y
LED
G
R
O
U
N
D
Pilot Valve
Main Valve
PV
MV
AB
A
B
2
1
3
4
Figure 3: Connection Diagram
Electrical
Connections

8 G—G770BGJ 100% Lockout, Microprocessor-Based Intermittent Pilot Ignition Control
Use only an exact replacement pilot burner/igniter-sensor assembly.
Instructions for installing the pilot burner/igniter-sensor assembly are
typically provided by the appliance manufacturer. If that information is not
available, follow these basic instructions:
•The pilot burner/igniter-sensor assembly must be positioned for easy
access and mounted so that the pilot burner flame is properly
positioned with respect to the main burner flame.
•The pilot burner must be located so that the flame receives an ample
supply of clean air (free from products of combustion).
•The pilot flame must be free from drafts, the full force of main burner
ignition, and falling scale that could hinder main burner flame
ignition.
•Ensure that the main burner flames do not strike any part of the pilot
burner. The spark gap is factory set at 2.54 mm (0.10 in.), nominal.
•Mount the assembly securely to the mounting surface using metal
screws.
!
WARNING: Fire 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
test:
1. With the gas and thermostat off, turn on power to the appliance.
2. Turn the thermostat to a high 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 with a soap solution.
Pilot
Burner/Igniter-
Sensor Assembly
Checkout and
Startup
Procedure

G—G770BGJ 100% Lockout, Microprocessor-Based Intermittent Pilot Ignition Control 9
6. Turn the thermostat to a high setting and verify successful ignition
and a normal run condition for at least 3 minutes. If the appliance fails
to run, see the Service Checkout Procedures section.
7. Do a leak check on all pipe joints downstream of the gas valve.
8. Turn the thermostat down for at least 30 seconds and then back up
again. Verify successful ignition at least three times before leaving the
installation.
Due to variations in wiring and valve options, it is advisable to measure
the actual current draw of the heating system at the thermostat location.
Open the thermostat contacts and connect an AC ammeter across the
terminals. A clamp-on meter with a ten turn multiplier can also be used.
Remember to divide the reading by ten for the actual current value. See
Figure 4 for meter connections.
Set the thermostat heat anticipator to 0.2A plus the total of the rated gas
valve currents.
W
R
To
Heatin
g
S
y
stem
AC Ammeter Low Scale Settin
g
Ten Turns
Clamp-on Ammeter
(
Divide readin
g
b
y
ten.
)
W
R
To
Heatin
g
S
y
stem
Figure 4: Current Measurement for Thermostat Heat Anticipator
Thermostat
Heat Anticipator

10 G—G770BGJ 100% Lockout, Microprocessor-Based Intermittent Pilot Ignition Control
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?
!
WARNING: Fire or Explosion Hazard. Do not attempt servicing
or troubleshooting when the LED is flashing. The
control automatically energizes the system and could
cause personal injury or property damage.
•Is 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
- more than 16 flameouts
- a defective control
There are three potential system failure conditions:
•no spark, and system does not work
•spark present, but pilot does not light
•pilot lights, but main valve 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