Johnson Controls G770BGJ User manual

Installation Sheets Manual 121

Gas Combustion Combination Controls and Systems G

Technical Bulletin G770

Issue Date 0498

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

Trial for

nition

Flame

sensed? Run

Flameout?

Number of

trials = maximum

allowed?

Sixteenth

flameout? Interpur

Lockout

End

Yes

Thermostat

callin

for heat? Yes

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

Main Burner

Ground

Power

Suppl

Pilot Burner/

niter-Sensor

Assembl

G770BGJ

nition Control

SENSE

THS

M.V.

P.V.

Pilot Gas

Suppl

LED

Pilot Valve

Main Valve

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.

Heatin

stem

AC Ammeter Low Scale Settin

Ten Turns

Clamp-on Ammeter

(

Divide readin

ten.

)

Heatin

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

Table of contents

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