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Johnson Controls G670, Installation Sheet, Page: 18 / 24

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18    G

G670 Intermittent Pilot Ignition Controls Technical Bulletin

No

Yes

Yes

No

Turn supply voltage on

Yes

No

No

No

Yes

Turn off supply voltage

No

No

Yes

Yes

No

Yes

Yes

No

No

Start

Yes

Operate system several complete cycles

End

Yes

Is system wiring

per manufacturer’s

instructions?

Correct

wiring

Open thermostat

contact for

30 seconds

Close thermostat

contacts and wait 30%

of the Y79 lockout time 

Is a

spark

present?

System was

in lockout

Determine the reason for lockout.

Conduct microamperage test as

outlined in Figure 16, 

starting at  A .

Is 24 VAC present

between Terminal 2

and ground?

Check the high voltage

cable. Is it securely

connected to the spark

transformer?

Connect
securely

Is 24 VAC

present between

Terminal 1

and ground?

Replace

G670

Is 24 VAC present

on secondary

of transformer?

Replace transformer if

proper voltage is present

on primary of transformer

Is high

limit

closed?

Reset

high limit

Turn supply

voltage on

Replace

cable

Is condition of high

voltage cable good

(not brittle, burnt, 

or cracked)?

Is spark

electrode ceramic

cracked?

Replace

pilot burner

Is spark gap

0.1 in. and

located in pilot

gas stream?

Replace

G670

Correct or

replace pilot

burner

Replace the Y79 with

the appropriate

G600 ignition control

(contact Johnson Controls

Technical Support).

Figure 17: G670/Y79A No Spark, and System Does Not Work

Summary of Contents for G670

Page 1: ...the main burner gas valve in response to a call for heat from the system thermostat When the call for heat is satisfied the thermostat opens and the G670 de energizes the pilot and main burner gas valves Following are the application requirements of the G670 control The G670 can be used with equipment with a maximum firing rate of 117 kW 400 000 Btu hr Any application greater than 117 kW 400 000 B...

Page 2: ...be used in a well vented or outdoor application Agency Listing CSA AGA CGA Certificate Number 112520 0 19 Specification Standards ANSI Standard Z21 20 CSA C22 2 No 199 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...

Page 3: ...ence of the pilot flame If the pilot flame goes out with the thermostat still calling for heat the G670 will de energize the main gas valve and provide a continuous spark at the pilot burner s electrode When the pilot flame is re ignited and detected by the pilot flame sensor the main gas valve is energized and the spark is shut off The G670 de energizes the pilot gas valve and main burner gas val...

Page 4: ... in any way do not use it WARNING Shock Hazard Avoid electrical shock and equipment damage Disconnect electrical power and turn off the gas before wiring the control 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 install...

Page 5: ...pade connection the crimp on connector must be cut off 1 Slide the rubber boot up the cable 2 Cut the lead just above the connector see Figure 4 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 5 4 Ensure the lead is inserted all the way into the spark...

Page 6: ...ure 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 6 through 9 for wiring diagrams All wiring should be in accordance with the NEC and all other local codes and regulations The high vo...

Page 7: ...able Pilot Burner Ground Figure 6 Replacement Wiring Diagram if the Original Control is a G67AG R W Y Thermostat 1 2 4 3 Jumper 5 6 MV PV Limits in the Thermostat Line Only 24 VAC Power Supply Pilot Burner Ground Ground Terminals Flame Sensor High Voltage Cable Install the jumper supplied with the replacement control between Terminals 2 and 6 Figure 7 Replacement Wiring Diagram if the Original Con...

Page 8: ...gh Limits In This Line Only Black Brown White Install the jumper supplied with the replacement control between Terminals 2 and 6 Figure 8 Wiring Diagram for G670 with Y79B _ _ R W Y Thermostat 1 6 2 4 3 Jumper Y79 THS MV PV 5 Flame Sensor High Voltage Cable Pilot Burner Ground 24 VAC High Limits In This Line Only Power Supply White Red Black Figure 9 Wiring Diagram for G670 with a Y79A _ _ ...

Page 9: ...e 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 Test for gas leaks on all pipe joints and connections upstream of the gas valve with a soap solution 6 Turn on the thermostat to the highest setting and verify successful ignition and a normal run con...

Page 10: ...omplished by opening the thermostat contacts lowering the set point 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 10 IMPORTANT Measuring the current with an ammeter will energize the system Wait until the gas valve and inducer energize before taking a current draw measurement Ten Turns W R W R AC Amme...

Page 11: ...ain valve does not come on Determine the failure condition then use the respective flowcharts on the following pages to troubleshoot the system Perform the procedures in the Checkout and Startup Procedure section after any servicing CAUTION Label all wires prior to disconnection when servicing controls Wiring errors can cause improper and dangerous operation Verify proper operation after servicing...

Page 12: ...ostat and limit contacts closed Close contacts Check for proper voltage at transformer primary and secondary Is circuit wiring providing 24 VAC to Terminal 6 Replace cable Is high voltage cable in good condition not brittle burnt or cracked Turn on supply voltage Connect securely Is spark gap 0 1 in and located in pilot gas stream Is spark electrode ceramic cracked Correct or replace pilot burner ...

Page 13: ...nd Replace G670 Make sure pilot line is not kinked or obstructed Check for clean orifice Is inlet gas pressure per manufacturer s specifications Replace pilot valve Correct gas pressure Is pilot spark gap 0 1 in and located in pilot gas stream Correct or replace pilot Check for drafts Shield as necessary and check for clean orifice WARNING Explosion Hazard Do not use a match to test for presence o...

Page 14: ...rminal 3 and ground Replace main valve Is sensor ceramic cracked Is cable grounded out Is sensor or sensor connector shorted out to metal surface Is there continuity and good insulation in the sensor cable Replace cable Disconnect main valve lead from Terminal 3 Disconnect sensor cable from Terminal 4 Replace sensor Connect DC microammeter between sensor cable terminal and Terminal 4 Observe corre...

Page 15: ...n Terminal 1 and ground Replace G670 Check the high voltage cable Is it securely connected to the spark transformer Connect securely Turn supply voltage on Is 24 VAC present on secondary of transformer Replace the transformer if proper voltage is present on primary of transformer Is high limit closed Reset high limit Replace cable Is condition of high voltage cable good not brittle burnt or cracke...

Page 16: ...e Is 24 VAC present between ground and pilot valve terminals of Y79 Is inlet pressure per manufacturer s specifications Is gas at pilot Make sure the pilot line is not kinked or obstructed Check for a clean orifice Is spark gap 0 1 in and located in the pilot gas stream Correct or replace pilot burner Check for drafts Shield as necessary and check for clean orifice Replace G670 WARNING Explosion H...

Page 17: ...n valve terminal on the Y79 and ground Connect securely Replace main valve Is sensor or sensor connector shorted out to metal surface Is there continuity and good insulation in the sensor cable Replace cable Is cable grounded out Correct Replace sensor Disconnect main valve lead from Terminal 3 Disconnect sensor cable from Terminal 4 Connect DC microammeter between sensor cable terminal and Termin...

Page 18: ...tween Terminal 2 and ground Check the high voltage cable Is it securely connected to the spark transformer Connect securely Is 24 VAC present between Terminal 1 and ground Replace G670 Is 24 VAC present on secondary of transformer Replace transformer if proper voltage is present on primary of transformer Is high limit closed Reset high limit Turn supply voltage on Replace cable Is condition of hig...

Page 19: ...bstructed Check for clean orifice Replace pilot valve Is gas at pilot Is inlet gas pressure per manufacturer s specifications Correct gas pressure Is pilot spark gap 0 1 in and located in pilot gas stream Correct or replace pilot Check for drafts Shield as necessary and check for clean orifice WARNING Explosion Hazard Do not use a match to test for presence of gas Figure 18 G670 Y79A Spark is Pres...

Page 20: ...l 3 and ground Replace main valve Is sensor ceramic cracked Is cable grounded out Is sensor or sensor connector shorted out to metal surface Is there continuity and good insulation in the sensor cable Replace cable Disconnect main valve lead from Terminal 3 Disconnect sensor cable from Terminal 4 Replace sensor Connect DC microammeter between sensor cable terminal and Terminal 4 Observe correct po...

Page 21: ...t Ignition Controls Technical Bulletin 21 1 6 2 4 3 Jumper 5 Positive Lead to Terminal 4 Negative Lead to Flame Sensor Electrode Pilot Burner Assembly Y99AU 2 Multimeter Figure 20 Meter Hookup to Measure Flame Sensing Circuit ...

Page 22: ...22 G G670 Intermittent Pilot Ignition Controls Technical Bulletin Notes ...

Page 23: ...G G670 Intermittent Pilot Ignition Controls Technical Bulletin 23 Notes ...

Page 24: ...70 Intermittent Pilot Ignition Controls Technical Bulletin Notes 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 ...

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