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Well Mclain CGA

Travis_2 Member Posts: 4
I have just recently install a Well Mclain CGA-6 boiler with intermitt. spark ign. I have had trouble ever since it was new sensing flame. I have checked all the grounds to the boiler and within the boiler. I even installed a ground wire from the ignition module directly to the burner. This greatly improved it, but still misses ignition every once in awhile. I also replaced the module and the flame sensor to eliminate them. Has anyone had this problem, or does anyone have any suggestions for me?


  • Empire_2
    Empire_2 Member Posts: 2,343
    Flame UA

    What is the Micro amp reading in the pilot circuit??? Also Make sure you have a positive ground at the Incomming power source. 120vac to ground.. Also make sure that the mechanical ground AT THE PANNEL is there. OHM oput the common and the ground wire. Power OFF of course..
  • Robert O'Connor_7
    Robert O'Connor_7 Member Posts: 688

    Sometimes airborne contaminants can cause problems with the sensor. Do you see if any of the indicator lights are flashing before it retries? I'd check voltage polarity to the module and gas pressure...Robert O'Connor/NJ
  • Boiler Guy
    Boiler Guy Member Posts: 585

    in the line to the boiler is absolutely critical. Does your wire to the boiler have a ground wire as well as a true neutral?
  • Travis have you checked

    the system using the procedures in the CGa Boiler Manual?

    Watch on this sytem as I have had a case where the end switch on the vent damper kept opening up.

    The following checks can be used on most systems:



    1. Not touching metal surfaces

    2. No more than 36" long

    3. Connections clean and tight. The "kanthal" rod should be cleaned with a soft clean emory cloth.

    4. Visual Inspection - no cracks, breaks in ceramic. The igniter cable is not dried out or cracked. The boot is in good condition. If there is a white powdery substance on the cable that is the result of ignition cable "outgassing" the cable should be replaced.

    5. The ignition cable has electrical continuity - use a continuity tester or the Ohms scale on multi meter.

    a. Check from tip of igniter to the connector on the module with it disconnected from module. You should have continuity. The resistance should be about .1 of an ohm.

    b. Run up and down the tip looking for variable resistance or breaks in continuity (sign of a break down) and should be replaced. The cable on single rod system may give you spark but will not return a micro-amp signal.

    c. Go from the tip of the igniter to ground - you should not have continuity - if you do it is shorted to ground at some point. This would cause a no spark or weak spark condition.

    6. Check for intensity of spark

    a. Remove igniter cable from the module connection.

    b. From the module connection to the igniter cable an arc should jump at least a 1/2" gap.

    c. The spark gap on most systems from the tip of the igniter to the ground connection is 1/8". If the spark will jump across 1/2" with good intensity it should be able to jump across 1/8" with no trouble at all.

    Note: - Hold the igniter cable with insulated pliers and slowly move the connector on igniter cable toward the high voltage connection on the module with the module energized. The spark should jump across the open gap.


    Nuisance shut downs or no operation at all can be caused by a poor or erratic ground connection.

    1. From the ground (GND), usually green wire, terminal on the module check for continuity to some portion of the boiler or furnace. It is best to check on an unpainted and clean surface. The gas pipe is a good point. YOU SHOULD HAVE CONTINUITY! ! If you do not then you could experience erratic or no operation at all.

    a. It may be necessary to establish a good connection to ground by using a wire with a clamp onto the gas line or equipment chassis and connecting it to the ground terminal of the module. All connections should be clean, unpainted and good metal to metal contact. When you look at the wiring diagram for the equipment and see a ground symbol this type of symbol showing the use of a chassis ground be careful that you have a good connection.



    This next check is the beginning of your electrical checks and is best done at the secondary of the 24 volt transformer. Many transformers today have the terminals on the secondary labeled "C" and "R" this will assist you with this check. If this check indicates that in fact "R" is 24 volts and "C" is zero (0) volts then the primary polarity is correct. If it indicates the opposite then the primary wiring needs to be corrected: example the black wire on primary side should be hot the white wire neutral (ground) or zero volts.

    Once all of these preliminary checks have been completed then the electrical troubleshooting of the system should begin. The manufacturers sequence of operation, connection wiring diagram, ladder diagram and any trouble "trees" that are available should be used along with a good multimeter.

    When you check microamps it should be 2 to 10 microamps normal 3 to 5. Monitor with the burner running to see if you have any combustion problems.

    At the same time do a combustion analysis:

    you are looking for O2 6% to 9%

    CO2 6.7% to 8.5%

    Flue Temp 300 to 375 degrees

    CO 50 to 100 PPM air free.

    Check Draft on both sides of the draft hood after the vent damper. You should have -.02 before the draft hood.
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