Ground fault Isolation problem on alarm

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Old 12-06-15, 07:22 AM
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Ground fault Isolation problem on alarm

I have a interesting and difficult problem with my Concord 4 Panel. I can really use a hand.

The unit has been giving a GROUND FAULT error. I am fairly confident it came from nowhere but cant be sure.

The panel has an automation superbus module connected to a computer via serial cable. The computer has a headphone jack connected to a 12 volt amp on its own power supply. Note- computer runs on 12v, on separate power supply as well.

With the headphone jack connected the panel instantly throws a GROUND FAULT error. When I remove the headphone jack connection the code clears.

With the headphone jack connected, if I remove the serial connection to the automation module the code also clears.

I'm GUESSING (??) the 12volt amp is sending (-) to one part of the headphone which is also feeding back to the computer and serial grounding?

I turned off ground fault reporting for now, but I'd really like to resolve this.

HELP
 
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Old 12-06-15, 08:18 AM
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The panel has an automation superbus module connected to a computer via serial cable.
What exactly is that module ?
Anything that connects to an alarm system should be ground isolated.
 
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Old 12-06-15, 08:32 AM
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Interlogix 60-783-02 SuperBus 2000 Automation Module

Any help on how to isolate that?
 
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Old 12-06-15, 08:37 AM
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That tells me that the audio amp circuits in your computer are not electrically isolated from the serial/usb ports. Does the ground fault show if the computer and the security system are plugged into the same electrical power circuit?

Sometimes you can get this sort of grounding glitch if two devices connected like this are on different phases in the electrical grid in the house (different sides of the breaker panel)

Otherwise, this sounds like a computer chassis problem.
 
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Old 12-06-15, 08:43 AM
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You may have to disconnect the ground wire from pin 5 of the DB-9 connector at ONE end only.

I'm looking into the problem further.
 
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Old 12-07-15, 08:19 PM
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I'm not aware of what this "module" does but the general rule is, if you are using an external DC power supply hooked to an alarm panel, you must make the grounds on each of the power sources common. Run a wire from a negative (ground) terminal of the alarm panel to the negative (ground) terminal of the power supply of the module.
 
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Old 12-07-15, 09:27 PM
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The problem is that you cannot connect earth ground to the "GND" connection of the panel. When you ground that Concord panel you connect the building ground to the metal shroud... not the GND terminal.

When you connect a grounded device via the DB-9 cable you are grounding the GND terminal causing the ground fault indication. In the past when I've had similar problems..... I'd open the ground in the DB-9 cable.

They make adapters that isolate the grounds for you. The link is one example.....
Ground Isolated Serial Connector
 
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Old 12-10-15, 02:26 AM
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I purchased a ground loop isolation device for the headphone jack and the problem vanished.

Thank you everyone for your time!
 
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