NAC Panel short issue

[Mmares179]

Not sure how many people on here are familiar with National Time & Signal systems but I am at a loss on how to fix the issue I am having.

I am getting a trouble on one of the NAC panels whenever the system is in alarm condition, system is normal otherwise. The NAC Panel is showing a short on one of the two output circuits. I originally thought it was one of the devices that was causing the issue, but could not locate any. I then removed the wires from the troubled circuit and fired the system again, the NAC circuit still showed up as having a short. I ordered a new panel thinking the issue was within the panel itself. I just finished swapping all the parts from within the panel and I am getting the same issue. Any thoughts?

 

[tortuga]

The NAC Panel is showing a short on one of the two output circuits.

How did you test for shorts?
Whats the model of the panel?
Are you sure your 24DC supply is putting out the correct voltage?

 

[Mmares179]

There’s an indicator light inside the NAC that signifies a short on each output. Theres also indicator lights for ground fault and open circuits as well, though none of these are lit. There’s also a trouble that populates on the main panel saying there’s a short on that output circuit, but only during an alarm condition.

I used a multimeter to test for the short. The circuit is only shorted in alarm conditions though.

I got 22VDC on the circuit.

The panel is a D900-RPS-SG from National Time and Signal

 

[tortuga]

Sounds like a shorted diode in a horn or horn or strobe is wired backward. Did you check that all the horns and strobes on that circuit are working and wired correctly?
I'd bring a device or two down to the NAC panel and connect it to the circuit with a end of line resistor and measure voltage in supervisory and alarm. the put everything back and measure voltage in supervisory and alarm again.

 

[Crash117]

Does your system have individual battery back up in each panel? Under normal conditions, not much load but in alarm more load is uncurred. Depending on your system, it may be powered continuously through the battery and the transformer only sends power to the battery. If it/they ( if there is more than one) are not able to handle the load, could cause a fault condition.