Minerva Mx-4000 False Fire Alerts btw 19:00 to 6:00

Hi All,

I hope you all are feeling well. I am writing to seek advice and help in troubleshooting of false fire alerts in Camp Residential Fire Alarm System (Tyco : Minerva -4000) located in gas field.
Its Minerva 4000 system having following specs:
Loop A: 132 Devices
Loop B: 132 Devices
Loop C: 177 Devices
Loop D: 120 Devices.

Problem:
Random false fire alerts appeared and cleared after 5 sec from different zones in evening on Loop D. It happens only in evening up to early morning (Timing 19:00 to 6:00) rest all time system work normally.

Note: (Nothing from Loop A, B, C as all working properly for 24/7)

Event Log Details:
Different SDs from Loop D INPUT ON for 5 or 10 sec then INPUT OFF (19:00 to 6:00 only)
Sometimes Auto Function Test Failed for random Smoke detectors.
Fire Alerts coming from random smoke detectors from different zones. (Not specific Area)

Remedial Actions:
Following remedial action performed but still problem exists:
1- Replaced Loop D card with new one.
2- Interchanged power supplies.
3- Replaced Interface card with new one.
4- Isolated individual JBs (1~8) and powered up rest all system to check faulty device.
5- Cleaned dirtiness of all devices Max threshold 25%.
6- Isolated complete Loop D from card and transfer its 30% load to Loop A. Assigned IPs from 133 onwards , configured and connected Loop D devices into Loop A. Result: False Fire alert started in Loop A at same timing from different A loop locations.
7- Performed Megger test to check insulation all found Ok.

Q: What do we mean by Input ON and Input OFF ?
Q: What is Force Day Mode?

Any suggestion would be highly appreciated

Contact Details:
Whats app:
+92-3013116328

Sorry, I don’t think most of us have experience with EN54 panels. We’re mostly from an NFPA/UL or ULC background (US/Canada).

Some concepts we have in common though. It sounds from your last test like it is related to loop field devices on loop D. It may be just one. I knew someone who traced a problem like this with a scope meter. Some device was causing an odd looking waveform on the on the circuit, so they removed them one by one until it went away on the meter.

Could also be related to resistance or capacitance of the circuit. Just test it with your meter and see if it is within manufacturer’s specs. Measure resistance with the end of line shorted. If the circuit uses shielded wire, check integrity of the shield and that it is not grounded anywhere other than the panel.

Could be digital noise bleeding onto the loop somewhere, though less likely if the wiring is shielded.

Is the circuit overloaded with devices according to manufacturer’s specs?

Do you have different sensitivity that applies during night time? This could be related but doesn’t seem like the root cause. Probably the panel is seeing some analog obscuration value from the detectors that exceeds the night threshold but not the day. To solve this, though, you need to find out what’s causing that signal.

I assume you’ve established that the residents are not habitually smoking at night time!