Zone maintenance! MS-2

So when I pulled the pull station it took 3 seconds before it went into alarm amongst a maintenance light that came lit. Once I reset the panel it never came back, so I don’t know what that means. Also is my wiring right?, zone one wires go to i3 NO and C, power comes from 24volt resettable, and then another pair of wires in NO and C down to the pull station with a resistor.? Zone two wires go into system sensor 2400 th, and another pair of wires going from pos and neg from the two wire smoke into the pull station with a resistor?, then my horns on the nac, with a resistor on the last horn. That’s how I have it wired.

That’s happened to me once before too. It was probably just a glitch in the CPU, as long as it sends the panel into alarm there’s nothing to worry about.



From what you described, you have everything wired perfectly fine. The only problem I can really see is that for zone 1, you should technically have an EOLR (End Of Line Relay) for your 4-wire i3. Leaving it as it is would be perfectly okay for a hobby system, the only problem you’d ever run into would be the detector not being monitored for troubles by the panel. So, for example, if you remove the head from the base, the panel won’t go into trouble.

This may be a bit of a bump a moderator is free to call me on it if so, however I believe I know specifically what is going on here.

The MS-2 and MS-4 are compatible with System Sensor i3 devices, meaning that i3 smokes can send “dirty” and “freeze” signals to the panel as well as “trouble” and “alarm.” The MS-2/MS-4 will periodically “poll” the i3 devices, which is to say it injects an electric signal onto the IDC, and any abnormal i3 smoke can signal its’ fault back, by modulating the voltage on the IDC. The panel listens for specific modulations and will activate a “supervisory” or “maintenance” condition where indicated. It’s quite possible that when you pulled your pull station, the panel was in the process of trying to poll any i3 detectors on the zone, and your pull station activating interrupted the poll/reply, causing the panel to misinterpret the alarm signal on its first pass. The MS-2/4 is a VERY simple panel running VERY simple software and it can pretty much only run one instruction at a time, so it is more prone to errors like that. It’s also why (aside from verification which is by design a delay) that sometimes an alarm takes a few more seconds to be recognized. Panels like the MS-5/MS10UD are more sophisticated and tend to make use of smoothing algorithms and advanced verification features to discern input signals clearly (and can even tell the difference between a conventional smoke detector vs a pull station alarming on the same IDC).

Honestly, there’s nothing to worry about. If it happens again try referring to the panels owner’s manual, or contacting the manufacturer. Like he said, as long as it goes into alarm you’re good. Personally I like having a bit of a delay. Am I the only one?