Resistance of door holder magnet.

You don't dick around with fire doors in a school.

Get a professional in.

RL

Hipot the branches for integrity.

Look for exposed areas that are subject to damage or intentional interference - remember that this is a building full of active gremlins.

RL

If this uses sealed glass Reed Switches then the resistance, when changed state (either N.O. or N.C.), should be virtually zero ohms. 470R sounds like a problem either in line resistance or the switch itself.

John :-#(#

Well, you don't measure magnet resistance... If you're talking about magnetic door contact switches, they should read 0.1 ohm give or take. Now, some door contacts have what's called "end of line" resistors installed. The idea is that the panel monitors a known resistance instead of a pure open or closed situation to make sure the contact isn't jumped out to fool the panel into thinking the switch is in circuit. The value of the resistor depends on what the panel manufacturer specs out.

How do you know it's shorting out the 24V line? Is there an error code at the panel?

Hi Rick,

I don't do Simplex panels much but it would seem to me that something on that NAC circuit being used for the door holders is intermittently failing. First I would suggest changing the NAC circuit to one that may not be in use or available. I am assuming that the Door Holder circuit is on a NAC output that is programmable to various options. This is true of a Silent Knight Panel. Simplex...... don't know.

Since the Door Holders would be all in Parallel if one would fail the others would still hold. So I would not think is would be just one failing unless it was a dead short. If it would be dead short then I can't imagine it would be intermittent.

The other thought would be when you check the voltage output at the panel are you reading exactly 24vdc or something higher?? Like maybe 25vdc to 28vdc. That would indicate that the output may be part of the Battery Charge Circuit. If yes, then the Backup Batteries could be pulling the circuit down to a point where the Door Holder can't hold. This is just a guess of a maybe??

Again it comes back to the DC Voltage supply that may be weak to some degree and there is a component on the board that is failing for some unknown reason. And moving the Door Holders to another circuit could be the fix but not the answer.

That is about all I have at this point.

Good Luck!!

Les

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The newer ones may be internally rectified, for use in AC or DC circuits. This would produce a High-Z reading for low test voltages. A diode test might show continuity.

Normal coil Z between 280 and 600R, depending on model. (that's derived from current rating and voltage on the sales sheet).

You should probably replace the battery ~6-8yrs, whether healthy or not.

RL

Rick,

If I may suggest that you pose your question to the newsgroup alt.security.alarms

There are a few old guys there that have been in the business for a long time. If nothing else it will cause them to think a little extra for the challenge.

Again good luck!!

Les

Good thought. Not a tech myself, but have been an engineer overseeing building maintenance and battery charging on fire systems has been a significant problem often overlooked.