Resistors in the panel

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Old 03-12-18, 11:12 AM
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Resistors in the panel

The original installers (in 2005) put a resistor at each zone in the panel: The black wire on the zone, then the resistor end is coupled with the end of the white wire with the other resistor end in the COM.
Does that make any sense? Since they put resistors in the panel, I am assuming (with pretty good certainty) that there are no EOL resistors. So are the panel resistors serving any purpose?
 
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Old 03-12-18, 11:37 AM
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What does the panel serve?
 
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Old 03-12-18, 11:44 AM
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Those are called EOL (end of line) resistors. They are supposed to be installed at the end of each zone. They are put there to monitor the wiring for opens and shorts. However most "installers" find it much easier to just put them at the panel rather than where they should be.
 
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Old 03-12-18, 02:14 PM
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The panel zones are the alarm sensors (motion, door, window, etc) This is on a NX-8.
 
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Old 03-12-18, 02:19 PM
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So they actually work in that position? They show a change in resistance if the circuit is shorted/broken/faulted? Or are they just for "show"?
 

Last edited by SugarMom; 03-12-18 at 02:20 PM. Reason: addition
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Old 03-12-18, 02:21 PM
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If the zone point is configured to require an EOL..... then they are needed.
 
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Old 03-12-18, 02:37 PM
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Okay, I am not schooled in this stuff, and am going by You Tube and manuals to get this job done. Is a resistor necessary for the panel to register a fault? I would think that the "opening" in a NC line or vice versa would register the change in resistance needed for the panel. It is an all or none kind of thing. If the sensor is closed in a NC situation and shows a fault, the sensor is junked or the wire is broken. How does the resistor help?
 
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Old 03-12-18, 03:19 PM
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The resistor doesn't "help". It's either required to be in the circuit or it's not.

I'm assuming your panel requires EOL resistors. That means..... for a circuit to show closed or normal.... it needs to include the resistance of the resistor. I'm in commercial alarms. The EOL resistor is ALWAYS placed at the end of the loop which usually puts it at the contact switch. Putting it at the end where it belongs allows for the monitoring of the actual wiring.
 
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Old 03-12-18, 04:18 PM
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Continuing about Resistors in alarm panel:
I know that without a proper EOL resistor ACTUALLY AT the EOL, a short in a wire between the panel and the sensor will not register. But then again, when you open the window or door, or walk in front of a motion sensor, it will not ding dong at the keypad if there is a short in the wire. Right?
See this tutorial: really helpful for the needy (like me): https://www.youtube.com/watch?v=RltY3SlH-o4
So...if a circuit is a hardwired circuit with a resistor at the panel, and the wire is shorted between the panel and the contact, it will still register as a closed circuit. If this contact is then opened (like a door), and there is a short between the panel and the sensor, the panel will not register an opening. So, then what is the purpose of a resistor at the panel? Can't I just do without? What don't I understand?
This is a NX-8, which will be replaced by a NX-8E in a residential home.

Tomorrow, I will be asking about wireless sensors, resistors and zone characteristics...
We think that our smokes are correct: hard wired/AC with an EOL resistor right after the BRK relay to convert to DC right before the panel. And when one smoke is tripped, they all trip and sound the alarm. Than again I can't change them.
 

Last edited by SugarMom; 03-12-18 at 04:33 PM. Reason: corrections, more corrections
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Old 03-12-18, 04:38 PM
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When you put a short directly on a zone point..... the point is shorted. When the point is normal.... the point is ok.... not shorted and not open.

Just to get a little technical. When there is nothing connected to an alarm point.... the voltage measured at that point is 5v. That's called "open circuit" or faulted. When the point is shorted.... the point measures at 0v....that's called a short.... not a fault. When the the EOL resistor is connected across the point..... the voltage is 2.5v. This is a normal point.

You could very well have AC/battery type smoke detectors with a relay to trip the alarm panel. That is a very common setup. One thing must be remembered...... with this type of system.... if there is a power failure.... the smoke detectors will not notify the alarm panel if there is a smoke condition. Each smoke detector will still operate as designed but it will not "talk" to the others or the alarm panel.
 
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Old 03-12-18, 05:28 PM
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Another thoughtYeah, I have to think about that a bit...the alarm industry brings up the word "fault" on the keypad when the contact is open or a motion is tripped AND when the contact is actually closed but not "saying" it is closed (in other words...just not working correctly).

All of our non-smoke zones are NC. Actually, I just found a zone type characteristic that "enables end-of-line resistor defeat on zones that are not fire or keyswitch zones."
Glossary: "End-of-line resistor defeat: If programmed, the NX-8E makes zones 1-8 for normally closed operation only, eliminating the need for EOL resistors on these zones. When a zone is programmed for normally closed operation, a short on that zone does not change the loop condition, and an open on that zone produces a faulted condition. Any priority zone (I think they mean like fire) ignores this feature"

Thank you for all of your input PJmax!!

So, my original question put out there: Can I eliminate having resistors AT the panel on all of our NC zones?
 
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Old 03-12-18, 06:05 PM
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Yes.... just program the points to not need an EOL resistor.
 
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Old 03-13-18, 03:07 AM
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Some of the earlier versions of the NX panels did not have the option to disable the EOL requirement, thus the resistors installed at the panel. This is not uncommon when installing a system in a location that had the door and window contacts prewired at construction, so they didn't want to open walls or remove contacts to install the resistor at the true end of line.

Essentially they converted the system into a basic NC system with this scheme.

You have two choices: Use the system as configured, or pick one device on each zone to be the EOL and move the resistor to that device.

That text about the NX-8E is specific to the _8E_ if your system is just NX-8, disabling the EOL isn't an option. The newer V2 panels also have the EOL disable feature.
 
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Old 03-14-18, 06:25 AM
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Thanks, Mr. Ron and PJmax! Will be putting in a NX-8E this week...will put new questions in a new post.
 
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