Hardwire flood detector & EOLR

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Old 06-20-16, 01:28 PM
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Hardwire flood detector & EOLR

I will be adding my first wired zone to my Vista 20P -- a GRI 2600 water sensor.

The GRI 2600 manual notes this is a NC device.

I was planning to add it as a hardwired zone as "EOLR" type in *56 programming, and add the 2K resistor in series on the zone loop.

But now I'm wondering - is there any point to me doing the EOLR on a flood detector? From my reading, it seems the only benefit of the EOLR in the NC loop is to detect a short in the wire.
 
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Old 06-20-16, 03:18 PM
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The End-of-Line (EOL) resister monitors both short circuits AND open circuits in the wiring. If the routing of the cable is such as to preclude any physical damage the EOL might be seen as unnecessary but in my opinion as long as you have the option you should use it. Having an open circuit on a normally closed alarm loop would give the same response as an alarm. With the use of the EOL resistor it gives a trouble alarm. Having a short circuit will negate the alarm from functioning without the EOL resistor while with the resistor it wall give a trouble signal.
 
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Old 06-20-16, 03:41 PM
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Furd, thanks.

Question about this part of your response:
Having an open circuit on a normally closed alarm loop would give the same response as an alarm. With the use of the EOL resistor it gives a trouble alarm.
On a NC circuit, how does the panel know an open circuit is trouble vs alarm? Wouldn't open circuit on NC cause alarm in all cases, whether the EOLR is used or not?
 
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Old 06-20-16, 04:11 PM
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Excellent question and I'm sorry to say, one I need to think about for a while. It may depend upon where the EOL resistor is located, I'm not sure. Maybe one of the REAL alarm technicians can explain it.
 
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Old 06-20-16, 09:21 PM
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With a NC loop, the benefit would be if it gets shorted -- A bigger benefit is with a NO loop [usually life safety] you would then get a trouble if the loop gets cut.

The EOL [for NC] is usually the installer's choice [not necessary] in a residence since you can monitor the system more closely than a business/public system. If you use it, 'at the device' is the recommended location even though most alarm installers will put it in the panel.

Some systems use resistor packs which can give you four states: opened, closed, shorted, cut -- depending on your level of security [though I've only used them for card access].
 
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Old 06-20-16, 10:47 PM
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When programming the hardwire zones, and selecting "EOL" as the hardwire type, how does the panel know whether the sensor is acting as a NO or NC sensor? (I plan to use ZT 08).
 
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Old 06-21-16, 06:50 PM
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If you are using an EOL circuit, if there were mixed NC and NO devices on the circuit, the resistor would be across the last NO device. In that configuration, opening one of the series NC devices would produce an open circuit and thus an alarm/fault. If the NO device changes states (closes) it produces a short across the input, and again an alarm/fault.

A straight NC circuit doesn't need the resistor because it only recognizes an open circuit as an alarm/fault.
 
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Old 06-21-16, 08:44 PM
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Ron, if I have an NC device on EOL circuit and use the resistor in series, doesn't that also give me an alarm/fault if the circuit is shorted?
 
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Old 06-21-16, 09:11 PM
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Only if the short is across the resistor. That's why the EOL has to be across the last NO device. If you were to put the resistor at the motherboard terminal strip, shorts downstream would not show as a fault, because the circuit would be seeing the expected resistance.

This is one of those things were a little fundamental series, parallel and combination circuit knowledge helps: Basic Electrical Theory | Ohms Law, Current, Circuits & More
 
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Old 06-21-16, 11:00 PM
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Hi Ron,

Thaks for the info - I totally get that for a circuit with both NO and NC devices on it. My comment about NC EOLR referred to case of only having a NC device and no others on the loop (getting back to my original post of hardwiring a NC water sensor).
 
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Old 07-07-16, 02:18 PM
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I wanted to give folks an update on where I ended up with this project.

Turns out, the GRI 2600 water sensor unit I'm using is a sealed unit, and so there's no way to splice in an EOLR at the sensor end without splicing into the factory fly lead very close to the sensor, which I'm not interested in doing.

So my whole question is moot.

I've got the 2600 hooked up to my Vista 20P as a NC hardwired zone, and it's doing great.
 
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Old 07-07-16, 02:45 PM
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The way I would normally add an EOL to such a device would be to attach the resistor to the lead, outside the housing, and shrink tube it.

If you have it working, and it's all happy, that's all that matters.
 
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