+-


Alarm Monitoring

Alarm Monitoring

Members Online

53 Guests, 1 User
murphy62

Alarm Installer Search and Reviews




Myalarminstaller.com

Author Topic: why is it not a good practice to put EOLR's in panel  (Read 1828 times)

bsquared

  • Member
  • *
  • Posts: 9
  • Karma: +0/-0
    • View Profile
why is it not a good practice to put EOLR's in panel
« on: November 21, 2008, 11:14:41 AM »
Hey all--

I'm new to the entire installation process, but was curious...why is it not good to put EOLRs in the panel?

I have just learned that the previous installer of some detectors in my new home didn't include any resistors in his install (motion detector, doors, etc.) so when I powered up my system I had to keep it in NC to keep it from faulting.

I've got enough 2k resistors to fix the problem, but I don't know how much trouble it would be to unhook the sensors away from their locations and place the resistor in the right place.  Putting it in the panel will be super easy, but if it provides no benefit to do so, I may need to go ahead and place them at the device.  Before I did the work though just thought I'd ask some people that were in the know.

For added reference, there's only one sensor per zone, and when I add my own smoke detector I will put that one in the right place at the device.

Thanks!

jrw248

  • Gold Member
  • **
  • Posts: 19
  • Karma: +0/-0
    • View Profile
Re: why is it not a good practice to put EOLR's in panel
« Reply #1 on: November 21, 2008, 12:32:28 PM »
EOLRs are in place so the panel can 'supervise' the zone. If the wiring opens, the panel will report a 'trouble'
code. If you place the EOLR at the panel, wiring problems (except a short) wouldn't be detected. The EOLR
resistance is still seen by the panel.

dad22

  • Security Expert
  • ****
  • Posts: 180
  • Karma: +0/-0
  • I'm a llama!
    • View Profile
Re: why is it not a good practice to put EOLR's in panel
« Reply #2 on: November 21, 2008, 01:07:37 PM »

If I may expand a bit -

                     EOL resistor
   Sensor ___ /\/\/\/\/\/_________________________________________________________Z1
   |
   |_________________________________________________________________________com 

In the above configuration, with the resistor, correctly,  at the 'end' of the run, the panel sees
the correct resistance (2200, 5600, etc ) on the zone.
If the sensor is 'opened' the resistance goes to infinity and the panel 'trips' indicating an
alarm. ( NC configuration )

Any shorting ( jumper, chafing, whatever, as shown below ) between the panel and the sensor will cause the zone to read 0 ohms ( instead of the resistor's rating, cause the resistor has been bypassed and is out of the 'loop' ) indicating trouble with that zone.

                EOL resistor
   Sensor ___ /\/\/\/\/\/_________________________________________________________Z1
   |                                                                        | jumper
   |____________________________________|____________________________________com 


Without the resistor, the zone could be shorted ( jumpered, bypassed etc. ) accidentally or
intentionally, as shown below and you would never know from the panel that there was a problem.
                                                                                                                                   
   Sensor ____________________________________________________________________Z1
   |                                                                        | jumper
   |____________________________________|____________________________________com 

If the resistor is 'at the panel' the zone could be 'shorted' anywhere and the panel would still
read the resistors rating without 'knowing' that the circuit was no longer going all the
way out and back 'through' the sensor.
 
Sensor ____________________________________________________________/\/\/\/\/\/\_Z1
   |                                                                        | jumper
   |____________________________________|____________________________________com 

Hope this helps

   




   

bsquared

  • Member
  • *
  • Posts: 9
  • Karma: +0/-0
    • View Profile
Re: why is it not a good practice to put EOLR's in panel
« Reply #3 on: November 21, 2008, 01:54:52 PM »
thanks dad and jrw...i think i understand now that if i put the EOLR on the low wire right before it goes into the panel terminal i essentially won't be making the system any better than it is now.

I'll start digging tonight to see how hard to get in the devices themselves.  Hopefully the won't be too hard to get to next to the device!

Thanks again for the guidance...

JinCT

  • Gold Member
  • **
  • Posts: 17
  • Karma: +0/-0
  • Snaking walls for 10 yrs
    • View Profile
Re: why is it not a good practice to put EOLR's in panel
« Reply #4 on: November 21, 2008, 02:13:33 PM »
Assuming you have a unfinished basement. Instead of pulling the contacts out of the doors or windows which can at times be daunting, you can install the resistor from the basement right underneath the door or window. If there is slack on the wire its normally not to difficult to splice the resistor in there. Its the same principle as installing right at the contact minus that few inches the wire goes up to the door or window. Also it does not make a difference if your on the high or low side of the zone.
Sorry.... I didnt bring my magic wand.

Static

  • Pro-Tech Advisor/Moderator
  • Security Guru
  • *****
  • Posts: 3767
  • Karma: +136/-0
    • View Profile
Re: why is it not a good practice to put EOLR's in panel
« Reply #5 on: November 21, 2008, 11:37:37 PM »
If it's just a house, why bother with EOLs? If you regularly test your system and don't have unsupervised strangers in there tampering with things, they're not really necessary.
I have all the answers . . . some of them are correct.

bsquared

  • Member
  • *
  • Posts: 9
  • Karma: +0/-0
    • View Profile
Re: why is it not a good practice to put EOLR's in panel
« Reply #6 on: November 22, 2008, 03:30:44 AM »
Thanks, Jin.  Unfortunately no basement, no crawlspace either...I'm on a slab.

Static, you bring up a good point.  Last night, I was taking a look at one of my recessed door contacts and noticed that the wire slack at first blush didn't appear to be enough to readily insert the 2k resistor.  So I'm re-evaluating if I want to add them.

The one thing that concerns me...say I've got the system set, and an intruder enters one of my delay entry zones (faulting the zone), and during the delay cuts the wire(s) on a contact without an EOLR.  Will the system still alarm at the end of the delay period?  If so, my system may be robust enough for me as-is.

To really compromise a NC loop, would the intruder have to either a) cut it in an unarmed state, and hope I didn't test to note that the particular zone wasn't responding anymore, which would then let him come back some other time after the remainder of the system was supposedly armed or b) somehow cut it even in the armed state but before the the zone is faulted?  Would scenario b) allow him to after cutting open the door without faulting, or would the moment he cut the wires register as a fault?

The answers to these questions may be really obvious to a lot of you!  If so, thanks for bearing with me (and perhaps getting a little chuckle at the same time) :)

Static

  • Pro-Tech Advisor/Moderator
  • Security Guru
  • *****
  • Posts: 3767
  • Karma: +136/-0
    • View Profile
Re: why is it not a good practice to put EOLR's in panel
« Reply #7 on: November 22, 2008, 01:29:14 PM »
If the system is armed and an intruder forces open a delay door the entry delay will begin. There is nothing he can do now to stop the inevitable; the alarm will sound if the correct code is not entered. Period.

To circumvent your NC wired system an intruder would have to either:
a) Get access to the site while the system is disarmed (more likely in a business situation). Next he would need to find the wire going to the particular door/window/motion where they plan to come in. Once he has found this cable,  short out the conductors for the protective loop and effectively bypass that device. This must all be done without your knowledge. He can then return later and enter through this point undetected assuming you have not noticed the problem and had it fixed.
b) While the system is armed, approach your house from the outside. Then he must locate and short out the correct wire without faulting the zone and causing an alarm. At this point he can enter undetected. Keep in mind that he is outside and all your wires are inside.

Either of these situations is possible, but not very likely. Anybody with the skill and determination to do this is not going to be interested in your crappy TV and Windows98 computer; they'll have much bigger targets in mind. 
I have all the answers . . . some of them are correct.

bsquared

  • Member
  • *
  • Posts: 9
  • Karma: +0/-0
    • View Profile
Re: why is it not a good practice to put EOLR's in panel
« Reply #8 on: November 22, 2008, 06:42:49 PM »
Thanks, Static.

That puts me at ease, except for that minor paranoia stemming from your easily found knowledge of my crappy tv.  :)


 

Powered by EzPortal