EOL resistors on an HAI OP2--proof they don't belong at the panel end?

[js19707]

( .. sigh, I know, there's been lots of discussion around EOL resistors here. but please bear with me .. )

OK, so I have a guy putting in my HAI OP2 and doing a (mostly) wired sensor install (it's a retrofit). So far they have done a great job with all the hard work I didn't want to do myself (and they've been pretty fast). I didn't think to ask him about whether he was going to use EOL resistors or not, given the diversity of opinions that seem to exist on the subject. After asking him about this today, it sounds like he is planning to use EOL resistors, but is placing them at the panel. He says this is standard practice and he has done many installs in this manner.

Yes, I know people here have said that it's as good as not using them at all (as in this post here), but I am having some trouble explaining why.

For a NC sensor, it appears that EOL resistors are wired in series with the contact (as shown in the HAI install manual ).

Based upon the discussion in this thread, it appears that the value of having an EOL resistor at the sensor end of the circuit is that any short that occurs will be between the panel and the resistor so that to the panel there is a drop in resistance (the circuit has been short-circuited).

I couldn't find any clear statement of this on the HAI website or in their manual. Is there some definitive reference I could point to in order to resolve this discussion?

 

[CollinR]

Go up in your attic and take a needle and stick it through a door switch's lead, this is how a burgalr would do it.

If EOL is installed correctly alarm will activate, if EOL is in the panel SNAFU.

Simple easy real world example, wel this atop the name with makes it pretty obvious where it should go.


That said enough people in OK put them at the panel that it has become standard practice and hence fines aren't issued for it.

 

[BraveSirRobbin]

http://www.cocoontech.com/index.php?showtopic=711

 

[Steve]

Just because it is 'standard practice' doesn't make it right. It just means that most installers are well, lazy and don't want to do it the right way. EOL's are put in the panel for one reason only - for a panel that requires it and the installer doesn't want to put it where it belongs. In better panels, like the Elk and I believe HAI, you can configure a zone as NC and not have to use it. So, I would confirm 100% that the Omni can be configured to not use EOL, then tell the installer to just leave them out. It will give you a neater install and work exactly the same way.

 

[BrettS]

As the others have said (and provided links for) the EOL resistors do no good if they're installed in the panel (well... maybe they'll help if the last inch of wire between the resistor and panel is compromised, but otherwise they'll do no good )

That said, however, there is a lot of debate in the industry about whether EOL resistors are really necessary in a residential installation... particularly if all of your wiring is hidden within the walls anyway. The chance of anyone trying to open your walls (from the outside) and locating your alarm wiring and trying to short it out is pretty much zero.

In a commercial installation, particularly one with concrete or metal walls where some of the alarm wireing is exposed then EOL resisters definitely make sense.

Personally I wouldn't worry about it too much (and I don't use EOL resistors in my own alarm), but don't let the installer talk you into believing that they're doing anything beneficial.

Brett

 

[ASIHome]

Just because it is 'standard practice' doesn't make it right. It just means that most installers are well, lazy and don't want to do it the right way. EOL's are put in the panel for one reason only - for a panel that requires it and the installer doesn't want to put it where it belongs. In better panels, like the Elk and I believe HAI, you can configure a zone as NC and not have to use it. So, I would confirm 100% that the Omni can be configured to not use EOL, then tell the installer to just leave them out. It will give you a neater install and work exactly the same way.

The thing to watch there with the HAI is if you have even one NO device or add one later you have to then turn on resistors and put them on everything. This is also the case if you add an expansion enclosure. The best thing to do is just leave resistors turned on and put them where they belong. It will save time in the long run.

 

[Sandpiper]

I couldn't find any clear statement of this on the HAI website or in their manual. Is there some definitive reference I could point to in order to resolve this discussion?

No.

No matter what is said, the opinions will still vary. But please allow my 2 cents on this. I kind-of know what I'm talking about. I am a licensed installer with a fair amount of experience, plus I am a licensed master electrician, and licensed electrical engineer.

The purpose of an EOL in a burglar alarm circuit is very simple. It adds a small degree of protection to the circuit. It adds the ability to detect when the circuit is shorted in addition to the ability to detect when the contact is opened. If a burglar decides to short the wires to door contact, this will be detected just as if the door were opened.

Now for the negatives......EOLs are difficult to install in most cases. There is just not room at the device a lot of times, and this makes the installation difficult and makes future maintenance difficult. If it were easy to install, I'd say, yes, always install them......at the device (at the end of the line). However, they are not easy to install. And the value they add is very marginal. I have never heard of a case from any professional installer where a burglar attempted to short a sensor wire so the sensor would be bypassed. What I see most of the time is that the burglar just kicks the door in.

The other thing I see a lot is that EOLs are installed in the panel. This has been discussed a lot in this forum. They are useless in the panel. The reason you seem them there, is that the most common alarm panels are designed to require an EOL on zone 1, but not so on the other zones. That is, they cannot be programmed out on Zone 1. Plus...if I choose to program them out, this takes more time than to install a resistor in the panel. Most installers are in such a hurry that they do the quickest thing....just install the EOL in the panel.

With an Elk M1 or an HAI, programming them out is easy, so I hope to never see an EOL in one of those panels. Either put the EOL at the End-Of-Line or don't use them at all. The choice is yours.......

 

[upstatemike]

Another point of confusion in all of these threads is the difference between putting the resistors ON the panel vs AT or NEAR the panal. In the first instance you are simply wiring them in series with the loop right at the terminal strip which does no good as already explained. It is fine however to use 4 conductor wire and bring the end of the loop back to the area of the panel on the second pair of wires. In this configuration the the resistor is at the far end of the loop because the entire loop has been doubled back to the panel. The reason for doing this is twofold: 1- you have the resistors in a location that is convenient for troubleshooting, and 2- you have the end of the loop in a location where you can easily extend the zone to additional devices if you wanted to.

 

[js19707]

thanks all for the comments, i'm heading home from work now and will talk to the guy. i think his concerns around changing things around to put the resistors at the end is the amount of time and effort required, and the difficulty of squeezing them in where there is limited room.

upstatemike, i've never heard of what you're proposing but it sounds like a good solution where there isn't much room behind the sensor to fit the resistor. currently 2 of the 4 wires that run to the sensors are not doing anything so this might be a quick way of adding EOL resistors on the far end without having to wrestle with squeezing everything in.

so, IIUC, using this scheme would mean that a short across all four of the sensor wires would be detected, but a short across just two would not?

Another point of confusion in all of these threads is the difference between putting the resistors ON the panel vs AT or NEAR the panal. In the first instance you are simply wiring them in series with the loop right at the terminal strip which does no good as already explained. It is fine however to use 4 conductor wire and bring the end of the loop back to the area of the panel on the second pair of wires. In this configuration the the resistor is at the far end of the loop because the entire loop has been doubled back to the panel. The reason for doing this is twofold: 1- you have the resistors in a location that is convenient for troubleshooting, and 2- you have the end of the loop in a location where you can easily extend the zone to additional devices if you wanted to.

 

[upstatemike]

so, IIUC, using this scheme would mean that a short across all four of the sensor wires would be detected, but a short across just two would not?

No, not quite. Think of a normal loop as a pair of wires with the resistor installed at the far end. A short anywhere across these wires will be deteted because the resistor at the far end is shorted out. Now think of extending the loop with another pair of wires to make a loop that is longer but still has the resistor at the far end. A short anywhere along this new bigger loop will still short the resistor and alert the panel. If you fold that big loop back on itself so the resistor is close to the panel it is still one big loop and nothing changes if it is shorted. any wire shorted to the oposite wire (either inbound or outbound) will cause an alert on the panel. A short between an outboud wire and the same same wire coming back and could disable a normally closed contact located in the portion of the loop that is located beteen the points of the short. This is an extremely unlikely scenario.

Cutting or shorting all four conductors will definitely be detected.

Downside is that the second pair of wires needs to be spliced through at each device so if space is tight you have to additional connectors to fit into the splice.

 

[Steve]

And if you can fit all the connectors, you can just as easily fit the resistor and have alot less wire and headache. In this case its not practical anyway since I'm sure all they ran is 22/2. If you will really have all those potential issues like ASI said, then I would just let them do their thing and let them put them in the panel, but at least still try to be neat about it. It's just sad HAI has some of those requirements since the Elk you can custom program each zone with no caveats like that.

 

[Sandpiper]

And if you can fit all the connectors, you can just as easily fit the resistor and have alot less wire and headache. In this case its not practical anyway since I'm sure all they ran is 22/2. If you will really have all those potential issues like ASI said, then I would just let them do their thing and let them put them in the panel, but at least still try to be neat about it. It's just sad HAI has some of those requirements since the Elk you can custom program each zone with no caveats like that.

I was just about to say the same thing.

What takes up the space is the "beanie", not the resistor. Since the "4/C with the the EOL in the panel" idea adds an extra beanie, you may as well include the resistor at the sensor instead of splicing for the loop-back.

Plus, I prefer to pull 2/C to contacts for doors. You need as much room in the little 3/8" hole as you can get. When using 4/C for contacts, the extra 2 wires really get in the way many times.

 

[Steve]

Of course there are always options. I think most installers are not going to take the time, but you could avoid the Beenies and just solder the EOL with heat shrink OR you can use the George Risk (GRI) contacts with the embedded EOL. That way, you get the EOL where it belongs, there are no additional wiring concerns AND you keep your panel neat and free of EOLs. The only downside is the contacts cost more and depending on what EOL you need, it may have to be special ordered. I don't know the the HAI panel takes, but Automated Outlet has the GRI contact with 2.2k EOLS for the Elk here. They may also stock the regular 110's also.

 

[gatchel]

I love EOL discussions

 

[briankelly63]

I love EOL discussions

The real solution is to have contacts and switches that are "active", powered components which send digital supervison (similar but more constant than wireless) to the panel zone. Shorting, disconnecting etc would disrupt the flow of supervisory information and trigger the zone. Another thought in todays world is that if (big if) current components and connections were more stable than they actually are each zone could be set to a particular resistance / impedance. Any change and the zone would trigger.