4 Wire Fire Alarms + EOL Resistors

jasonreg

Member
Hi, for those following the saga you will recall that I have discovered that my DSC system has been installed without the use of EOL resistors on any device with the exception of the Smoke Detectors.
 
I have three smoke detectors all homerun to the panel.  The wires are all then by color twisted together and installed in a single zone.  There is a 5600Ω across the zone and COM input on the panel.  Now as the rest of the system is wired without EOL resistors and are NC circuits I am wondering.....
 
Question 1 - Why is the smoke wired this way? (Edit - I may have now figured part of this out - all smoke seem to be NO devices and require the EOL resistor to function but in further reading it seems that the smokes should be run in series with an EOL at the end of the run - mine are homerun so not quite sure what to do here).
 
Question 2 - Can I (should I) split the smokes into individual zones and place an EOL resistor at the smoke detector end of the wire?  This is a little confusing as it seems that there is only a single entry for EOL installed or not in section 13 of the programming?
 
Question 3 - Are there any other devices for which EOLs would be highly desired?  It is not practical for me to add them to all sensors as the house is fully finished but it would not be too hard for CO detectors, motions and the like.
 
Many Thanks,
 
1. Because either the original installer didn't care or didn't know....but the short of it is they negated any supervision. They also didn't provide a power supervision relay.
 
2. That is one option. You would need 3 power supervision relays.
 
3. Any life safety or critical device should have them installed. Protective circuits, unless it's a single device/zone or a NO device...the benefits dwindle.
 
Thx DEL.  Can you please confirm that if I replaced the smokes (seven years old so within a couple of years of replacing them anyway) with something like the GE541NCSXTE then all I would need to add would be the appropriate EOL resistor (i.e. these devices have a built in power supervision relay)?  The DSC supervision relay looks like it is already half the price of a new smoke detector - or am I getting this wrong?
 
Also, where can one buy the resistors on line?
 
jasonreg said:
Also, where can one buy the resistors on line?
I recommend ebay.
For example, less than $2 for 100 x 2.2k 5% with free shipping.
They're all made overseas anyway, so it doesn't matter if you buy them from Boston, Bejing, or Bangkok.
 
Thanks fellas,  digikey shows them (in lots of 500.....) but none available. Any idea where to get them in smaller quantities?  Even with spares I should be good at 50 or so.
 
Small question - I assume 1W is sufficient?  They show both 1 and 2W
 
thx
 
Get 1/4 W resistors, which will be more than sufficient.  1W is overkill.  A 1W resistor is physically large and will be more difficult to work with in tight spaces.
 
Search for "1/4W 5600 ohm resistor"  and/or "5.6K resistor" on eBay or Amazon.  You can buy 50 to 100 for a few bucks, including shipping.  The ones that ship from China will take a few weeks to arrive, so keep that in mind.
 
So for the record, here is my final solution to this particular issue.  The older DSC boards (mine included - Vers 4.14) could only be set EOL on or off - all zones. So while I could add EOLs to smokes, it would be problematic for others (kind of an all or nothing proposition).  However in the newer DCSC boards (and for sure in Vers 4.6) one can select the use of EOLs on a per zone basis (for the first eight zones only).  So, I can add them where practical and highly desired for the safety sensors, and not worry about trying to dig in doors and windows to reach them all.
 
A couple of quick purchases (1864 Vers 4.6), a PC5204 (to resolve my power issues discussed in another thread) and another expansion PC5108 and I am off to the races.  Oh, and the new panel and expansion board came with a bunch of resistors so that was resolved as well!
 
Thanks for all the help so far.  Going to get this up and running, spend the March break with the kids and then figure out where to go HA-wise (though it is looking like since I am sticking with DSC for now, I am looking at either not tying into the panel or getting into the Vera 3 mindset).
 
jr
 
Hi folks, I do have one other unanswered question in this thread.  Can anyone please confirm that the GE541NCSXTE smokes I refer to in post #3 are a suitable replacement for my existing smokes?  My plan is to split them into individual zones adding power supervision relays (in this case built in) and adding EOL resistors.  Is there a down side to splitting them into separate zones? 
 
Thx
 
Hi RAL, yes I did read that post from DEL and it was quite helpful to understand the issues in play.  In my case, the three 4-wire smokes are currently all home-run to the panel.  There are no power supervision relays or EOLs installed at the detectors themselves.  Further, the wires at the panel are then twisted together and added to the panel as a single zone with one EOL twisted into the mix.  See here for a pic:
 
[sharedmedia=gallery:images:709]
 
What I am trying to do is determine the best way to make the best fixes, given the restraints that is does not seem practical to loop them together into a single zone (unless I suppose I try to do that at the panel....).  I also have a rather large house (3 story, 4500+ sq ft) with one smoke on each floor. 
 
Thoughts/recommendations?
 
Change to a 2 wire fire zone, replace 3 detectors (sub $100)
 
Done.
 
OR

Pull 4 more conductors to 2 of the smokes, install the relay at the smoke with no wire added.
 
Be happy you didn't have a wiring issue or power issue with the smokes as installed.
 
DEL/RAL, Thanks again for the input and continued counsel.  A few additional questions if I may:
  1. 2 Wire option. Seems pretty straight forward, use the existing extra connectors to return the signal back to the panel, connect to the next sensor and so on.  Add the proper resistor to the last detector and we are gtg.  Any downside to using 2 wire smokes?  I do see that I need to use those specified for my panel (in this case FSA-210 series);
  2. Cannot pull new wire without causing damage in main living areas (low WAF factor).  The GE541NCSXTE 4 wire detectors I refer to above have an end of line power supervisory relay integral to the detector.  Acknowledging the comments about multiple fire zones from DEL here and in the other thread, would I be better off with the 2 wire approach, or three separate zones using these detectors and an EOL resistor?; and
  3. There are areas which should (IMO) have fire detectors and do not (i.e. the bedrooms and other areas).  I cannot pull new wire upstairs unless I go wading through the attic and the three feet of blown-in insulation (yes, a Canuck here).  Thoughts on wireless detectors and how this affects the panel (multiple zones etc.) would be appreciated.
This is not ideal - I get that (can't wait to build our own).  Just trying to make the most out of my current situation without causing undo damage to finished areas.  I should note that there are existing 110V detectors/alarms on all three levels tied together per building code.  This LV system of detectors are what is tied into the DSC 1864 alarm panel.  They do not need (I don't think) to make each other sound on alarm as they will trigger the main alarm sirens so I do not think I need any reversing relays.  I do want (I think) power supervision which does not appear possible on the 2 wire option.
 
Thx again for all input.
 
1. There are many detectors that are listed for many panels. Personally, I like System Sensor, and most, if not all, manufacturers have a compatibility document on the interwebs. Generally there's not much of a downside besides all the detectors should be the same make.
 
2. The same issues exist whether or not you have a separate relay or integral unit.
 
3. I'd run the wire personally.....which is worse to the WAF....you in the attic or her having unmatched detectors.
 
2 wire detectors are inherently supervised in their nature, the loop is both the power and the circuit and supervised by an EOLR. A 4 wire detector separates power and the circuit which is why you need the relay....to ensure there is power on the loop/detector otherwise the loop would seem normal to the panel at all times.
 
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