4 wire smoke EOL Relay?

[benze]

Hi,

I'm looking at adding some 4wire smokes to my M1G installation, and realize that I need an EOL relay to ensure that power is not lost on the smokes. I have no issues with that. One thing i do have issues with is the cost that some of these companies sell their EOL Relays for. As far as I can tell, a simple 4$ Form C or Form B relay from my local electronics store should do the trick just fine. Is there any value / justification to spending 20$ on a relay from System Sensor instead of just using a simple one?

Thanks,

Eric

 

[icellama21]

If you are confident in your electronics abilities(aka ability to solder/connect wires), grab a 12V SPST relay and the appropriate EOL resister.

1) Connect the coil to the +12V at the end of the line.

2) Connect one relay contact to one end of the resistor

3) Connect the other relay contact and the resistor to the ends of the zone/signal line


+12V---------$ --------------------------------- Smoke Detector --------------- Smoke Detector ------------ Zone Input
Ground-------$ / -------- Resistor ------------ Smoke Detector --------------- Smoke Detector ------------ Zone Input

Just be careful with life safety devices and make sure to test your smoke detectors regularly.

 

[Digger]

I would be very careful using just any relay for an EOL Relay on a smoke zone or any other life safety application even though in theroy they could work just fine as icellama21 states.

The mfg's of the smoke detectors use specific relays for a reason to insure operation and also limit the amount of standby current since they are always energized. An off the shelf relay may draw 50 or 60 ma (or even more) where some of the EOL Relays draw a lot less (so not so drain your system battery prematurely when ac poser is lost) What is the minimum trip level and hold current of the off the shelf relay? Will it cause an unnecessary trouble condition under ac fail and low battery? Will a transient damage it? Has it been evaluated to operate from 0 to 49 degrees C (32 to 122 F) in case it is installed in an attic or other uncontrolled enviroment? There are many other tests and requirements for such a device.

Mfg's like system sensor have their products evaluated by a third party lab such as UL, ETL, CSA etc to insure that they meet the NFPA and other requirements. An off the shelf relay even if it is UL, ETL, or CSA Listed or Recognized may not meet the requirements for Residential and or Commercial Fire applications as just any relay has not been evaluated to UL985 Residential Fire and/or UL864 Commercial Fire and NFPA72 etc.

Granted an EOL Relay on a smoke zone is for power supervision and the detector should/would still operate if powered "my opinion" is not to cut corners with anything to do with life safety devices.

 

[benze]

If you are confident in your electronics abilities(aka ability to solder/connect wires), grab a 12V SPST relay and the appropriate EOL resister.

1) Connect the coil to the +12V at the end of the line.

2) Connect one relay contact to one end of the resistor

3) Connect the other relay contact and the resistor to the ends of the zone/signal line


+12V---------$ --------------------------------- Smoke Detector --------------- Smoke Detector ------------ Zone Input
Ground-------$ / -------- Resistor ------------ Smoke Detector --------------- Smoke Detector ------------ Zone Input

Just be careful with life safety devices and make sure to test your smoke detectors regularly.

Thanks for the confirmation. However, one thing I am struggling with right now is the ability to daisy chain multiple smokes on a single zone with home-run 4-wire conductor. Am I missing something obvious, because it seems that there is no way to do this with 4 wire conductor. I need to daisy chain the power from one smoke to another to get a true EOL relay that protects the entire chain. If I run power to each from the panel, then there is no way for a single relay to protect all of them. I would need a relay at the end of the power chain, which would mean at each smoke. Of course, only one EOL resistor for the entire zone.

The only way I can figure out how to do the appropriate daisy-chaining with home-run cable is with 5 conductor cable.

Am I missing something obvious here?

Thanks,

Eric

 

[icellama21]

Am I missing something obvious here?

Thanks,

Eric

No, you figured it out. Although it is technically possible to homerun most smokes with 5-conductor(shared grounds), it is a BAD idea. Your EOL protection may not be effective, one of the ground wires becoming disconnected can have unpredictable results, hard to protect against shorts/overcurrent, false alarms, etc, ect, etc.

You need to use 6 or 8(ideal) conductors to home run. I'd use 8 conductors, that way your power is on a loop for monitoring too. If you only have 4 conductors, put each smoke on a seperate zone with its own EOL, or go to 2-wire.

 

[icellama21]

I should also add a disclaimer:

If you are at all unsure about this, or are looking to save a few bucks on life safety devices, buy some cheap battery smoke detectors instead. Don't plan your primary system with an eye toward saving a few dollars on wire and relays. Make sure you have a professional supervise your work if you are not fully confident.

 

[Lagerhead]

As others have said, it doesn't make sense to trifle with life-safety systems. Some useful wiring guidelines are here:
http://www.systemsensor.com/pdf/bulletins/...-guidelines.pdf
http://www.systemsensor.com/pdf/A05-1003.pdf

 

[benze]

As others have said, it doesn't make sense to trifle with life-safety systems. Some useful wiring guidelines are here:
http://www.systemsensor.com/pdf/bulletins/...-guidelines.pdf
http://www.systemsensor.com/pdf/A05-1003.pdf

Thanks for the links. The second one is quite interesting.

Eric

 

[benze]

I should also add a disclaimer:

If you are at all unsure about this, or are looking to save a few bucks on life safety devices, buy some cheap battery smoke detectors instead. Don't plan your primary system with an eye toward saving a few dollars on wire and relays. Make sure you have a professional supervise your work if you are not fully confident.

Wasn't as much a question of saving a few dollars. 20$ is not going to make it or break it in the long run. Was more a question of if there was justification for using a brand name relay as opposed to a generic relay. But your reasoning regarding UL/ULC testing, current draws, temp controls, etc make total sense.

Thanks,

Eric

 

[icellama21]

EDIT: Post to which this response was directed was deleted, modifying for clarity.

The EOL module has a NO relay to supervise the 12V power to the smokes. The relay supervises the power supply, the resistor supervises the zone wiring. The relay coil is powered by the 12V supply for the smoke detector. When the smoke detector has power the relay is closed(i.e. its "abnormal" state). If the power is cut the relay opens(its "normal" state) and removes the EOL resistor from the circuit causing a trouble alarm.

The module need to go at the end of the chain to supervise all of the devices.

 

[icellama21]

I also want to add a more powerful disclaimer in case anyone reads this thread later.

Some courts have ruled that improper smoke detector installation can be criminally negligent. If you don't know what you are doing, hire a professional. You do not want to be liable for what happens 20 years after you sell the house. Always use stand-alone battery-powered smoke detectors as backups.

 

[benze]

EDIT: Post to which this response was directed was deleted, modifying for clarity.

The EOL module has a NO relay to supervise the 12V power to the smokes. The relay supervises the power supply, the resistor supervises the zone wiring. The relay coil is powered by the 12V supply for the smoke detector. When the smoke detector has power the relay is closed(i.e. its "abnormal" state). If the power is cut the relay opens(its "normal" state) and removes the EOL resistor from the circuit causing a trouble alarm.

The module need to go at the end of the chain to supervise all of the devices.

Thanks for the clarification. Sorry for deleting the post that you were responding to, but I realized after I wrote it up that I was confusing a NO relay to a NC one. In my mind they were suggesting the use of a NC relay as a EOL relay, which made no sense at all. Guess that's what happens when you think about things at 1am.... Once I realized that it was a NO relay, then everything made perfect sense.

Thanks,

Eric