Home Running Smokes or Running in Series?

[BryanE]

What are the pros and cons of home-running 4-wire smokes to running them in series? Of the two, what's the most common method of wiring up smokes and why?

 

[tmbrown97]

pro #1 - saving zones!

And don't hold me to this - someone who knows more needs to chime in, but if they're all interconnected, I believe you can have them all alert when only one detects smoke; that way even if the smoke is down the hall, the alarms in every room go off for more advanced warning.

 

[mustangcoupe]

Series Install:

I agree with Pro #1 ToddB posted it does save you zones, and I beieve the reversing relay is to trigger all the smokes But I cold also be wrong.

Con #1 You don't know which smoked is the problem, when home running them some people have talked about tieing it all into their automation system and lighting a "safe Path to exit" based on which one caused the alarm.

Home Run:

Pro #1 hmmm none that I can quickly think of other then the con above reversed as a pro

Con #1 Lots and Lots of extra wire

 

[Digger]

Just to clarify you need a reversing relay only if the smokes have sounders. If they dont you need an End of Line Relay (not reversing).

Using 4 wire smokes is more expensive since you need 4 conductors and an End of Line Relay (assuming no internal sounders) where with 2 wire smokes you need 2 conductors and an End of Line Resistor.

I personally went with the 4 wire smokes all on individual zones. My wire runs to the zone expander remote cabinet on the top floor were short (10 to 12 feet for the bedrooms and hallway tops) and I got the EOL Relays at cost from work.

 

[ano]

If you do wire all the smokes to one zone, that doesn't always mean you have no idea which smoke tripped. Often the smokes will have a method to tell you which has tripped, until you reset them with a power cycle. Usually their LED will keep flashing in someway. Not all smokes do this, but some do.

 

[mustangcoupe]

While you are correct with that statement Ano, what I was saying was that without going to look to see what tripped you could already know and have an escape plan or backup plan being executed.

 

[Digger]

If you do wire all the smokes to one zone, that doesn't always mean you have no idea which smoke tripped. Often the smokes will have a method to tell you which has tripped, until you reset them with a power cycle. Usually their LED will keep flashing in someway. Not all smokes do this, but some do.

Actually NFPA and UL268 require multiple station smoke detectors (what you would use on an alarm panel) to have a visual indicator for the detector that trips until the zone is reset.

If the alarm goes off in my house I know where the fire is immediately since the ELK M1 announces the zone (Master Bedroom etc).

 

[gatchel]

I use 4 wire and there is one zone with several detectors on that zone. If there is a fire, I really don't care where it is. My house isn't that big. I just want everyone out.

 

[apostolakisl]

I've installed 3 different alarm systems made by 3 different companies and all 3 had a designated zone for smoke detectors which they recommended you use rather than separate them. There must be good reason for doing it this way. I would say that having your alarm know which part of your house was on fire would only be useful if your house was beyond rediculously huge. Like 50,000sf or more. Anything smaller and it would seem to me that the smell and sight of smoke/fire would likely tip you off far before you would even think to start scrolling through menu screens on your alarm panel.

In short, I would do it the way everyone else does it. It's just too important an alarm to find out there is a glitch because you did it different.

 

[pete_c]

I just recently installed 4-wire smokes / CO detectors in my home to my HAI panel. It was a learning experience.

I am using both reversing and eol relays. One reversing relay for the smokes and one for the CO's. A unique eol relay per zone.

 

[Digger]

I've installed 3 different alarm systems made by 3 different companies and all 3 had a designated zone for smoke detectors which they recommended you use rather than separate them. There must be good reason for doing it this way. I would say that having your alarm know which part of your house was on fire would only be useful if your house was beyond rediculously huge. Like 50,000sf or more. Anything smaller and it would seem to me that the smell and sight of smoke/fire would likely tip you off far before you would even think to start scrolling through menu screens on your alarm panel.

In short, I would do it the way everyone else does it. It's just too important an alarm to find out there is a glitch because you did it different.

Most manufacturers of Residential Fire Alarm Panels have one or two 2 wire smoke detector zones and the remainder can be 4 wire smoke detector zones. Commercial panels sometimes have more 2 wire smoke detector zones (I am working on a new one right now with eight 2 wire smoke zones and 255 that could be 4 wire or addressable smoke zones).

2 wire smoke have the advantage of being less expensive and "sometimes" easier to install and other times more difficult (depending on your wire run). With 2 wire smoke detectors it is not good practice (usually stated in manuals) mix detector types on a zone. There is also a limitation on the amount of detectors per zone (usually 10 to 20 which should be enough for most residential installs).

Certian things to keep in mind is that if you use 2 wire smoke detectors with sounders you can not put a conventional thermal detector on the zone as it would present a dead short on the zone if it trips and would disable the sounders. If you have more than one conventional thermal detector on the same zone and one trips for rate of rise you will not know which one trips (there may be one or two models that can but I have never seen them). 2 wire smoke zones require a little more effort in the design of an alarm panel (firmware wise and sometimes hardware) so manufacturers usually only put 1 or 2 on a panel (for residential that is all that is needed).

With all smoke detectors on a single zone if you get an alarm you start evacuating and help comes (if your panel reports) and the fire department gets there and starts searching where the fire might be (if you had multiple zones they know where to start looking and not all fires product heavy smoke as it could be still contained in a wall etc). With detectors on multiple zones if a second zone trips that is usually an indication that the fire is not a false alarm and that it is a serious fire. Also if you have a problem with the wiring on a single zone with all detectors you have no protection until it is repaired.

There is really nothing wrong with 2 wire smoke detectors or having all smoke detectors on one zone, however, there are a few advantages (nothing earth shattering etc) of having smoke detectors on multiple zones. Either way the bottom line is to have enough of them properly installed, maintained, and tested often.


Remember not every 2 wire detector is compatible with every panel. Make sure to follow the alarm panel installation instructions carefully.

 

[BryanE]

Thanks guys, you all have excellent points.

I don't really want to know where the fire is either, I just want my family out of the house. I think having them zoned by level would be useful but per room sounds like overkill and I wouldn't want a family memeber investigating if an alarm did go off... that's the fire departments job.

Obviously there is the time when you're cooking and they go off but generally you understand why that occurred and can simply reset them.

 

[pete_c]

In the MW I left the contractor installed 120VAC smokes in place and just added the HAI ones separately. The smokes are not in every room in the house but rather just cover areas.

In FL right now have smokes in every room in the house...but the setup is totally different with two great rooms and everything off the side of these rooms (and all 9-foot ceilings). Not sure what my approach would be now to adding HAI panel connected smokes there.