Wire gauge on smokes

[newalarm]

Alright, trying to get some more info on wireing gauge on smokes. I did not plan right and installed 22/4 wire instead of 18/4. But I am seeing too that there is special red (fire resistant) sheating cable that may be required by code. We are in DC if that makes a difference. home is a townhouse, three floor, 1000sf per floor. There is basement rental that i want to zone separate, plus separate garage, also zone separate.

We already have a hardwired 120v smokes in each room of the house that was required by code. I am installing these smokes and thermal as a backup. and to be monitored in case we were not home and a fire broke out. I was looking at installing 1 per floor except on main living floor where i would put two. I want to add thermals in kitchen and furnace room on separate zones.

System is Elk M1G

Questions:

1. If this is installed as a secondary system, does it need to meet code in wiring?

2. I was told that in ordered to qualify for monitored discount on insurance, you had to have a smoke in each room of the house. true?

3. since my runs are so short, i was told 22/4 would be fine. What is the reason behind the 18AWG cable?

4. I had originally planned on homerunning each smoke so that it could be monitored on its original zone (may still need to do this for some areas (external garage, rental in basement). The Relay though takes up a good amount of power and would add to the panel load. are relays necessary?

5. DELInstallations had recommended just going with a 2 wire smoke install (I could do this for the main house). Are there any legal/code issues with doubling up the 22/4 cable?

6. Lastly, how do you calculate load with 2 or 4 wire configurations? Does one use less than other?

Appologies for restarting a new thread, but my last one was hijacked.

thanks

 

[wuench]

First of all, per code, it needs to be 18ga Firewire (red in color) so it can be recognized for what it is. And you'll have to check code in your area but I think it's every bedroom, hallway outside bedrooms. No smokes in kitchen or garage due to false alarms.

If you already have 120V interconnect smokes you can just replace with something like GE350Cx's. They are 120 but only one needs to be connected to the panel.

 

[Linwood]

No smokes in kitchen or garage due to false alarms.

But no restrictions on rate of rise alarms there, right? I was about to put one each in the laundry room and the garage (had a recent scare in the laundry room -- no fire, but link completely clogged the metal pipe, much faster than I would expect).

 

[newalarm]

First of all, per code, it needs to be 18ga Firewire (red in color) so it can be recognized for what it is. And you'll have to check code in your area but I think it's every bedroom, hallway outside bedrooms. No smokes in kitchen or garage due to false alarms.

If you already have 120V interconnect smokes you can just replace with something like GE350Cx's. They are 120 but only one needs to be connected to the panel.

Again, since i already have a system that meets code, i need to meed code with a secondary system? I don't want to put two sets of smokes in each space. I guess the red is to know that you should not cut that wire? but if it was cut, the alarm panel would know anyway.

I thought tieing into a 120v sys was a nono. plus if we lost power, then the smokes would no longer work with elk?

 

[newalarm]

I guess an alternative would be to replace the smokes with thermal detectors. Though alert time would be decreased. what gauge does thermal detectors need to be on and does it need to be fire wire?

 

[wuench]

I think anything you add needs to meet code, no matter what you have today. And code is a set of minimum requirements, no reason you can't exceed them, so I would use firewire for everything you add LV. Your local inspector has the final say, and the primary purpose of meeting code, for you, is to have your insurance company pay any claims. As they will use any excuse to get out of paying a claim. So take everything said here with that in mind, whatever you decide to do needs to be cleared with an inspector and your insurance agent (and I would get it all in writing). Also for your rental to get occupancy, the inspectors word is what counts there.

But in general, you can tap into your 120V, they should be interconnected and battery backed up with 9V batteries and the Elk has battery backup so I don't think a power outage is an issue. I would be consistent in whatever you do so if you do decide to go 120V and want to add more detectors stick with that. Some inspectors require 120v no matter what and will not accept a low voltage solution in their interpertation of code. If you want to go LV in the second unit maybe that's ok, but I would stay consistent in each area (that's just my opinion).

Rate of rise detectors are not the same as smokes so if you are trying to protect bedrooms,etc, they will not suffice, code-wise, and are a bad idea in general. For kitchen, attic, garage, that is all you can use, due to the false alarms smokes cause in those areas. Think about it, do you want to know when something catches fire, or when the fire reaches the ceiling? When the fire is at the ceiling in a bedroom, it's a moot point.

 

[ecborgoyn]

I would also like to hear about smoke detector current loading calculations. I've read the System Sensor spec sheets and do not totally understand the terminology and what I'm reading. For instance, for a 2WTA-B device, they say the max alarm current is 130 mA, limited by panel. What does this mean? This can't be for each device sensor in the loop... If I use the 2W-MOD2 and RRS-MOD devices how is the current load changed? The specs on 4-wire devices make more sense to me.

Please don't take this as 'hi-jacking' the thread. I'm attempting to amplify and restate one of your questions.

 

[Sandpiper]

Alright, trying to get some more info on wireing gauge on smokes. I did not plan right and installed 22/4 wire instead of 18/4. But I am seeing too that there is special red (fire resistant) sheating cable that may be required by code. We are in DC if that makes a difference. home is a townhouse, three floor, 1000sf per floor. There is basement rental that i want to zone separate, plus separate garage, also zone separate.

We already have a hardwired 120v smokes in each room of the house that was required by code. I am installing these smokes and thermal as a backup. and to be monitored in case we were not home and a fire broke out. I was looking at installing 1 per floor except on main living floor where i would put two. I want to add thermals in kitchen and furnace room on separate zones.

System is Elk M1G

Questions:

1. If this is installed as a secondary system, does it need to meet code in wiring?

2. I was told that in ordered to qualify for monitored discount on insurance, you had to have a smoke in each room of the house. true?

3. since my runs are so short, i was told 22/4 would be fine. What is the reason behind the 18AWG cable?

4. I had originally planned on homerunning each smoke so that it could be monitored on its original zone (may still need to do this for some areas (external garage, rental in basement). The Relay though takes up a good amount of power and would add to the panel load. are relays necessary?

5. DELInstallations had recommended just going with a 2 wire smoke install (I could do this for the main house). Are there any legal/code issues with doubling up the 22/4 cable?

6. Lastly, how do you calculate load with 2 or 4 wire configurations? Does one use less than other?

Appologies for restarting a new thread, but my last one was hijacked.

thanks

A1. Local codes vary across the US. Most jurisdictions require a complete system which meets code. Normally they will say that If you want to add additional coverage, that is not a problem. Additional coverage would probalby not meet code, per se, but you already have met code with the other system. So essentially, I would say no, the extra sensors do not need to meet "code".

A2. Depends on the insurance company. They will expect you to have a code system so that would be the first requirement. Most companies will offer a discount for a monitored system, but I dont believe they stipulate how many have to be monitored. I believe having just 1 will qualify for most companies.

A3. This is a local code issue. The NEC and other NFPA standards do not specify what size wire you need to use. Technically 22/4 is fine, but I have heard of many jurisdictions requiring the 18 guage. If you use 18 AWG then you should be fine for 99.9 % of the jurisdictions in the US. I think that is why the 18 guage is so popular for FPL (firewire).

A4. By relays, I assume you mean end-of-line relays. Yes, end-of-line relays are required for 4-wire smokes. Some 4-wire smokes have a built in relay. This relay is used to monitor the power circuit and will cause a trouble on the signal circuit when power is lost.

A5. By doubling, do you mean paralleling the conductors? I would not, as it should work fine on two conductors, but I have this done many times. I'd recommend using 2 of the 4 conductors and spare the other two.

A6. The specification for the smoke will state the consumption. Just add them up.

 

[apostolakisl]

Comments

1) Only your insurance co can tell you what they will give you a discount for and what might exclude you from coverage after a loss. You must deal directly with them and, as mentioned, have it in writing.

2) In a 2 wire system, caculating load is an excercise that you can do for your own personal satisfaction. 2-wire systems must be matched to the panel and the panel manufacturer will tell you exactly which models and how many of them can be used.

3) 4-wire systems would require you calculate load for the power side. It is unlikely you would exceed it, but you should add it up anyway and check to see how that matches up to your panel. The alarming leads have no load consideration, they work like any alarm zone, open/closed/eol resistor.

4) If you want to use 2 wire system and you want to put each one on its own zone, you will need an adapter. Your panel probably only has a single zone for 2 wire. The adapter will make a 2-wire detector look like a 4 wire detector to the panel (it accepts an alarm on the 2-wire system and outputs a simple open/close connection for a normal zone to plug into). The adapter of course needs to be matched to the 2 wire units you are using. If you already have home runned 4 conducter wires, it would seem rather silly to do it this way. If you want 2 wire detectors to all be on thir own zone, you will need those home runned as well, but only 2 wires. The deal is, if you daisy chain, all detectors on that daisy chain are 1 zone. The only exception, is if you use addressable detectors, but you aren't going to do that.

5) Check with your local inspector on the 18 guage/jacket type.

6) Check with your local inspector on whether adding a system above and beyond code is required to also meet code. If it is monitored, they may make you stick to code since they want to avoid false alarms.

 

[Del91574]

First of all, per code, it needs to be 18ga Firewire (red in color) so it can be recognized for what it is. .

Red is not a code requirement for cabling, may be a local requirement, but not necessary.

5) Check with your local inspector on the 18 guage/jacket type.

Appropriate advise, but of note, the lightest AWG that is "allowed" is 18 AWG, with individual conductors sized to 26 AWG. The code is ambiguious regarding this, but the intent and spirit of the code is that the lighter AWG is typically used in harnesses and ribbon cabling commonly used in these systems and the field wiring should not be less than 18 AWG, and preferably solid (there's reasons for this).

The cable doesn't need to be jacketed, it can be a zip/parallel cord, just needs to meet the FPL rating or acceptable substitute. AWG is oversized in the case of voltage drop or circuit distance, but for the most part, is not a large factor in 90% of the residential installs out there, unless the circuit leaves the building and goes to another building, in which case, lightning supression is going to be required.

 

[Sandpiper]

Appropriate advise, but of note, the lightest AWG that is "allowed" is 18 AWG, with individual conductors sized to 26 AWG. The code is ambiguious regarding this, but the intent and spirit of the code is that the lighter AWG is typically used in harnesses and ribbon cabling commonly used in these systems and the field wiring should not be less than 18 AWG, and preferably solid (there's reasons for this).

I have heard of local codes requiring this, but none of the national codes require #18. Can you please elaborate on what code you are referring to?

 

[Del91574]

The specific article is in the NEC, 760:179B.

Quote is: B Conductor Size. The size of conductors in a multiconductor cable shall not be smaller than 26 AWG. Single conductors shall not be smaller than 18 AWG.

I've had the point argued in my state with the electrical review board regarding some large projects and what the state fire marshal and electrical inspector viewed this code statement. We had the NEC review board provide a statement as to what the requirement was, as this was a 9 digit project that was being held up/tagged. I also had to deal with this code requirement during my tenure at a major fire panel manufacturer.

Their statement was that the intent and definition of the code requirement is that harnesses and ribbon cables are the 26 AWG statement, with field wiring being the 18 AWG statement. There are a lot of creative interpretations of this code article as to what it allows and doesn't allow. Since this code article is ambiguious, the stance that the majority of the industry has taken is that field wiring is a minimum of 18AWG for IDC circuits, however items such as a combination system keypad or non-essential piece of equipment, while not part of the IDC, may be required by a local AHJ to be wired using fire alarm methods and cabling, which includes the AHJ requiring a hardwired AC connection and not a plug in system transformer, or in the case of power supplies, a plug in whip that many installers tend to use. That said, 22 AWG is available in a FPL rating, however it's intended for ancilliary devices and not an IDC or similar.

The statement regarding solid vs. stranded, is while stranded is allowed, the problem lies if the cable, especially lighter AWG's, is nicked while stripping or the strands start to break off when twisted under wire nuts or while being worked, that the ampacity of the cable will be negatively affected and not be known, as continuity still exists, however when the full load of a NAC, DAL, or speaker circuit (25/70V) is applied, that the cable will fail.

Also, the statement regarding red, while it may be a local requirement or good idea, it's not a required item, nor are red boxes, covers, EMT, fittings or any other item, it's typically only done for identification purposes, as the larger systems tend to have the same sized conductors and wiring methods as regular electrical circuits.

 

[newalarm]

Thank you everyone for all the great responses. I just bought some 18/4 red sprinkler wire FLPR which i assume should be ok. All they had at HD and did not have time to order it or go to specialty place. I will install wire tomorrow.
If I daisy chain smokes, i can also daisy change thermal in same zone?
Has anyone found thermals in kitchen worth the trouble? i would figure that by the time a fire gets going, the smokes would pick up the fire way before a thermal in the kitchen if it broke out there. my smokes are going to be in adjacent spaces, the foyer and dinning room, separated by a doorway (without a door).

 

[apostolakisl]

Thank you everyone for all the great responses. I just bought some 18/4 red sprinkler wire FLPR which i assume should be ok. All they had at HD and did not have time to order it or go to specialty place. I will install wire tomorrow.
If I daisy chain smokes, i can also daisy change thermal in same zone?
Has anyone found thermals in kitchen worth the trouble? i would figure that by the time a fire gets going, the smokes would pick up the fire way before a thermal in the kitchen if it broke out there. my smokes are going to be in adjacent spaces, the foyer and dinning room, separated by a doorway (without a door).

GE (perhaps others) makes a smoke/thermal detector that you might consider. It has a local sounder for smoke (does not send alarm to panel) and a thermal that does send alarm to panel. Basically the idea is alert someone who is home to smoke in the kitchen without calling the fire department, but if it gets so hot in the kitchen that there must be something more than burnt toast, call the fire dept.

Myself, I put a smoke detector in the room next to the kitchen.

Daisy chaining thermal with thermal/smokes is fine.

 

[Sandpiper]

The specific article is in the NEC, 760:179B.

Quote is: B Conductor Size. The size of conductors in a multiconductor cable shall not be smaller than 26 AWG. Single conductors shall not be smaller than 18 AWG.

Where I come from 22/4 is multiconductor cable. Single conductors may or may not have jackets, but are "single". We don't do single conductor wiring around here. Maybe they do that in Chicago where conduit is required everywhere.

So again, I say the code does not require 18AWG, but I can see that the NEC reference you mentioned may cause a lot of arguments.