Line voltage smokes


The city inspector just threw me a curveball by saying that all smokes are required to be line-voltage - no low-voltage allowed. I was planning to install an Elk M1G and I'd still plan to do that for other uses, but is there any way (or any reason) to have the Elk interact with the smokes? Just when I thought I had a good grasp of the situation it's all muddled again.


If you have to install 120 AC supplied smokes you may want to pick up a smoke detector that can do this AND supply a contact closure based if it or any other of the 120 AC smokes go off (only need one of this type in your "chain"). I did a post with some info HERE.

I'm not an expert installer so you may also want to wait for others to reply. :unsure:
JonR said:
The city inspector just threw me a curveball by saying that all smokes are required to be line-voltage - no low-voltage allowed.
Are you sure he didn't say that you must have 110 volt smoke detectors and you can have low voltage detectors in addition?

Initially, the electrician told me they are only required to install one line-voltage smoke and that I could do the rest as low-voltage. However, he later came back and said that all of the smokes required by code had to be line voltage. I called the city to verify and got the same answer. Apparently the code just changed recently on this. I'm sure I could add some additional smokes of my own but that would be redundant.


Thanks for pointing me in the right direction - I should have been paying more attention to those threads! It looks like the GE ESL350 is the way to go - I'll run it past the electrician.

JonR said:
I'm sure I could add some additional smokes of my own but that would be redundant.
I'm a firm believer in redundancy when it comes to fire protection. The last couple of installs were done with 120 volt detectors and System Sensor 2 wire smokes connected to the M1. I like the backup battery on the 12 volt system that will keep the smoke operating in case of a power failure or fire. The "clean me" feature is nice too. The 120 volt smokes had no battery backup.
20 to 1 odds that the people you have talked to are WRONG, but unfortunately, even if you are right, argueing with the inspector means you ultimately lose.

Most inspectors are former contractors who learned thier trade under an apprentice system. They might not call it a master/apprentice relationship, but vast majority of trades are taught this way. They don't go out and get a 4 year college degree teaching them to be an electrician. Instead, they are hooked up with a more experienced worker who teaches them the skills. The only problem with this is if the teacher doesn't expand his (or her to be fair) horizons, then the student does not learn anything "new".

Originally, houses did not have smoke detectors, and people died. So smoke detectors became required and builders installed battery operated smokes. The public didn't change the batteries or took the batteries out, and more people died. So NFPA 72 (which is the basis of 99% of the fire code related laws) was changed to require power from the mains. Note that this does not mean they must be 110VAC smokes, just that they receive power from a continuos commercial source.

Every new house requires smokes, while most alarm systems (even in new houses) are installed as add-ins. So builders installed the easiest (and cheapest) means of meeting the requirement, which meant 110 VAC hardwired smokes. And the "master" taught the "apprentice" to install hardwired 110 VAC smokes. And because that was the only way he ever saw things done, it soon became "THE WAY" to do it, and therefore, "what the law requires".

I would give one more try to discuss (not argue) the issue with the inspector. Point out that this is NOT some cr*p you would pickup at Radio Shack. In fact, it's significantly better than the junk installed by ADT and their likes. It is a UL Approved Residential Fire and Burglar-Alarm Panel. It has multiple approvals by UL, and is also approved by the CA State Fire Marshall. It is powered by commercial mains and battery power, and meets the requirements of NFPA 72. Stress that this solution is better than plain AC powered smokes, because 1) they are powered by both battery AND mains, 2) they can be monitered by a central station, and 3) they are supervised for wiring problems, power problems, and in some cases, dirt. Emphasize that you want to meet the code requirements IN THE SAFEST WAY POSSIBLE. Once they understand that you know what you are talking about and are not trying to take a shortcut, the majority of the inspectors I've dealt with will okay the installation. The better ones actually take the time to quiz me, so that they will be informed the NEXT time they come across something like this.

And if he still insists on 110 VAC smokes, well suck it up and impliment one of the solutions mentioned above. :unsure:
The NEC requires smokes in certain locations and that they are linked to trigger each other when one trips. This only works when 120v power is present, if, say, lightning struck the house, started a fire and knocked out the power, the only device that would sound is the one that detected the smoke. Certain cities or areas may have amendments to these requirements. I don't know where you are located. System smokes are a lot better than 120v smokes. For reasons stated above. We use model System Sensor 2 & 4WTAB. They have an integral heat detector & an audible base. We always place horn/sirens outside sleeping areas and recently started using a polarity reversing relay to activate the audible base on all smokes. In addition, the code places detectors for life safety, we place detectors in additional locations to further protect the home. Ocassionally the inspectors refered to fact that the devices did not trigger each other. (causing an audible in each bedroom). That is the reason we started looking at the reversing module. Our installations are much better than the code requirements. Most inspectors see that we meet (and exceed) the intention of the code and have always accepted our systems. I would say, discuss your system and show him how it meets the code req. Then ask him to specify where in the NEC you can find the section. (Then check footnotes and exceptions.) Good luck.

I'm girding myself for a visit to city hall to discuss this with the inspector. I need to do this now so that, if successful, I can tell the electrician to stop wiring for their smokes. Thanks for all the "talking points." CDC - since you've used both the 2-wire and 4-wire System Sensor smokes, could you (or anyone else) give me a quick course on how both are wired to the Elk M1G along with the RRS-Mod so that they all sound on an alarm? Can the Elk do either the "alarm/bell output" or the "alarm relay contact"?

Here are the RRS-Mod install instructions

In the 4-wire diagrams, is the "detector power" the input zone and "aux power" the SAUX? From reading other threads, it seems that the "Bell/Alarm Circuit" can come from Output 2. What is the "Initiating Device Circuit"? A separate output zone? I knew it could be done but hadn't gotten around to figuring it out yet.

I was leaning toward using 4-wire smokes so that I could separate them into zones (one per floor). Would I need one RRS-MOD per zone? I'm trying to have ready answers if the inspector probes into this area.

Many thanks,

JonR, we have not combined 2-4 wire smokes on the same job when using the RRS. I'm not sure that it won't work, we just have not done it yet.
What is the "Initiating Device Circuit"?
. This is the zone on the panel, ie 1-16, defined as FIRE zone type. The red & black leads on the module are +/- 12v that you will use to power the smokes (SAUX) in normal operation. The yellow & orange leads are +/- 12v that will power the smokes when there is an alarm. Notice in the diagram that "+" becomes "-" and "-" becomes "+" to the smokes. Write a rule to activate an output when a fire alarm is tripped. This will be the +12v trigger (the purple lead). Write another to cancel the output after timeout or with code to silence.
Would I need one RRS-MOD per zone?
If you tie all your smoke power wires to the output of the module (brown/white) then when the relay activates, all polarities will be reversed. Remember to use EOL(end of line) relays on each zone/wire to properly supervise all wiring. Your inspector may want to see this also. I'm not sure how clear that was because I need my hands to get most points across. Good luck.

Success! I spoke with the electrical inspector today and he was very receptive. He said he wants to see two things:

1) A UL sticker when he opens the panel door on the Elk
2) When he tests one smoke all of them should sound

On the first of those, is there a UL sticker on the panel as shipped or is that something else that requires some kind of post-install certification?

Thanks for all the help,

JonR said:
On the first of those, is there a UL sticker on the panel as shipped or is that something else that requires some kind of post-install certification?
If it is one of the UL listed panels, it is next to the on/off switch.
My understanding is that you need a reversing module per zone (if you use sounding detectors on that zone). When in the normal state the detectors are connected to the zone (through the module) and when a detector goes into alarm the module connects the detector to the aux power in reverse polarity and sounds all of the sounders on that zone.

But to me there is a catch (maybe I am thinking into this to much though). If you have multiple zone with these modules and one detector on zone 1 goes into alarm then all of the detectors on all zones with these modules will sound (triggered by the panel). To me that is good and bad. Since to make the detectors sound you are removing them from the zone and if the fire was to spread to another zone you would not know it because the panel will not see the detector go into alarm.

Granted you are already evacuating and calling the CS but when the fire department arrives they see where the fire originated but not where it spread to.

In a residential application it is most likely not a big deal and i am probably "digging" to deep (and everyone thought the name was from my dog who digs holes in the backyard). In a commercial application I wonder how the NFPA handles this?
you need a reversing module per zone
No. You need a reversing module for each POWER SOURCE. In simple terms, you want to reverse the power to all the smokes with sounders, causing them all to go off. In terms of power, there is no distinction between zones, ie the smoke doesn't care were the power comes from, as long as it get 12 VDC.

If all of the smokes are powered from the main can, then you only need a single reversing relay, as there is only one power source. If however, you have all ther first floor smokes powered from the main can, but the second floor smokes go to a zone expander with it's own power supply in a seperate can, then you would need a second reversing relay for that power source. And so one.

On my home system, I have the main can, plus 3 zone expanders (second floor, basement, garage), so I have 3 reversing relays (Main, second, basement). The garage has only heat detectors, so it doens't need a reversing relay.

i am probably "digging" to deep
Yes, you are. ;) Generally, if there is enough smoke to trip more than one smoke, you are talking about ALL the smokes.

One other word of warning. Take some time connecting all the power wires. Because they are larger (18 gauge vs 24 gauge), and more of them going to a single point, they can easily start to look messy. Inspector looks at the mess, says to himself "this guy must be a joker", and all of a sudden you get downchecked (and no, I have no idea how some of the Borg installs get passed, other than the inspectors not checking since it came from a big company). I bring everything into terminal strips, but any method that looks neat and professional will suffice.