replace 120 vac Smoke Detectors, voltages, protocols, 2-wire, 4-wire, options?

My house is wired with 120vac smoke detectors.  I'm going to be installing an ELK system shortly.  Although my current smokes are interconnected, I do not believe that I can connect them to the ELK without an additional module.  If so, what is the preferred method?
 
Are there any 120VAC smoke detectors recommended that can be easily integrated with the ELK?
 
I have a single 6-wire unused com wire run to the attic and back to the alarm panel.  I'm trying to avoid have to run new power wires (and don't know that code would allow) from the alarm to the smokes.  A lot of what I'm reading has been dumbed down and makes it hard to follow.  Anyone got a simple explanation of the devices; using electrical jargon is fine. operating voltages, relay states, communication protocols.
Thanks

Short answer is no. There's plenty of reading why this is not a good idea to do.
 
Preferred method would be to divorce the wiring from the 120VAC and change the method to be 100% LV and compliant to the AHJ and building code.

I left the 120VAC contractor smokes in place and put in my own LV near the 120VAC smokes.  A bit of an eye sore but after a year or so it was not too noticeable.

Yes leave the 120V smokes in place as they are required by code. Adding an ELK does not change this requirement, and when you sell your house, they will be required, ELK or not. Think of those smokes as the local fire alarm to get you out of a burning house. The ELK will alert you remotely and will call the fire department. If you look at the stats of how many people die each year in house fires, even with the required smoke alarms, it will be clear you can't have too many smoke alarms. 

And the built in smokes should be replaced every 10 years and CO detectors every 5 years.

ano said:

Yes leave the 120V smokes in place as they are required by code. Adding an ELK does not change this requirement, and when you sell your house, they will be required, ELK or not. Think of those smokes as the local fire alarm to get you out of a burning house. The ELK will alert you remotely and will call the fire department. If you look at the stats of how many people die each year in house fires, even with the required smoke alarms, it will be clear you can't have too many smoke alarms. 

Click to expand...

Not true.
 
The AHJ has the final decision (however the insurer also typically has a stake). I have yet to meet an AHJ that will not allow the retrofit replacement of LV detectors that supersede or replace the existing HV detectors provided the same design criteria is met. Nowhere does code forbid the installation of LV smoke detectors in the place of HV smoke alarms (note the verbiage). The only time I've seen them NOT allowed is when the AHJ dictated their operation to meet the IRC (which documentation was provided) and then the subsequent argument that the alarm panel can be powered down (installed a transformer hardwired to breaker, cited the same is true with 120V units unless connected with a branch circuit).
 
The biggest item is the consideration of tandem ring and standby and alarm times required to be compliant, but nowhere does the code state this can't be done. Backup battery sized correctly and reversing relay, there is nothing that makes them non-compliant for any code out there, barring a local code that modifies the IRC.

DELInstallations said:

Not true.
 
The AHJ has the final decision (however the insurer also typically has a stake). I have yet to meet an AHJ that will not allow the retrofit replacement of LV detectors that supersede or replace the existing HV detectors provided the same design criteria is met. Nowhere does code forbid the installation of LV smoke detectors in the place of HV smoke alarms (note the verbiage). The only time I've seen them NOT allowed is when the AHJ dictated their operation to meet the IRC (which documentation was provided) and then the subsequent argument that the alarm panel can be powered down (installed a transformer hardwired to breaker, cited the same is true with 120V units unless connected with a branch circuit).
 
The biggest item is the consideration of tandem ring and standby and alarm times required to be compliant, but nowhere does the code state this can't be done. Backup battery sized correctly and reversing relay, there is nothing that makes them non-compliant for any code out there, barring a local code that modifies the IRC.

Click to expand...

Rules vary widely by state and local government. Any blind statement being made to cover ALL areas is always likely to be wrong in many places.  Many of the most recent codes are requiring the backup battery in smoke alarms to have a 10 year battery, be clearly marked with an expiration date, and individually have a "hush" feature.  Where can I get one of these 10-year ELK batteries?  Or the "hush" feature?  Check your local regulations and with your local inspectors for the most relevant and up-to-date info.  Don't guess with fire safety.

I left the old alarm combo automation panel in old house and it was removed over time (1-2 years). 

ano said:

Rules vary widely by state and local government. Any blind statement being made to cover ALL areas is always likely to be wrong in many places.  Many of the most recent codes are requiring the backup battery in smoke alarms to have a 10 year battery, be clearly marked with an expiration date, and individually have a "hush" feature.  Where can I get one of these 10-year ELK batteries?  Or the "hush" feature?  Check your local regulations and with your local inspectors for the most relevant and up-to-date info.  Don't guess with fire safety.

Click to expand...

Ano,

You're missing the facts as a hobbyist vs. someone who deals with municipalities and AHJ's daily in the trade. You're citing non-related information relevant only to smoke alarms and not system based smoke detectors and host systems. Smoke alarms may be required to have a hush button or 10 year battery, however no code mandates smoke detectors and system based alarm systems to require such as this functionality is native in their operation (and governed by the NFPA). There is a HUGE difference in what a smoke alarm is and what a smoke detector is and their functionality, listing and operation, which is generally lost on the consumer or hobbyist.
 
You need to consider UL 217 vs UL 268 and UL 864, which clearly define what and how....In fact, IBC 2015 explicitly allows “Smoke detectors listed in accordance with UL 268 and provided as part of the building fire alarm system shall be an acceptable alternative…” (IBC 2015 – Section 907.2.11.7)
 
Smoke alarms are not intended (or generally listed) to be connected to a listed FACP as an IDC, so that rules that scenario out. Nowhere does the IRC, NFPA or NEC forbid the installation or like replacement of smoke alarms with smoke detectors if the original system design criteria is met with the like system (tandem ring, backup battery standby time, power source).Whether or not the end user decides to install the system in a non-compliant manner, that's an issue. 
 
The IRC is what state laws are drafted from in 99% of the municipalities in the US (or a combination of the IRC/IBC and UCC). Barring a unique ammendment to the IRC within state statutes within your area (usually the IRC is made tighter or the local custom requires something completely different....like Pete in Chicagoland and conduit for all electrical). The most recent change that would be applicable to residential fire alarm would be the removal of the verbiage (ambiguity) that formerly required an annual test/inspect on residential fire.
 
When in doubt, yes, contact the AHJ, but nowhere within code does it forbid the installation of one system over another or mandate one system can't supercede or replace the other.....
 
If you'd like to discuss code, definitions and the like, send me a message and I'll set aside some time to walk you through all the fine details and sections with what is commonly and incorrectly cited by some AHJ's as non-compliance and what the methods are necessary to make the installation compliant.