With the latest edition of NFPA 72 recently published, it makes sense to kick off the new year with new rules for fire alarm systems. Sometimes there will be new rules that we have to learn (as with Class N circuits); other times it will just be a new way of looking at an existing rule (sleeping areas).
Just remember, every year, our new year’s resolution should be to strive to provide the best life-safety coverage for the money spent. Happy 2016 loyal readers!
New SLC Class
A new class of signaling line circuit (SLC) has been added to the 2016 edition of NFPA 72, called Class N (think “N” for “Network”). Any new, optional Class N pathways must provide the following features:
1. Class N pathways must include two or more pathways where operational capability of the primary pathway and a redundant pathway to each device is verified through end-to-end communication. Exception: When only one device is served, then only one pathway shall be required.
2. A loss of intended communications between endpoints will be annunciated as a trouble signal.
3. A single open, ground, short or combination of faults on one pathway cannot affect any other pathway.
4. Conditions that affect the operation of the primary pathway(s) and redundant pathway(s) will be annunciated as trouble signals whenever the system’s minimal operational requirements cannot be met.
5. Primary and redundant pathways are not permitted to share traffic over the same physical segment of wiring.
The use and Level of Class N conductors will be determined through a risk analysis process involving the alarm system’s owner and those who will be using the emergency system. When the owner’s Network wiring pathway — or private Ethernet circuit — is determined to need a higher level of security to separate maintenance and other data from the life-safety data, it will be assigned a “Shared Pathway Level.”
The permitted sharing levels defined in NFPA 72 are Level I, Level II and Level III. Level 1 pathways is not required to segregate life safety data from non-life safety data, but must prioritize all life safety data over non-life safety data. Level 2 pathways must segregate all life safety data from non-life safety data. Level 3, the highest level pathway, must only connect equipment that is dedicated to the life safety system. Devices connected to the owner’s network having non-critical functions are excluded from the requirements of Class N circuits.
Classification of Bedrooms
We should all be familiar with the specific requirements for audible and visual notification appliances in bedrooms and sleeping areas as long-standing provisions of NFPA 72. Most AHJs are savvy enough to recognize that new homes advertised as having rooms called a “den” or “study” are really just another name for an extra bedroom if that room contains a built-in closet.
The A/V requirements will be expected to pass final inspections based on this “den” actually being another sleeping area; however, have you ever considered how apartment and some condo occupants similarly use their living rooms as a guest or even as a full-time bedroom? Because of this, you should provide notification to treat these living rooms as the sleeping areas that they often are.
Additionally, if the apartment or condo is intended to be occupied by those stating that they are hearing impaired, then in addition to the 177 and/or 110 candela strobe lights, 520 Hz audible appliances will also need to be provided.
The good news is, in these same spaces, you may be able to provide the required automatic smoke and CO detection for the living room (sometimes bedroom) at no additional cost. If you measure 21 feet from the edge of the farthest bedroom door toward the “living room” and mount this one detector already required to be located “outside each sleeping area,” then both requirements — one outside each sleeping area and one inside each sleeping/living area — will have been met.
Greg Kessinger is SD&I’s fire alarm and codes expert and a regular contributor. Email him your fire & life safety questions at [email protected].
