NFPA 72 Permits Internet Monitoring

Our nation’s infrastructure is quickly moving from copper wires to a fiber optics and wireless communication backbone. If your prospect/customer uses a full-time Internet service, or uses an existing full-time data network connection such as LAN or WAN, then IP fire alarm system monitoring is possible.

Selling the concept
AHJs aren’t required or expected to be electronic engineers or certified information technology (IT) technicians. In other words, they don’t have to understand how a system works in order to approve an installation using this new type of equipment. IP monitoring doesn’t have its own section heading in the 2007 edition of NFPA 72; instead, it is generically addressed in Section 8.6.4, “Other Transmission Technologies.” This section stipulates that the AHJ must allow IP monitoring when it is in “conformance” with this section: “ Conformance. Other transmission technologies shall include those transmission technologies that operate on principles different from specific transmission technologies covered by this chapter and shall be permitted to be installed if they conform to the requirements of this subsection and to all other applicable requirements of this Code.” Conformance simply entails mounting, wiring and programming the equipment in strict accordance with the manufacturer’s printed instructions packed with the equipment.

DACT vs. IP at the central station
The DACT will auto-transmit a supervised daily test signal to test the communication signal capability and also test the communication path simultaneously. This means the DACT will only have to work once during a 15-minute reporting window for the remote station to see that all’s well. The central station must also receive an IP communicator’s test signal once every 24 hours but it monitors the network path at least once every 300 seconds, which is 288 times a day, not the once-a-day used by a DACT. Some receivers can even perform this path test more often, but this may cause another problem. Increased testing of the path increases the odds that the remote station will experience a latency/network delay issue during one, if not several, of these hundreds of “keep alive” signals expected each day. Currently, NFPA 72 doesn’t allow the instant switchover to a GRPS path to stand in for a missed signal from the wired IP network path.

DACT vs. IP at the protected premises
When using a DACT as the communication method, section allows up to four minutes to elapse before the loss of any DACT communication channel (usually two phone lines) is annunciated at the protected premises. This means the customer usually isn’t bothered with trouble signals from the DACT during routine telco maintenance, storms and other momentary phone service outages. Section “Transmission Channels” specifically allows IP monitoring to be used as a backup reporting method for a DACT, but the communication path failure timer is still four minutes. However, for some reason, when the IP network is used as the only communication method, the failure of any communication path must be indicated at the remote station within five minutes. Therefore, to reduce the number of potential trouble signals from once every four minutes to every five minutes, you could simply use the DACT as the optional backup to the IP. Obviously, since this is a relatively new type of reporting method, the codes have yet to catch up with the technology, and as seen in this example, don’t always make the most sense. Remember that IP monitoring for fire alarm systems is allowed by the National Fire Alarm Code as a backup to a DACT under A(7) or as a standalone method if complying with Section 8.6.4.