In regard to “Advances Help Eclipse Fire Fatalities” (see SSI‘s annual Fire Market Report, May 2010), as a contractor that has participated in four recent projects utilizing mass notification systems (MNS) I find one disturbing fact: COST.
Another disturbing fact is if NFPA is partnering with DoD, then heaven help the private sector. DoD is the biggest money waste wagon when it comes to development of military programs. The military branch of government has historically been shown to waste vast sums of financial resources of government.
After being in this business for more than 20 years, it can be summed up one way: A well maintained and tested standard fire alarm system suffices for evacuation and safety. Many good systems operate for 25 years or more.
Adding MNS and the resultant cost deters development. Example: DoD requires a separate strobe for MNS activation, and a clear fire strobe for fire situations. How ridiculous is that?! It begs the question, one speaker, one strobe, why not?
NFPA needs to get on a five- or 10-year cycle because keeping up with codes now is an impossible task. More and more local governments will reject the constant changes and opt for longer regulatory enactment periods, due to cost.
And now NFPA is commingling with DoD Unified Facilities Criteria (UFC) – not good. The public is understandably becoming more skeptical each day.
Dan Dysinger Jr.
Via E-mail
Relay Article Trips Up
June 2010’s “Fire Side Chat” (“Relays Play Critical Role in Subsystem Integration”) by Al Colombo has an error. On page 40 you have a diagram of Form A, B and C relays with the note: “Most of the time relay nomenclature assumes the relay is powered.” This is wrong.
All relay nomenclature assumes the relay is unpowered. I’ve been in the business for almost 30 years, and worked in R&D in relay development for Honeywell, so I know this to be true. My tech school teachers used to say, “A normally open relay is open when it is laying on a table, not wired to anything.” That has stuck with me.
Keep up the interesting articles!
Patrick Griffith,
Business Relationship Mgr.
Pro-Tec Design
Minneapolis
AL COLOMBO REPLIES: The caption should have said that it’s possible to run across a relay labeled as having an energized coil. The best way to assure the electrical state of relay contacts is to test them with an Ohm meter.
Originally, relay nomenclature assumed the relay coil was energized. In subsequent years, relay manufacturers have changed this to assume a de-energized coil, but you will still find relays out there that have “with coil energized” or the equivalent on the label or in the specifications.
To address another reader’s concern regarding switch contacts, switch nomenclature originally assumed the switch mechanism to be in its natural, unengaged position. In the early days, you had to buy a NO (normally open) switch to derive closed contacts with a closed door. Edwards System Technology (EST) was one of the last holdouts to label its roller ball switches in this manner.
In subsequent years, switch/contact manufacturers have changed this to specifically address the security industry’s need for labeling with regard to application. Thus, now when you buy a NC (normally closed) switch, it’s assumed that the door is engaged, which means the door is in its closed position.
