Linear Heat Detectors 1

[EEJaime]

Hello all,

This is both a code question as well as a technology question. Recently, I started doing some work for another of our offices where I noticed a fundamentally different approach to Fire Alarm System design.

This is for public schools, K-12 in California. We are required to install a fully automatic fire alarm system.

Many buildings will have dropped ceilings which will result in smoke detector coverage on the ceiling and heat detector coverage above the ceilings. Still basic stuff. Where I saw a difference is when I noted that this office was specifying the ceiling space heat detectors as "Linear Heat Detectors". These are lengths of multiple conductor cables of known resistance which initiate an alarm when temperatures exceed their temperature rating. Much of this is very similar to spot type detectors and the provisions of NFPA 72 are still referenced. For the system specified, "

http://www.protectowire.com"

the installation seems to be a lot more complex and hence costly than using spot type detectors.

I am not sure we are using this in its intended application.

It seems that once the system goes into alarm the "sensor" is permanently damaged and must be replaced.

It seems a complex and first cost intensive system.

And appears to be a maintenance and servicing nightmare.

Does anyone have experience with these systems? Another manufacturer is "FARENHYT", (at least the manufacturer's used the same marketing/branding company-LAME NAME INC).

Do any of you AHJ types have any issues with these systems, especially the detector wire laying directly on top of the ceiling grid and tiles? Is this code compliant? There appears to be no codes directly speaking to linear heat detectors. This even according to the Installation Guide on the Protectowire site.

Look forward to any information available.

Regards,
EEJaime

 

[stookeyfpe]

It's not that hard Jaime. The section states ..the AHJ... When I was an AHJ I had no problem amending the code to eliminate nebulous provisions such as Section 5.5.2.2. In your particular case, you haven't even asked what the number one cause of fire in Group E occupancies is or the highest probability location where ignition occurs. Answer: Arson, in bathrooms based on NFPA FIDO data.

So if the number one cause of fire is frustrated kids wanting out of class or are retaliating and it occurs in a bathroom, which has an extremely low fuel load, how does anyone justify heat detection in a Type II building with a noncombustible lay-in ceiling? I can't based on the loss data.

In my career I sat on two NFPA committees and worked hard to avoid this kind of broad brush, open door language. Nothing against the fire alarm providers, but language like this is nothing more than a full employment act.

Now that the 06 IBC requires automatic sprinklers in Group E occupancies with a fire area > 12K square feet, most of these fire alarm issues will go away. Unfortunately, its going to become really ugly and expensive in the 2012 IFC with voice communication systems in Group E occupancies.

That's another story for another time.

Finally, I am not a fan of the GOD definition. I doubt if many of you have ever assumed the responsibility of a fire code official so you don't know what goes on the decision making process. Second, the permit is approved only when the design professional justifies compliance with the adopted codes and standards. From this discussion I'm learning that some jurisdictions are complicated and may go overboard - that's a fact of life (see the IRS Tax Code). Just be careful about calling kettles black. I can tell you some of my stories about PEs and AIAs who were sanctioned because of their gross errors and omissions in my jurisdictions.

 

[cdafd]

EEJaime

I guess you need to look at the cost of the protectowire type system versus the cost of regular heats???

seems like the maintenance is going to be about the same problem

good thing is hopefuly addessable, so alittle easier to find which device in alarm

 

[EEJaime]

cdafd,
That is exactly the case, but the major difference I see is that with a standard spot type, I have one or two detectors, in known locations. I pop a couple of tiles, get the ladder up, climb, unscrew, test or replace. Done. with this linear type, I have to take virtually the entire ceiling down. Figure out where the wire is supported, and not just replace the melted portion, I have to take the entire thing down and replace it. Whether it is attached to the structure, hangers, wire clips, whatever. Above lighting, ductwork, conduit, etc.... Seems much more labor intensive.
EEJaime

 

[pipesnpumps]

Well this thread has digressed. EEJaime, I agree it will be hard to get the AHJ to buy-in. If you ensure everything in the above ceiling space is limited combustible AND has a smoke developed index of <50, AND they are intelligent enough and confident enough to buy-in to that equivalency, that may be the only hope.

Stookey, I wouldn't take offense to be called a Giver Of Determination. For me it is a joy and a privilege to serve the tax payer, and I could care less what phrases people come up with. I heard that phrase from another AHJ and thought it was funny. Even I have to admit, not all AHJ's are fair and reasonable, just as not all PE's know their elbow from a hole in the ground.

Tonight I will sleep well again, knowing I caught an inferior design today. Multiple-row pallet flow-through racks designed as double row. no hydrant flow data. no fire pump. 24 ft high warehouse required to be designed for class IV commodities. Yep, today I got to play GOD, again, and maybe one day in the future will have kept a bad day from being a tragedy. Fire protection is such a great career field, I love that it is much more prescriptive and "black and white" than other engineering fields.

 

[EEJaime]

pipesnpumps,

You are right, this thread has blasted off tangentially, I will give it a rest. It is still good to know that there are those professionals out there who bring that old school sense of responsibility and duty to their jobs. Thank you. Have a good night's sleep and a good weekend.

Regards,
EEJaime