Fire alarm system with adressable smokes

[lu302dan]

I am working on installing a new fire alarm system for a new shopping mall. We are installing the fire alarm system for the entire mall. All of the system is being installed in EMT. The contractor is using different types of cables and conductors in the same conduit. I know this is permitted as long as it is part of the same system, but the application does not seem right to me.

The general foreman on the job is using #16 THHN conductors for the strobe and smoke circuits, Type FPE twisted-shielded cable for the horn circuit, and a 2-pair 16 twisted cable that does not have an outer jacket for the data loop circuit that adresses the smoke detectors.

My question is why is why is he using a twisted-shielded pair FPE cable for the horn circuit?

Shouldnt the data circuit be the twisted-shielded cable?

As it is now, this data cable is being ran in the same conduit as two other current carrying circuits, the strobe circuit which is THHN wire, and the horn circuit which is twisted-shielded cable.

I think someone is making a big mistake here and the adressible circuit may not function properly?

I'm no expert at fire alarm systems, but this seems wrong to me?

 

[iwire]

Re: Fire alarm system with adressable smokes

lu302dan, This sounds wrong to me also.

Each panel manufacture has there own requirements that must be followed.

I have done some addressable systems that do not require shielded cable on the initiating circuit, some say the use of conduit is the shield.

Most panels I have worked on specify that the initiating loop be kept separate from the notification circuits.

Bottom line is before the wiring goes in you need specs from the panel manufacturer and you must follow them.

You can get all kinds of intermittent troubles if you do not follow the specs, and tech support will be non existent once they see the field wiring was done improperly.

16 AWG sounds small for horn strobes in a mall due to the length of the runs, we mostly use 14 AWG or 12 AWG for notification circuits.

The panel specs will show wire size required for different run lengths.

Also they should give you a total permitted resistance figure.

[ July 27, 2003, 09:29 AM: Message edited by: iwire ]

 

[hurk27]

Re: Fire alarm system with adressable smokes

Keep in mind that twisted pair wire is self shielding as this is why we can run cat rated phone and data cable in buildings without conduit or any shield.
Every twist causes the signal to be 180 deg out of phase which causes a self cancelation of the interferance.

 

[iwire]

Re: Fire alarm system with adressable smokes

hurk 27 I understand what you are saying but I am not sure if that is always correct.

Maybe someone here or yourself could make this more clear to me.

Take the case of a microphone input for a PA system, if it is not shielded along with being twisted you will have hum and other interference.

Confused

Bob

 

[hbiss]

Re: Fire alarm system with adressable smokes

Well, it could be that the shield on the cable for the horn circuit is there it keep the interference in. Some horns have an interrupter that causes a great deal of interference. A shield can work both ways you know.

Other than speculating though, why don't you get a copy of the manual for the fire panel and see what the specs are for yourself? That would be the first place I would look since each system can be different and we have no idea which one you are talking about. Like you admit, you are no expert and we don't know the specifics. Nothing you said sounds that outlandish and the instructions to run this wire must have come from someplace, hopefully from someone who has done this a few times before. The only way I would make an issue of this is with a copy of the specs in my hand.

 

[lu302dan]

Re: Fire alarm system with adressable smokes

I do believe that we will be installing the internal guts to these FRACP's this week. I will look for the specs, but I bet that they have been pulled out of the panels and filed in the general foreman's file folder. I do know that we began wiring the system before the panel's were even ordered! Hopefully, the specs were included in the bid package and the project manager passed it on to the general foreman. I'm just trying to cover my *** here. I dont want my head to roll because of someone elses mistake. Not to mention the lawsuits that will be filed from the mall owner...Thanks for all of your reply's..Dan

 

[ron]

Re: Fire alarm system with adressable smokes

Were there any shop drawing for the project? They will indicate the proper cable.

 

[iwire]

Re: Fire alarm system with adressable smokes

Dan if you can get the panel model number and manufacture you can call them for this sort of info or try their web site.

Many times the first prints I get in the field are only good for device locations.

The prints might show 4 - 14 AWG THHN in 3/4" EMT but by the time the customer has do "value engineering" wire types can change as we will substitute manufactures and wiring methods (MC) as needed to get the price down.

About the time the equipment arrives I get the "real" drawings from the equipment supplier.

 

[roger]

Re: Fire alarm system with adressable smokes

Who is the FA manufacturer; Simplex, Edwards, Notifier, Pyrotronics, or whoever? They will certify the system, (NFPA 72 Form 13 I think) let them give you their drawings and specs, (shop drawings) then have them visit the site to critique your work, this is included in their fee.

Roger