Ampacity - Fire Alarm

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Pat M

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I have a question about derating factors for ampacity calculations (specifically for fire alarm systems)

In NEC, (2005 version) 760.23 states that we are to determine "conductor ampacity without applying the derating factors of 310.15 to the ampacity calculation." Does this mean that the "Correction Factors" for different temperatures in Table 310.16 (Allowable Ampacities of Insulated Conductors Rated 0 Through 2000 Volts, 60 degress C through 90 degress C) are not to be applied? I ask this because 310.16 through 310.19 is referenced in 310.15.

Thanks,

Pat
 
I'm not sure if they intended the ambient temp. adj. factors to be applied.

But do you really have a Non-power-limited fire alarm, and are you really using single conductors in conduit for the wiring to the devices? And do you really need 15 amps or more? If not, it doesn't seem like the derating would mater.

I've never been sure if a fire alarm was power limited or not, but from another recent post (I just read about 5 min ago), I got the impression that all the modern fire alarms are power limited.

Also, the 760 language you mention has changed a lot in the 2008 code. They now refer to table 402 for smaller conductors.
 
Thanks for the replies. Honestly, the reason I am looking for an answer on this is because I am taking a state exam on fire alarm systems next Tuesday and ampacity (i believe) is going to be a part of the test.
 
non power limited alarms I've run into were solely antique line voltage alarms on antique navy bases
 
In Just about every fire alarm panel on the market today, there are "Non_Power Limited" circuits. You'll find that most "Power boosters" used to power audible circuits, are NPL.

Typically, the 24 VDC output from a fire panel is NPL. What is very often PL are NAC (Notification Appliance Circuit), IDC (Initiating Device Circuits), and SLC (Signaling Lince Circuits).

With respect to 760.23 (2005 edition), or 760.43 (2008 Edition), the "...without..." using the derating factors of 310.15 (2005 and 2008 editions) only apply to 14 AWG circuits. Most fire alarm devices are rated to use larger than 14 AWG wire.

Now that I've looked into this, I'm going to have to read up on 310.15 as I currently have such a situation. In most cases the wire is 8 AWG, however in some, it's 4. I'm currently trying to find a way to Buss this larger wire once inside a remote junction boxes, down to smaller wires as the Class I, Div 2 fuse holders I'm using can only handle 6 AWG and smaller wires. Our problem isn't power, it's voltage drop.

Regards,
Dan
 
Ok...Ya got me on that one. That's why I wrote "In just about every fire panel..." rather than "In every fire panel...":D.

We don't market the FireLite brand but do market their sister company, Notifier, Siemens, a few others, and a European brand. Both Notifiers' and Siemens' are also power limited, however we normally use an "AlarmSaf" brand because we often need more Amps, than they offer.

From a "...I'm taking a test..." stand point understanding the code is important. The mistake we often see is the mixing of PL and NPL circuits in either the same conduit (PL not installed as NPL), the same junction box without separation, or on terminals where there is insufficient separation from terminals were PL wires (i.e. 300 v insulation) are terminated. I just wanted to caution others not to take for granted that all systems use PL circuits.

I'll shut up now...:D
 
DM2-Inc said:
Ok...Ya got me on that one. That's why I wrote "In just about every fire panel..." rather than "In every fire panel...":D.

We don't market the FireLite brand but do market their sister company, Notifier, Siemens, a few others, and a European brand. Both Notifiers' and Siemens' are also power limited, however we normally use an "AlarmSaf" brand because we often need more Amps, than they offer.

From a "...I'm taking a test..." stand point understanding the code is important. The mistake we often see is the mixing of PL and NPL circuits in either the same conduit (PL not installed as NPL), the same junction box without separation, or on terminals where there is insufficient separation from terminals were PL wires (i.e. 300 v insulation) are terminated. I just wanted to caution others not to take for granted that all systems use PL circuits.

I'll shut up now...:D
Click to expand...

AlarmSaf doesn't make NAC panels. Just linear power supplies. Their products are not UL 464, 864 Listed either. IMHO Their siren/strobes are really flimsy. I have found their products to be disappointing.

I would swear on a stack of NFPA 72's that no one manufactures NPL FACP anymore. If they do I would rather not think about how ridiculous that is.

I'm sure there are a few NPL fire alarms still in use, but no one should not work on one. I would inform the customer they need to drop some $$$$$.$$
 
Pat M said:
Thanks for the replies. Honestly, the reason I am looking for an answer on this is because I am taking a state exam on fire alarm systems next Tuesday and ampacity (i believe) is going to be a part of the test.
Click to expand...

Sounds like their test could use some updating. There was another thread about 125 Hz and all the other frequencies used for power back in the 1800's. Maybe you should bone up on that too :D
 
nhfire77 said:
AlarmSaf doesn't make NAC panels. Just linear power supplies. Their products are not UL 464, 864 Listed either. IMHO Their siren/strobes are really flimsy. I have found their products to be disappointing.
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AlarmSaf does make "...NAC Panels." as is evident by http://www.alarmsaf.com/nac.html
nhfire77 said:
I would swear on a stack of NFPA 72's that no one manufactures NPL FACP anymore. If they do I would rather not think about how ridiculous that is.
Click to expand...
I don't dispute that much of what's on the market today is PL. But there are products, fresh on the market, that have NPL circuits. As an example the 24 VDC output of a Siemens XLS panel power supply is NPL and this equipment hasn't been out for ever. As I stated earlier, I wasn't trying to dispute the statement that they no longer exist, but rather advise that they do and there are issues surrounding mixing PL and NPL circuits (which has nothing to do with the original post)

nhfire77 said:
I'm sure there are a few NPL fire alarms still in use, but no one should not work on one. I would inform the customer they need to drop some $$$$$.$$
Click to expand...
I don't want to detract any further from the focus of this thread, so I'll simply agree that most systems use PL circuits. For people taking tests, one thing that often occurs is that they'll take the wrong edition of the referenced standards with them (assuming Open book) and provide the wrong answer to the test, not necessarily the wrong answer. I noted that the reference in the original post was to a section that had changed in the 2008 edition of the code. The city of Houston is on an older section of the code as well so from a questions and answers approach, it's worth verifying the year of the referenced standard in the test.
 
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DM2-Inc said:
I don't dispute that much of what's on the market today is PL. But there are products, fresh on the market, that have NPL circuits. As an example the 24 VDC output of a Siemens XLS panel power supply is NPL and this equipment hasn't been out for ever. As I stated earlier, I wasn't trying to dispute the statement that they no longer exist, but rather advise that they do and there are issues surrounding mixing PL and NPL circuits (which has nothing to do with the original post)
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The Siemens XLS firefinder 24 VDC output that is NPL is for internal power only, its not an aux output for devices.

You stated previous to my post that:

"Typically, the 24 VDC output from a fire panel is NPL."

That is untrue. Typically it is PL. Siemens is one of the only one like that.
 
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