2 Hour Rated Feeders 1

[horsegoer]

Hello. Engineer is asking for several EM feeders to be 2 hour rated. Would the following s deem EMT and THHN two hour rated?

1. The full length run in a 2 hour rated shaft and room?
2. Run in fully sprinkler area?


Also if the feeder is run exposed outdoor does that alleviate the 2 hour rating?

Thank you.

 

[waross]

Do you mean a 2 hour fire rating?
We ran across this years ago when an architect wanted fire rated drop in fixtures.
After a lot of research, the general answer was that electrical equipment installed according to the code was inherently adequate for the location.
If you are looking for an ampacity greater than the continuous rated ampacity, that is an electrical code issue.
The time/current profile of your load must be acceptable to the appropriate code rules.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[horsegoer]

Sorry yes 2 hour fire rated. So what about 1 and 2? Suffice? Trying to get around using MI, or Vitalink.

 

[waross]

Fire ratings generally apply to penetrations in a fire rated surface.
In our instance we were asked to verify that 2' x 4' drop in fixtures would have an equal fire rating to the drop ceiling in which they were installed.
In your case it looks as if the engineer wants the emergency feeders to withstand an external fire for 2 hours.
Mineral Insulated cable is a good solution.
It will remain in service until the heat melts the copper.
The terminations will probably fail at a much lower temperature.
Any suggestions as to an alternate solution may be best addressed to the engineer.
This is not to discourage the posting here of possible solutions to be submitted to the engineer.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[horsegoer]

So if EMT were run as I listed above would it be considers 2 hour fire rated protected? Thanks

 

[jmbelectrical]

Assuming that you are based in the United States, NEC 700.10 requires 2-hour fire protection for emergency feeders serving high-rises or assembly occupancies exceeding 1,000 people. The following strategies are permitted:

1. Installation of feeders within fully-sprinkled spaces
2. Use of UL2196-compliant, 2-hour feeder conductors
3. Use of 2-hour fire barrier material (Fire-rated conduit wrap)
4. Routing feeders within a 2-hour assembly and separated from all other conductors
5. Encasement of feeders within 2 inches of concrete

A couple of things to keep in mind:

1. NFPA 13 defines "fully sprinkled" as including fire sprinkler coverage above suspended ceiling systems. Your project probably does not meet the definition of a fully-sprinkled building. I say this because it's been my experience that most do not.
2. If you route emergency feeders within a 2-hour assembly/chase, it must be free of feeders derived from any other system.
3. Fire-rated conduit wrap is costly and susceptible to damage, so I would discourage you from using it.
4. There is a misconception that mineral-insulated (MI) cable is your only choice when it comes to UL2196-compliant conductors. At one time this was true, but it is no longer the case. Several manufacturers now offer UL2196-compliant, 2-hour, fire-resistive conductors that are somewhat similar to THHN. When routed within metallic conduit, the conduit typically cannot contain zinc. (Verify with the manufacturer.)

The NEC section referenced above does state that 2-hour fire protection is required for feeders routed *inside* of the building, so I suppose that you could circumvent these requirements by remaining outside of the building. I would encourage you to confirm this with the engineer, the AHJ, or both.

 

[horsegoer]

JMB thanks a lot. BTW is there an option to quote a message here? Forums usually have the selection but I don't see it.

A few questions.

Say you have the feeder run horizontally on one floor and that entire floor is fully sprinkled and none of the others floors are, would that that satisfy item 1 of your message?
If a feeder that is required to be 2 hour fire rated/protection run outside( exposed to the outdoors) does it need 2 hour fire protection?

 

[jmbelectrical]

horsegoer,

You raise a great question. The NEC states that one (1) fire protection strategy is to be used, but it doesn't necessarily prohibit multiple strategies from being used, if that makes sense. My opinion is that the use of multiple fire protection strategies for the same facility or the same set of feeders is perfectly appropriate and satisfies the intent of the Code. I would strongly encourage you to verify this with the engineer and/or AHJ.

The NEC indicates that these fire protection requirements apply to emergency feeders *within* high-rises and *within* assembly occupancies exceeding 1,000 persons. I would argue that these requirements would not apply to feeders located outdoors. Again - verify this with the engineer and/or AHJ.