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Ratings of Electrical rooms
September 12, 2019
7:49 am
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tower_26@hotmail.com
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NEC 450.42 - Walls and Roofs of transformer vaults need to be fire rated of 3-hours.  Exception: if fitted with sprinkler system, the rating can be dropped to 1-hour.

July 18, 2006
3:22 pm
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dr. j
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Yep. 2002 version:

8.14.10 Electrical Equipment.
8.14.10.1 Unless the requirements of 8.14.10.3 are met, sprinkler protection shall be required in electrical equipment rooms.
8.14.10.2 Hoods or shields installed to protect important electrical equipment from sprinkler discharge shall be noncombustible.
8.14.10.3 Sprinklers shall not be required in electrical equipment rooms where all of the following conditions are met:
(1) The room is dedicated to electrical equipment only.
(2) Only dry-type electrical equipment is used.
(3) Equipment is installed in a 2-hour fire-rated enclosure including protection for penetrations.
(4) No combustible storage is permitted to be stored in the room.

July 18, 2006
10:14 am
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inspectagator
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"unless enclosed in 2 hour fire resistive construction, per NFPA 13. We run across many owners and/or AHJ''s that prefer the rating to the sprinklers."

So is this in NFPA 13?

July 17, 2006
4:58 pm
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dr. j
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[QUOTE] NEC 450.21(B) requires that dry-type transformers over 112 1/2 kVA be installed in a transformer room of fire-resistant construction. [/QUOTE]Please forgive the Mechanical Engineer intrusion, but we end up dealing with the dampers.

The electrical engineers in our office tell me that most of the transformers they specify meet the exceptions to the quoted section, so in reality almost no electrical rooms need fire ratings (by code, locally adopted amendments notwithstanding).

However, there is another situation where an "electrical room" may be rated - with or without transformers. In a fully sprinklered building, the electrical room needs to be sprinklered also, unless enclosed in 2 hour fire resistive construction, per NFPA 13. We run across many owners and/or AHJ''s that prefer the rating to the sprinklers.

July 17, 2006
3:23 pm
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paul curry
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In covered malls (IBC 402.4.6) they require 1 hr rating if they open into exits/corridors.

Our jurisdiction requires 1 hr. on all electrical rooms unless disconnect is located outside of room (outside of building).

July 17, 2006
11:52 am
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bpholland
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[QUOTE]In general, service equipment rooms (non-trans) I dont think have a requirement? [/QUOTE]Not per the NEC.

July 17, 2006
11:48 am
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inspectagator
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I recall that, thank you, ...In general, service equipment rooms (non-trans) I dont think have a requirement?

July 17, 2006
10:55 am
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raider1
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NEC 450.21(B) requires that dry-type transformers over 112 1/2 kVA be installed in a transformer room of fire-resistant construction. That section goes on to state that fire-resistant construction means a construction having a minimum fire rating of 1 hour.

To the best of my knowledge that is the only requirement in the NEC for a 1 hour fire-rated room.

Chris