Fire Rating Assembly - PVC Conduit (01/03/2001)
Passing PVC Through A Fire Rated Assembly
Mike, I'd like to run my grounding electrode conductor in PVC, but I need to go through a fire rated concrete deck from floor to floor.
Q1. Is it legal to run PVC through a fire rated floor if it is fire caulked?
Mike Holt's Answer: Yes. Section 300-21 states that electrical installations in hollow spaces, vertical shafts, and ventilation or air-handling ducts shall be made so that the possible spread of fire or products of combustion will not be substantially increased. Openings around electrical penetrations through fire-resistant-rated walls, partitions, floors, or ceilings shall be firestopped using approved methods to maintain the fire resistance rating.
FPN: Directories of electrical construction materials published by qualified testing laboratories contain many listing installation restrictions necessary to maintain the fire-resistive rating of assemblies where penetrations or openings are made. An example is the 24-in. (610-mm) minimum horizontal separation that usually applies between boxes on opposite sides of the wall. Assistance in complying with Section 300-21 can be found in these directories and product listings.
Mike Holt's Comment: My answer really doesn't solve this person's problem. Since this is a fire rating issue (I'm not an expert on this subject) I need someone to explain exactly how PVC can be installed through a fire rated assembly. Let's assume the PVC is 1" and the fire assembly is a concrete floor between occupancies. How can the installation be installed so that it meets the NEC requirements and it's cost effective?
Q2. If not can I change to EMT the raceway to EMC and pass it through the floor than back to PVC without having to bond the piece of EMT?
Mike Holt's Answer: No. Section 250-64(e) States that the metal enclosures for grounding electrode conductors shall be electrically continuous from the point of attachment to cabinets or equipment to the grounding electrode, and shall be securely fastened to the ground clamp or fitting. Metal enclosures that are not physically continuous from cabinet or equipment to the grounding electrode shall be made electrically continuous by bonding each end to the grounding conductor.
Response No. 1
We are not electrical engineers but we understand that NEC does not prescribe method of firestopping and refer to the building code requirements. The model building codes prescribe firestopping tests as per ASTM E814 (UL 1479) test protocol. Manufacturers of firestopping sealants have listings (test designs that have been tested and witnessed by 3rd party testing agency), which would permit the firestopping of specific electrical penetration. The rationales of these tests are to ensure the rated building assemblies being penetrated continue to perform as its intended purpose. The assembly is exposed to a standard time-temp and does not address specific electrical fires. Hope this helps.
From: Ed Lin
Response No. 2
I was copied on e-mail from David Penasa of BPLW Architecture and you, concerning firestopping. If you ever need assistance with firestopping electrical penetrations in rated assemblies, please contact our Engineering Dept mailto:email@example.com or me.
Talk to a manufacturer. I just heard a great presentation at my office given by Alan Powell firstname.lastname@example.org of Passive Fire Protection Partners http://www.firestop.com. I'm sure he would be glad to answer your question in great detail.
David A. Penasa, PE
Response No. 3
Before putting something through a fire rated assembly, it is best to:
1) Refer to the plans to determine exactly what type of assembly the architect has designed. This will/should be noted by a design number (for example W-L-1011, or UL 243) and then,
2) Cross-reference it to the UL Fire Resistance Directory, Vol 2. This is the only way you can be sure what types of materials have been tested with what system. If you do it this way you will meet every requirement placed on you!
Response No. 4
There is an approved method: an entumensent sealing kit, (I may have misspelled the word) it expands when heated (as in a fire) and crushes the hot PVC tightly. It is made specifically for PVC pipe and is an UL listed assembly.
Earl C. Dean
Response No. 5
I think the solution is relatively simple. The PVC conduit does not need to be continuous, so
the installer can stop short a couple of inches of the concrete wall/deck on both sides, pass the
grounding conductor through the hole and filling the hole with fire retardant caulk, or fitting. Potential
manufacturer: ROX @ http://www.roxtec.com/.
There are others with UL approved caulking material.
Laszlo Z Weress
Response No. 6
The answers given were correct. The type fire construction should be detailed on the plans, by
UL number (or other design number) and construction details. The people who sell fire caulk will be
glad to provide you an approved method to seal the penetration, if you buy from them especially so.
You need to know:
- The required time rating of the assembly. 1 hour/2 hour/3 hour/4 hour
- The construction details and number of the wall or floor assembly.
- The penetration. Metal conduit is different from PVC. 4" is different from 1/2" Cables are different.
- The approval of the building inspector, the general contractor, the architect, the electrical inspector.
I know that sounds extreme, but each of these may have veto power over what you do. This is not
to say that they are likely to reject an approved method backed up by documentation. But a prudent
person would be prepared.
Many times it is not as difficult as one might think. A piece of romex or service entrance cable can penetrate a one hour sheetrock wall with only secure support (staples to framing members) and a bead of fire caulk that fills an annular space of approximately 1/4" all the way around the cable and the depth of the sheetrock. That is only a squirt on each side. If someone knocks out a 4" hole to run the cable all bets are off. If the hole is so tight the material cannot go around the cable but only a fillet on the surface, it is not proper. Have the details, have the manufacturer's installation instruction, and get approval on the first floor before doing the entire building.
Often the poured concrete floors have large openings and require a support on the bottom, a packing of mineral wool, and a final layer of 1/2" - 1" of fire caulk. Sometimes it is easier to contract with a fire sealing specialist. Or dedicate a person/crew to do that only. Neatness counts and saves expensive material.