NEC 300.11 (2005), Devices on Ceiling Tiles

[DM2-Inc]

I'm in a debate with an electrician who's responsible for installing a fire detection system that our company designed. Our contract is with the end user and this equipment was free issued to the electrician, so I have no contractual relationship with them.

Our drawings don't show an installation detail for the installation of a smoke detector on a suspended ceiling tile because we assumed the electrician would install it correctly. He's disagreeing with me. I'm getting ready to state my position and wanted to make sure I was correct and wasn't missing anything.

Chapter 3 of the NEC (2005 edition) addresses “Wiring Methods and Materials”. Section 300.11 addresses “Securing and Supporting” and states:

(A) Securing in Place. Raceways, cable assemblies, boxes cabinets, and fittings shall be securely fastened in place. Support wires that do not provide secure support shall not be permitted as the sole support. Support wires and associated fittings that provide secure support and that are installed in addition to the ceiling grid support wires shall be permitted as the sole support. Where independent support wires are used, they shall be secured at both ends. Cables and raceways shall not be supported by ceiling grids​

To my mind, this means that if I install a smoke detector on a suspended ceiling I must:
1 - Use a "T-Bar" hanger to span between the grid.
2 - Attach the junction box to the "T-Bar" hanger.
3 - Run a support wire from the junction box to the structure above the ceiling tile.

If I'm interpreting 300.11 incorrectly, or should be referencing some other section of the code please let me know.

What 300.11 isn't telling me, and I can't find the reference for, is that I can't Sandwich the ceiling tile between the junction box and the smoke detector base...correct? What's the code reference?

Any help is appreciated

 

[480sparky]

My guess is the 'electrician' will say, "We've always done it this way before....."

How 'bout 314.20?

314.20 In Wall or Ceiling.
In walls or ceilings with a surface of concrete, tile, gypsum, plaster, or other noncombustible material, boxes employing a flush-type cover or faceplate shall be installed so that the front edge of the box, plaster ring, extension ring, or listed extender will not be set back of the finished surface more than 6 mm (? in.).
In walls and ceilings constructed of wood or other combustible surface material, boxes, plaster rings, extension rings, or listed extenders shall be flush with the finished surface or project therefrom.

Or 314.23?

(D) Suspended Ceilings. An enclosure mounted to structural or supporting elements of a suspended ceiling shall be not more than 1650 cm3 (100 in.3) in size and shall be securely fastened in place in accordance with either (D)(1) or (D)(2).
(1) Framing Members. An enclosure shall be fastened to the framing members by mechanical means such as bolts, screws, or rivets, or by the use of clips or other securing means identified for use with the type of ceiling framing member(s) and enclosure(s) employed. The framing members shall be adequately supported and securely fastened to each other and to the building structure.
(2) Support Wires. The installation shall comply with the provisions of 300.11(A). The enclosure shall be secured, using methods identified for the purpose, to ceiling support wire(s), including any additional support wire(s) installed for that purpose. Support wire(s) used for enclosure support shall be fastened at each end so as to be taut within the ceiling cavity.

 

[DM2-Inc]

Hey...Thanks.

Is my interpretation of 300.11 seem correct to you?

 

[480sparky]

Hey...Thanks.

Is my interpretation of 300.11 seem correct to you?

It give you a good running start. Cross the finish line first with 314.

 

[david]

314.23 Supports.

I am sorry I do not agree with your point 3. The scope of article 300 is dealing with wiring methods.

I would direct you to 314.23 supports
Support wires are not required but if you use them they would need to be secured to the building structure and the ceiling grid secured at both ends.

You need to secure the box support to the ceiling grid with the provided clip or some other mechanical means.

 

[ActionDave]

314.23 Supports.

I am sorry I do not agree with your point 3. The scope of article 300 is dealing with wiring methods.

I would direct you to 314.23 supports
Support wires are not required but if you use them they would need to be secured to the building structure and the ceiling grid secured at both ends.

You need to secure the box support to the ceiling grid with the provided clip or some other mechanical means.

I agree with David's dissagreement.

David's of the world unite and we will be an unstoppable force! Join us!!

 

[cadpoint]

To me:

There's many ways that engineering services are bought and one condition was stated by the OP!

Yes you could well qualify an item to be used, by using details, isometric's, photo's, or specifications, I don't think such specifications can ever be fully covered, well OK on BIG, big jobs where everything is Listed, "USE
this, or submit a substitution submittal!

Again if only in respect to how your service was sold to the client, your in-the loop or not, after the design /plan is released.

Your design presents an implied application of a particular discipline, how the end user gets there, well that's really out of your hands.
Maybe the EC is clueless, well maybe not...

I don't think your giving the installer enough credit. Well wait, let me think about that...

No wait, your plan is only a road map, creativeness is NOT out the window. It's a cardboard cut out, no it's not, it's a design...
It's endless as to the statements describing a drawing in the field!

I've had many, many discussions with a friend, an EE about where, when and why, he would have to apply the engineering aspect TO A DESIGN.

Only tonight was the story, much like your situation, electrician says,
"I'm not going to use his design", and gezz there's been five phones calls
from the electrician, "Well, help me out, Mr. Engineer..."

I could only state to him, after hearing this; Well why five, why didn't you cut him off at one and state. "I'm working for the client, your working for the client, why don't you do what's on the plans, Oh yeah that’s right your not installing per the plan!... oh and it's not on the plan, right, but it is what the client wants and I agreed to design this."

The electrician was in trouble over not following the plans, well when the last time that happened?

UL code issues and Building Code issues are involved in respects to ceiling tiles you might go visit some of the sights and you might find some free details to scribe, as well as the manufactures site that reflect the correct support devices on the electrical side.
All are designed with small weight limits in respect to ceiling tiles, and structures that support them.

 

[Pierre C Belarge]

Or 314.23?

(D) Suspended Ceilings. An enclosure mounted to structural or supporting elements of a suspended ceiling shall be not more than 1650 cm3 (100 in.3) in size and shall be securely fastened in place in accordance with either (D)(1) or (D)(2).
(1) Framing Members. An enclosure shall be fastened to the framing members by mechanical means such as bolts, screws, or rivets, or by the use of clips or other securing means identified for use with the type of ceiling framing member(s) and enclosure(s) employed. The framing members shall be adequately supported and securely fastened to each other and to the building structure.
(2) Support Wires. The installation shall comply with the provisions of 300.11(A). The enclosure shall be secured, using methods identified for the purpose, to ceiling support wire(s), including any additional support wire(s) installed for that purpose. Support wire(s) used for enclosure support shall be fastened at each end so as to be taut within the ceiling cavity.

There is more than one permitted method to install the boxes that smoke alarms/detectors will be attached to.

One of the ways is to follow the highlighted section above...it is a very common method. Remember, this is a smoke and not a lighting fixture.

Also, be aware that there are local standards out there and you should consult with your building department for a copy, if they have local standards.

 

[480sparky]

.......... Remember, this is a smoke and not a lighting fixture..........

Does it make a difference?

 

[JohnJ0906]

300.11 may not be enforceable. See 760.3

 

[DM2-Inc]

760.25 (NPLFA Circuit Wiring Methods) and 760.52(B) (760.52 Wiring Methods and Materials on Load Side of the PLFA Power Source), both make reference to 300.11.

760 doesn't specifically make reference to 314, however 760.25 states:

760.25 NPLFA Circuit Wiring Methods. Installation of non-power-limited fire alarm circuits shall be in accordance with 110.3(B), 300.11, 300.15, 300.17, and other appropriate articles of Chapter 3.​

Power Limited is a different:

760.52 Wiring Methods and Materials on Load Side of the PLFA Power Source

(B) PLFA Wiring Methods and Materials. Power-limited fire alarm conductors and cables described in 760.82 shall be installed as detailed in 760.52(B)(l), (B)(2), or (B)(3) of this section. Devices shall be installed in accordance with 110.3(B), 300.11(A), and 300.15.​

It would seem that if the installation is installed using NPL wiring, 314.23 would be enforceable but not if it's installed as PL. I'm thinking that 760.25 and 760.52 could use a little re-write.

If the installation is PL, don't you still have to install a junction box for a smoke detector on the ceiling?

 

[nhfire77]

technically you do not need a j box, but if you don't, you are a hack. The device just cannot be supported by its wiring only, but then you get into can you add any weight to the ceiling grid?

This is a sticky situation due to interpretation of the ....neat and workman like... and other sections

 

[DM2-Inc]

Well...by virtue of the fact that both the PL and NPL sections of 760 reference 300.11, I read that you need to support the device. I admit this doesn't state that a junction box IS required but I would guess that's somewhere else in the code. I also know that neither the ceiling tile, nor grid, is listed to "Support" devices of any type. That however is a condition of the listing of the ceiling, and requires deeper digging into approvals.

In a discussion with one ceiling manufacture sometime ago, I was advised that it comes down to the rating of the ceiling and the "Assembly". He (the ceiling manufacture) responded that they have never tested their ceiling assembly with the tile or grid providing a "Supporting" means for the device. As a result, he stated that you won't see anything in their "Approval" which prohibits it. Based on their Listing requirements and documentation they're required to provide as part of the Listing, if the installation instructions don't indicate that you can mount equipment on the tile or grid, than it's prohibited. UL's logic to this is that there are too many variations which would need to be addressed and would require a manual with "...can't do this...". He stated that their installation instructions are intended to demonstrate "How to install" and not "How Not to install" their ceiling system.

The installation of a device, without a junction box, would require that device to be Listed to permit such an installation method, wouldn't it?

Is anyone aware of such a device?

If there is such a device, I'm guessing it might be a smoke detector...yes?

 

[bmwpilot]

One more question regarding 300.11 (a)

One more question regarding 300.11 (a)

I know it is not permissible under 300.11 (a) to utilize the ceiling supports or ceiling for raceway support. However, I do not see where it says that the anchor in the ceiling that supports the ceiling wire cannot be used to also support the wire for the raceway.

Does anyone have a particular experience where this was questioned?