Fire ratings for low voltage wire

[TED]

I admit that this is not really Christmas centric however installing network wiring allows computers to get online which enables them to access Planet Christmas if desired. ;)Also it affects my income and therefore my Christmas lighting purchases. (So in reality it's not but at least it's in the electrical forum!) Anyway, I don't know why I didn't think to ask this question here before!

I've always been confused by the fire ratings for network cable (cat3/5/5e/6 etc). I know that Plenum rating means that the wire will not give off toxic fumes in a fire and is therefore approved for use in air handling spaces. (In my mind an air handling space would be the ducts for the heat and air but you don't run wires there obviously.) From what I understand inside a wall between the studs is an air handling space and requires the use of plenum rated wire (if no conduit is used). How about a drop ceiling? Is the area above a drop ceiling an air handling space? (I'm thinking yes but not sure.)

Next there's Riser rated wire which I have seen defined as what you use whenpenetrating multiple floors. What if that is also an air handling space? I would think in most cases it would be since you would probably be inside the walls. I've wondered if there is something about riser rated wire that makes is stronger for long vertical runs but I don't really think this is it.

I see a lot of instances where plain ol' PVC jacked wire is run in all these places and I feel pretty sure that it does not meet codes (fire codes anyway). Where can plain PVC be used? Only in conduit? I've also seen Riser rated wire used in areas where I really thought Plenum should have been used.

My approach to this is to always use plenum rated wire for everything because I believe it to be the best kind to have in case of a fire. I feel like this is a good way to do it but would like to know that I'm doing it in a way that meets all the codes. Can anybody shed some light on this?

TED

[deepabyss]

Hey Ted there is two types of air conditioning systems in a commercial building . 1 has the return duct system that uses a separate duct system for the return air .the second uses the free air space above the drop/harcieling as the return which means all available space . the second is where you have to be more careful with fire rating main reasonif something catches fire in the free air space most like it will have some type of plastic coating on it. when it burns it produces a toxic gas the rturn system pulss it bac tto the airhandler just like in your home the re distributes through the clean air system if this happenesmany prople can be injured and possibly killed from the toxic fumes. if you do run this in the open system by bode it has to be installed in a metal conduit or insulated by a fire proof insulation. hope this helps

[Tony Furst]

Ted,

You are mostly correct in that any part of a ceiling or wall space used to convey air for the buildings HVAC system can be classified as a plenum. Generally this is the space above a lay-in ceiling used for return air. As for inside walls that depends on the building, but generally in commercial buildings returns are held to the ceiling space to reduce installation costs.

Now onto the wire ratings there are basically threeratings for low voltage cabling insulationCL2, CL2P & CL2R, and before somebody tells me I'm wrong yes there are a bunch more classifications but these are the three most common non-application specific ones.

Anyhow the differences among them are relatively simple CL2P is plenum rated and has low smoke production and low fire spread, CL2R has a lower vertical flame spread rating versus CL2P.

The CL2 portion of the designator means that is is UL approved for use on NEC Class 2 circuits i.e. 30 volts or less and power limited.

Tony

[-klb-]

TED wrote:
I know that Plenum rating means that the wire will not give off toxic fumes in a fire and is therefore approved for use in air handling spaces.

A slight clarification. Plenum cable will not give off fumes as easily as other cable. However, once the fire gets bad enough, it generally gives of fumes of considerably higher toxicity than non plenum cable. The idea is that it won't be giving off toxic fumes before the fire alarms go off, and that you will have more time to exit the building before toxic fumes are present.

Of course, with the way plastics technology keeps advancing, this may nolonger be true, but I have not heard anything about safer cleaner plenum cable.

- Kevin

[Entropy]

I do a lot of work with low-voltage wire in commercial and industrial buildings.

The simplified rules that we use can be boiled down to:

If it's exposed, it's in conduit or other hard raceway.

If it's in concealed ceilings or walls or air units, it's plenum wire.

If it's in underground conduit then it's waterproof PVC jacketed.

Of course the spec might say otherwise but that another forum.

[AI]

Next there's Riser rated wire which I have seen defined as what you use whenpenetrating multiple floors. What if that is also an air handling space? I would think in most cases it would be since you would probably be inside the walls. I've wondered if there is something about riser rated wire that makes is stronger for long vertical runs but I don't really think this is it.

Wouldn't Riser cable be smokeless too like Plenum only stronger for vertical runs?AI

[TED]

Entropy wrote:
I do a lot of work with low-voltage wire in commercial and industrial buildings.
The simplified rules that we use can be boiled down to:
If it's exposed, it's in conduit or other hard raceway.
If it's in concealed ceilings or walls or air units, it's plenum wire.
If it's in underground conduit then it's waterproof PVC jacketed.

That sounds like a good "rule of thumb". I like it. I take a very similar approach. As I mentioned above I generally use plenum rated wire for everything. I do on occasion leave some wire "exposed" depending on the location. Anexampleof this might be ifit is in aback room or wiring closetwhere there are other exposed wires. I generally cable tie it to something solid so that no one can pull on it.

TED

[TED]

AI wrote:
Wouldn't Riser cable be smokeless too like Plenum only stronger for vertical runs?AI

Based on the information in Tony's response to my original post I would say the main feature of Riser is that in long vertical runs flames will not spread up the wire as quickly as it would with other types therefore reducing the spread of fire from floor to floor. Strength does not appear to be an issue. I'm not sureif Riserrated wire is as good as Plenum rated wirefor low smoke production. If it is then I would assume it could be used interchangably with Plenum rated wire. Tony can you give any more clarification on this?

TED

[Tony Furst]

Ted,

You are correct, riser cable is plenum cable with a lower smoke spread rating, the down side is that it is more expensive than regular CL2P.

Tony

[inspector4]

My last reply got the ax (lost in the transition to this new forum)- but it would be my opinion that per the National Electrical Code- Plenum wire where required has no allowable substitute.
By code, you may substitute plenum rated wire where risor rated wire is required.
I know Tony was going to verify this.


Steve

[Tony Furst]

Correct, plenum can be used in place of riser but not the other way around

Tony