hbiss
EC, Westchester, New York NEC: 2014
- Location
- Hawthorne, New York NEC: 2014
- Occupation
- EC
The following is taken from the telecom board-
http://www.sundance-communications.com/forum/Forum24/HTML/000081.html
and I thought I would run it by here. Unless there is a local amendment this guy has a lot of misconceptions but he makes some of it sound credible. Am I missing something?
Some of you contractors out there may have the luxury of using plenum cable everywhere. Unfortunately, that's not always legal but is not being enforced by local officials. It is being enforced here, if just a technicality. Reinspections result in additional revenue for the city or county. You can imagine how I feel about this.
You see, most plenum rated cable has excellent low-smoke producing properties in a HORIZONTAL environment, but has awful properties when installed in a VERTICAL installation. Some plenum jacket materials are actually more flamable when installed vertically than riser-rated (CMR) cable.
The National Electrical Code states that all materials used "shall be approved for the purpose". Type CMP cable (plenum) is traditionally approved for use in plenum spaces. Recently, most manufacturers have changed their jacket formula to be accepted in horizontal plenum or vertical (riser) applications but that's not universal practice by all manufacturers, nor is it mandatory.
Still, just because plenum cable costs more than PVC (non-plenum) doesn't mean it can be used everywhere. Cost is not what determines compatibility; it's how it is rated by Underwriter's Laboratories or accepted by your local authority having jurisdiction (AHJ).
Bottom line: CMR (riser-rated) cable doesn't burn well when installed vertically but it burns like crazy in a horzintal environment;
CMP (plenum-rated) cable doesn't burn much when installed horizontally but goes up in flames when installed vertically.
Technically, it's not legal to wire a single family residence, townhouse, etc. with type CMP (plenum) cable, just like it's not legal to run type CMR (riser) cable in a plenum ceiling.
Those of you out there using CMP cable for everything might be enjoying the convenience of stocking only one type of cable, but a sharp electrical inspector might come along and change your way of thinking.
So you asked, how do I know so much about this? We have strict requirement to prove NEC knowledge (through verified continuing education credit courses) each year when our 30+ licenses are renewed.
We had to rewire an addition to a hospital plus another job involving 130 residential condiminiums a few years ago because the installation DID NOT require the use of plenum-rated cable where we had installed it. We thought by using the most expensive cable, we were safe. We failed inspection. This was due to the fact that the wiring wasn't installed within air return plenums. In these cases, the National Electrical Code's "material approved for the purpose" mandated that since the wiring wasn't in an air return plenum environment, plenum (CMP) cable wasn't the material approved for the purpose. It was cheaper to replace it than to fight the inspector.
Most manufacturers have had their plenum-rated cable models dual-rated now, but you might not ever know if you are using an older model. We found out that some of the cable we just received last month is still not dual-rated.
Again, more expensive isn't always better.
We run miles of CAT3 for voice annualy and unless otherwise mandated, that's our norm. As for data, the customer calls that shot. Still, we always verify if it's a plenum environment......The NEC seems to be trying to keep us from spending money on CMP when not necessary. No problem here!
________________________________________________
My response to him was:
I would like to agree with you but I can't see where you are getting your information from, certainly not from the NEC.
If you look at any of the cable hierarchy substitution tables in the NEC (for instance 800.53)you will see that a plenum rated cable is at the top of the heap and can be substituted for any of the lesser types such as riser and general purpose. There is absolutely nothing in the NEC that would prohibit plenum rated cables use in vertical runs or residential construction.
I believe your inspector is taking the descriptions of the different types of cables in 800.51 (A) through (E) literally without understanding the the substitution hierarchy which is included in every NEC article having to do with low voltage wiring.
Unless your state or jurisdiction has adopted the NEC with ammendments that would contradict this it appears from what you say that your classes are also making the same serious mistake. They wouldn't happen to be taught by the inspector would they?
I just got a shipment of Commscope plenum CAT5e the other day and I don't know what you are talking about. Why would there even be a reason to dual rate a plenum rated cable? I'll check into this but I think your information is totally wrong and it seems it has cost you a lot of money.
-Hal
http://www.sundance-communications.com/forum/Forum24/HTML/000081.html
and I thought I would run it by here. Unless there is a local amendment this guy has a lot of misconceptions but he makes some of it sound credible. Am I missing something?
Some of you contractors out there may have the luxury of using plenum cable everywhere. Unfortunately, that's not always legal but is not being enforced by local officials. It is being enforced here, if just a technicality. Reinspections result in additional revenue for the city or county. You can imagine how I feel about this.
You see, most plenum rated cable has excellent low-smoke producing properties in a HORIZONTAL environment, but has awful properties when installed in a VERTICAL installation. Some plenum jacket materials are actually more flamable when installed vertically than riser-rated (CMR) cable.
The National Electrical Code states that all materials used "shall be approved for the purpose". Type CMP cable (plenum) is traditionally approved for use in plenum spaces. Recently, most manufacturers have changed their jacket formula to be accepted in horizontal plenum or vertical (riser) applications but that's not universal practice by all manufacturers, nor is it mandatory.
Still, just because plenum cable costs more than PVC (non-plenum) doesn't mean it can be used everywhere. Cost is not what determines compatibility; it's how it is rated by Underwriter's Laboratories or accepted by your local authority having jurisdiction (AHJ).
Bottom line: CMR (riser-rated) cable doesn't burn well when installed vertically but it burns like crazy in a horzintal environment;
CMP (plenum-rated) cable doesn't burn much when installed horizontally but goes up in flames when installed vertically.
Technically, it's not legal to wire a single family residence, townhouse, etc. with type CMP (plenum) cable, just like it's not legal to run type CMR (riser) cable in a plenum ceiling.
Those of you out there using CMP cable for everything might be enjoying the convenience of stocking only one type of cable, but a sharp electrical inspector might come along and change your way of thinking.
So you asked, how do I know so much about this? We have strict requirement to prove NEC knowledge (through verified continuing education credit courses) each year when our 30+ licenses are renewed.
We had to rewire an addition to a hospital plus another job involving 130 residential condiminiums a few years ago because the installation DID NOT require the use of plenum-rated cable where we had installed it. We thought by using the most expensive cable, we were safe. We failed inspection. This was due to the fact that the wiring wasn't installed within air return plenums. In these cases, the National Electrical Code's "material approved for the purpose" mandated that since the wiring wasn't in an air return plenum environment, plenum (CMP) cable wasn't the material approved for the purpose. It was cheaper to replace it than to fight the inspector.
Most manufacturers have had their plenum-rated cable models dual-rated now, but you might not ever know if you are using an older model. We found out that some of the cable we just received last month is still not dual-rated.
Again, more expensive isn't always better.
We run miles of CAT3 for voice annualy and unless otherwise mandated, that's our norm. As for data, the customer calls that shot. Still, we always verify if it's a plenum environment......The NEC seems to be trying to keep us from spending money on CMP when not necessary. No problem here!
________________________________________________
My response to him was:
I would like to agree with you but I can't see where you are getting your information from, certainly not from the NEC.
If you look at any of the cable hierarchy substitution tables in the NEC (for instance 800.53)you will see that a plenum rated cable is at the top of the heap and can be substituted for any of the lesser types such as riser and general purpose. There is absolutely nothing in the NEC that would prohibit plenum rated cables use in vertical runs or residential construction.
I believe your inspector is taking the descriptions of the different types of cables in 800.51 (A) through (E) literally without understanding the the substitution hierarchy which is included in every NEC article having to do with low voltage wiring.
Unless your state or jurisdiction has adopted the NEC with ammendments that would contradict this it appears from what you say that your classes are also making the same serious mistake. They wouldn't happen to be taught by the inspector would they?
I just got a shipment of Commscope plenum CAT5e the other day and I don't know what you are talking about. Why would there even be a reason to dual rate a plenum rated cable? I'll check into this but I think your information is totally wrong and it seems it has cost you a lot of money.
-Hal
