What is a plenum space and what isn't?
- Thread starter johnpage
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fc
Senior Member
- Location
- New Jersey
Re: What is a plenum space and what isn't?
If you are installing the cable in ducts, plenums, and other spaces used for environmental air. That would determine it.
You may want to look at NEC and 770.154 ( A )
If you are installing the cable in ducts, plenums, and other spaces used for environmental air. That would determine it.
You may want to look at NEC and 770.154 ( A )
ryan_618
Senior Member
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- Salt Lake City, Utah
Re: What is a plenum space and what isn't?
You can't use fiber cable in a duct or a plenum. See 300.22(B). You can, however, use it in "other spaces used for enviromental air" as discussed in 300.22(C), such as the space above a ceiling or below a floor. In those applications, you will need plenum cable or a plenum raceway with plenum cables installed in it.
You can't use fiber cable in a duct or a plenum. See 300.22(B). You can, however, use it in "other spaces used for enviromental air" as discussed in 300.22(C), such as the space above a ceiling or below a floor. In those applications, you will need plenum cable or a plenum raceway with plenum cables installed in it.
- Location
- Massachusetts
Re: What is a plenum space and what isn't?
Take a look at 800.51(A)
Ryan I do not think 300.22(B) applies to article 800.
Take a look at 800.51(A)
ryan_618
Senior Member
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- Salt Lake City, Utah
Re: What is a plenum space and what isn't?
Bob, I am not following you.
I think 800.52(C) would apply, if it were a communications circuit.
This, however, is for fiber optical cable, so I think 770.53 applies, which means they can't be instaled in a duct or plenum.
Bob, I am not following you.
I think 800.52(C) would apply, if it were a communications circuit.
This, however, is for fiber optical cable, so I think 770.53 applies, which means they can't be instaled in a duct or plenum.
- Location
- Illinois
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- retired electrician
Re: What is a plenum space and what isn't?
Ryan,
I don't think that "cable" is equipment and also that section only addresses "other spaces used for environmental air". 800.51(A) tells us that "plenum" cables are listed for use in "ducts, plenums, and other spaces used for environmental air". I think that these sections need to be revised so that the same rules apply to both power and low voltage systems.
I still looks like 770.53(A) also permits "plenum" rated fiber to be installed in ducts without regard to 300.22.
Don
Ryan,
I don't think that "cable" is equipment and also that section only addresses "other spaces used for environmental air". 800.51(A) tells us that "plenum" cables are listed for use in "ducts, plenums, and other spaces used for environmental air". I think that these sections need to be revised so that the same rules apply to both power and low voltage systems.
I still looks like 770.53(A) also permits "plenum" rated fiber to be installed in ducts without regard to 300.22.
Don
ryan_618
Senior Member
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- Salt Lake City, Utah
Re: What is a plenum space and what isn't?
But these sections also require compliance with 300.22. 300.22(B) does not allow these wiring methods to be installed.
EDIT: I see your point on 800.51, to an extent. I think all this section is saying is that in order for a cable to have a "P" at the end of it, it must be listed as plenum rated. I don't believe this in and of itself permits its use in a duct or plenum, however.
800.53 also requires compliance with 300.22. Because these cables are not permitted by 300.22(B), they are not allowed in a duct or plenum, even if plenum rated. They are, however, permitted in "other spaces".
[ July 19, 2005, 08:59 AM: Message edited by: ryan_618 ]
But these sections also require compliance with 300.22. 300.22(B) does not allow these wiring methods to be installed.
EDIT: I see your point on 800.51, to an extent. I think all this section is saying is that in order for a cable to have a "P" at the end of it, it must be listed as plenum rated. I don't believe this in and of itself permits its use in a duct or plenum, however.
800.53 also requires compliance with 300.22. Because these cables are not permitted by 300.22(B), they are not allowed in a duct or plenum, even if plenum rated. They are, however, permitted in "other spaces".
[ July 19, 2005, 08:59 AM: Message edited by: ryan_618 ]
Re: What is a plenum space and what isn't?
770.3 (B) requires you to follow 300.22 but has an exception as permitted in 770.154(A).
In 770.154(A) permission is given for plenum rated fiber cable to be installed in ducts,plenums, and other spaces used for enviromental air...
Fred Bender
770.3 (B) requires you to follow 300.22 but has an exception as permitted in 770.154(A).
In 770.154(A) permission is given for plenum rated fiber cable to be installed in ducts,plenums, and other spaces used for enviromental air...
Fred Bender
ryan_618
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- Location
- Salt Lake City, Utah
Re: What is a plenum space and what isn't?
It only allows if it is installed in compliance with 300.22. 300.22(B) does not allow it.
Re: What is a plenum space and what isn't?
770.154 broken down sentence by sentence.
first sentence: cables installed in ducts... gives permission for plenum rated optic fiber cables to be installed in these areas.
Second sentence requires abandoned cables to be removed.
Third sentence has restrictions for non plenum rated cables to be installed in compliance with 300.22
Fourth sentence: Listed raceways with plenum rated cable may be installed in ducts and plenums as described in 300.22(B)...
Unless I am missing something, with the specific exception in 770.3(B) that states "as permitted in 770.154(A)" I conclude that plenum rated optic fiber cables are allowed in ducts, plenums, and other air-handling spaces.
Fred Bender
770.154 broken down sentence by sentence.
first sentence: cables installed in ducts... gives permission for plenum rated optic fiber cables to be installed in these areas.
Second sentence requires abandoned cables to be removed.
Third sentence has restrictions for non plenum rated cables to be installed in compliance with 300.22
Fourth sentence: Listed raceways with plenum rated cable may be installed in ducts and plenums as described in 300.22(B)...
Unless I am missing something, with the specific exception in 770.3(B) that states "as permitted in 770.154(A)" I conclude that plenum rated optic fiber cables are allowed in ducts, plenums, and other air-handling spaces.
Fred Bender
- Location
- Illinois
- Occupation
- retired electrician
Re: What is a plenum space and what isn't?
Ryan,
I agree with Fred. 770.3(B) requires compliance with 300.22, but has an exception. This exception says that 300.22 does not apply to the installations permitted in 770.154(A). This section reads in part, "(A) Plenum. Cables installed in ducts, plenums, and other spaces used for environmental air shall be Type OFNP or OFCP." This is clearly a permission to install "P" rated cables in ducts and plenums.
Don
Ryan,
I agree with Fred. 770.3(B) requires compliance with 300.22, but has an exception. This exception says that 300.22 does not apply to the installations permitted in 770.154(A). This section reads in part, "(A) Plenum. Cables installed in ducts, plenums, and other spaces used for environmental air shall be Type OFNP or OFCP." This is clearly a permission to install "P" rated cables in ducts and plenums.
Don
fc
Senior Member
- Location
- New Jersey
Re: What is a plenum space and what isn't?
Don
I would agree with you. That's the way I read it.
Don
I would agree with you. That's the way I read it.
georgeswe
Senior Member
- Location
- The Republic of Southern California
Re: What is a plenum space and what isn't?
DOnt know if anyone covered it but plenum areas are the areas where the ceiling is being used to transfer Supply or Return air. (mostly in multy story buildings) Where the return air is runnign above the T-bar and not in individual ducts. Important to determine that to be able to charge accordingly since the Plenum rated ovewr the PVC is usually 3 times the cost for Material )
just my 2 cents
DOnt know if anyone covered it but plenum areas are the areas where the ceiling is being used to transfer Supply or Return air. (mostly in multy story buildings) Where the return air is runnign above the T-bar and not in individual ducts. Important to determine that to be able to charge accordingly since the Plenum rated ovewr the PVC is usually 3 times the cost for Material )
just my 2 cents
sceepe
Senior Member
Re: What is a plenum space and what isn't?
Don't fall into the trap of thinking that plenums occur only above lay in ceilings. They can be below the floor or in vertical shafts in multistory buildings. Some inspectors even argue that if the building has transfer air ducts between spaces, those spaces are plenums because they are used for "environmental air".
From a design perspective, you never know exactly how the air flow in a commercial building will be designed. Play it safe and use plenum rated cable for anything that is not in conduit (i.e. cabletray). Otherwise take your chances with the inspector.
Don't fall into the trap of thinking that plenums occur only above lay in ceilings. They can be below the floor or in vertical shafts in multistory buildings. Some inspectors even argue that if the building has transfer air ducts between spaces, those spaces are plenums because they are used for "environmental air".
From a design perspective, you never know exactly how the air flow in a commercial building will be designed. Play it safe and use plenum rated cable for anything that is not in conduit (i.e. cabletray). Otherwise take your chances with the inspector.
ryan_618
Senior Member
- Location
- Salt Lake City, Utah
Re: What is a plenum space and what isn't?
I don't know guys. For example, 800.154(A) says "Listed plenum communications raceways shall be permitted to be installed installed in ducts and plenums as described in 300.22(B)..."
The question then becomes: What is menat by the term "described"? Are they describing the section and it's requirements, or are they describing the physical duct and/or plenum?
Talking with a few nationally renowned code experts, they are describing the section and requirements of the section. I can certainly see how this is read either way though.
I don't know guys. For example, 800.154(A) says "Listed plenum communications raceways shall be permitted to be installed installed in ducts and plenums as described in 300.22(B)..."
The question then becomes: What is menat by the term "described"? Are they describing the section and it's requirements, or are they describing the physical duct and/or plenum?
Talking with a few nationally renowned code experts, they are describing the section and requirements of the section. I can certainly see how this is read either way though.
- Location
- Illinois
- Occupation
- retired electrician
Re: What is a plenum space and what isn't?
Ryan,
I fully agree that listed plenum communication raceways must be installed per 300.22(B), and that plenum rated cables must be used within that raceway, but the code did not apply the same rules to plenum cables. I don't agree with the code rule, but it clearly permits the use of "P" rated cables in ducts and plenums as well as other space used for envriomental air.
Don
Ryan,
I fully agree that listed plenum communication raceways must be installed per 300.22(B), and that plenum rated cables must be used within that raceway, but the code did not apply the same rules to plenum cables. I don't agree with the code rule, but it clearly permits the use of "P" rated cables in ducts and plenums as well as other space used for envriomental air.
Don
ryan_618
Senior Member
- Location
- Salt Lake City, Utah
Re: What is a plenum space and what isn't?
You guys are right. I have been thinking about this all afternoon, and I think you guys are right.
You guys are right. I have been thinking about this all afternoon, and I think you guys are right.
sandsnow
Senior Member
- Location
- Southern California
Re: What is a plenum space and what isn't?
It is not.
It is an "other space used for enviromental air".
If you've ever seen a large air handler on the roof and opened the door and saw the supply or return fan motor sitting in the chamber; that is a plenum.
Two different things and different requirements in 300.22
That's a commonly missapplied term in calling the space above a T-Bar ceiling a plenum.
It is not.
It is an "other space used for enviromental air".
If you've ever seen a large air handler on the roof and opened the door and saw the supply or return fan motor sitting in the chamber; that is a plenum.
Two different things and different requirements in 300.22
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