View Full Version : type tc in class1 div 2
I'm currently install type tc in a class 1 div 2 area. My concern is this, when I drop out of cable tray to enter a non explosionproof box, I plan on doing so using ridgid metal conduit.
Do I need to seal the conduit with cable inside per 501.15 E 1, last sentance, or does this only apply to a box that is required to be explosion proof?
Also, do I need to use a cgb when entering the ridgid from the tray or would a standard ground bushing (to bond ridgid pipe) be ok?
rbalex
06-08-2008, 10:26 AM
In general, a seal is not required for non-explosionproof enclosures.
Give great consideration to proper bonding though. See 501.30. It is not required but often prudent to include an EGC in the TC cable.
The UL product standard considers Type TC to be a “[c]able with a gas/vaportight continuous sheath…,” but it is not tested to determine if it is “… capable of transmitting gases or vapors through the cable core….” Assume that it is, so Section 501.15(E)(3) also applies. In general, a seal is still not required for the application as you have described it.
A CGB may be needed to comply with Section 501.10(B)(6). Check for obvious termination tensile stress.
Thanks Bob. Can I still use an open conduit on my stub ups to the tray in a classified area, assuming I'll fill with duct seal? My main intent there is to use a bonding bushing to bond the pipe. We'll have a 2/0 bare running the length of the tray to bond conduit, enclosures,etc., so I'd rather bond there instead of fighting bond bushing's, bonding myer's hubs inside the box.
BTW...I surfed this forum quite a while yesterday. I find it to be very useful and has many knowledgable members.
rbalex
06-08-2008, 03:38 PM
“Open conduits” are acceptable and no seals (including duct seal) are required from what you have described so far. Just be careful to bond properly. See Section 250.100 as referenced in 501.30(A)FPN.
The cable tray itself is commonly a suitable EGC, so the #2/0 is probably redundant. It is a commonly added feature though.
Edit Add: BTW welcome to the forums. :)
Yeah, the 2/0 is a standard the company I'm working for uses instead of a jumper at each section of tray. It's sometimes frustrating, but at the same time, I've always got a good source to ground handy in the tray. The ductseal is something else they like to see as a company standard to prevent water, dust, etc. getting into the enclosures.
They also want me to use bonding type liquidtight connectors on my instruments in this plant (transmitters, solenoids, level switches). I will do it as it's there project, but is it really necessary? The way I read section 500, it brings some questions to mind.
I guess I don't consider a transmitter a power utilization load. Are they just over bonding or do they have a point? We always pull an egc with everything, and every instrument will be bonded.
weressl
06-09-2008, 10:18 AM
“Open conduits” are acceptable and no seals (including duct seal) are required from what you have described so far. Just be careful to bond properly. See Section 250.100 as referenced in 501.30(A)FPN.
The cable tray itself is commonly a suitable EGC, so the #2/0 is probably redundant. It is a commonly added feature though.
Edit Add: BTW welcome to the forums. :)
The conduit should not be left open and the cable should be terminated at the entry point for stress relief. Conduit should be installed as a complete system and therefore all openings be closed, unless it is not to be used as a raceway, but as a support system. In that case the conduit should be left open on both ends and the cable terminated at the end device via an approved means.
Good luck in maintaining the bending radius of the cable in the conduit fittings that you may install in the run. If you size the conduit for cable fill, the bending radius given by the corresponding fittings will not be sufficient.
rbalex
06-09-2008, 10:41 AM
With regard to the OP, the controlling text is Section 300.18, Exception.There is no requirement that the raceway be left unconnected at both ends, although it would be permitted. However it must be bonded properly at both ends.
The conduit should not be left open and the cable should be terminated at the entry point for stress relief. Conduit should be installed as a complete system and therefore all openings be closed, unless it is not to be used as a raceway, but as a support system. In that case the conduit should be left open on both ends and the cable terminated at the end device via an approved means.
Good luck in maintaining the bending radius of the cable in the conduit fittings that you may install in the run. If you size the conduit for cable fill, the bending radius given by the corresponding fittings will not be sufficient.
The conduits will basically be nipples extending to the tray (straight piece of pipe about 4' long). I would just drop the cable in tray to the box, but some of these operators could bust an anvil with a toothpick!! I've tried pulling tray cable through fittings before and realize it's a disaster unless you oversize the fitting by a size or two.
I would think it would be ok if I used a cgb on the tray side of the conduit and a myers hub with a bonding lug on the box end, though.
rbalex
06-09-2008, 10:50 AM
Unless the transmitter is part of an intrinsically safe system, the need for proper bonding is the same as any other device. (I don’t want to imply proper bonding is unnecessary for IS either, it just isn’t quite as serious) If the LFMC it is to be used as the EGC, the fittings must already be listed for grounding/bonding under Section 250.118(5).
It does sound a bit like the facility has had bonding problems in the past. There may be a little over caution, but nothing seems extreme.
weressl
06-09-2008, 11:14 AM
With regard to the OP, the controlling text is Section 300.18, Exception.There is no requirement that the raceway be left unconnected at both ends, although it would be permitted. However it must be bonded properly at both ends.
Except when you connect the conduit at the other end directly to the enclosure, whatever degree of protection you provide at the tray end of the conduit now will constitutes the degree of protection provided for the enclosure itself. A pop-on bushing provieds no degree of protection what soever. So if it is a NEMA 1 box the connection should be the same. Of it is a Nema 3, 3R or 4 box a CGB type conenctor is in order.
Furthermore the cable should be secured at the point of entry to relieve stress at the conductor termination point.
weressl
06-09-2008, 11:21 AM
Unless the transmitter is part of an intrinsically safe system, the need for proper bonding is the same as any other device. (I don’t want to imply proper bonding is unnecessary for IS either, it just isn’t quite as serious) If the LFMC it is to be used as the EGC, the fittings must already be listed for grounding/bonding under Section 250.118(5).
It does sound a bit like the facility has had bonding problems in the past. There may be a little over caution, but nothing seems extreme.
Cable tray systems are often installed as discontinous systems. That and corrosion often leads people to wonder if they have sufficiently low impedance to trip on ground fault. The green wire in the tray is a kind of of visual assurance that there is.
I just have to smile when they still do that even though they have a HRG system.
I agree that ground wire in the cable is the best solution.
Except when you connect the conduit at the other end directly to the enclosure, whatever degree of protection you provide at the tray end of the conduit now will constitutes the degree of protection provided for the enclosure itself. A pop-on bushing provieds no degree of protection what soever. So if it is a NEMA 1 box the connection should be the same. Of it is a Nema 3, 3R or 4 box a CGB type conenctor is in order.
Furthermore the cable should be secured at the point of entry to relieve stress at the conductor termination point.
I was planning on taking care of the stress at termination point with anchor points screwed into the backplate and tyraping the cable at a couple points. I've found a large base by t and b that will accomodate a #10 bolt and holds quite securely. Between that and a cgb, I would think I'd be covered.
weressl
06-09-2008, 01:29 PM
I was planning on taking care of the stress at termination point with anchor points screwed into the backplate and tyraping the cable at a couple points. I've found a large base by t and b that will accomodate a #10 bolt and holds quite securely. Between that and a cgb, I would think I'd be covered.
I don't think the Ty-wrap is necessary. The CGB takes care of both issues.
rbalex
06-10-2008, 08:15 AM
Except when you connect the conduit at the other end directly to the enclosure, whatever degree of protection you provide at the tray end of the conduit now will constitutes the degree of protection provided for the enclosure itself. …Nonsense; from what National Standard did you get this assertion?
weressl
06-10-2008, 11:00 AM
Nonsense; from what National Standard did you get this assertion?
When you install a NEMA 4 box what kind of connections are allowed to be made to it. Doesn't the connections need to maintain the NEMA rating of said box?
If you install a NEMA 4 box and you require a connection to a NEMA 1 box, wouldn't the interconnecting item would need to maintain the higher rating?
Wouldn't you secure the cable at the point of entry?
When you leave the conduit open don't you allow free contaminants, including water to freely enter?
Matter of fact we have found waterfull of motor pecker-heads as the result of this type installation. In MCC's where a single ~2' vertical conduit with pop-on bushing was utilized to 'drop-in' several cables allowed the free passage of dust to enter and accumulate in the MCC eventually resulting in dust carbonization, tracking and overflash.
As I said if you leave both end of the conduit open and make proper cable termination into the target device, I see no problem.
rbalex
06-10-2008, 11:04 AM
When you install a NEMA 4 box what kind of connections are allowed to be made to it. Doesn't the connections need to maintain the NEMA rating of said box?
If you install a NEMA 4 box and you require a connection to a NEMA 1 box, wouldn't the interconnecting item would need to maintain the higher rating?
Wouldn't you secure the cable at the point of entry?
When you leave the conduit open don't you allow free contaminants, including water to freely enter?
Matter of fact we have found waterfull of motor pecker-heads as the result of this type installation. In MCC's where a single ~2' vertical conduit with pop-on bushing was utilized to 'drop-in' several cables allowed the free passage of dust to enter and accumulate in the MCC eventually resulting in dust carbonization, tracking and overflash.
As I said if you leave both end of the conduit open and make proper cable termination into the target device, I see no problem.In other words - there is no such Standard.
weressl
06-10-2008, 11:37 AM
In other words - there is no such Standard.
Standards, manufacturers installation instructions, proper installation practice, the not-so-common common sense are all come into play.
The attached document may contain some of the referenced standards.
1782
[QUOTE=weressl]When you install a NEMA 4 box what kind of connections are allowed to be made to it. Doesn't the connections need to maintain the NEMA rating of said box?
If you install a NEMA 4 box and you require a connection to a NEMA 1 box, wouldn't the interconnecting item would need to maintain the higher rating?
Wouldn't you secure the cable at the point of entry?
When you leave the conduit open don't you allow free contaminants, including water to freely enter?
Matter of fact we have found waterfull of motor pecker-heads as the result of this type installation. In MCC's where a single ~2' vertical conduit with pop-on bushing was utilized to 'drop-in' several cables allowed the free passage of dust to enter and accumulate in the MCC eventually resulting in dust carbonization, tracking and overflash.
As I said if you leave both end of the conduit open and make proper cable termination into the target device, I see no problem.
I'm not quite sure what you are refering to as "pop on bushings", but in response to your other questions,
The ty rap with base I was talking about earlier should provide adequate support for the cable where it enters the enclosure and duct sealing around the ground bushing where the cable enters the coduit should prevent contaminents from entering the jbox. (It does because we've done it in other industrial facilities and duct seal work fine).
I'm not against using cgb's on a coupling at the end of my conduit, but would prefer ductseal or some other sealing method. This would allow installing more than one cable in a nipple, which with a large number of small cables is nice.
weressl
06-10-2008, 03:35 PM
[quote=weressl]When you install a NEMA 4 box what kind of connections are allowed to be made to it. Doesn't the connections need to maintain the NEMA rating of said box?
If you install a NEMA 4 box and you require a connection to a NEMA 1 box, wouldn't the interconnecting item would need to maintain the higher rating?
Wouldn't you secure the cable at the point of entry?
When you leave the conduit open don't you allow free contaminants, including water to freely enter?
Matter of fact we have found waterfull of motor pecker-heads as the result of this type installation. In MCC's where a single ~2' vertical conduit with pop-on bushing was utilized to 'drop-in' several cables allowed the free passage of dust to enter and accumulate in the MCC eventually resulting in dust carbonization, tracking and overflash.
As I said if you leave both end of the conduit open and make proper cable termination into the target device, I see no problem.
I'm not quite sure what you are refering to as "pop on bushings", but in response to your other questions,
The ty rap with base I was talking about earlier should provide adequate support for the cable where it enters the enclosure and duct sealing around the ground bushing where the cable enters the coduit should prevent contaminents from entering the jbox. (It does because we've done it in other industrial facilities and duct seal work fine).
I'm not against using cgb's on a coupling at the end of my conduit, but would prefer ductseal or some other sealing method. This would allow installing more than one cable in a nipple, which with a large number of small cables is nice.
Dux seal is no different than duct tape, with the exception that duct tape IS developed and approved to seal minute air-leaks in a crimped sheet-metal duct-work.
Dux seal compound is a temporary repair, fix in my book I would never use it for permanent installation. On the other hand my industry maybe subject to much harsher conditions than others. I just know what works and what isn't. Although it is resistant to shrinking it is not immune to it. Let me know if you intend to have a maintenance program going along with that to check for leaky patches.:grin:
As the profit pressures grow and the available workforce shrinks our primary objective is to minimize installations that require attention. Usually complex machinery, switchgear and control systems are much more complex and requiring higher skill so I wouldn't want to insult our skileld technicians to look for leaky seals.
I like to specify and use devices that are designed for the specific purpose, and select the best design for that specific use and refrain from inventive 'other uses'. I believe for example that the best multicoinductor sealing product is made by Roxtec. http://www.roxtec.com/ Even though it is an offshore product, it is superior in performance and flexibility to the other US made ones.
[quote=wyo1]
Dux seal is no different than duct tape, with the exception that duct tape IS developed and approved to seal minute air-leaks in a crimped sheet-metal duct-work.
Dux seal compound is a temporary repair, fix in my book I would never use it for permanent installation. On the other hand my industry maybe subject to much harsher conditions than others. I just know what works and what isn't. Although it is resistant to shrinking it is not immune to it. Let me know if you intend to have a maintenance program going along with that to check for leaky patches.:grin:
As the profit pressures grow and the available workforce shrinks our primary objective is to minimize installations that require attention. Usually complex machinery, switchgear and control systems are much more complex and requiring higher skill so I wouldn't want to insult our skileld technicians to look for leaky seals.
I like to specify and use devices that are designed for the specific purpose, and select the best design for that specific use and refrain from inventive 'other uses'. I believe for example that the best multicoinductor sealing product is made by Roxtec. http://www.roxtec.com/ Even though it is an offshore product, it is superior in performance and flexibility to the other US made ones.
These are slick, but don't get me from a conduit to a box or tray. I would prefer to not leave much exposed cable outside of the tray as I'm sure these operators are capable of trashing it somehow. Also, we'll be running some 100 hp motors @ 480 volts, so these and other power cables will create quite a hazard.
Too bad there isn't an electricaly rated expanding foam!!:rolleyes:
weressl
06-10-2008, 06:23 PM
[quote=weressl]
These are slick, but don't get me from a conduit to a box or tray. I would prefer to not leave much exposed cable outside of the tray as I'm sure these operators are capable of trashing it somehow. Also, we'll be running some 100 hp motors @ 480 volts, so these and other power cables will create quite a hazard.
Too bad there isn't an electricaly rated expanding foam!!:rolleyes:
Up to 200HP is usually TC-ER cable and there is a 2-3' exposed length of cable between the cable channel or basket tray riser to the pecker-head.
Larger than 200HP motors are MV and the cables are usually CLX or armored/jacketed and exposed the same way as above.
"II. Installation
336.10 Uses Permitted. Type TC cable shall be permitted
to be used as follows:
.....
(7) In industrial establishments where the conditions of
maintenance and supervision ensure that only qualified
persons service the installation, and where the cable is
continuously supported and protected against physical
damage using mechanical protection, such as struts,
angles, or channels, Type TC tray cable that complies
with the crush and impact requirements of Type MC
cable and is identified for such use with the marking
Type TC–ER shall be permitted between a cable tray
and the utilization equipment or device. The cable shall
be secured at intervals not exceeding 1.8 m (6 ft).
Equipment grounding for the utilization equipment
shall be provided by an equipment grounding conductor
within the cable. ........"
Maybe I haven't been clear enough here. The tray cable is dropping to junction boxes used as termination points (nothing but term blocks and pdb's) and from there to motors, instruments, etc., everything is run in grc and sealtight.
Personally, I would never run a tray cable exposed (rated or not) to a motor or instrument anywhere near an area a mechanic may have to work on something. I don't care what kind of connector you run it through, it will still most likely get stepped on, pulled out of peckerhead, cut. The only time we do this is when using type tc-hl or coated mc (anything with a metal sheath).
weressl
06-11-2008, 09:41 AM
Maybe I haven't been clear enough here. The tray cable is dropping to junction boxes used as termination points (nothing but term blocks and pdb's) and from there to motors, instruments, etc., everything is run in grc and sealtight.
Personally, I would never run a tray cable exposed (rated or not) to a motor or instrument anywhere near an area a mechanic may have to work on something. I don't care what kind of connector you run it through, it will still most likely get stepped on, pulled out of peckerhead, cut. The only time we do this is when using type tc-hl or coated mc (anything with a metal sheath).
It seems like that the JB introduces another termination point and that is another point of failure and adding to the cost of installation.
Sealtight breaks, pulls out not unlike the TC. The installation method has been in use for 40 years with no recorded higher incident rate than any others. On the contrary, people would sooner step on a conduit to reach somewhere than on a cable.
It seems like that the JB introduces another termination point and that is another point of failure and adding to the cost of installation.
Sealtight breaks, pulls out not unlike the TC. The installation method has been in use for 40 years with no recorded higher incident rate than any others. On the contrary, people would sooner step on a conduit to reach somewhere than on a cable.
The jb's are necessary to facilitate the removal of unclassified panels that came with the skids that are in a classified area. (Would have been pretty extensive and pricy rewiring the whole thing.) Point taken on the sealtight, maybe I'm just old fashioned that way.
I still have to respectfully disagree with your assumption that a guy needs the cgb's at the conduit end, but I will probably use them outside to keep water out of the boxes.
Thanks for the info.
ontherox21
06-18-2008, 11:01 PM
[quote=wyo1]
Dux seal is no different than duct tape, with the exception that duct tape IS developed and approved to seal minute air-leaks in a crimped sheet-metal duct-work.
Dux seal compound is a temporary repair, fix in my book I would never use it for permanent installation. On the other hand my industry maybe subject to much harsher conditions than others. I just know what works and what isn't. Although it is resistant to shrinking it is not immune to it. Let me know if you intend to have a maintenance program going along with that to check for leaky patches.:grin:
As the profit pressures grow and the available workforce shrinks our primary objective is to minimize installations that require attention. Usually complex machinery, switchgear and control systems are much more complex and requiring higher skill so I wouldn't want to insult our skileld technicians to look for leaky seals.
I like to specify and use devices that are designed for the specific purpose, and select the best design for that specific use and refrain from inventive 'other uses'. I believe for example that the best multicoinductor sealing product is made by Roxtec. http://www.roxtec.com/ Even though it is an offshore product, it is superior in performance and flexibility to the other US made ones.
Thank you for your kind words. I'm the regional manager for Roxtec in Texas and not to push the product or anything, but if you have questions concerning entering multiple cables into a box or building I'd be more than happy to assist. Feel free to PM me.
vBulletin® v3.7.3, Copyright ©2000-2010, Jelsoft Enterprises Ltd.