Open bottom on trough

[Electroplaxes]

Ok any thoughts on this method? Take a trough, cut a larger opening, stub all your underground up into said trough, form around the trough and pour a concrete pad around the pipes tight to the bottom of the trough. Run tapcons from inside the trough into pad to "mechanically connect" everything together. For the most part it gets approved, but every once and awhile I'll run into a hiccup with an inspector. I'm just curious if I can get a few more arguments in my favor for this install. The most used code against this is....

300.12Mechanical Continuity ? Raceways and Cables. Metal or nonmetallic raceways,cable armors, and cable sheaths shall be continuous between cabinets, boxes,fittings, or other enclosures or outlets.​

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Exception No. 1:? Short sections ofraceways used to provide support or protection of cable assemblies fromphysical damage shall not be required to be mechanically continuous.

Exception No. 2:? Raceways and cablesinstalled into the bottom of open bottom equipment, such as switchboards, motorcontrol centers, and floor or pad-mounted transformers, shall not be requiredto be mechanically secured to the equipment.

​

I've attached a drawing if my description is unclear. My two arguments back. Conduit connected to pad ---> pad connected to trough ---> mechanical connection. Also it may not be manufactured with an open bottom, but it is still equipment in terms of I now have it as part of my switch board. Who knows, maybe I'll find out that I shouldn't be doing it this way at all and will correct my ways.

*NOTE: I only apply this method with PVC underground as there is no need for electrical continuity to the raceway.

 

[roger]

IMHO it's perfectly fine. If Exception #2 said;

Exception No. 2: Raceways and cables installed into the bottom of open bottom switchboards, motor control centers, and floor or pad-mounted transformers, shall not be required to be mechanically secured to the equipment.

it would be a different story but, by using the words "such as"

Exception No. 2: Raceways and cables installed into the bottom of open bottom equipment, such as switchboards, motor control centers, and floor or pad-mounted transformers, shall not be required to be mechanically secured to the equipment.

it leaves room for other items as well.

Roger

 

[infinity]

If you can cut out that big hole why can't you simply make KO's?

 

[Electroplaxes]

If you can cut out that big hole why can't you simply make KO's?

I know I only show four pipes in the drawing. So yes, for four holes just knock it out. But when have more, you can cut a 6"x 24" cut out and it is much quicker then measuring and lining up say 30 some odd pipes.

 

[weressl]

Ok any thoughts on this method? Take a trough, cut a larger opening, stub all your underground up into said trough, form around the trough and pour a concrete pad around the pipes tight to the bottom of the trough. Run tapcons from inside the trough into pad to "mechanically connect" everything together. For the most part it gets approved, but every once and awhile I'll run into a hiccup with an inspector. I'm just curious if I can get a few more arguments in my favor for this install. The most used code against this is....

300.12Mechanical Continuity ? Raceways and Cables. Metal or nonmetallic raceways,cable armors, and cable sheaths shall be continuous between cabinets, boxes,fittings, or other enclosures or outlets.​

Exception No. 1:? Short sections ofraceways used to provide support or protection of cable assemblies fromphysical damage shall not be required to be mechanically continuous.

Exception No. 2:? Raceways and cablesinstalled into the bottom of open bottom equipment, such as switchboards, motorcontrol centers, and floor or pad-mounted transformers, shall not be requiredto be mechanically secured to the equipment.

​

I've attached a drawing if my description is unclear. My two arguments back. Conduit connected to pad ---> pad connected to trough ---> mechanical connection. Also it may not be manufactured with an open bottom, but it is still equipment in terms of I now have it as part of my switch board. Who knows, maybe I'll find out that I shouldn't be doing it this way at all and will correct my ways.

*NOTE: I only apply this method with PVC underground as there is no need for electrical continuity to the raceway.

My problem would be more with the workmanship of such assembly as the metallic box in direct contact with concrete would be subject to corrosion.

 

[Electroplaxes]

My problem would be more with the workmanship of such assembly as the metallic box in direct contact with concrete would be subject to corrosion.

If it were outdoors I would agree and maintain my .25" gap as per code. But in an indoor installation what would cause corrosion?

 

[weressl]

If it were outdoors I would agree and maintain my .25" gap as per code. But in an indoor installation what would cause corrosion?

Just because it is indoors it does not necessarily mean moisture-free, especially the floor level. Plain condensation on concrete floors in unconditioned room is the most common culprit, but there are tons of other sources.

 

[Electroplaxes]

Just because it is indoors it does not necessarily mean moisture-free, especially the floor level. Plain condensation on concrete floors in unconditioned room is the most common culprit, but there are tons of other sources.

Well if that's the case then every 4sq box mounted on a masonry or precast wall falls in that catagory.