Need bushings?

[JoeNorm]

If I have PVC conduits coming into a ground box and I'm using URD wire (direct burial rated) do I need bushings for all the pipe ends?

Generally I use them just out of a professionalism standpoint but are they really necessary? In my opinion a nicely reamed pipe does the same thing without the bushing.

 

[infinity]

So the conduit just stubs into the box without any type of terminal adapter? IMO if the pipe is properly cut and reamed a bushing would serve little purpose.

 

[JoeNorm]

Yes, just enters an underground "box" from underneath. So the the pipe does not come though the wall of any enclosure.

 

[kwired]

So the conduit just stubs into the box without any type of terminal adapter? IMO if the pipe is properly cut and reamed a bushing would serve little purpose.

I was taught to ream the ends of PVC when ending underground (used for emerging from below grade for direct burial conductors) almost from day one as an apprentice in the field. Don't install direct bury all that often but did for a temp service one time and inspector happened to see it while trench was still open and insisted I need a fitting on the end of that raceway and reaming it is not good enough. I remember looking at code and it basically does say that, but common sense never prevails in those kind of situations

 

[infinity]

IMO it's a judgement call based on the four options listed in 300.4(G)(4).

300.4(G) Fittings.
Where raceways contain 4 AWG or larger insulated circuit conductors, and these conductors enter a cabinet, a box, an enclosure, or a raceway, the conductors shall be protected in accordance with any of the following:
(1) An identified fitting providing a smoothly rounded insulating surface
(2) A listed metal fitting that has smoothly rounded edges
(3) Separation from the fitting or raceway using an identified insulating material that is securely fastened in place
(4) Threaded hubs or bosses that are an integral part of a cabinet, box, enclosure, or raceway providing a smoothly rounded or flared entry for conductors. Conduit bushings constructed wholly of insulating material shall not be used to secure a fitting or raceway. The insulating fitting or insulating material shall have a temperature rating not less than the insulation temperature rating of the installed conductors.

 

[curt swartz]

I have always installed bell ends in underground boxes. Occasional on small raceways I'll use a terminal adapter with plastic bushing if supplier is out of bells.

 

[wwhitney]

IMO it's a judgement call based on the four options listed in 300.4(G)(4).

I believe you've misparsed the first sentence of 300.4(G)(4); the part you bolded does not stand on its own as an option for compliance. The full sentence is parsed as "Threaded hubs or bosses (that are an integral part of a (cabinet, box, enclosure, or raceway)) providing a smoothly rounded or flared entry for conductors." So for something to qualify under 300.4(G)(4), it needs to be a threaded hub or boss, it needs to provide a smoothly rounded or flared entry for conductors, and it needs to be an integral part of a cabinet, box, enclosure, or raceway.

Cheers, Wayne

 

[curt swartz]

We also have:

352.46 Bushings.
Where a conduit enters a box, fitting, or other enclosure, a bushing or adapter shall be provided to protect the wire from abrasion unless the box, fitting, or enclosure design provides equivalent protection.

 

[infinity]

I believe you've misparsed the first sentence of 300.4(G)(4); the part you bolded does not stand on its own as an option for compliance. The full sentence is parsed as "Threaded hubs or bosses (that are an integral part of a (cabinet, box, enclosure, or raceway)) providing a smoothly rounded or flared entry for conductors." So for something to qualify under 300.4(G)(4), it needs to be a threaded hub or boss, it needs to provide a smoothly rounded or flared entry for conductors, and it needs to be an integral part of a cabinet, box, enclosure, or raceway.

Cheers, Wayne

Nope I read it correctly. The part about smoothly rounded or flared has nothing to do with hubs or bosses.

 

[wwhitney]

Nope I read it correctly. The part about smoothly rounded or flared has nothing to do with hubs or bosses.

If I understand your proposed interpretation correctly, it would be written as (bolded parts are added or changed):

"Threaded hubs or bosses that are an integral part of a cabinet, box, or enclosure; or a raceway providing a smoothly rounded or flared entry for conductors."

But that is not what it says. The subject of (4) is "threaded hubs or bosses", so it only applies to threaded hubs or bosses, as long as they meet the limitations in the text that follows. The point of 300.4(G)(4) is that bell boxes and the like adequately protect the conductors without any separate fitting or insulating material, which are the alternatives allowed in (1) through (3).

Given 352.46, this question of how to parse 300.4(G)(4) is moot for the OP.

Cheers, Wayne

 

[infinity]

If I understand correctly, your interpretation would be written as (bolded parts are added or changed):

"Threaded hubs or bosses that are an integral part of a cabinet, box, or enclosure; or a raceway providing a smoothly rounded or flared entry for conductors."

But that is not what it says. The subject of (4) is "threaded hubs or bosses", so it only applies to threaded hubs or bosses, as long as they meet the limitations in the text that follows.

Cheers, Wayne

A hub is integral to the box and must be smooth by default because you cannot install a bushing on a hub.

 

[Little Bill]

I have always installed bell ends in underground boxes. Occasional on small raceways I'll use a terminal adapter with plastic bushing if supplier is out of bells.

Are you talking about the bell end of the conduit?

 

[wwhitney]

A hub is integral to the box and must be smooth by default because you cannot install a bushing on a hub.

Sure, so you can't use 300.4(G)(1) or (2) with a threaded conduit going into a bell box. You could still use (3). But because of (4), you don't have to. (4) does not apply to a bare raceway end.

Cheers, Wayne

 

[wwhitney]

Are you talking about the bell end of the conduit?

I believe he's referring to the fitting shown below. E.g. google "conduit bell end".

Cheers, Wayne

 

[Little Bill]

I believe he's referring to the fitting shown below. E.g. google "conduit bell end".

Cheers, Wayne

That looks similar to a box adapter.

 

[letgomywago]

I always used regular pvc couplings but my boss does like the end bells. I don't like using them because they take space on the van that couplings will for sure get used.

 

[JoeNorm]

Bell Ends are about 4X the cost of a TA+Bushing

 

[Greentagger]

As stated previously, required per 352.46.

 

[infinity]

As stated previously, required per 352.46.

Yes that removes any argument from 300.4.

 

[kwired]

If I understand your proposed interpretation correctly, it would be written as (bolded parts are added or changed):

"Threaded hubs or bosses that are an integral part of a cabinet, box, or enclosure; or a raceway providing a smoothly rounded or flared entry for conductors."

But that is not what it says. The subject of (4) is "threaded hubs or bosses", so it only applies to threaded hubs or bosses, as long as they meet the limitations in the text that follows. The point of 300.4(G)(4) is that bell boxes and the like adequately protect the conductors without any separate fitting or insulating material, which are the alternatives allowed in (1) through (3).

Given 352.46, this question of how to parse 300.4(G)(4) is moot for the OP.

Cheers, Wayne

If the subject of (4) is threaded hubs or bosses then the last two sentences don't even belong in (4) as you wouldn't be using a bushing or other insulating fitting with a threaded hub or boss.