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fool4jesus

05:27AM | 10/26/05
Member Since: 06/20/05
53 lifetime posts
Bvelectrical
I've done quite a bit of normal indoor house wiring, and I know by code you need to use a clamp (either built-in or a metal connector) to securely hold the cable into the box.

Now, I'm using conduit (RNC) for wiring my hot tub outside. I've never worked with conduit before, but it looks pretty straightforward. My question is whether I need a separate clamp to anchor the wires to the box, or if having the conduit clamped is sufficient. I can't find anything that says the latter; but I can't find anything at the store that resembles a clamp for conduit.

The wires are held in pretty securely in the conduit, of course. But I don't know if this will pass code and if not, what to do.


househelper

07:06AM | 10/26/05
Member Since: 03/31/05
265 lifetime posts
If you are using conduit, you should be using individual conductors. No wire clamp is required.

fool4jesus

07:40AM | 10/26/05
Member Since: 06/20/05
53 lifetime posts
Thanks for the response. But that brings up your comment about cables in the conduit. I should have been more precise. The long run, from the outdoor panel/disconnect box to the tub, will be individual #6 wires. So there's no problem there, assuming I make the conduit big enough.

But then there's the run inside the house from the indoor panel to the outdoor one. I was planning on using regular 6/3 cable between there, including through a short (approx 12" total) run on conduit into the house. Why can't I use this? NEC chapter 9, table 1, notes 4 and 5 (and maybe 2) indicate that I can run this 6/3 cable through the short run into the house.

Thanks for all your help.


fool4jesus

09:21AM | 10/26/05
Member Since: 06/20/05
53 lifetime posts
While I'm at it, I have 3 questions about bends in the conduit. First, the code says a maximum of 360 degrees of bend. What if that is not sufficient? Let's say I need to zig-zag the conduit in a Z shape to get around some kind of obstacles. If I end the runs with junction boxes whose only purpose is to break up the long conduit runs, would that fix the problem? Do we know the purpose of this 360 degree rule?

Second, my entire conduit run is accessible directly. Its only purpose is to protect the conductors from water. (In fact, I'd just use UF cable, except that they specified that the ground wire needs to be a separate green conductor.) I'm using PVC. Is there any reason not to build a little at a time and string the wires simultaneously, thereby avoiding the problems associated with pulling the wires around the bends in the conduit? Seems a lot easier.

Finally, I am a little confused at how does the 360 degree rule apply to flexible nonmetallic conduit (LFNC). NEC paragraph 356.26 says the 360 degree thing "between pull points". What are pull points?


househelper

10:01AM | 10/26/05
Member Since: 03/31/05
265 lifetime posts
You breakup the conduit run with pull points, which may be junction boxes or LB's (conduit bodies with holes at right angles). It is a lot easier to pull wire thru if you don't have to make a lot of turns.

Putting the conduit together with the wire already in is not as easy as it would appear and is not advised, it is too easy to damage the wire.

Technically, a continuous piece of LFNC does not have any bends. You could use a combination of rigid PVC and LFNC to make your run. How far is it between the disconnect and the tub?

If you use a short run of conduit as physical protection for the cable, staple the cable at the first possible point after the cable exits.

fool4jesus

10:18AM | 10/26/05
Member Since: 06/20/05
53 lifetime posts
Thanks for your comprehensive answers. I'm gonna learn this stuff yet...

You breakup the conduit run with pull points, which may be junction boxes or LB's...

Oh ok ... so if I use LBs I can actually exceed the 360 degree limit, as long as the run between LBs has no greater than 360? So the 360 limit is actually for pulling purposes (because of the associated strain on the cables, I assume).

Technically, a continuous piece of LFNC does not have any bends.

That makes sense ... but then I don't understand what 356.26 is talking about. Maybe if you connect LFNC with rigid angles?

You could use a combination of rigid PVC and LFNC to make your run. How far is it between the disconnect and the tub?

That was exactly my plan. The distance is probably typical - about 6'. But of course the wire distance is longer because it's not a straight line. I planned on running RNC almost to where it would enter the tub body, then LFNC after that. I know the latter is limited to 6' - the LFNC is going to be 3-4 feet, terminated at the control panel inside the tub body.

If you use a short run of conduit as physical protection for the cable, staple the cable at the first possible point after the cable exits.

So then this short 12" run counts as physical protection (chapter 9, table 1, note 2). I was hoping so. :-)


fool4jesus

11:26AM | 10/26/05
Member Since: 06/20/05
53 lifetime posts
As I read the Annex C tables:

- Table C.5 tells me that 3/4 is the size of LFNC that I need for my hot tub wires (#6 THHN/THWN, 3 conductor+insulated ground)

- Table C.11A tells me that 1/2 would be acceptable for rigid PVC conduit

So, I'll use 3/4 all the way through. Does this sound reasonable?


househelper

02:53PM | 10/26/05
Member Since: 03/31/05
265 lifetime posts
Use 3/4 the whole way and you only have to buy one size clamps, bodies and connectors.

fool4jesus

05:04PM | 10/26/05
Member Since: 06/20/05
53 lifetime posts
I'm pretty new at reading those tables so I just wanted to make sure. Thanks for all your help!
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