Trying to choose wire for subpanel???

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Old 10-21-19, 01:45 PM
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Trying to choose wire for subpanel???

Ok. I have a detached carport I want to run power to. I will have a 15a lighting circuit, a 20A circuit for receptacles, 30A 120V for my travel trailer parked behind it, and a 30A 240V for welder. It's just gonna be me so there won't be a bunch of tools going on the 20A circuit while the welders running full tilt and the trailer being occupied (AC, micro, etc). So I was thinking of just putting a 60A breaker in the main. I found 4444 aluminum direct burial for 1.08 a foot and would just run a couple LBs and conduit just to get to depth (how I ran my 10/2 UFB for my other trailer anyways). Or I found for a total of .92 a foot 4 individual runs of xhhw (4446) and would run pvc conduit the whole way LB to LB. Carport already has a separate ground rod at the corner. I know to unbond the neutral and ground bars in the sub. What wire would you run in the walls to get from the main to the LB? I don't think you can run xhhw in a wall/no conduit, right? Will 4ga even fit in a 60A QO breaker? Is there a better wire to choose between buildings there's so many damn choices like ser seu mhf etc...


I found the product data sheet for the breaker but here's word for word on the wire size. "AWG 8...AWG 2 copper or aluminium" not sure how to interpret that.

I've been trying to figure this out myself but I would like to close my walls up soon and need to figure out this wiring thing.

This is a job somewhat in the middle of nowhere no permits no inspectors. I mean I'm sure somebody somewhere would love to take my money but even "official" people around here have told me "around here you just do stuff yourself and say nothing..."
 
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Old 10-21-19, 02:58 PM
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#4 will fit in a 60A breaker with no problems. Use 4-4-4-6 Al SER for the inside run, installs like NM (Romex). To splice to the individual wires running to the carport you'll need a junction box because in most cases a LB does not have the required volume by code needed for splices. The XHHW is a good choice for the run in conduit.
 
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Old 10-21-19, 04:52 PM
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Thanks. Now with the junction box I've only always messed with LBs or other parts already containing the slip fitting like the small pvc single gang boxes. When I drill the larger pvc junction box and glue in the box adapter to attach the conduit do I need to do the same to the flat back of the box so that there is something stubbed through the wall into the house or would just a hole in the back of the box and wall be enough since I'll silicone the box to wall to keep rain from getting into the wall cavity?
 
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Old 10-21-19, 08:11 PM
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You need a clamp on back of box to secure the cable. It's best to pass a nipple through the wall and use a threaded coupling with a Nm style clamp on the end. Remove the lock ring from the Nm clamp and screw the clamp into the threaded coupling. If you need to make a turn once inside use a LB and place the Nm clamp on the end of the LB to secure the cable entering the LB. You could also have junction box inside passing the conduit through the wall to a LB .
 
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Old 10-26-19, 01:10 AM
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314.16... I've found discussions on forums. I've found online calculators that only go to 6awg. I've even find a site with the beginning of the table only dealing with <6awg and wanting me to start an account to continue reading further. Connection to outside will be on a closet wall so I wouldn't mind a large blank plate on the wall inside and lb looks cleaner on exterior than a large box to me. If you have access to the full table could you tell me the required volume for 8 conductors (6 4awg and 2 6awg) with no other devices in the box but obviously wire connections for all 4 splices. Seeing as how there's a decent quantity of wires that are going to be pretty rigid to deal with I figured a metal box would be easiest. Found a 4 gang metal box 2 1/2 deep I think says 67 in^3 and found the larger 4 gang that's 1 7/8 deep with the stand off plate that necks up to the common 4 gang size that combined gives me 101 in^3 if I'm not mistaken but best info I can find is each 6awg conductor requires 5 in^3 based on the rest of the table I'd guess 4awg is somewhere between 8-9 in^3 per conductor?
 
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Old 10-26-19, 04:48 AM
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Box volume doesn't apply for wires larger than 6awg. Instead:


314.28(A)(2) Angle or U Pulls, or Splices. Where splices or where
angle or U pulls are made, the distance between each race-
way entry inside the box or conduit body and the opposite
wall of the box or conduit body shall not be less than six
times the metric designator (trade size) of the largest race-
way in a row.

Exception: Where a raceway or cable entry is in the wall of
a box or conduit body opposite a removable cover, the dis-
tance from that wall to the cover shall be permitted to com-
ply with the distance required for one wire per terminal in
Table 312.6(A).
[This is 2" for 4awg]

The distance between raceway entries enclosing the
same conductor shall not be less than six times the metric
designator (trade size) of the larger raceway.

When transposing cable size into raceway size in
314.28(A)(1) and (A)(2), the minimum metric designator
(trade size) raceway required for the number and size of
conductors in the cable shall be used.



 

Last edited by Luke M; 10-26-19 at 05:19 AM.
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Old 10-28-19, 06:14 PM
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Ok. hope I'm doing it right. I am going through a 2x6 wall and am going to have a LB outside the wall, stub through the wall with pvc to a male thread. Bought a 6x6x4 metal box to drill a hole in to clamp to LB where box is in wall flush with drywall but cover still accessible. A hole will be drilled on the top of the box for a clamp for the SER to enter through.
 

Last edited by maddmatt02; 10-28-19 at 07:13 PM.
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