Junction box for my splice in the attic

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  #1  
Old 08-30-15, 05:28 PM
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Junction box for my splice in the attic

I need to make two wire splices in the attic.

One is for a tankless electric water heater. Requires 6-3 wires.

The other is for a kitchen range, which also require 63 wires.

The location of the splice in the attic right above the kitchen wall. Actually I didn't have to splice the kitchen range wiring, but when they originally ran the wiring for the range (two home owners ago), they ran short on the wiring, and so they made a splice inside the panel for about 18". The splice was big and always in the way when I need to rewire things, so what I did was I loosened up a few straps in the attic and was able to pull the length I need into the panel, which means on the other end it's short. So I just pulled the whole thing back up to the attic. So I need a splice there.

The hot water heater is further away, but it so happens I have enough wiring to make the run, but not in a single piece, I need to splice them together and it so happens the best location is also right above the kitchen wall.

So my question is, can I put connect FOUR NM-b 6-3 wires into one 4" square metal box, a 2.5" deep one, to make two splices? Seems it would be tight just from the shear size of the wire? Or do I need two individual boxes one for each splice? Or use a 4-11/16" box?
 
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  #2  
Old 08-30-15, 06:39 PM
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Each #6 is 5 cubic inches. For two 6-3 cables you need a box larger than 35 cubic inches.
 
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Old 08-30-15, 08:13 PM
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OK, I looked up the box fill calculations.

I have to make two splices of two pairs of 6-3 wires. The wire is three #6 conductors and the ground is #10.

So basically I have 12 #6 conductors and 4 #10 entering the box, making a total of 8 splices. This comes to 105 cu in minimum.

If I use a 4" square box 2-1/8" deep that's 30 cu in, if I add an extension ring to it that makes it 51 cu in.

So that means if I am trying to splice only one pair (not two pairs) I cannot do that with one 4" square box with an extension ring? If I look up the box capacity I would need to buy TWO 6" METAL BOX for what I need? A 6" box to facilitate just splicing a 6-3 wire?
 
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Old 08-30-15, 09:08 PM
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I didn't have to splice the kitchen range wiring, but when they originally ran the wiring for the range (two home owners ago), they ran short on the wiring, and so they made a splice inside the panel for about 18". The splice was big and always in the way when I need to rewire things, so what I did was I loosened up a few straps in the attic and was able to pull the length I need into the panel,
A plan B or maybe plan A would have been to put the splice box near the panel and not moved the existing cable. Just ran a short new length into the panel.
 
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Old 08-30-15, 09:42 PM
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A plan B or maybe plan A would have been to put the splice box near the panel and not moved the existing cable. Just ran a short new length into the panel.
That was one of the considerations and I quickly ruled that out due to the number of conduits coming into the panel from the top were many and already congested. The KO holes on the top of the box were used up except one. There is simply no way I would be able to find space above the panel to insert a box; and I am not inclined to run new conduits to come in through the side.
 
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Old 08-31-15, 11:39 AM
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Something is wrong with your math. 12 x 5 = 60, plus a ground.
 
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Old 08-31-15, 11:53 AM
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Is the water heater cable long enough to reach the range without a splice? If so, you could swap them and only have one splice box in the attic. Otherwise, get a pair of deep 4-11/16" boxes and some of the big blue wirenuts.
 
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Old 08-31-15, 04:04 PM
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Something is wrong with your math. 12 x 5 = 60, plus a ground.
I was using some online box fill calculator...perhaps my input was incorrect.

Number of #6 Wires Terminating in the Box: 12
Number of #10 Wires Terminating in the Box: 4
Number of #6 Wires Spliced in the Box: 12
Number of #10 Wires Spliced in the Box: 4
Number of Wires that Pass Thru Box: 0
Number of Wire Loops Greater than 12": 0
Number (Gang) of Devices to be mounted to the box:0
Largest Wire Size Connecting to Devices: #6
Size of Equipment Grounding Conductor that enters the box: #10

When I hit calculate it returns 142.5 cu in.

Now may be I don't have any wires terminating in the box and all I need to put in are the splices?

Number of #6 Wires Terminating in the Box: 0
Number of #10 Wires Terminating in the Box: 0
Number of #6 Wires Spliced in the Box: 12
Number of #10 Wires Spliced in the Box: 4
Number of Wires that Pass Thru Box: 0
Number of Wire Loops Greater than 12": 0
Number (Gang) of Devices to be mounted to the box:0
Largest Wire Size Connecting to Devices: #6
Size of Equipment Grounding Conductor that enters the box: #10

That comes back with 72.5 cu in.
 
  #9  
Old 08-31-15, 04:07 PM
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Is the water heater cable long enough to reach the range without a splice? If so, you could swap them and only have one splice box in the attic. Otherwise, get a pair of deep 4-11/16" boxes and some of the big blue wirenuts.
Yes I could do that, that would eliminate the splice to the kitchen range, but that means with the wires I have I need to make two splices in series to make it to the water heater, unless I buy a new coil of 50' long 6-3 wire which I'd rather not. So either way I am looking at two splices.
 
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Old 09-01-15, 07:14 AM
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For box fill, you count all of the grounds as one conductor. In your last calculation, change it to one #10.
 
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