Depends.
- If the conductors are 6 AWG or smaller.
- There is enough free space.
- It's not a short radius conduit body.
- The volume is durably and legibly marked by the manufacturer.
Only then can the conduit body contain splices.
In your specific case, I don't see the volume listed in the specifications section on the Home Depot page. So you'd have to check the fitting itself, to determine if the manufacturer has marked the volume. You didn't say what size wires you're pulling, so I can't answer that definitively. You also didn't mention the number of conductors, so it's impossible for me to do the fill calculations.
The Codez
National Electrical Code 2014
ARTICLE 314 Outlet, Device, Pull, and Junction Boxes; Conduit Bodies; Fittings; and Handhole Enclosures
II. Installation
314.16 Number of Conductors in Outlet, Device, and Junction Boxes, and Conduit Bodies. Boxes and conduit bodies shall be of an approved size to provide free space for all enclosed conductors. In no case shall the volume of the box, as calculated in 314.16(A), be less than the fill calculation as calculated in 314.16(B). The minimum volume for conduit bodies shall be as calculated in 314.16(C).
(C) Conduit Bodies.
(1) General. Conduit bodies enclosing 6 AWG conductors or smaller, other than short-radius conduit bodies as described in 314.16(C)(2), shall have a cross-sectional area not less than twice the cross-sectional area of the largest conduit or tubing to which they can be attached. The maximum number of conductors permitted shall be the maximum number permitted by Table 1 of Chapter 9 for the conduit or tubing to which it is attached.
(2) With Splices, Taps, or Devices. Only those conduit bodies that are durably and legibly marked by the manufacturer with their volume shall be permitted to contain splices, taps, or devices. The maximum number of conductors shall be calculated in accordance with 314.16(B). Conduit bodies shall be supported in a rigid and secure manner.
(3) Short radius conduit bodies. Conduit bodies such as capped elbows and service-entrance elbows that enclose conductors 6 AWG or smaller, and are only intended to enable the installation of the raceway and the contained conductors, shall not contain splices, taps, or devices and shall be of sufficient size to provide free space for all conductors enclosed in the conduit body.
Examples of short radius conduit bodies
Capped Elbow
Box Fill Calculation
For each current carrying conductor that terminates within the box, you'll add 1. So if you're pulling one ungrounded (hot) conductor, one grounded (neutral), and one grounding conductor. If you want to splice within the box, the calculation would look like this.
Ungrounded (hot) 1
Ungrounded (hot) 1
Grounded (neutral) 1
Grounded (neutral) 1
--------------------------
4
If grounding conductors are used, you'll add 1.
Current Carying 4
Grounding 1
--------------------------
5
Once you have the conductor count, you'll use Table 314.16(B) to determine the required volume.
NOTE: You'll always base the calculation off the largest conductor used. so if you have a #14 grounded (neutral) and a #12 ungrounded (hot), you'll use 2.25 because of the #12. If you're using grounding conductors that are a different size than the current carrying conductors, you'll multiply them separately (#12 hot, #12 neutral, #14 ground = 2 x 2.25 + 1 x 2.00).
14 AWG
If the largest conductor used is 14 AWG, you'll multiply the conductor count by 2.00 according to Table 314.16(B).
`5 * 2.00 = 10.00'
Which means the box must have a volume of at least 10 cubic inches, if you want to splice within it.
12 AWG
If the largest conductor used is 12 AWG, you'll multiply the conductor count by 2.25.
5 * 2.25 = 11.25
So in this case, the box must have a volume of at least 11.25 cubic inches.
3 Ungrounded (hot) Conductors
If you were pulling 3 ungrounded (hot) conductors, the calculations would look like this.
Ungrounded (hot) 1
Ungrounded (hot) 1
Ungrounded (hot) 1
Ungrounded (hot) 1
Grounded (neutral) 1
Grounded (neutral) 1
Grounding 1
--------------------------
7
14 AWG
7 * 2.00 = 14 cubic inches
12 AWG
7 * 2.25 = 15.75 cubic inches
There is nothing in Code that says that a metal box can't be part of the fault current path -- this is done all the time in systems that use AC, MCI-A, or metal conduit. (Personally, I'd use a self-grounding receptacle to save the ground clip and pigtail for neatness' sake, even though it doesn't get scored against box fill.)
If you are curious, btw, look up NEC section 250.148.
Best Answer
This is THHN wire in conduit. I do conduit pipe repairs and conduit-body replacements all the time.
That conduit body is not repairable.
You cannot splice inside a conduit body. They don't have the needed space. Also you need 12" of slack to even think about a splice in a junction box.
Mark and document
First, you make sure every wire is marked in a unique manner, typically by wrapping tape around the wires near the ends (both ends). You may need to use diagnostic methods to suss this out, e.g. Unhook one white wire and see what loses power. However in this particular case, it looks like your installer used a rainbow of wire, making this stupid easy. This is why wire comes in 12 colors.
Then you document where each wire goes. Photos and colored tape helps.
Easiest direction to pull
Then you decide which end has the fewest bends and will be easiest to pull. Unhook all the wires and add a string to the mix, so you can pull the string through. (it's not terribly hard to run a string through an empty conduit if you skip this step). Pull them back to the defect point. When they are near, wrap the bundle with tape, so they don't separate. Pull off the string if you added it. When pulling with string, watch out for hot parts of your panel - this is why I don't like to do it. Don't pull too hard, go back to the other site to correct any wire snags, so you don't rake the wire across a sharp edge.
Make repairs. Try to work around the ends of the wires, if you must pull/push them beyond the work area, try to do this absolutely no farther than necessary so you can grab it firmly with needle nose pliers. Otherwise things get harder, you must pull it all the way out and do a "proper pull".
Push and tease
Once repairs are complete, grab the wires. Wrap the bundle with wires staggered, starting at the first exposed wire end, to make the bundle as easy as possible to push through the conduit. Bend the nose of the bundle so it doesn't hug the edge of the pipe (otherwise it will hang up on fittings). If you pulled a string through, add that string to the bundle, and pull. Be gentle, if it feels like you might break the string, stop, and use the string to pull through a better string.
Or I usually push them back the way they came. This can sometimes be tedious. The answer here is not force but finesse. Force will only bend/crumple the wires inside the pipe. I do about 90% of my pulls with this push-tease technique. This will be easy until you hit the first bend, then harder. It can be near impossible after two 90's. I am not beneath temporarily disassembling a bit of conduit to help things along, but mainly, I build conduit with a lot of access points.
If push-tease doesn't work, then break out the regular pulling tools - fishing tape, rope, bit of cloth and a vacuum cleaner, etc.