I want to add some old outlet to a new circuit to release some stress (breaker keep going off). I want to fish a new wire thru the attic to the existing receptacle box (so i dont need to find the old wire thru the wall) and just splice the old wire and keep it in receptacle box with the new wire, I was wondering if that cause a problem? It a old house (1920)
Absolutely not! You can't make a circuit into a ring and double-feed it, for one thing it has a good chance of going BOOM. Fixing this is a two-step process.
First, lift the veil
Go out and get a $30 gadget called a "Kill-a-Watt". Get the slightly upscale one that stores measurements. This is a gadget that goes between your appliance and the wall, and measures how much power it uses. You are interested in amps, typically 0 to 12.
You know which particular circuit goes out all the time, so you know which receptacles are served by that circuit. Go to every single one of them, and for each thing plugged into them, plug them in through the Kill-a-Watt and measure their amps while you are using the gadget. Get a notepad and make an entry for each gadget.
Now you know that breaker you are always resetting, it will have a number, either 15 or 20. That figure is also amps, and it is your hard maximum for that circuit. You may be able to reach some obvious conclusions at this point. Because you're not blind anymore, you can see exactly what is causing your woes. And surprise, that lamp is really not a big deal, but that coffeemaker sure is, who knew?
For instance, you might need to switch that 12.4A heater down to "low" (5.3A) when running the 8A laser printer.
Also think about where other receptacles from other circuits are, and what's in those. Now you know which loads are the fat ones, it could be as easy as moving a load to a nearby receptacle that's on a different circuit.
Second, make a map
Now diagram out where all the receptacles are on that circuit, and make a best guess at how they are connected through the walls. Now pay very special attention to where your loads are.
Now you can think about where you can split the circuit so that a) you can put big loads that matter on opposite sides of the split, and b) this is possible to wire.
Next up, you sever the circuit so instead of one string, it is now 2 or 3 strings, fed from an intermediate point. You must not make loops.
But if you can find the right point, you may even be able to run 2 cables, and sever the circuit into 3 separate circuits. Imagine your string looks like
And you find that you can fish cables down to point G. In this case, run TWO cables to G. One of the cables, you use use to power G-H-I. The other, you feed back to the line that came from F.
You can't feed the A---F string from both ends, so you must sever it somewhere, e.g. Between C and D. However because you mapped the system, you know your big loads (23A of them) draw from D and E, so you sever it there, putting them on different circuits. You open up box D and disconnect the line to E and tape it off, and you open up box E and disconnect the line to D and tape it off. If you taped off the wrong wires, that outlet will be dead, so switch em. Now you have
/---------------------\ / /------------------\ | / / | | Panel----A-B-C-D CUT E-F-/ G-H-I
So you see, this is now 3 circuits feeding those receptacles instead of one.
This may be a good place to get some professional help.