Hi..could use a little help and thanks in advance. Turned on the TV, plugged in the tree and the power in that area went out..for seconds only. Then it came back on. Decided to plug in an electrical heater, then the power in that are went again. did the circuit breaker dance and none were popped, but redid them all anyway. No luck. Any advice on wht to do next?

Hi, I am upgrading the electrical circuits in my home, and there are 2 older circuits that are wired in a way I have never seen before. A 3 conductor cable (similar to Romex, but with a cloth outer jacket instead of plastic) goes from the main panel to a sub panel. In the main panel the 3 wires, black, white and red, are connected as follows: white to the neutral bus bar, black to a 15 amp breaker, and red to a 15 amp breaker. In the sub panel, there are 2 BX cables, each with a black and a white wire. The 3 white wires are connected, and the red from one of the breakers is connected to the black wire of the first branch circuit, and the black from the other breaker is connected to the black to the second branch circuit. This means that the 2 branch circuits are sharing the same neutral wire. Is this a method that was once allowed? It seems unsafe. I could run another 3 wire cable to the sub panel, and give each branch circuit its own neutral wire. I thought it might be a good idea to wrap the red wire of the existing cable with green tape at both ends and use it as a grounding wire between the main and sub panels. Is this the right solution?