The conduit coming in on the left carries a 15 A MWBC. In this junction box, it splits to the brown-to-black wire for the furnace, and the orange wires to some basement lights (top) and an upstairs bedroom (right) where there is an infrared sauna.
Problem is, the orange side of this MWBC also runs some outlets in the kitchen, and the outlet in our data closet. So when the furnace, sauna, and toaster all happen to be on at the same time, the circuit trips. Generally this only happens when someone is in a very important zoom call.
I would like to move the bedroom to its own separate circuit. Ideally I would take the connection out of this junction box into a new one. Problem is, there are no more accessible junction boxes on that branch -- to the right of this photo, the conduit goes into a wall and gets buried.
Is there any issue with bringing a completely separate circuit into this same junction box as a new run of NM from the panel? This approach has been used elsewhere in the basement when adding new branches, but not for new circuits, as far as I can tell. Would I need to cut the conduit back and add a new junction? If so... how do I cut the conduit off without cutting through the wires inside?
Some additional info...
- The house is 100 years old, in Madison, WI.
- Electrical is a mix of conduit (which is often full), BX, and NM. I haven't seen any knob and tube in use yet, but there's evidence of its existence in the past.
- Conduit is only used on the basement ceiling. Basement is unfinished and too shallow to ever be finished.
- The conduit leading to the junction box shown here follows a circuitous path of very full conduit and two other junction boxes, also full.
- The MWBC is handle tied, but in such a way that one side can trip at a time. However, I do have to turn both legs off to reset the breaker.
EDIT: I think I figured out why this is so messed up...
There is a dedicated 20 A MWBC for most of the kitchen outlets. But at some point (probably during kitchen renovation) a junction box was buried in the wall -- for one outlet, the cable in the box is 12 ga, but where the other end comes out in the basement, it's 14 ga. So that outlet has to be on a 15 A circuit.
To solve my problem, I'm going to move the furnace to a dedicated circuit, and put the bedroom/sauna to this leg of the 15 A MWBC, so it will be on the opposite leg from the kitchen outlet. The sauna is rated for a 15 A circuit.