Okay, let's break this down and address your situation systematically. Dealing with old wiring and MWBCs can be tricky, so caution is paramount. Since you've already started disconnecting, we'll focus on safely and correctly finishing that task and then verifying your work.

IMPORTANT SAFETY PRECAUTIONS - READ CAREFULLY! Turn off the power! The absolute most important step is to turn off the breakers that supply the circuits you're working on. Double-check that the power is off by using a non-contact voltage tester (a "tic tester") at each receptacle before touching any wires. Even with the breaker off, there could be stray voltage from shared neutrals or other unexpected sources. Work Methodically

Don't rush. Take your time at each receptacle and clearly identify the wires you're disconnecting.

Documentation

Label everything as you go. Use masking tape and a marker to label wires before disconnecting them. Label with the wire color (e.g., "Red - Disconnected Circuit") and location (e.g., "Living Room Receptacle 1"). Take photos before and after each step. This will be invaluable if you run into problems later.

Electrical Gloves and Eye Protection

Consider wearing insulated electrical gloves and safety glasses for added protection.

If Uncertain, Call a Professional

If at any point you feel uncomfortable or unsure about what you're doing, stop and call a qualified electrician. It's better to be safe than sorry. Working with electricity is dangerous, especially with old wiring.

Step-by-Step Disconnection and Verification1. Identify the Disconnected Red Wire at Each Receptacle

You've already started this, but make sure you're consistently identifying the red wire that was part of the removed circuit.2.

Disconnect the Red Wire

At each receptacle, carefully disconnect the red wire. If the red wire is connected with a wire nut, remove the wire nut and untwist the wires. If the red wire is connected to a terminal screw on the receptacle, loosen the screw and remove the wire.

Cap the Red Wire

Immediately after disconnecting the red wire, cap it with a wire nut. This is crucial to prevent it from accidentally touching anything and creating a short circuit. Use a wire nut that is appropriately sized for the wire gauge you're using.

Tuck the Capped Red Wire

Carefully tuck the capped red wire back into the electrical box.3.

Inspect Remaining Wiring

While you have the receptacle out, inspect the remaining wiring in the box. Look for:

Damaged Insulation

Cracked, brittle, or frayed insulation on any wires.

Loose Connections

Wires that are not securely connected to the receptacle or to each other.

Overcrowding

Too many wires crammed into the box, which can lead to overheating.

Aluminum Wiring (If Applicable)

If you have aluminum wiring, it requires special handling and connectors. If you suspect you have aluminum wiring, definitely consult an electrician. Address any issues you find, or plan to address them. Loose connections should be tightened. Damaged wiring might need to be replaced.4.

Reinstall Receptacle (Temporarily)

Carefully reinstall the receptacle into the box. Don't force it. Secure the receptacle with the screws.5.

Repeat at Each Receptacle

Go through steps 1-4 at every receptacle that was connected to the removed red wire circuit.6.

Neutral Wire Concerns - Very Important! Since it's an MWBC, the neutral wire could be shared. This is where things get complicated, and incorrect handling can create a dangerous situation. Do not disconnect any neutral wires unless you are absolutely certain that the corresponding black/hot wire is disconnected at both ends. An open neutral on a MWBC can cause dangerous voltage imbalances and damage equipment. Here's how to proceed: Trace the Neutral

Try to trace the neutral wires back to the panel. You're looking for a single neutral wire that serves both the removed red circuit and the still-active black circuit.

If the Neutral is Shared

If the neutral is indeed shared, you have two main options:

Leave the Shared Neutral As-Is

This is generally the safest option, provided you are confident that the remaining black circuit's load is within the neutral's capacity (wire gauge). If there is no indication of overheating on the neutral wire before you disconnected one of the circuits this is likely the correct path to take.

Rewire with Separate Neutrals (Highly Recommended but Requires More Work)

The best long-term solution is to run a new neutral wire for the remaining black circuit back to the panel. This eliminates the shared neutral and the associated risks. This will likely require the most work, but is the safest and most reliable solution.7.

At the Breaker Panel



Disconnect the Red Wire

Locate the red wire in the breaker panel that corresponds to the removed circuit. Disconnect it from the breaker.

Cap the Red Wire

Cap the disconnected red wire in the panel with a wire nut.

Label the Wire

Label the capped wire clearly (e.g., "Disconnected Red Circuit - DO NOT USE").

Remove the Breaker (Optional)

You can optionally remove the breaker for the red circuit.8.

Verification and Testing



This is crucial! Visual Inspection

Before turning the power back on, double-check all your connections and make sure everything is properly capped and tucked away.

Turn on the Breaker

Turn on the breaker for the remaining black circuit.

Voltage Testing

Use a multimeter to verify that you have the correct voltage at each receptacle connected to the remaining black circuit (typically around 120V). Test between the hot (black) and neutral, and between the hot (black) and ground.

Receptacle Tester

Use a receptacle tester to check each receptacle for proper wiring (hot, neutral, and ground).

Load Test

Plug a lamp or other small appliance into each receptacle to ensure it's working correctly.

Important Considerations



Old Wiring Problems

Old wiring often has brittle insulation and loose connections. Be very gentle when handling the wires.

Non-Metallic Sheathed Cable (Romex)

If your wiring is Romex (plastic-sheathed cable), check the condition of the sheathing. If it's damaged, you may need to replace sections of the cable.

Grounding

Ensure that all receptacles are properly grounded. If you find any receptacles that are not grounded, you may need to run a new ground wire.

Arc Fault Circuit Interrupters (AFCIs)

Depending on your local electrical code, you may be required to install AFCIs on certain circuits, especially in bedrooms.

MWBC Imbalance

Now that you have removed one of the circuits, make sure the circuits are not overloaded. You may need to balance the electrical load across both legs to avoid tripping breakers.

Permits

Depending on the scope of your work and your local regulations, you may need to obtain an electrical permit.

Summary of Key Points



Safety First

Always turn off the power and take precautions to protect yourself from electric shock.

Systematic Approach

Work methodically and label everything.

Inspect Carefully

Look for damaged wiring, loose connections, and other potential problems.

Neutral Wire Handling

Be extremely careful when dealing with neutral wires on MWBCs. An improperly handled neutral can be dangerous.

Verify Your Work

Use a multimeter and receptacle tester to ensure everything is wired correctly.*

Know Your Limits: If you're unsure about anything, call a qualified electrician.This process is detailed, but it's necessary to ensure the safety and reliability of your electrical system. Take your time, be careful, and don't hesitate to call a professional if you need help. Good luck! Flag for review