Okay, that's a fascinating and slightly concerning situation. The strong magnetic field is definitely a red flag and points to the likely source of the hum/vibration. Here's a breakdown of troubleshooting steps, focusing on the magnetic field issue

Understanding the Problem
Electromagnetic Fields (EMF)

All AC circuits produce EMF. A balanced load typically creates a weaker, more localized EMF. Your observation of an intensely shaking magnet suggests an imbalance in the EMF around the panel and service wires.

Likely Causes

This imbalance typically arises from:

Significant Imbalance in Current

A large difference in current between the two "hot" legs (L1 and L2) of the 240V service.

Loose Neutral Connection

A compromised or loose neutral connection is a prime suspect. The neutral is the return path for unbalanced currents, and a poor connection can cause erratic current flow and strong EMF.

Faulty Appliances/Loads

Occasionally, a malfunctioning appliance or load can inject harmonics or DC current into the system, disrupting the balance.

External Interference

While less likely, strong external EMF sources (like nearby industrial equipment, power substations, or even a malfunctioning transformer on the pole) could theoretically contribute, but they rarely cause this level of localized effect.

Troubleshooting Steps (in order of priority)1. Neutral Connection Inspection (CRITICAL - TURN OFF POWER BEFORE TOUCHING ANYTHING)



Main Panel Neutral Bus

This is the most likely culprit.

Power Off

Turn off the main breaker. Double-check with a multimeter that the panel is indeed de-energized. SAFETY FIRST!

Visual Inspection

Carefully inspect the neutral busbar and all connections to it. Look for:

Loose Screws/Terminals

Tighten any loose screws firmly.

Corrosion/Oxidation

Clean corroded connections with a wire brush or appropriate contact cleaner. Consider replacing severely corroded connectors.

Burn Marks/Discoloration

Indicates overheating, which often signifies a loose connection. Replace damaged components.

Proper Wire Gauge

Ensure all wires are sized correctly for the breaker/lug they are connected to.

Neutral-Ground Bond (If Applicable)

In your main panel, the neutral and ground are bonded. Ensure this bond is secure and in good condition. Do not confuse this with subpanels where the neutral and ground should be kept separate.



Meter Base Neutral Connection

This is where the utility's neutral connects to your wiring.

DO NOT TOUCH THIS YOURSELF. Contact your electric utility to inspect this connection. It's their responsibility, and messing with it can be dangerous and illegal. Tell them you suspect a loose neutral and are getting EMF issues and vibration in your panel.

Service Entrance Neutral Conductor

Inspect the neutral conductor where it enters the panel. Check for any damage, cuts, or signs of overheating.2.

Current Measurement on Individual Legs (with the panel powered and operational)



Clamp Meter (Amprobe)

Use a clamp meter that can measure AC current.

Measure Each Leg Separately

Clamp the meter around each service wire individually (one at a time). Record the current (amps) on L1 and L2.

Analyze the Difference

A significant difference (e.g., more than 10-20% difference) between L1 and L2 indicates a major imbalance in the load. This is a key clue. For example if L1 is reading 45 amps and L2 is reading 10 amps that would point to this as the source of the problem.3.

Identify Heavily Loaded Circuits (if a current imbalance is found)



Turn off breakers one by one

With the clamp meter still on the service wires, systematically turn off branch circuit breakers (one at a time) and observe the change in current on L1 and L2. This will help you pinpoint which circuits are contributing most to the imbalance.
4.

Investigate Problematic Circuits



Check for Ground Faults/Shorts

If you've identified a circuit causing a large current imbalance, use a multimeter to check for continuity between the hot wire and ground/neutral. A low resistance reading indicates a fault.

Inspect Outlets and Devices

On the problematic circuit(s), visually inspect outlets, switches, and connected appliances for damage, loose wires, or signs of overheating.

Test Appliances

Unplug appliances one by one on the problematic circuit(s) to see if the current imbalance disappears. This can help you identify a faulty appliance.5.

Voltage Measurements (with the panel powered and operational)



Voltage between L1 and Neutral

Should be approximately 120V.

Voltage between L2 and Neutral

Should be approximately 120V.

Voltage between L1 and L2

Should be approximately 240V.

Monitor for Voltage Fluctuations

A fluctuating voltage, especially on the neutral, can indicate a loose neutral connection.6.

Harmonic Analysis (Advanced)

If you suspect harmonics are the issue (though less likely in a residential setting unless you have a lot of non-linear loads like LED lighting with poor power factor correction, variable frequency drives, or electronic ballasts), you would need a specialized meter that can measure Total Harmonic Distortion (THD). High THD can contribute to EMF issues.7.

Consult a Qualified Electrician

If you're not comfortable performing any of these steps, or if you've exhausted these troubleshooting methods and the problem persists, call a licensed and experienced electrician. Explain the symptoms, the magnet test, and the troubleshooting steps you've already taken.

Important Safety Notes



Electricity is dangerous. If you are not comfortable working with electrical panels, do not attempt to do so. Call a qualified electrician.

Always turn off the main breaker before opening the panel and working on connections.

Double-check that the panel is de-energized with a multimeter before touching anything inside.

Wear appropriate personal protective equipment (PPE), including safety glasses and insulated gloves.

Follow all applicable electrical codes and regulations.

Regarding the Magnet Test

While the magnet test is a good indicator of a strong EMF, it's not a precise measurement. Don't rely on it solely for diagnosis. Use it in conjunction with other measurements and observations.

Summary:*The most likely cause of your problem is a loose or corroded neutral connection. Start by carefully inspecting the neutral busbar in your main panel and, if possible, having the utility check the neutral connection at the meter base. If that doesn't resolve the issue, systematically investigate current imbalances and potentially faulty appliances. Flag for review