Okay, let's break down the situation and try to assess the risk of hidden damage. You're right, nobody can definitively say "yes" or "no" without a proper inspection, but we can make an informed assessment.

Understanding the Problem Overcurrent

The circuit was subjected to approximately 31 amps of continuous current when it's designed for a maximum of 30 amps (breaker rating) and a safe continuous load of 24 amps (80% of the breaker rating).

Heat

Excessive current generates heat due to the resistance in the wiring, connections, and breaker. The warm plug is a direct indication of this.

Cumulative Damage

Overheating, even if it doesn't immediately trip the breaker, can cause degradation of insulation, loosening of connections, and eventually, increased resistance, more heat, and ultimately, failure.

Factors Increasing the Risk of Hidden Damage Age of Wiring

Older wiring is more likely to have insulation that is already brittle and prone to degradation.

Type of Wiring

Aluminum wiring is more susceptible to problems with connections due to its expansion and contraction properties. While unlikely for a dryer circuit, it's worth knowing.

Quality of Installation

Poorly tightened connections, back-stabbed outlets (less common in dryer circuits but still possible), and damaged insulation during installation all contribute to increased resistance and hotspots.

Continuous Load

EV charging is a continuous load, meaning it operates at or near its rated current for extended periods. This is much more stressful than occasional dryer use.

Breaker Response

Breakers are designed to trip based on time and current. A slight overload might not trip them immediately, especially if the breaker is old or has been subjected to repeated tripping in the past. This is especially true if the ambient temperature around the breaker panel is elevated. The higher the ambient temperature, the faster the breaker will trip. But it is not a linear relationship and will require specific understanding of the breakers characteristics to determine.

Why the Breaker Didn't Trip Immediately (and why that's not reassuring)



Breaker Tolerance

Breakers have a tolerance range. A 30-amp breaker might not trip exactly at 30 amps. It might trip slightly above, and it takes time for the thermal element inside the breaker to heat up and cause the trip.

Ambient Temperature

The breaker's tripping behavior is affected by the ambient temperature around the breaker panel. If the panel is in a cool location, the breaker might take longer to trip.

Cumulative Effect

The breaker might have been slightly weakened by the overcurrent, even if it didn't trip.

Assessing the Risk & Recommending Action

Based on what you've described, I would be concerned about the possibility of hidden damage. The warm plug is a red flag. Here's a breakdown of the risk level and recommendations: Significant Risk

The circuit was overloaded, and the plug got warm. That is a clear indication of a problem.

Recommendations (in order of importance)


Immediately cease using the 30-amp circuit for EV charging until it has been inspected by a qualified electrician.2. Electrician Inspection

Have a qualified electrician inspect the entire circuit, especially the following:

The receptacle

Look for signs of melting, discoloration, or looseness. Replace the receptacle with a high-quality, heavy-duty receptacle.

The wiring

Check the wiring gauge to ensure it's appropriate for a 30-amp circuit (usually 10 AWG copper or 8 AWG aluminum - verify with a professional!). Inspect the insulation for brittleness or damage.

The connections

Check the connections at the receptacle, at the breaker, and at any junction boxes in between. Tighten any loose connections (with the power off, of course!).

The breaker

Inspect the breaker for signs of overheating or damage. Consider replacing the breaker as a preventative measure.3.

Thermal Imaging

The electrician can use a thermal imaging camera to look for hot spots in the wiring and connections while the circuit is under load. This is the best way to find hidden damage. However, it is important that the electrician understand proper EV charging circuits to test the circuit properly.4.

Derate if Necessary

If the wiring is marginal or has any signs of degradation, consider derating the circuit to a lower amperage and using a smaller breaker (e.g., a 20-amp breaker). But only after the electrician determines this is safe and appropriate!* This might involve replacing the receptacle as well. This would reduce the risk of future overloads.

In summary: Don't assume that because the breaker didn't trip, everything is fine. Err on the side of caution and have the circuit inspected. The cost of an inspection is far less than the cost of repairing electrical damage or, worse, dealing with a fire. Stop using the circuit for EV charging until the inspection is complete. Flag for review