At 360 Home Inspections, we use infrared cameras during home inspections. These cameras can't see through walls, but can often alert us of problems with a house that can't be seen with the naked eye.
When using infrared cameras, we often come across warm circuit breakers, warm dimmer switches, and even warm electrical panels during our home inspections. So how warm is too warm? It depends, there's no one size fits all answer.
As a home inspector, what I'm not so concerned with is the temperature itself, but instead I'm concerned about the meanings behind unexpected temperature differences, aka anomalies.
For example, a properly wired, functioning dimmer switch can get hot to the touch. I've found that a 65-degree temperature rise is normal for a maxed-out dimmer. If the ambient temperature is 71 degrees and a dimmer switch is at 136 degrees, I'd be concerned. First, I'd figure out how many watts the dimmer is rated for. I'd then make sure there wasn't too much being controlled by the dimmer.
When a circuit breaker has a lot of current flowing through it, it will get warm. If I find a warm circuit breaker while, again, using an infrared camera, I take a logical approach. First, is there a good reason for the circuit breaker to be warm? For example, a 240-volt appliance like an air conditioner will definitely warm up a circuit breaker while it's operating, that's not a problem.
AFCI Circuit Breakers
It is normal for Arc-Fault Circuit Interrupter (AFCI) circuit breakers to run warm. Lot's of energy is flowing through AFCI circuit breakers causing the breakers to run warm. This again, is normal.
There is not a one size fits all solution or answer for different houses, so it's a good idea to check for these anomalies throughout your home to help prevent overheating of electric wiring, breakers or fixatures. During your home inspection, we do just that!