I certainly agree that a home inspector should not reply on a ‘digit test’ to locate a hot breaker - in fact most should not touch anything inside the panel at all. I also agree that it is good to have definitive data to give the client. Personally I use an IR thermometer and can easly identify hot spots that way. True, I cannot give them a picture, but it gets all the informaion that is required. However, as a H.I. what I report is my observation, without saying in absolute terms how it should be repaired or that anything absolutely has to be replaced. So far, I had had no kickback on any such things I have reported from electricians or clients. Should that happen I am fully prepared and willing to meet the electrician at the house to resolve the problem together. If it was hot when I reported it, it will still be hot when I return and it will be repaired.
Again, I am not saying H.Is not fully experienced in electrical work should proceed in this manner - each should proceed in accordance with his experience and training, consistent with safe inspection practices.
I use a Fluke Ti10 for commercial and industrial electrical inspections of 480/277, 240/120, 240/208 & 208/120 distribution panels. The temperature rise on a wiring terminal at a point to which the insulation of a wire is brought up as in actual service shall not exceed 122ºF (50ºC). Terminations for 100% rated circuit breakers: the temperature rise on the termination shall not exceed 140ºF (60ºC).
When checking distribution panels and you find a hotter than normal breaker check the breakers MFG rating. When doing commercial and industrial you have to check both the rating of the overcurrent device and cross-referencing the conductor’s heat rating with the NEC. Here is a great link for more understanding. [Circuit breakers operating tempatures](file:///C:/Users/final/Downloads/Temperature%20Rise%20MCCB%20Limits%200600DB1603%20(1).pdf)
A few more thoughts- The normal heat generators inside the circuit breaker are the main contacts, bi-metal for tripping, electronics, and power supplies, causing the circuit breaker body to increase in temperature. The body of the circuit breaker can be hotter than the terminations since the load wires act as heat sinks. Each circuit breaker family or frame will have its own heating characteristics due to different designs, so not all circuit breakers run at the same temperature. For example in a residential distribution panel; a 20 Amp load through fifty feet of #12 AWG Cu wire generates approximately 32 watts, due to resistance (1.6 Ohms per 1000 ft.). The wire stays cooler because it dissipates the heat over the length of the wire compared to the home wiring, the circuit breakers generate very little “heat”, even though the circuit breaker temperature is higher since the heat is more concentrated. In an industrial inspection and some commercial applications, the length of wire may be much shorter and the heat factor is very important and must be checked along with the overcurrent device. Hope that helps.
Thermal electrical inspections are the easiest thermal applications to do, but not really.
There are a couple of other things that are significant other than just the temperature of a component that no one seems to talk about. The first is what is the amperage load on the circuit with reference to its maximum capacity rating.
If you have a 20 amp circuit breaker at a temperature of 98°F (below the critical level) and the amperage draw on the circuit is 5 A. What will the temperature rise going to be if you load the circuit with the other devices that are not running? There are calculations to give you an apparent temperature rise. We certainly do not want to just turn everything on and “see what happens”. And we certainly cannot dismiss this condition because it doesn’t meet the high-temperature limit.
Also, you must consider what type of components are on the circuit you are testing. Are they inductive loads or resistance loads? Do they run intermittently or nonstop? You’ll find lighting loads that get things much hotter than anything else in a panel. Lighting is a resistance load that stays on continuously during operation of the building. Being a resistance load, the amperage draw is consistent. There are no load variations or startup spikes from inductive loads such as HVAC equipment. They tend to store heat over time, especially within the circuit breaker.
So I hope inspectors give more consideration to something hot, or what is not. It can go either way without the additional data.
As others post, “this is outside the scope of a home inspection”. If you use an infrared thermometer or infrared imaging equipment during a building inspection, you are stepping outside of the home inspection standards, and they no longer apply. You’re either in by doing it right, or you’re out and should just leave it alone.
Amp load and max capacity is everything. When I do industrial electrical inspections I have to do load calculations all the time. I did a large chicken plant in Decatur Alabama it took me days to do one portion of the plant. My report ended up being about 125 pages a week later after I did the load calculations and cross reference the heat factors for the conductors and overcurrent devices with the NEC.
Glad you mentioned about what components are on a particular circuit. It’s important to understand if they are inductive or resistance loads.
I agree with you wholeheartedly that just a hotspot is not enough, but it is a good starting point. If somebody detects overcurrent device that’s above the rating of that device AKA breaker then that is worth calling out. Most inspectors that I know don’t go very deep into the electrical inspections with thermal imaging cameras primarily because they just simply don’t know how. I’ve been an electrician for over 45 years and have installed everything from residential to industrial to PV’s
I travel among the Georgia international chapters to teach the inspectors on electrical inspections. Of course the first course of action is safety. Thanks for such a good response, I’m teaching the north Georgia chapter of internachi electrical inspections for those who want to go deeper into commercial inspections. When I have to do a commercial electrical inspection or industrial I’ll take a couple of inspectors with me to show them what’s going on.
There are too many camera owners that will not invest in the required training.
They find a hot spot w/o knowing how hot is too hot. Whether they are taking a direct or indirect reading, or what is causing the problem by correctly tuning the camera properly (and using the right camera).
Finding low temperatures which are actually a serious problem are a significant concern.
I agree, the type of load isn’t really relevant unless were talking about a load that is continuous versus intermittent or variable. A 10 amp motor running continuously for 12 hours will generate the same amount of heat in the conductors as a 10 amp heater running continuously for 12 hours.
That is correct, but in thermography “variable” often pushes things over the top.
Deferred maintenance is most often the cause. Even excessive maintenance can be the cause. Over lubrication of a bearing can increase load and can be significant dependent upon the horsepower involved.
Just recently I was working in a communication center and found an extremely hot breaker/circuit. I tracked it down and found that it went to an ice cream freezer in a break room, plugged in with an extension cord. The condenser was smoking hot. Further inspection showed it completely clogged. Excessive head pressure and voltage drop created the problem. When I returned for a follow-up, a dedicated circuit was added and the equipment was cleaned. No indication of heat in the breaker panel. This condition was on an interior wall circuit.
This was a very large facility with a very large break room (rather a cafeteria). There were dozens of high amperage food-service equipment in this room sharing branch circuits.
