IR Pics of Natural Gas Furnace & 30 Amp Breaker

These IR pictures were taken today from a 19 year old gas furnace and 30 amp breaker (notice the temperature of the top of furnace and breaker). The house also had extensive termite damage, polybutylene plumbing, mold inside the garage, and required a new roof and HVAC system. Ouch!



what temperature is too hot for a 30 amp breaker?

From the Square D website:

[size=2]"Square D circuit breakers can be applied in ambient temperatures within the
range of -10°C to 60°C (14°F to 140°F). This document provides guidelines
to follow when adjusting for ambient conditions."

So if it may be used in 140F ambient, it would be expected that it may operate at a higher temp but be derated above some chosen temp. What is hot to us may not be “hot” to a breaker that was designed to operate in hot conditions.

Check with the manufacturers instructions and limitations.

What type of furnace is that?

What Camera you using (model, etc).

Hey Dan,

I have the Flir B Cam SD.Very long battery life.

exactly, the breaker can operate at 140 so what is the Ouch ? Seems everyone gets these cameras and reports anything that is red as a flagged area.

Just because the breaker is manufactured to operate within the given temperature range doesn’t mean there isn’t a problem. Looking at the other breakers with a greatly different temperature range makes one wonder why this double pole breaker is running at such a different temperature.

My first thought was it was a split bus with this breaker feeding the lower section, but the conductors don’t look large enough and don’t take the path of the normal feeds. My second guess is either the water heater or an electric baseboard/wall heater. Both suck up the juice, especially when we first start testing.

So Kip… what was the breaker operating?

1st; a gas furnace runs on 120vac.

You are showing a 240VAC. Wrong label?

2nd the furnace your showing may likely get that hot during operation.
I can’t tell by any photo (IR is the worst), buy you appear to have a non-induced natural draft furnace with an air break inside the furnace where it is hot.

Do you have any other information for us?

The temperature differential between the breaker shown in the IR picture and the temperature of the other breakers was 60 degrees, which presents a potential fire hazard. I would consider a potential fire hazard as a red flag. The “ouch” comes from the price tag to repair the problems with the house as listed in my original post.

Were all other breakers loaded to the same level/% as the “hot” one?
Did you use a clamp-on meter to obtain/compare amps?

Do we have a standard to guide us and any test /safe level #'s against which we can compare what we can find in the field.

Did you consult the breaker manufacturer’s literature or contact them to see if they considered the temps a problem?

Dear All:

The Standard for Infrared Inspection of Electrical Systems & Rotating Equipment provides detailed inspection procedures and reporting requirements as well as operating temperature limits for in-service electrical devices. It also provides an IEEE formula that allows one to calculate the maximum allowable temperature for any operating electrical component.

While it is possible for some untrained infrared imager operators to ‘cry wolf’ without any justification, I believe that is not the case here.

Referring to the thermal image and allowing that the measured temperatures are reasonably accurate, the body of the circuit breaker is at or above 140°F or 60°C. The line side connections of the breaker connections appear to be operating higher still.

According to the above-referenced Standard, the maximum allowable temperature for a molded case breaker is 60°C at 100% load. For breakers operating at lighter loads, this number would be lower. Although load readings were not provided, it is unlikely that the subject breaker was carrying 30 amps.

Were this my inspection, I would have reported this breaker as an exception. Based upon experience with similar items, I would expect that the observed thermal pattern was due to either:

  • an internal defect such as a loose or deteriorated contact or
  • a loose or deteriorated line side connection

Should you be interested in obtaining a copy of the Standard for Infrared Inspection of Electrical Systems & Rotating Equipment, copies are available from the Standards section of the Infraspection online store.

Please feel free to give me a call directly if you need further info.

Thanks Jim!

I have used my IR Thermometer on breakers and all of them were 140+ because it was 115 degrees outside where the service panel was located.

Breakers operating under a load were 160+ with no apparent problems in a new service panel positioned directly in our hot Arizona sun.

Yeppers Dale. :smiley:

Actually, I think you prove the point, Dale.

It is not as much about the temperature by itself as it is about one particular breaker being significantly hotter than the rest, given similar conditions and loads. I see pretty hot panels in garages in our summers too, AFCI in these can be 20 - 30 degree warmer when they group them.

I would have probably noted this breaker to, based on the limite dinformation here. If I see one breaker that much hotter than the other in the panel. (I used to use my IR thermometer too, before my camera.)

There seems to be some information missing (or maybe I’m missing something) but…

  1. What is the breaker powering?
  2. Is the component in operation, or in an energized condition at the time of the thermograph?
  3. What is the amperage rating of the component/system?
  4. What wire gage is used on the circuit?
  5. Is there anything else on the circuit?

Sometimes being hot is normal. I wouldn’t say that its bad or good without more information.

You can’t say its bad without other information, you are correct.

However, at some point HI’s my be going beyond there limits.

They must be careful, but recommending further evaluation is in order here. Studying the thermal patterns of the scan provide a lot of information as to what is going on if you are trained to recognize them. This is sufficient for further investigation.

However, real-life scenarios out there will often result in a verbal conflict between electricians and home inspectors using thermal imaging. So, I caution this approach. I recommend the inspector be further trained and purchased the appropriate equipment so that you can conclusively report the defect as being significant.

When we elect to go beyond our scope by using thermal imaging, we cannot be falling back on the home inspection SOP. We must formulate our own SOP which is safe to the inspector and provides enough information to work with.

Nobody has answered my question yet, but this is a two pole 240 V breaker. Gas furnaces do not run on 240 V in residential applications!

We must consider whether this is a direct or indirect reading, as Jim is pointing out, the source of heat is out of view and likely an indirect measurement regardless of whether it is a defective breaker or blindside connection. Very low temperature rises can be significant when they are indirect readings.

The amount of electrical current flowing through the circuit is vital information needed to determine at what capacity the breaker is loaded. The circuit should be loaded to a least 30% capacity for scanning. If we have 140°F breaker under a 5% load there is a serious issue there. What’s going to happen at 90%? A fire?

As for the hot furnace, the other information needed is consideration of the static air pressures of the utility room. Is this a back drafting condition? Is the flu properly installed? Etc.

I say time and time again, it is vitally important that you fully understand exactly what you’re pointing the camera at when using thermal imaging. You must understand what the baseline should be and you must understand the working components to conceptualize what is happening in the thermal scan.

There is a lot of things you can do with a thermal camera, but you need to use some restraint in your business practices do not claim to be able to do them all just because a manufacturer or trainer says it can be done. Stick with what you know.

Has anyone taken a hammer to a circuit breaker lately?
If you don’t know what’s going on inside, it’s difficult to visualize the thermal signature.

My interpretation of the scan posted is that there is a bad circuit breaker connection at the line side bus. The electrical circuit is not overloaded but it is loaded. The thermal pattern of the other circuit adjacent breakers, appeared to be heat radiating/conducting from behind these circuit breakers.

And yes, a 66° indirect temperature rise in a residential service is substantial and requires immediate evaluation.

When trying to determine if the circuit is overloaded, you must include a large portion of the wiring throughout the panel. In this scan, there’s not very much wiring in view for this evaluation. It is best to take multiple scans at different ranges/angles when you have an apparent anomaly.

We are all commenting in vaccum on this one. What was the ambient temp? This is important as Dale pointed out. In AZ I am guessing that you have to upsize the wire to account for the increase in ambient and downgrade the rating to accomodate - so, as mentioned already - manufacturer guidelines to play a part in the final analysis. I would also like to point out that the spot may be pointing to a section of the bus in between the breakers. The emissivity is set to .90 which would not return an accurate temperature reading for a shiny bus bar - a close up digital photo would clear that up.

As for the furnace flue - 300 is not that hot for this type of furnace and again what does the surface look like where the spot is trained. We could be seeing some reflection from the vent pipe as this is a likely a material that will reflect infrared. Unless there was a visible defect I would not be so suspect of th condition.

Yep!! Depending on type of flue, size, height, etc, 300F may be the least temp required for a decent draft.