Temperature at breaker

[cdkee]

Hi all,

I've been charging my car via my dryer 14-30 outlet and a Splitvolt.

Temperatures everywhere (the cable, mobile connector brick, Splitvolt) seem fairly normal, a little warm, but nothing that is alarming.

However, the breakers themselves are hot when charging after a while. At 24A, the breaker for the dryer circuit got to 125 degrees F before I got worried and lowered the amperage for the charge. The temperature was hottest at the edge where the neutral bus bar would be. Ambient temperatures can be hot, 90-95 degrees F in the garage.

Is this delta between ambient and temperature at the breaker normal? Would appreciate everyone's experience if they've noticed anything similar.

Thanks

 

[Sophias_dad]

Hi all,

I've been charging my car via my dryer 14-30 outlet and a Splitvolt.

Temperatures everywhere (the cable, mobile connector brick, Splitvolt) seem fairly normal, a little warm, but nothing that is alarming.

However, the breakers themselves are hot when charging after a while. At 24A, the breaker for the dryer circuit got to 125 degrees F before I got worried and lowered the amperage for the charge. The temperature was hottest at the edge where the neutral bus bar would be. Ambient temperatures can be hot, 90-95 degrees F in the garage.

Is this delta between ambient and temperature at the breaker normal? Would appreciate everyone's experience if they've noticed anything similar.

Thanks

Its acceptable, for sure. 125F is only 51.7C, well below the 75C rating of the breaker terminal,

It might be worth noting that the wire ampacity should be considered reduced a bit due to the ambient temperature, but its probably not a big deal.

 

[Randy-12]

If you are concerned about temps I would if it were me make sure lugs securing all wires all properly tightened.

 

[cdkee]

Thanks for the replies. I just wanted to know if other folks have felt their breakers during charging or measured temps to compare what is normal.

Sounds like it's normal though.

 

[dgbehrends]

I just checked mine with a heat temp gun and it said the 60amp breaker pulling 48 continuous amps was at 105F.

 

[MN-MS100D]

I hesitate to post this, but from UL Standard 489 and EATON (CH) test data:

• Most molded case circuit breakers tested are suitable for use at 40°C (104°F) ambient temperature continuous use. The terminals are endurance tested in the lab to allow a maximum temperature rise (not absolute temperature) of 50°C above ambient temperature at full rated current before the breaker (termination) is damaged.
• The maximum temperature allowed on handles, knobs, and other surfaces subject to user contact during normal operation shall not exceed 60°C (140 °F) on metallic and 85 °C (185 °F) on nonmetallic surfaces.

Please do not read into these paragraphs that you should run your breakers HOT, or ignore hot spots in a panel. Safety testing in a lab to meet listing criteria is different than the real world. Thermal runaway is a very localized phenomenon and can destroy a breaker and burn your house down regardless of "lab test data".

Same goes for receptacles. See Sandy Munro video.

 

[dgbehrends]

I looked up my receipt from Graybar electric and my breaker is a
Square D - QO260CP QO 60 Amp Two-Pole Circuit Breaker made by Schneider Electric also known as QO
A google search and some review reading leads me to believe it's a high quality breaker so I can sleep a little better at night.