Update on replacing my Tesla 14-50 adaptor with Hubbell HBL9451C 14-50 plug.
First, (background) I got frightened on March 13, 2014, when my Tesla 14-50 adaptor felt hot. When I measured it using an IR meter it was running 68 °C (154 °F), that is 43°C above ambient. I promptly replace the 14-50 outlet and my adaptor temperature went down to 54°C, which was 32°C above ambient. This for me, is still too hot. 32°C above ambient being too hot is also supported by ANSI/IEEE Standard 242-1986, IEEE Recommended Practice for Protection and Coordination of Industrial and Commercial Power Systems, that recommends insulated conductors maximum safe operating temperature to be 60°C. Note, if this outlet happens to be placed on a southern facing wall on a hot day the ambient temperature could be as high 50 °C. That would give an operating temperature of my Tesla adapter to be 50°C + 32°C = 83 °C! It is not surprising that there has been few fires and/or melted connectors. This is an insufficient safety margin.
When I replace the Tesla 14-50 adapter with a Hubbell 14-50 plug my replacement results were, to get an “apples-to-apples” comparison, a 12°C drop in temperature (were the cord connects to the 14-50 plug). Note, when my Tesla adaptor was running 54°C the cord measured 50°C (28°C above ambient). When I replace the Tesla 14-50 adapter with the Hubbell 14-50 plug the cord measured 38°C (only 16°C above ambient). This is a 43% temperature drop using the Hubbell 14-50 plug versus the Tesla adapter (much better). So, needless to say, I sleep much better at night now when my Tesla starts charging at 40 Amps. at midnight.
Now that I cut off my Tesla 14-50 adaptor and it has one inch leads sticking out, I can take a closer look at the adaptor’s resistance and see where the heat is being generated, the 14-50 contacts versus Tesla round connection pins plus internal connection. Using a four probe micro ohm meter, the total 14-50 adaptor resistance when plugged into a good 14-50 outlet was 4.35 milliohms. The Tesla 14-50 plug (without Tesla’s connectors and internal connections) with outlet connector measured only 1.57 milliohms (0.69 pin 1 + 0.87 milliohms pin 2), that is a 2.78 milliohm reduction or 64%. So that means the Tesla pins plus connector plus and internal wire connections added 2.77 milliohms of resistance (1.22 milliohms red wire + 1.55 milliohms black wire) to the Tesla 14-50 adaptor. So, when it comes to heating up my 14-50 adaptor 64% of the heat comes from Tesla’s round pins + connector + internal connections and 36% of the heat comes from the 14-50 plug and outlet connector. So, to say that high temperatures on the 14-50 outlet was the fault of the outlet may be over simplification. So it would seem, that in the infamous garage outlet fire may have been helped along by the heat added by the Tesla internal wiring versus by just a bad 14-50 outlet alone.
Parting comments, because of the additional resistance Tesla added to their adapter versus a standard 14-50 plug (like the Hubbell HBL9451C) the Tesla adapter should of be de-rated. Note, continuous duty of 50 Amp. plug is only 40 Amps. So, by my calculations the Tesla 14-50 adaptor should have been de-rated by resistance they added by their internal “small” round connectors and internal connections. By my calculations (based on a sample size of one) that would be: Power(14-50) = Power(Tesla adapter) or I[SUB]de-rated[/SUB]^2 x R[SUB]Total[/SUB] = I[SUB]40[/SUB]^2 x R[SUB]14-50[/SUB] or I[SUB]de-rated[/SUB] = Sq-Root(40^2 (1.56/4.35)) = 24 AAC. So, by my calculation the 40Amp. Tesla adaptor should of be de-rated to 24 Amp. to get the same safety margins as a Hubbell 14-50 plug.
Comments / Suggestions ?
I will test the Tesla newly designed 14-50 adapter they are sending out in the mail when I receive it to see if it is any better. More to come, Jim.
First, (background) I got frightened on March 13, 2014, when my Tesla 14-50 adaptor felt hot. When I measured it using an IR meter it was running 68 °C (154 °F), that is 43°C above ambient. I promptly replace the 14-50 outlet and my adaptor temperature went down to 54°C, which was 32°C above ambient. This for me, is still too hot. 32°C above ambient being too hot is also supported by ANSI/IEEE Standard 242-1986, IEEE Recommended Practice for Protection and Coordination of Industrial and Commercial Power Systems, that recommends insulated conductors maximum safe operating temperature to be 60°C. Note, if this outlet happens to be placed on a southern facing wall on a hot day the ambient temperature could be as high 50 °C. That would give an operating temperature of my Tesla adapter to be 50°C + 32°C = 83 °C! It is not surprising that there has been few fires and/or melted connectors. This is an insufficient safety margin.
When I replace the Tesla 14-50 adapter with a Hubbell 14-50 plug my replacement results were, to get an “apples-to-apples” comparison, a 12°C drop in temperature (were the cord connects to the 14-50 plug). Note, when my Tesla adaptor was running 54°C the cord measured 50°C (28°C above ambient). When I replace the Tesla 14-50 adapter with the Hubbell 14-50 plug the cord measured 38°C (only 16°C above ambient). This is a 43% temperature drop using the Hubbell 14-50 plug versus the Tesla adapter (much better). So, needless to say, I sleep much better at night now when my Tesla starts charging at 40 Amps. at midnight.
Now that I cut off my Tesla 14-50 adaptor and it has one inch leads sticking out, I can take a closer look at the adaptor’s resistance and see where the heat is being generated, the 14-50 contacts versus Tesla round connection pins plus internal connection. Using a four probe micro ohm meter, the total 14-50 adaptor resistance when plugged into a good 14-50 outlet was 4.35 milliohms. The Tesla 14-50 plug (without Tesla’s connectors and internal connections) with outlet connector measured only 1.57 milliohms (0.69 pin 1 + 0.87 milliohms pin 2), that is a 2.78 milliohm reduction or 64%. So that means the Tesla pins plus connector plus and internal wire connections added 2.77 milliohms of resistance (1.22 milliohms red wire + 1.55 milliohms black wire) to the Tesla 14-50 adaptor. So, when it comes to heating up my 14-50 adaptor 64% of the heat comes from Tesla’s round pins + connector + internal connections and 36% of the heat comes from the 14-50 plug and outlet connector. So, to say that high temperatures on the 14-50 outlet was the fault of the outlet may be over simplification. So it would seem, that in the infamous garage outlet fire may have been helped along by the heat added by the Tesla internal wiring versus by just a bad 14-50 outlet alone.
Parting comments, because of the additional resistance Tesla added to their adapter versus a standard 14-50 plug (like the Hubbell HBL9451C) the Tesla adapter should of be de-rated. Note, continuous duty of 50 Amp. plug is only 40 Amps. So, by my calculations the Tesla 14-50 adaptor should have been de-rated by resistance they added by their internal “small” round connectors and internal connections. By my calculations (based on a sample size of one) that would be: Power(14-50) = Power(Tesla adapter) or I[SUB]de-rated[/SUB]^2 x R[SUB]Total[/SUB] = I[SUB]40[/SUB]^2 x R[SUB]14-50[/SUB] or I[SUB]de-rated[/SUB] = Sq-Root(40^2 (1.56/4.35)) = 24 AAC. So, by my calculation the 40Amp. Tesla adaptor should of be de-rated to 24 Amp. to get the same safety margins as a Hubbell 14-50 plug.
Comments / Suggestions ?
I will test the Tesla newly designed 14-50 adapter they are sending out in the mail when I receive it to see if it is any better. More to come, Jim.
