NEMA 14-50 Supply cable heat data

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daveo4EV

daveo4EV

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@Vim Schrotnock I don’t know “how“ the neutral would be used for anything related to vehicle - the J-1772 specfication only has 5 “counductors” at the plug - if you look closely there are only 5 actual connections inside the plug

2 high voltage AC connectors
2 low voltage pilot-pins (dc communcation?)
1 ground connector

given than EVSE is nothing more than a relay (a giant switch) with some minor signally electronics to communicate with the vehicle…

_IF_ an EVSE was going to use the neutral wire from the NEMA 14-50 plug - there is _NO_ physical wire for it in the actual J-1772 plug with 240 volts because the high voltage pins are both “hot” - and pilot pins are low voltage in the specification…

also _any_ EVSE that supports modular adapter cables (like the Porsche one and Tesla) allow you plug the same EVSE into either a 14-50R or 6-50R plug - one of those plugs has a neutral and the other doesn’t - so the EVSE clearly functions with the absense of a neutral when using the manufacture’s provided adpter/supply-cable…

I welcome any evidence of any EVSE supporting the J-1772 standard requireing or using the netrual - but first you’ll have to tell me which of the 5 connecting pins shown below is the Neutral with used with a 240 volt source…

Porsche Taycan NEMA 14-50 Supply cable heat data 8D61EFD1-9676-4A36-BFFC-CA215904D79A
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mike-taycan

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If it was just warm, then I probably wouldn't be concerned but as @KenU experienced (and I am experiencing the same), the at 40 amps the cable are hot to the touch and in my case, in particular, my circuit breaker is way too hot after just an hour or so of charging at 40 amps.

The fact that many of us are experiencing this issue and in several cases having breakers trip or charging sessions stopped due to overload, something has to be figured out. Since many of us have different wiring setups installed for our chargers, the only common thing among us is the PMCC itself. So we just have to figure out the cause so we can get it taken care of.
I am totally with you. That’s not right. It’s very interesting why we are having different experiences with similar setups. Do you have the ability to put an amp meter on wires connected to the breaker to see how many amps you are actually pulling? Could the charger be misrepresenting the amp draw? That measurement from a clamp meter would be super helpful.
 
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daveo4EV

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while I agree the amp measures from/at the breaker would be good - i believe it to be un-necessary

what I have observed is as follows
  1. the PMCC unit reports 39.4 amps - which is about 9.6 kW
  2. the vehicle software on the console screen reports 8.68 kW - which is about right for charging losses from the charging unit’s actual draw to power being added to the battery
  3. separately my solar system has both “consumption” and “production” meters - separate - when my PMCC is charging at 40 amps the consumption metrics as reported by the whole house consumption meter show an increase of about 9.6 kW
  4. I also have another whole house consumption meter by Rainforest that talks wirelessly to the utilities “smartMeter“ - PG&E - this _IS_ the meter used by the utility for billing purposed and is considered the “truth” - the data from the rainforest monitor also shows a incremental increase of about 9.6 kw when charging the Taycan - again inline with expectations.
while it may be possible for the PMCC to under-report it’s current draw - in my case there is no data to support that possibility - and in fact where there is data available, the data shows the reported draw is actually highly accurate.

others may have different experience - but in my case there is no reason to distrust the Porsche software.

Also the cable is behaving thermally right in line with expectations/predictions for 10 gauge wire under a 240v/40 amp current draw.

I do not believe the cable is electrically “unsafe” and while the cable is warm/hot I do not believe electrically it’s near any unsafe limits…

I do however believe any consumer device getting this hot under normal/approved use is unexpected - and general population knowledge over the years that “hot === bad” is causing people concern.

a more appropriate gauge wire would cause less heating and therefore be more inline with people’s experience and expectations for a high quality consumer grade device that cost 4x competitive products - and Porsche’s EVSE can be reasonably described as an expensive consumer grade device.

Electrically I believe there is no actual problem - I doubt the cable will melt or ever cause an electrical fault

I also believe Porsche should upgrade the cables free of charge to a new design to avoid the perception there is a problem given the obvious and observable heat profile under normal use. People don’t expect their electrical devices to be warm/hot to the touch under normal/expected use. This perception problem is also further exasperated by the supposed use case of the PMCC, with mobile being part of it’s name - it would be one thing if you as a customer were not expected to access/touch the plug - however as a mobile device Porsche clearly designed this to be used during travel and at any plug you may find, therefore they clearly expect you to plug/un-plug this device as often as you are charging while traveling - coming down from an overnight hotel stay an unplugging your mobile Porsche charger with a supply cable that is potentially too hot to touch is not a good experience…

I shudder to think how hot this cable would be at a track day plugged into a NEMA 14-50R in direct spring/summer sunlight with ambient temperatures north 90F - this is clearly a use case given Porsche’s promotion of the Taycan as a track capable vehicle and their insistence on providing a mobile charger with each order…

I’ll be able to report on cable temps under this exact scenario when I visit thunderhill sometime in the future with my Taycan - when I drive my EV’s there I often use Thunderhill’s RV hookups (NEMA 14-50R) to charge the Ev while I track my GT3 - I would normally bring my Tesla EVSE (which doesn’t get this hot under normal use) - but I’ll bring the Porsche PMCC specifically to gather data on this cable - it’s not unheard of for ambient temps well in excess of 95F during the day - I’m wondering how hot this supply cable would get under those outside sunny day normal use conditions.

Porsche should do the right thing here and redesign the North American NEMA 14-50 cable with 6 or 8 gauge wire which would mitigate the heat characteristics of 240v/40 amp charging and make the cable more manageable to human touch under a wider range of ambient thermal conditions.
 
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mike-taycan

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daveo4EV, well said and agree with all. Also, your other ways to measure power are confirmation. I won’t think the Porsche readings are wrong, but you never know. It’s their first version.
 

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I am totally with you. That’s not right. It’s very interesting why we are having different experiences with similar setups. Do you have the ability to put an amp meter on wires connected to the breaker to see how many amps you are actually pulling? Could the charger be misrepresenting the amp draw? That measurement from a clamp meter would be super helpful.
Of course, I cannot speak for HelfFL but my electrician put his clamp meter over everything: breaker, receptacle, wires , cables etc and all was normal output. In HelfFl's case, I'd certainly want my electrician to clamp meter test those, as well.
 


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6 is gauge of wire
3 is number of conductors
And realize that 6/3 Romex will have a 4th solid wire for ground that will be much smaller like 8AWG.

See resiance and power ratings at
https://en.m.wikipedia.org/wiki/American_wire_gauge
The 14-50 should be 8AWG minimum and 6AWG would run cooler. For a 1ft cable they should make it 6AWG as it's cheap enough. Neutral and ground can be smaller, only X & Y need be thick.
 

ron_b

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Is this a plug that would fit/connect specifically to the PMCC? Thanks
I cannot confirm this at all, I was just using a link provided in earlier post.

My recommendation is still setting the Porsche Charger Connect to 24-30 amps and wait for a statement from Porsche.
 
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Vim Schrotnock

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And realize that 6/3 Romex will have a 4th solid wire for ground that will be much smaller like 8AWG.

See resiance and power ratings at
https://en.m.wikipedia.org/wiki/American_wire_gauge
The 14-50 should be 8AWG minimum and 6AWG would run cooler. For a 1ft cable they should make it 6AWG as it's cheap enough. Neutral and ground can be smaller, only X & Y need be thick.
Your table shows exactly my point. AWG 10 with a 90C insulation rating has a 40 amp capability. Check out the table.
 


ron_b

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There is simply no way that the Porsche engineers would make such a simple and basic mistake as to supply a wire gage AND INSULATOR that is not rated for their application. 10 gage copper wire is rated for 40 amps with the proper insulation:

10-gauge solid copper wire in general has a resistance of almost exactly 1 ohm per 1000 feet. The rating is limited by how much heat the insulation was designed to withstand. NEC 60/75/90 deg C rated insulated wire is rated for 30/35/40 amps respectfully. From this information, you can figure out the maximum length of wire that is safe to use for a particular voltage and load. Or, you can calculate the maximum load for a particular voltage and wire length. Or max voltage for known load and length.
@Vim Schrotnock I have a lot of respect for you; however, for this topic I feel Porsche has screwed up. They are delivering in many countries and the nema 14-50 is really only popular in the USA. I can imagine it fell through the cracks. As you can see in the photo from @daveo4EV at https://www.taycanforum.com/forum/threads/nema-14-50-supply-cable-heat-data.1940/post-25636 the cable has a 16 amp rating written on it. To pull 40 amps continuous on such a cable is reckless. Perhaps in a well ventilated area it can work but this is a portable charger and as such no assumptions can be made as to how close the cable is too flammable items. It should be 6AWG or at least 8AWG.
 

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Your table shows exactly my point. AWG 10 with a 90C insulation rating has a 40 amp capability. Check out the table.
I did check out the table, I see the 90C rating. But if you check out that pigtail you will see it has a maximum temperature rating of only 50C.
Also a user handle cable should never be allowed to get to that kind of temperature. people could easily have it sitting in a garage next to a greasy rag. That cable spec was a mistake and Porsche will have to send new ones, IMHO.
 
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I am a little surprised that the temperature from the PMCC to the car is higher than your temperature and have no explanation. However, it seems the temperature range across the charging system in my garage is more consistent, ranging from 99º - 114º F.
I’m not -my ambient temps were 68F or less - yours were higher - so your cable was warmer - your measures seem inline and consistent with a “fixed” temperature rise from the electricity + ambient temperatures - leading to a final number slightly higher than mine.
 

Vim Schrotnock

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I did check out the table, I see the 90C rating. But if you check out that pigtail you will see it has a maximum temperature rating of only 50C.
Also a user handle cable should never be allowed to get to that kind of temperature. people could easily have it sitting in a garage next to a greasy rag. That cable spec was a mistake and Porsche will have to send new ones, IMHO.
I don't have the pigtail to reference, all I can say is that a NEMA 14-50 cable with the proper insulation is rated to carry 40 amps with a temperature rating of 90C. 90C is quite hot, but that is what the Porsche NEMA cable is rated. The cable has three current carrying conductors and one ground.

I have attached a link to the actual NEMA standards guide. Please note that the 10 AWG wire is rated at 40 amps with 90C insulation, which is what the Porsche 14-50 connector is.
 

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Toby Pennycuff

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Here's a picture of the information tag wrapped around the 14-50 power whip (7PP-971-678-ED, also known as "Charge cable for mains socket"):

Porsche Taycan NEMA 14-50 Supply cable heat data PMCC Power Whip 08042020
 

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@Vim Schrotnock I don’t know “how“ the neutral would be used for anything related to vehicle...
The neutral (along with one of the "hots") COULD be used to enable 120v power to a simple "logic" circuit inside the charger. Not saying this is factually the case, but its possible...
 

Vim Schrotnock

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Here's a picture of the information tag wrapped around the 14-50 power whip (7PP-971-678-ED, also known as "Charge cable for mains socket"):

PMCC Power Whip 08042020.jpg
Toby - unless I'm missing something, this is a NEMA 6-x & 14-x, not a 14-50.
 
 




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