NEMA 14-50 Supply cable heat data

wmras

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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...
Not likely because the Charger is compatible with 6-50 and 6-30 cables, both have no neutral wire and are better IMHO.
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daveo4EV

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my NEMA 14-50 lables is similar - photo posted on this thread.
 

wmras

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The graph below from IS-Rayfast allows you to calculate the temperature rise versus current for a single wire in free air. A twisted pair of wires de-rates the current by 0.825 for the same temperature (or yields the temperature of 21% more current). Wires in a sheath would yield a slightly higher temperature and take longer to stabilize.

A pair (one hot wire down and one back) of twisted #10-gauge wires in free air at 40 amps would yield the temperature at the 48 amp intersection (left side of chart) and the red #10-gauge line (right side of chart). The temperature (C) is read at the bottom of the chart and equals ~45C above ambient. For example, if the ambient temperature is 30C (86F), the wire temperature would be ~75C (167F) in free air (after the temperature stabilized with 40 amps). A cable like the Porsche input cable would be somewhat higher and take longer to stabilize due to the outer sheath. This estimate is in the ballpark of those measured by others in this thread.

An industrial-grade #6-gauge (or #4-gauge if >50 ft.) supply circuit and receptacle will help dissipate excess heat. Metal conduit helps lower the heat and also makes it easier to change wires in the future.

The Porsche Mobile Connect Charger (PMCC) input cable is a VW part and rated for 105C. It is not likely to fail, but may be too hot to handle in a portable environment. A #6 or #8 gauge wire would be a cooler design and more consistent with US electrical code. Adding to the confusion are the three different ratings evident:
  • Charger allows 40 amps to be programmed
  • Input cable plug at the input to the charger is labeled 24A max
  • Input cable has a tag labeled 16A max
As is, the PMCC is not likely to be unsafe but it is not optimum. A 30 amp setting instead of 40 amps should lower the temperature rise to ~25C (on the verge of being too hot to hold at 20C ambient in free air). This would be my personal setting if away from the car.

Porsche Taycan NEMA 14-50 Supply cable heat data IS-Rayfast_TempIncreaseCurrent
 

Vim Schrotnock

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I think you're basically correct here. The 14-50 cable supplied by Porsche will get very hot under certain circumstances. Not hot enough to fail, but for some reason ($'s??) they chose the less expensive 10 gage wire, which could heat up to an uncomfortable temperature if charging at 40 amps in a high temperature environment.
 

wmras

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I think you're basically correct here. The 14-50 cable supplied by Porsche will get very hot under certain circumstances. Not hot enough to fail, but for some reason ($'s??) they chose the less expensive 10 gage wire, which could heat up to an uncomfortable temperature if charging at 40 amps in a high temperature environment.
Highly probable the cable was chosen because it exited in the VW system.
 


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daveo4EV

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keep in mind Porsched chose the less expensive cable on a $3200 EVSE for which expensive competitive products that have better components are $800 or less - I am highly disappointed in this particular choice by Porsche. They cheeped out on something that will be used every day by most owners and is a highly visible lapse of engineering judgement.

I agree the cable will not fail electrically - but it does get hot, and in more extreme mobile use cases (outdoors in the sun) will get extremely hot.

disappointment abounds that they screwed this detail up - :mad:
 
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daveo4EV

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@wmras 3 cheers for posting this excellent data - I think we understand the problem and we're all a bit disappointed.
 

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Toby Pennycuff

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Toby - unless I'm missing something, this is a NEMA 6-x & 14-x, not a 14-50.
No, this is the factory 14-50 power whip. I have two of them. The slightly melted one is with my dealer and Porsche.

Toby
 

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Not likely because the Charger is compatible with 6-50 and 6-30 cables, both have no neutral wire and are better IMHO.
Says who? Does the documentation indicate such? ..or have you just had "no problems" eliminating the neutral?
 
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daveo4EV

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Says who? Does the documentation indicate such? ..or have you just had "no problems" eliminating the neutral?
yes - Porsche ships and documents compatibility with NEMA 6-50 & 6-30 supply cables - Porsche provides/sells these supply cables for the PMCC - so they must be compabilty and they do not magically provide a neutral for the charger - listed on their eMobility options list - these plugs have no neutral connector since there is no neutral in this plug type - 240 volt appliances have operated for years on 3 connectors plug types (hot + hot + ground) - water heaters, electric dryers, ovens, stove tops, arc welders, klins, tire warmers (the 6-30 plugs in the garages at Laguna Seca have no neutral)

In addtion all major EVSE manufactures have NEMA 10-xx and NEMA 6-XX plug compatible EVSE’s that they ship as UL approved devices - again these configuration will lack a neutral wire - the internals of the Tesla Wall connector (a hard wired device) have only 3 hook ups - hot + hot + ground - there is no place to attach a neutral wire on the interior of most EVSE’s - if you order a hardwired version of an EVSE from ClipperCreek - the bare-whip only has 3 wires - hot + hot + ground…

the neutral wire is unused in an EVSE application/device and there is ample evidence if you simply review the industries installation guides for the hardwired alternatives of their plug based products.

the EVSE industry provide NEMA 14-xx plug types (4 blade configuration) for compatibility and easy of use, not because they use/require a neutral - it’s also true that the most common 50 amp circuit in North America is the NEMA 14-50 plug due to it’s near universal adoption by the RV industry as a 50 amp hookup for 240-volt/120-volt power - so they make NEMA 14-xx alternative so that you can use their EVSE with NEMA 14-xx plugs you’ll encounter in the wild.
 

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Says who? Does the documentation indicate such? ..or have you just had "no problems" eliminating the neutral?
Given I ordered the 6-50 cable for my PMCC, I'd say Porsche says it's ok. You just need the 2 hots to get 240V in the US.
 

ron_b

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Given I ordered the 6-50 cable for my PMCC, I'd say Porsche says it's ok. You just need the 2 hots to get 240V in the US.
Though I certainly agree that all EVSEs that I can imagine would never use neutral, I just wired a NEMA 14-50 last weekend and use 6-3 wire which had a 8AWG ground wire too. I provided all 4 to my NEMA 14-50 receptacle as I would want it to be a general purpose outlet.

Of course the pigtail cable to PMCC can just carry 2 hots and ground.
 
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daveo4EV

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yes it would be best practice when wiring up a NEMA 14-50 plug in one's garage to wire up the neutral - otherwise it can only be used by 240 volt appliances that do not require a neutral - if you plug an RV into a NEMA 14-50 plug- the RV expects the neutral for it's 120 volt usage inside the vehicle - lacking a neutral in the 14-50 plug would be bad ju-ju if you try and use a 120/240 volt devices that expected it from the 14-50 plug type.

I've wired my one NEMA 14-50 in my garage with only 3 wires (bad DaveO!) but I've also labeled it EVSE ONLY so now I'm good ;)
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