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Don't use a $5 range outlet for EV charging

nerdralph.blogspot.com

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Re: Don't use a $5 range outlet for EV charging

#11

Post by LUmBULtERA »

abakker wrote: post #9
bryanlarsen wrote: post #7

Earlier quoted context omitted.

Car chargers only pull 12A from a 15A circuit.

Yeah - you'll see that I mentioned that - if that is true, then great. But, IMO, it's worth verifying. Even more worth double checking if the building is old, or an extension cord is involved.

It's definitely true on a Tesla using their mobile charger. The car will report on its screen exactly what it's charging at. When I charged at 120v (before getting a hardwire charger installed), the car reported charging at 12 amps.

Re: Don't use a $5 range outlet for EV charging

#12

Post by jasonpeacock »

I need to see evidence of this "overheating and melting the outlet". Electrical code requires downrating of actual capacity to prevent things like this.

You're far more likely to see damage due to loose connections - either the wires are not fully secured to the outlet, or the plug is not fully seated & snug, both of which cause overheating.

Re: Don't use a $5 range outlet for EV charging

#14

Post by egberts1 »

CaliforniaKarl wrote: post #13

> Even though the 14-50R outlet is technically a 50A outlet, when used as a kitchen range plug, they are often wired on a 40A circuit. This is permitted by the Canadian Electrical Code rule 26-744 5). I wonder if the US National Electric Code allows this.

The “50” in 14-50R refers to the maximum "rated" amperage allowed through the receptacle. Load-wise, to avoid melted connector, you don't plug something with load capacity of more than 37-ish ampere thru this 14-50R receptacle.

The OP is confusing load rating vs. capacity rating.

However, computed loads are always adequately under the breaker size, and beneath wire capacity, and below the receptacle rating, all three and each components of a circuit.

Many urban building codes often demand the 14-50R receptacle to match the 6/3 COPPER (not Romex) wire and 50A breaker size, often as a response to mass introduction of EV.

NEC 2018/2022 is unchanged about the permissible used of 50A-rated receptacle with smaller 40A breaker but NEC code firmly states that a breaker cannot exceed 8/3 AWG wire rated capacity and many types of 8/3 sheathing barely supports 50A; that's because NEC is all about load-rating, well beneath its rated capacity.

Naturally, in light of those NEC "restrictions", if an EV charger calls for a 50A RATED circuit (because charger performs at nominal load operation at 37A-ish, you'll want all three components of the circuit to each carry 50A. This is the part where the former electric stove/range 8/3 wire failed to meet the new EV charger's demand.

If the EV charger is rated for 60A but operates nominally at 46A, DO NOT go the 50A installaion route. Go with 60A. Operating your load capacity near its rated capacity is potential meltdown situation, especially if weather turns hot, Hot, HOT!

Also for 50A rated EV charger in the high-temperature area (garage), 8 AWG copper wire and 6 AWG aluminum wire are not NEC-code recommended despite having the 50 AMP to 60 AMP ampacity rating (NEC code); go with 6/3 copper.

For most residential garage having 50A-rated EV charger, that means 6/3 (non-Romex) copper AWG, 50A breaker, and 14-50R receptacle. Open-air carport and year-round cooler weather region can NEC-wise get away with (but local/urban electrical code may prevent) the use of 8/3 AWG copper (but no aluminum) wires.

Re: Don't use a $5 range outlet for EV charging

#15

Post by Kirby64 »

egberts1 wrote: post #14
CaliforniaKarl wrote: post #13

> Even though the 14-50R outlet is technically a 50A outlet, when used as a kitchen range plug, they are often wired on a 40A circuit. This is permitted by the Canadian Electrical Code rule 26-744 5). I wonder if the US National Electric Code allows this.

The “50” in 14-50R refers to the maximum "rated" amperage allowed through the receptacle. Load-wise, to avoid melted connector, you don't plug something with load capacity of more than 37-ish ampere thru this 14-50R receptacle. The OP is confusing load rating vs. capacity rating. However, computed loads are always adequately under the breaker size, and beneath wire capacity, and below the receptacle rating, all three…

What's your math on this? I don't understand how you're getting to 37A.

A 50 amp rated outlet (backed by a 50 amp rated breaker, and wire capable of handling 50 amps) is fully NEC compliant if you run it for 40 amps continuously (80% derating) or 50 amps temporarily (which NEC defines as a load expected to continue for 3 hours or more). EV chargers fall under the 80% derating. I'm not aware of any EV charger that uses 37A. They either support 40A (80% of 50A), 32A (80% of 40A), or 48A (80% of 60A).

Re: Don't use a $5 range outlet for EV charging

#16

Post by Kirby64 »

jasonpeacock wrote: post #12

I need to see evidence of this "overheating and melting the outlet". Electrical code requires downrating of actual capacity to prevent things like this. You're far more likely to see damage due to loose connections - either the wires are not fully secured to the outlet, or the plug is not fully seated & snug, both of which cause overheating.

Read any EV forum. Plenty of people with melted Leviton 14-50 outlets, despite having fully secure and tightened wires.

Re: Don't use a $5 range outlet for EV charging

#17

Post by egberts1 »

Kirby64 wrote: post #15
egberts1 wrote: post #14

Earlier quoted context omitted.

The “50” in 14-50R refers to the maximum "rated" amperage allowed through the receptacle. Load-wise, to avoid melted connector, you don't plug something with load capacity of more than 37-ish ampere thru this 14-50R receptacle. The OP is confusing load rating vs. capacity rating. However, computed loads are always adequately under the breaker size, and beneath wire capacity, and below the receptacle rating, all three…

What's your math on this? I don't understand how you're getting to 37A. A 50 amp rated outlet (backed by a 50 amp rated breaker, and wire capable of handling 50 amps) is fully NEC compliant if you run it for 40 amps continuously (80% derating) or 50 amps temporarily (which NEC defines as a load expected to continue for 3 hours or more). EV chargers fall under the 80% derating. I'm not aware of any EV charger that use…

I did take liberty here in saying 37A-ish (40A is code) because that's what some national fire marshalls are reporting about hot garage and reuse of range-type wiring for new purpose of EV charging.

It's the wire material and size issue in hot area.

Re: Don't use a $5 range outlet for EV charging

#18

Post by BizarroLand »

doe_eyes wrote: post #5

I hope I'm not too jaded, but this reads really weird to me. The author disses a "$5 range outlet" (even though I don't think they're usually that cheap), then talks about spending several hundred bucks on better outlets for "evaluation"... and the evaluation never comes. We just get a paragraph of innuendo without any real-world testing or even a thorough teardown. Do the plugs have any real-world design flaws, or i…

This blog seems to be one person's passion project. They can write whatever they want to in whatever manner they want to.

They're not required to weather your scrutiny or to pass your bar exam to be allowed to post whatever they want.

Aside from that, you raise good points, but you can very well ask your questions directly to the author using the comment section of their blog, you're somewhat more likely to get a satisfying answer there than here.

Re: Don't use a $5 range outlet for EV charging

#19

Post by Kirby64 »

egberts1 wrote: post #17
Kirby64 wrote: post #15

Earlier quoted context omitted.

What's your math on this? I don't understand how you're getting to 37A. A 50 amp rated outlet (backed by a 50 amp rated breaker, and wire capable of handling 50 amps) is fully NEC compliant if you run it for 40 amps continuously (80% derating) or 50 amps temporarily (which NEC defines as a load expected to continue for 3 hours or more). EV chargers fall under the 80% derating. I'm not aware of any EV charger that use…

I did take liberty here in saying 37A-ish (40A is code) because that's what some national fire marshalls are reporting about hot garage and reuse of range-type wiring for new purpose of EV charging. It's the wire material and size issue in hot area.

But, if it supports 40A charging it'll charge at 40 amps unless you back off the charging rate (which nobody does, typically). You'd always assume 40 amps for circuit purposes.

Re: Don't use a $5 range outlet for EV charging

#20

Post by ldbooth »

I worked at an EV charger manufacturer. This is a known issue. The issue is a 240V plug value engineered for non-continuous use for things like cooking and laundry loads (where amperage spikes but levels off at fairly low amps) versus a continuous 7-10 hour load like an EV/EVSE (where you have high amps continuously and lots of resulting heat transfer).

It's limited to home EV charging. This is one reason why given the choice between a NEMA plug source or a hard wired source (to circuit in Junction box), I would choose the wired source/circuit connection.

The plug manufacturers also know about the melted NEMA connector issue and are designing versions for continuous use at the higher price points mentioned.

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