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Discussion Starter #1
I was lucky to get one of the (mostly) free Blink chargers back in 2012 - free charger and most of the installation cost covered.

The electrician who installed it put in a NEMA 6-50 which the Blink plugs into.

The other day, my friend came over with a Tesla and he had a 6-50 adapter, so we plugged it in.

However, I noticed that Tesla's site says that with a 6-50 plug one should have a 50Amp breaker. Mine is definitely 40Amps.

His Tesla charged at 40 Amps and nothing tripped, so it seems fine, but I was wondering : what's proper electrical code for the breaker size : 40 or 50?
 

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Wiring size and length would determine the maximum load. If the 40 amp breaker didn't trip it must be safe.
 

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Continuous current load should be 80% of the circuit rating. This is why Tesla says you should have a 50 amp circuit for 40 amps of current draw.
 

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Wiring size and length would determine the maximum load. If the 40 amp breaker didn't trip it must be safe.
A 40A breaker is designed to be able to run 40A continuous without tripping. But that doesn't make it safe. Under the Code a 40A breaker should only be loaded to 32A continuous.

I have seen breakers burn because of poor contacts and they never tripped. A breaker is a last method of protection and is something you do not want to rely on as your only method of protection.

As a note I don't see an issue using a NEMA 6-50 connector on a 40A circuit as long as the connector is wired with a wire gauge it's designed to handle. But you have to make sure the load does not exceed the 80% breaker rating.

For those that are interested breakers can be all over the place with regards to trip sensitivity. But below is the minimum requirements.
At 110% rated current they must trip within 8 hours.
At 135% trip within 1 hour.
At 200% trip within 2 minutes.

Note a lot of bad can happen in minutes.
 

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My GE specified a 40-amp breaker and a 6-50 outlet. Recycled a stove circuit with 50-amp at the main. Installed a sub-panel with the recommended 40-amp breaker for the last 10'. Everything is #8 wire. Kind of overkill for Volt/ELR charging.
 

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It's in the name: the 50 in the 6-50 indicates the size of the breaker that it should be regulated with according to standardized electrical code. I have a NEMA 14-50 RV plug in my garage that's hooked into a 50A breaker but I charge a Volt with it... so way overkill but electrical inspector-approved (did it myself... so didn't have one come anyway, haha).
 

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The breaker size dictates the outlet, not the other way around. They don't make a 40-amp receptacle thus you use the next higher size available. Most electric ranges are on a 40-amp breaker with a 6-50 receptacle and it's all good and legal.

As mentioned above, you're only supposed to load a circuit to 80% of capacity, so a 40A breaker dictates that you draw no more than 32 amps. I believe that Teslas have precise control of the charge current via the 17" touchscreen for just such an occasion.

 

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So...... you got away with it but don't make a habit of it. You might let the smoke out of something and that's when it stops working.
 

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Discussion Starter #9
So...... you got away with it but don't make a habit of it. You might let the smoke out of something and that's when it stops working.
Thanks for all the replies. The real issue here as I see it is whether I have 50A capable wiring or 40A capable wiring. It sounds as if some electricians might be putting in 50A wiring with 40A breakers for some of us EVSE installations, in which case it would seem that running the circuit at 40A all day should be fine, since 40 = 80% of 50.

When I get a chance I'll go pop the cover and see what gauge of wiring is in there.
 

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Thanks for all the replies. The real issue here as I see it is whether I have 50A capable wiring or 40A capable wiring. It sounds as if some electricians might be putting in 50A wiring with 40A breakers for some of us EVSE installations, in which case it would seem that running the circuit at 40A all day should be fine, since 40 = 80% of 50.

When I get a chance I'll go pop the cover and see what gauge of wiring is in there.
50 Amps can run up to 168ft using 6-2 Copper or 4-2 Aluminum. 40 Amps can run up to 168ft using 8-2 Copper or 6-2 Aluminum. If you are less than 168 ft in length and have 6-2 copper or 4-2 Aluminum you can swap out the 40Amp breaker to a 50Amp with no issues for around $20.

The electrician may have installed a 40 amp breaker as an extra layer of security, or could have installed the NEMA 6-50 on undersized wire for plug compatibility. Checking the wire size is critical.
 
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