He isn't installing an HPWC (gen 1/2 Wall Connector), but a gen 3 Wall Connector that can draw 48 amp max. That said, you can't go wrong by oversizing the wire, as long as it fits correctly in the terminals.
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Gen 3 wall charger - connect to 80A breaker ok?
- Thread starter s14roller
- Start date
He isn't installing an HPWC (gen 1/2 Wall Connector), but a gen 3 Wall Connector that can draw 48 amp max. That said, you can't go wrong by oversizing the wire, as long as it fits correctly in the terminals.
Thanks! I’ll be sure to confirm what wire they are using. I may be overthinking it a bit since they are a licensed electrician and approved by Tesla, so chances are they know what they’re doing. Then again they said going with the 80A breaker would be fine…"#6 wire" is not specific enough. #6 Romex NM-B and UF-B would technically not meet code since you would have a 60 amp breaker protecting 55 amp wire (yes, I know the device only draws 48 amps ... until there is some sort of malfunction or short). #6 armored cable or 75C/90C wire in conduit will meet code.
Cerrowire Resources - Ampacity Charts
Ampacity is the maximum current that a conductor can carry continuously under the conditions of use without exceeding its temperature rating. Cerrowire's ampacity chart helps calculate the load requirement for a circuit.www.cerrowire.com
Mrbrock
Active Member
I understand it is Gen 3. If devices never drew more than ratings we wouldn’t need breakers to protect the wiring. If he leaves things as they are, something in the HPWC could short or otherwise malfunction and draw up to 80 amps and if the wiring from the sub panel to the HPWC is only rated for the HPWC Gen 3 specs at 60 amps then you are running 80 amps through 60 amp wiring which equals a fire.
Yes, very often people don't understand what the breaker is created for..
It's created - to protect the wire. The breaker amps number should be selected based on the wire that's connected to it, and not based on the devices that will use this wire to pull electricity.
SO, if the wire that is going from the breaker to a consumer is designed to handle 90A of load, you can use 80A breaker on this circuit. This means, that if somehow the consumer will decide to pull 100A from the circuit, the breaker will disconnect the line before the connected wire will be damaged because of excessive load.
If you pull 90A rated wire from the breaker to Wall Connector - you can use 80A breaker (not really needed, but still you can and it's safe).
If your wire rated less than 90A, you can't use 80A breaker. You need to downgrade the breaker amp to level 10A lower than your wire amperage.
It's created - to protect the wire. The breaker amps number should be selected based on the wire that's connected to it, and not based on the devices that will use this wire to pull electricity.
SO, if the wire that is going from the breaker to a consumer is designed to handle 90A of load, you can use 80A breaker on this circuit. This means, that if somehow the consumer will decide to pull 100A from the circuit, the breaker will disconnect the line before the connected wire will be damaged because of excessive load.
If you pull 90A rated wire from the breaker to Wall Connector - you can use 80A breaker (not really needed, but still you can and it's safe).
If your wire rated less than 90A, you can't use 80A breaker. You need to downgrade the breaker amp to level 10A lower than your wire amperage.
Maybe you should stay away from electricity and giving electrical advice. This is just plain wrong information. For a simple demonstration, lets take some 14 gauge copper romex. Its rated for 15 amps, so your advice suggests putting a FIVE amp breaker on it. Totally nuts.
Additionally, while the idea that the breaker is protecting only the wire from overheating is mostly correct, for hardwired items the innards of the item are also expected to be able to sustain overload until the max-expected-breaker-size trips without the device literally bursting into flames. An example might be a device with a motor that might seize up. For an HPWC this really isn't an issue since the only thing that's going to draw excess power is a terribly misbehaving Tesla.
It needs to protect the device as well. On this case the device is an evse not designed to have more than 48 amps drawn through it.
ATPMSD
Active Member
Everytime the subject of wire and breakers come up a lot of miss information is spread. So let’s just stick within the EVSE world and the Gen-3 wall connector (WC):
If you want to set the WC to a 60-amp setting the wire must be rated at 60-amps or greater, and the breaker must be 60-amps. The WC will charge the car at 48-amps. Note that #6 romex is rated to 55-amps and is not suitable for a 60-amp circuit.
If you set the WC to something lower, such as to a 50-amp setting, the wire must be rated at 50-amps or greater, and breaker must be 50-amps. The WC will charge the car at 40-amps.
If you want to set the WC to a 60-amp setting the wire must be rated at 60-amps or greater, and the breaker must be 60-amps. The WC will charge the car at 48-amps. Note that #6 romex is rated to 55-amps and is not suitable for a 60-amp circuit.
If you set the WC to something lower, such as to a 50-amp setting, the wire must be rated at 50-amps or greater, and breaker must be 50-amps. The WC will charge the car at 40-amps.
Okay okay... if we go down to that smaller gauges sure... 14 gauge wire limit is 20 amp (not 15 amps) - LINK, so for this wire, you need a 15 amp breaker.
I have said 10A less because higher amp two pole breakers don't have an increment by 5, they increment only by 10.
ATPMSD
Active Member
14 gauge wire is limited to 15-amps, you need to read the footnotes.
“Unless specifically permitted in Section 240.4(E) through (G), the overcurrent
protection shall not exceed 15 amperes
for 14 AWG, “
What do you mean "limited to 15-amps"?
The wire limit is 20 amps, and the wire protection (i.e. breaker) should not exceed 15-amps. The limit of wire always should be slightly higher than the limit of the breaker, otherwise, the wire will melt before the breaker switches off to protect it.
A standard circuit breaker will trip for one of two reasons:
When the instantaneous amperage being passed exceeds the maximum rating of the breaker it will trip off within a few milliseconds.
When the circuit breaker reaches its thermal limit, typically after delivering near the maximum amperage rating for the circuit over a period of time, the breaker will also trip off.
When the instantaneous amperage being passed exceeds the maximum rating of the breaker it will trip off within a few milliseconds.
When the circuit breaker reaches its thermal limit, typically after delivering near the maximum amperage rating for the circuit over a period of time, the breaker will also trip off.
ATPMSD
Active Member
Incorrect. The breaker can be equal too the wire’s rating. In the case of the wall connector, for example, we use a 60-amp breaker with 60-amp wire. What you are thinking of is applicable to the 80% rule. For our 60-amp circuit the 80% rule limits the continuous load to 48-amps, which matches the continuous load of the wall connector when it is set for a 60-amp circuit.
There is, of couse, no harm in using a more capable wire, but this is not a requirement.
Let us not forget the round-up rule, which totally obliterates your argument. (Note you can't use the round-up rule for EV circuits, sadly)
"(B) Overcurrent Devices Rated 800 Amperes or Less. The next higher standard overcurrent device rating (above the ampacity of the conductors being protected) shall be permitted to be used, provided all of the following conditions are met:
(1)
The conductors being protected are not part of a branch circuit supplying more than one receptacle for cord-and-plug-connected portable loads.
(2)
The ampacity of the conductors does not correspond with the standard ampere rating of a fuse or a circuit breaker without overload trip adjustments above its rating (but that shall be permitted to have other trip or rating adjustments).
(3)
The next higher standard rating selected does not exceed 800 amperes."
(Note: there's also 240.4(D) that specifically calls out no more than a 15 amp breaker on 14 gauge wire except in certain instances)
In addition, a quick search found me a both a 25 and 45 amp two-pole breaker from Square-D. For example... https://www.supplyhouse.com/Homeline-Series-Circuit-Breakers-30061000
Q0 breakers come in 35 amp two-pole.
sleepydoc
Well-Known Member
What's the difference between a sub panel with only one breaker and a disconnect? it's the same thing.
Yes, its essentially the same thing, for these purposes.
My response was to agree that having an 80 amp breaker would imply you NEED a (subpanel or disconnect) at the other end of the wire. A 60 amp breaker is allowed to be used without a subpanel/disconnect at the other end.
I'm still trying to figure out why this thread got resurrected after a solid year of inactivity.
Mrbrock
Active Member
Only if that wire is used as direct burial to feed an outlet or equipment. If it is used as NM wire (in wall), then it is treated like NM. 14ga is 15A. You get more amps with UF because it is underground or in free air (exposed to sunlight), not in a wall.
"UF-B may be directly buried or installed where exposed to sunlight. When used as an NM cable it must comply with the requirements in NEC 2008 and NEC 2011 Article 334."
Google can be a wealth of knowledge, but it can also be very dangerous. It can give you just enough info to get you into a lot of trouble.
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