Is it ok to hookup a 25A (20A conti) EVSE to 40A breaker?
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wwhitney
Well-known member
I would say that it depends on what your EVSE manual says. I googled the manual for the Clipper Creek LCS-25, and it calls for a 25 amp breaker.aFriend said:
Cheers, Wayne
ebill3
Well-known member
Yes. As long as the continuous load is not >32 Amps, you"re OK. The purpose of a breaker or a fuse is to protect the wire, not the device.aFriend said:
Good plan to future proof. If the 8 ga wire is THHN, I believe it is OK for a 50 Amp breaker, 40 Amps continuous. Not so if it is Romex type (three wires in a bundle).
iluvmacs
Well-known member
Check the documentation. Most would require the proper sized breaker, but you can leave in the heavier gauge wire. Swapping out the breaker some day down the road is cheap and easy (wire rarely is). As an example, the Schneider EVlink (30A EVSE) specifically calls out a requirement for a 40A breaker. Best to just do it right.
I wonder if there is a reason the manufacturers don't say minimum breaker size X. Do you think it has an impact on the UL testing? As Bill said the breaker is to protect the wiring and not the device. Obviously it doesn't hurt and is adding additional protection but this is a reoccurring theme.
If I were you I would contact the AHj (the city/etc who is in charge of electrical inspections) and explain to them you are installing an EVSE that uses a 25 amp breaker but are thinking of the future and want to install #8 and a 40 amp breaker and see if they have any issues with it.
If I were you I would contact the AHj (the city/etc who is in charge of electrical inspections) and explain to them you are installing an EVSE that uses a 25 amp breaker but are thinking of the future and want to install #8 and a 40 amp breaker and see if they have any issues with it.
rubear
Member
No, use the heavy gauge wire, but use a 25A breaker.aFriend said:
planet4ever
Well-known member
I don't understand all the concern. Is it OK to plug a 1A floor lamp into a 15A wall circuit?
Ray
Ray
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I don't agree that the Circuit Breaker is only to protect the wiring. It may also be relied upon to protect the EVSE. You need to refer to the installation instructions and the National Electrical Code because Underwriters Laboratories or other Nationally Recognized Test Laboratory (NRTL) may have conducted safety testing which relies upon a particular size circuit breaker. If this is the case, it would be included in installation instructions.
In the example given of a 1 amp floor lamp, the test lab probably would use a 20 Amp circuit breaker for all products up to 16 Amps when conducting a limited short circuit test. The 20 amp breaker would limit the length of time the short circuit would be available to set the lamp on fire. The same short circuit in the lamp that would not cause a fire with a 20 amp circuit breaker might cause a fire with a larger circuit breaker.
In the example given of a 1 amp floor lamp, the test lab probably would use a 20 Amp circuit breaker for all products up to 16 Amps when conducting a limited short circuit test. The 20 amp breaker would limit the length of time the short circuit would be available to set the lamp on fire. The same short circuit in the lamp that would not cause a fire with a 20 amp circuit breaker might cause a fire with a larger circuit breaker.
ericsf
Well-known member
The breakers protects the wire AGAINST an appliance malfunction or a short in the circuit. It's not intended to protect the appliance.
40AMP breaker with 8 AWG wire is fine. This wire size is rated for 50A so if something goes wrong the breaker will trip before the wire gets a chance to cause a fire. If you use a 12 or 16 wire behind a 40AMP breaker you've built what's commonly referred to as a toaster.
As for the sizing for a 25A EVSE, 40AMP is fine. You'll be able to upgrade to up to a 30A on this circuit.
40AMP breaker with 8 AWG wire is fine. This wire size is rated for 50A so if something goes wrong the breaker will trip before the wire gets a chance to cause a fire. If you use a 12 or 16 wire behind a 40AMP breaker you've built what's commonly referred to as a toaster.
As for the sizing for a 25A EVSE, 40AMP is fine. You'll be able to upgrade to up to a 30A on this circuit.
ericsf
Well-known member
That 1AMP lamp can't be connected on a larger circuit than what it's being rated. That's the point of having standard plugs for appliances to make sure that the circuit behind the receptacle is designed to only allow a maximum amount of current before the breaker trips. To be certified, an appliance with NEMA 5-15 plug has to have wiring able to hold 20A because that's the max current it can get on a receptacle of this type (up to 5-20). If it's too expensive to build a 1 AMP lamp with lots of 20A wire, then the appliance can have its own breaker (fuse) to protect that smaller wire.NoMoShocks said:
ebill3
Well-known member
Well, yes, 50 Amp if THHN wire in conduit, but not if a Romex type cable. There is a difference. Check your local code.ericsf said:
ericsf said:
ericsf, are you really trying to say that the #16 and #18 wire used in lamps, small appliances, etc. is rated for 20 amps?
NoMoShocks, could you provide a time current curve of a breaker that shows that during a short circuit event a 15 amp breaker takes longer than a 20 amp breaker? I think you might be confusing the two methods of action in a circuit breaker. I don't know how many amps a short circuit event is but considering a residential breaker is designed to be able to interrupt 10,000 amps I suspect any short circuit event is going to utilize the instantaneous tripping mechanism and not the time delay thermal trip mechanism. During a short circuit in the lamp there is no saving the lamp wiring but the circuit breaker can save the house wiring.
Ingineer
Well-known member
If is is our upgraded EVSE, it is fine to plug it into up to a 50A outlet using a proper adapter. The EVSE is internally fused and protected from overload.
If there are no instructions from the manufacturer, you need to determine is if all parts of the system (from the plug back) can handle a fault current until the 40A breaker trips.
For instance, the typical "1 amp lamp" can be plugged into a 20A breaker protected circuit, because it's wire will handle the fault current until the 20A breaker trips. Smaller gauge wiring, such as those used on xmas lights, can not handle the fault current, so the manufacturers install fuses in the plug that can protect the system.
-Phil
If there are no instructions from the manufacturer, you need to determine is if all parts of the system (from the plug back) can handle a fault current until the 40A breaker trips.
For instance, the typical "1 amp lamp" can be plugged into a 20A breaker protected circuit, because it's wire will handle the fault current until the 20A breaker trips. Smaller gauge wiring, such as those used on xmas lights, can not handle the fault current, so the manufacturers install fuses in the plug that can protect the system.
-Phil
Ingineer
Well-known member
If the lamp shorts, the #18 wire used in the lamp should survive long enough to trip the 20A breaker. The caveat is a sustained fault, such as arcing, that will keep the threshold below the trip curve of the 20A breaker, but still set fire to the wire. This is rare but possible, and this is why the AFCI (Arc Fault Circuit Interrupter) was introduced.QueenBee said:
-Phil
davewill
Well-known member
Here's my take. Changing the circuit breaker is fairly easy, and I feel confident doing it on a DIY basis. So I would change it out to 25a, and plan on putting the 40a breaker back if and when I upgraded EVSEs.
ericsf
Well-known member
No. What I was trying to say was that its not the panel breaker that protects such appliance but an internal fuse which rating must protect the weakest wire in the appliance. If you can build an appliance with all its wire 20amp rated in this case you don't need to protect it with its own fuse. Going either way is usually a design (wire vs fuse cost) decision.QueenBee said:
ericsf
Well-known member
IMHO you're wasting money on a 25a breaker. But as long as the wire you put in the wall can support 40amp, it's safe.davewill said:
ericsf said:
I admit I haven't dissected molded plugs so I am just assuming there are not hidden fuses in #16 and #18 lampcord type cords, are you saying there are? My point is just that there is nothing protecting for example this extension cord from being overloaded and melting: http://www.homedepot.com/p/Nonbrand-6-ft-16-2-Cube-Tap-Extension-Cord-HD-145-017/100672781#.Uc25kvnCZsI" onclick="window.open(this.href);return false;
ericsf
Well-known member
Yea. You could plug this in a 20 amp receptacle and power 3 appliances each drawing 4-5 amp. 15 amp continuous is what the 20amp breaker will allow. The cord is rated for 13amp. It will get warm but probably won't set a fire. But at this point I don't know really how this can be fool proof safe. I guess that's why we still have electrical fires.QueenBee said:
ericsf said:
Er? The solution is really clear and you already said that appliances have them, fuses. My point is just I doubt there is any lamp that is using #16 or #18 lamp cord which has an internal fuse to protect the cord. At least in the US, in the rest of the world isn't it common that plugs have fuses?
You are very incorrect when you say that a 20 amp breaker only allows 16 amp continuous (I assume that was a typo and you meant 16.) Although not a real world environment GE breakers are rated to not trip at 100% of their rating in 40 degree C open air. YMMV as to how well the breaker can breath when in a panel but my point is just that there aren't internal fuses protecting the #16 and #18 wiring that is used all over....
http://www.geindustrial.com/publibrary/checkout/GES-6202A?TNR=Time%20Current%20Curves|GES-6202A|generic" onclick="window.open(this.href);return false;
Which brand of circuit breakers are you using that will only allow 15 amps continuous on a 20 amp breaker?
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