240 outlet in garage and quad 20-40-40-20 circuit breaker

[dk10438]

Hi
when I purchased my house I had the contractor put in a plug into my garage anticipating an EV in the future. I recall he said that the panel was full but it wasn't a big problem. Anyway, a 10-50 plug was installed (not sure why it wasn't a 14-50) but I want to convert it to a 14-50 plug. I removed the plug and saw the 2 hot wires and the neutral attached the the plug as well as the ground which wasn't being used. I then went to the panel and saw a quad type breaker which looked similar to below. There are 2 20A slots on the "outside" and 2 40A slots in the middle. As you can see, there is a bridge between the 2 40's and a bridge between the 2 20's The 10-50 plug had the hot wires connected to one half of the breaker which was a 20A and 40A. So my question is this equivalent to a 60 A breaker (40+20) OR is this equivalent to a 20A (lowest rating of the the circuit breaker). And as I understand it, you should charge at no greater than 80% of the breaker capacity.

Thanks for the help!

 

[iluvmacs]

Whoa, there's a lot wrong here. First of all, it was not up to code to install a 10-50. Are you sure it isn't a 6-50?

Secondly, if it's actually wired to one of the 20's and one of the 40's, that's super bad. It needs to be on the two 40's. Right now it would trip if 20A is exceeded.

And to answer your question on that, no, you do not add the two numbers together. Think of the two breakers in series, not in parallel -- each one monitors for overcurrent on each "half" of your 240V power (one on each 120V leg), and if either detects that 40A is exceeded, it will trip both of them together, cutting off the entire circuit rather than just half of it.

 

[dk10438]

yeah, I'm thinking the contractor did this incorrectly. Not particularly confidence inspiring.. Doesn't make sense that a 20 and a 40 would be mixed together!

Not sure where the other wires are going, I've lived there for 3 years and it hasn't tripped so I'm thinking it must be going to the oven that draws 20A???

 

[iluvmacs]

Not sure where the other wires are going, I've lived there for 3 years and it hasn't tripped so I'm thinking it must be going to the oven that draws 20A???

There isn't a label on it? Yikes. Turn it off and see what doesn't work!

 

[BPeter]

Are you sure both wires are connected to only one half of the breaker? Each half of the breaker would be sharing the same power leg, so they're at the same voltage and you wouldn't be able to charge.

Double check, the car charger is probably connected to the two 40A sides.

For the other side, do you have any other 240V appliances? Electric stove? A/C? It's also actually possible to wire a double pole breaker for two 120V circuits, but they have to share a neutral, so that is also possibly what the 20A is being used for.

You can also just flip it yourself and see what stops working.

 

[mswlogo]

Yeah, it sounds like it's wired wrong based on your description. But I would ring it out to be 100% sure before changing anything.
If it is wired wrong that's a real blunder.

Also if the two 20 Amp circuits are two separate 120V circuits you should remove the bridge across the two breakers (hopefully that's the outer set). If the 20 Breakers are for a 240V circuit (2 hots) leave the bridge on.

You might want to share a photo of the actual install.

BTW any EV charging outlet "should be" (Code required or not) GFCI protected.

"EV" Charging is "Wet Conditions", probably only a bathroom has more risk than outlets next to a wet dripping car. P.S. A Wall Connector eliminates the need for a GFCI Breaker.

 

[habanero69]

Yeah, it sounds like it's wired wrong based on your description. But I would ring it out to be 100% sure before changing anything.
If it is wired wrong that's a real blunder.

Also if the two 20 Amp circuits are two separate 120V circuits you should remove the bridge across the two breakers (hopefully that's the outer set). If the 20 Breakers are for a 240V circuit (2 hots) leave the bridge on.

You might want to share a photo of the actual install.

BTW any EV charging outlet "should be" (Code required or not) GFCI protected.

"EV" Charging is "Wet Conditions", probably only a bathroom has more risk than outlets next to a wet dripping car. P.S. A Wall Connector eliminates the need for a GFCI Breaker.

I don't know of anywhere that requires by code a GFCI or ACI breaker for an EV outlet. Why would they? EV cables, at least Tesla, are make connections by the control power prongs before energizing high power, so unless there is a breach in the charging cable and you were to have the ability to touch internal bare wiring, there is no chance for shock. I'm not wild about standing in ankle deep water or the pouring rain and plug/unplugging my S, but I do it from time to time.

 

[dk10438]

Are you sure both wires are connected to only one half of the breaker? Each half of the breaker would be sharing the same power leg, so they're at the same voltage and you wouldn't be able to charge.

Double check, the car charger is probably connected to the two 40A sides.

For the other side, do you have any other 240V appliances? Electric stove? A/C? It's also actually possible to wire a double pole breaker for two 120V circuits, but they have to share a neutral, so that is also possibly what the 20A is being used for.

You can also just flip it yourself and see what stops working.

I'll double check. I was just checking to see how easy it was to change out the plug and then I saw the conduit going into the breaker box and I saw the wires going into the quad breaker. I didn't know what I was looking at but from my recollection, it was a red and white going into 1/2 of the quad with one wire going to a 20 and one wire going into a 40. I'm not an electrician but when I was thinking about it, it made no sense to have 1 wire from one the blades going into a 20 and another wire going into a 40.

 

[mswlogo]

I don't know of anywhere that requires by code a GFCI or ACI breaker for an EV outlet. Why would they? EV cables, at least Tesla, are make connections by the control power prongs before energizing high power, so unless there is a breach in the charging cable and you were to have the ability to touch internal bare wiring, there is no chance for shock. I'm not wild about standing in ankle deep water or the pouring rain and plug/unplugging my S, but I do it from time to time.

It's the plugging in of the UMC into the outlet that the issue (whether you ever touch it, is irrelevant, someone in the future might).
I have not read the code directly myself but I heard 2nd hand GFCI is now required for EV Charging.
Of course you are grandfathered in on prior code that it was not required.

For me, it was a no brainer that it should have always been required. For the few outlets I helped friend install all have GFCI. I'm not helping them unless they do. Finally the code kings came to there senses. It is also probably the reason why the 14-50 adapter is being dropped. Just one more reason to push folks towards a wall connector.

Because you are really better off installing a wall connector which avoids the GFCI breaker (cost) and with this quad breaker in this case it also solves it here.

Wall Connector solves these "corner" case issues. And to me, it's nice to leave your UMC in you car which is a "bonus". Just leave it there and forget it's there. It weighs little and you'll have it with you in a pinch (rather than plugged in at home).

 

[iluvmacs]

I don't know of anywhere that requires by code a GFCI or ACI breaker for an EV outlet. Why would they? EV cables, at least Tesla, are make connections by the control power prongs before energizing high power, so unless there is a breach in the charging cable and you were to have the ability to touch internal bare wiring, there is no chance for shock. I'm not wild about standing in ankle deep water or the pouring rain and plug/unplugging my S, but I do it from time to time.

Actually, the 2017 version of the NEC now requires it.

625.54 Ground-Fault Circuit-Interrupter Protection for Personnel. All single-phase receptacles installed for the connection of electric vehicle charging that are rated 150 volts to ground or less, and 50 amperes or less shall have ground-fault circuit-interrupter protection for personnel.

So if your state/municipality has adopted the 2017 version, then you need to put GFCI on any receptacle meant for EV charging.

 

[BPeter]

Yeah, it sounds like it's wired wrong based on your description. But I would ring it out to be 100% sure before changing anything.
If it is wired wrong that's a real blunder.

Also if the two 20 Amp circuits are two separate 120V circuits you should remove the bridge across the two breakers (hopefully that's the outer set). If the 20 Breakers are for a 240V circuit (2 hots) leave the bridge on.

You might want to share a photo of the actual install.

BTW any EV charging outlet "should be" (Code required or not) GFCI protected.

"EV" Charging is "Wet Conditions", probably only a bathroom has more risk than outlets next to a wet dripping car. P.S. A Wall Connector eliminates the need for a GFCI Breaker.

Do NOT remove the bridge unless you know what you are doing. If a double pole breaker is used to create two 120V circuits you MUST have the bridge in place, or else you can create dangerous situations.

I'll double check. I was just checking to see how easy it was to change out the plug and then I saw the conduit going into the breaker box and I saw the wires going into the quad breaker. I didn't know what I was looking at but from my recollection, it was a red and white going into 1/2 of the quad with one wire going to a 20 and one wire going into a 40. I'm not an electrician but when I was thinking about it, it made no sense to have 1 wire from one the blades going into a 20 and another wire going into a 40.

The quad breaker you are showing is basically two independent double-pole breakers in one box so that they can fit into two spots, instead of 4. Did the electrician replace a single double-pole breaker with this quad when he installed the EV charger?

But yeah, if both wires from the EV charger are going to only one half of the breaker it won't work. It is possible it goes into a 40A breaker on one side and 20A on the other side, and that would be wrong. But if your car is successfully able to charge at greater than 20A then that can't be the case.

 

[dk10438]

thanks for all the responses! The good news is that it is indeed hooked up correctly. I did a visual inspection again and I saw that both wires were going to the 40 A bridged breakers. Then I got the multimeter out and tested each blade and they measured 120V each. When I tripped the bridged 40A breakers, the blades showed no voltage. So I shouldn't charge past 32 A???

 

[ucmndd]

So I shouldn't charge past 32 A???

Yes.

 

[JPoldo]

So I shouldn't charge past 32 A???

Correct, because continuous use (several hours) current is derated 20% due to heating. I don't think you mentioned wire gauge. Hopefully it is #8 for short distances, #6 for long distance.

 

[mswlogo]

Do NOT remove the bridge unless you know what you are doing. If a double pole breaker is used to create two 120V circuits you MUST have the bridge in place, or else you can create dangerous situations.

That doesn't sound right. Please explain.

 

[dk10438]

Regarding the bridge, I think that's correct that it should not be removed because there are 2 live wires and if 1 wire is overloaded and trips the breaker, only 1 breaker would trip if the bridge was removed. ie, current would still be going to the plug via the other blade. Therefore the purpose of the circuit break would be defeated.

I have a related question though. It would seem to me that if each blade of the plug is providing 120 V and each blade (hot wire) is protected with a 40 A breaker (ie 2 40A breakers in parallel) then I should be able to charge at 80 Amps, not 40 Amps because each blade (hot wire) is providing the plug with 120V at 40A. If the car is pulling 40 A, then it should pull 20 A from each blade (hot wire). And therefore my true capacity would be 80% of 80A so 72A?

Can someone verify?

 

[iluvmacs]

I have a related question though. It would seem to me that if each blade of the plug is providing 120 V and each blade is protected with a 40 A breaker then I should be able to charge at 80 Amps, not 40 Amps because essentially the plug has 2 parallel circuits. Can someone verify?

They aren't in parallel, they are in series. In a simplified way, 40A flows in one and flows out the other (and reverses at 60Hz since it is AC). The "doubling" came in the form of voltage, not current.

 

[dk10438]

got it!

 

[mswlogo]

Regarding the bridge, I think that's correct that it should not be removed because there are 2 live wires and if 1 wire is overloaded and trips the breaker, only 1 breaker would trip if the bridge was removed. ie, current would still be going to the plug via the other blade. Therefore the purpose of the circuit break would be defeated.

I have a related question though. It would seem to me that if each blade of the plug is providing 120 V and each blade (hot wire) is protected with a 40 A breaker (ie 2 40A breakers in parallel) then I should be able to charge at 80 Amps, not 40 Amps because each blade (hot wire) is providing the plug with 120V at 40A. If the car is pulling 40 A, then it should pull 20 A from each blade (hot wire). And therefore my true capacity would be 80% of 80A so 72A?

Can someone verify?

If it's 240V (two hots) to One "Appliance" the bridge should be in place.
If they are two SEPERATE circuits 120V each. The bridge should be removed.

Also, something I actually learned on these forums. The "Bridge" is NOT for the purpose of tripping the opposite leg. It is purely for the operator of the circuit to control that when the breaker is MANUALLY turned on or off that they switch BOTH on or BOTH off. That is ALL the bridge is required to do. Now it might trip the other leg if only one leg tripped, but it is NOT a requirement. It is more of a flag to the operator that these two are paired and represent one circuit. And for safety reasons that when you shut that circuit off you know to shut both off.

You can probably even tell from that outer bridge on this quad breaker. The chances of the OUTER breaker tripping the other breaker is pretty low. It's too loosey goosey. It would just twist.

Some breakers are mechanically tied much more robustly internally with one switch lever (e.g. SquareD). And there may be applications that both sides MUST trip. But in the typically consumer panel it is NOT required to trip both legs.

If the outer breakers are being used for two independent 120V circuits the bridge should be removed and is no different than two (1/2) twin breakers. That is, if you had two twin breakers side by side it would be 4 independent circuits and no bridges. In this case just the pair in the center would be bridged to make one 240V circuit. The outer two would remain independent.

 

[BPeter]

If the outer breakers are being used for two independent 120V circuits the bridge should be removed and is no different than two (1/2) twin breakers. That is, if you had two twin breakers side by side it would be 4 independent circuits and no bridges. In this case just the pair in the center would be bridged to make one 240V circuit. The outer two would remain independent.

The reason I said not to remove the bridge unless you know what you are doing is because its possible that the double-pole breaker is being used to create two 120V circuits that share a neutral wire. Removing the bridge would be dangerous.

https://diy.stackexchange.com/a/12869