what gauge wire is needed for a 240 V 30 A circuit?

[caSteve]

I have a dedicated circuit with a 20A breaker and awg12 wire. If I hire an electrician to convert that circuit to a 240V 30A one, would they have to run new wire, or would the awg12 wire be reused?

 

[silentbutnotdeadly]

I have a dedicated circuit with a 20A breaker and awg12 wire. If I hire an electrician to convert that circuit to a 240V 30A one, would they have to run new wire, or would the awg12 wire be reused?

Minimum 10 awg, maybe larger depending on length of run to be safe.

 

[dgpcolorado]

I have a dedicated circuit with a 20A breaker and awg12 wire. If I hire an electrician to convert that circuit to a 240V 30A one, would they have to run new wire, or would the awg12 wire be reused?

You would need at least 10 gauge (or lower) wire for a 30 Amp circuit. 12 gauge is too small.

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[caSteve]

thanks -- very helpful!

 

[davewill]

If you're going to run new wire, you should go ahead and put in a bigger circuit, 50a, if your panel can support it. If you can get it to at least 40a, you'll be able to support all of the 30a EVSEs out there. Unless the wire run is long, the price difference should be minimal.

 

[tkdbrusco]

Just went through this. You need 8AWG or higher. 10 is too low for a continuous draw. There is a 10% buffer built in for continuos so even though 30A would theoretically be ok, most codes state that if its a continuous draw at 27A or higher, you will need 8AWG. Granted you likely won't have an issue with 10AWG if the run in short, but you will not be to code. You will also need a dual 40A breaker since you need to go one up for 30A continuous. You could even go to 6AWG if you want? This would future proof you for future EV chargers that may need more amperage.

 

[davewill]

Just went through this. You need 8AWG or higher. 10 is too low for a continuous draw. There is a 10% buffer built in for continuos so even though 30A would theoretically be ok, most codes state that if its a continuous draw at 27A or higher, you will need 8AWG. Granted you likely won't have an issue with 10AWG if the run in short, but you will not be to code. You will also need a dual 40A breaker since you need to go one up for 30A continuous. You could even go to 6AWG if you want? This would future proof you for future EV chargers that may need more amperage.

10 is fine for a 30a circuit, which is what the OP asked for. That will support up to a 24a EVSE.

 

[tkdbrusco]

He asked about a 30A circuit, but most EVSE's pull 27Amps, which will require 8AWG and a 40A circuit

 

[smkettner]

A 30 amp EVSE will require a 40 amp circuit and #8 wire.
You should have the equipment there for the electrician to review for the estimate.

 

[davewill]

He asked about a 30A circuit, but most EVSE's pull 27Amps, which will require 8AWG and a 40A circuit

Actually, no EVSEs I know about pull 27a. The LEAF with the 6.0 charger does, but the circuit has to match the EVSE not the LEAF. A 30a circuit is all you need for an EVSE Upgrade, for example. The LCS-25, and the TurboCord will also work on a 30a circuit. Most of the rest are 30a EVSEs which will require a 40a circuit.

 

[tkdbrusco]

He asked about a 30A circuit, but most EVSE's pull 27Amps, which will require 8AWG and a 40A circuit

Actually, no EVSEs I know about pull 27a. The LEAF with the 6.0 charger does, but the circuit has to match the EVSE not the LEAF. A 30a circuit is all you need for an EVSE Upgrade, for example. The LCS-25, and the TurboCord will also work on a 30a circuit. Most of the rest are 30a EVSEs which will require a 40a circuit.

That makes sense, which is what I have, a 30A EVSE on a 40A circuit. If he's running new wire anyways, he should probably shoot for that though. Future EVs are going to need something like that to charge overnight during non-peak time.

 

[Nubo]

He asked about a 30A circuit, but most EVSE's pull 27Amps, which will require 8AWG and a 40A circuit

Actually, no EVSEs I know about pull 27a. The LEAF with the 6.0 charger does, but the circuit has to match the EVSE not the LEAF. A 30a circuit is all you need for an EVSE Upgrade, for example. The LCS-25, and the TurboCord will also work on a 30a circuit. Most of the rest are 30a EVSEs which will require a 40a circuit.

And my Leviton uses 16A on a 20A circuit and is serving my 2015 LEAF as well as it did the 2012.

I did have the electrician pull 10 gauge wire though; I like the idea of overbuilding a circuit that's going to be pulling continuous high current. If nothing else, the reduced resistance will eventually pay for the cost of the heavier wire. :lol:

 

[ElectricEddy]

A 30 amp EVSE will require a 40 amp circuit and #8 wire.
You should have the equipment there for the electrician to review for the estimate.

+1

 

[caSteve]

Thanks everyone. I really was just asking about a 30A breaker, not a 30A EVSE. I'm aware of the 20% buffer for continuous draws, and I'll set my EVSE's current limiter to 24A. I actually have a dedicated 30A breaker circuit that I can use already, but the 20A circuit with 12 gauge wire that I was asking about is in a more convenient spot. If new wire didn't need to be run, I would have just paid someone to convert it. I think I'll just stick with my less conveniently located one though. I'm in a rental place right now, so any investment over a hundred bucks or so in rewiring isn't really worth it to me.

 

[smkettner]

If the 20 amp circuit is 240 volt you are in pretty good shape.

 

[knightmb]

He asked about a 30A circuit, but most EVSE's pull 27Amps, which will require 8AWG and a 40A circuit

Actually, no EVSEs I know about pull 27a. The LEAF with the 6.0 charger does, but the circuit has to match the EVSE not the LEAF. A 30a circuit is all you need for an EVSE Upgrade, for example. The LCS-25, and the TurboCord will also work on a 30a circuit. Most of the rest are 30a EVSEs which will require a 40a circuit.

My EVSE pulls 30a when charging, as measured with an amp meter directly from the breaker box, that is why I needed to run 8AWG wire to a 40a breaker for installation. 10AWG wire might work for it if the EVSE has custom switch settings to lower the power level provided to the vehicle so that is only pulls 27 amps for example (or less). It all depends on the distance from the main. If it is just a few feet cable run, then 10AWG could handle it, though it might make the wire get hot to the touch, shouldn't burn anything. But if it is a +40 feet cable run, no point in chancing a fire to save a few dollars on cable, just get the 8AWG and be done with the safety part.

 

[knightmb]

Thanks everyone. I really was just asking about a 30A breaker, not a 30A EVSE. I'm aware of the 20% buffer for continuous draws, and I'll set my EVSE's current limiter to 24A. I actually have a dedicated 30A breaker circuit that I can use already, but the 20A circuit with 12 gauge wire that I was asking about is in a more convenient spot. If new wire didn't need to be run, I would have just paid someone to convert it. I think I'll just stick with my less conveniently located one though. I'm in a rental place right now, so any investment over a hundred bucks or so in rewiring isn't really worth it to me.

If your EVSE has the current switches, you could set it for 16A and stick with the 12 AWG run to keep the convenient spot. If adding more charge time isn't a big deal, go for the convenience part

 

[srl99]

Thanks everyone. I really was just asking about a 30A breaker, not a 30A EVSE. I'm aware of the 20% buffer for continuous draws, and I'll set my EVSE's current limiter to 24A. I actually have a dedicated 30A breaker circuit that I can use already, but the 20A circuit with 12 gauge wire that I was asking about is in a more convenient spot. If new wire didn't need to be run, I would have just paid someone to convert it. I think I'll just stick with my less conveniently located one though. I'm in a rental place right now, so any investment over a hundred bucks or so in rewiring isn't really worth it to me.

If your EVSE has the current switches, you could set it for 16A and stick with the 12 AWG run to keep the convenient spot. If adding more charge time isn't a big deal, go for the convenience part

Actually, the Siemens (a very good unit) DOES allow you to set an internal dial for lower current, but they still require a 30A circuit.

 

[QueenBee]

Just went through this. You need 8AWG or higher. 10 is too low for a continuous draw. There is a 10% buffer built in for continuos so even though 30A would theoretically be ok, most codes state that if its a continuous draw at 27A or higher, you will need 8AWG. Granted you likely won't have an issue with 10AWG if the run in short, but you will not be to code. You will also need a dual 40A breaker since you need to go one up for 30A continuous. You could even go to 6AWG if you want? This would future proof you for future EV chargers that may need more amperage.

You are getting a few different things confused. The continuous load is different from the circuit size. The OP asked about a 30 amp circuit. We would then presume that the OP has an EVSE which requires a 30 amp circuit. Because of the continuous duty rating a 30 amp circuit can only be used for a 24 amp continuous load. Note that the NEC requires a 20% buffer not 10%.

A good example of an EVSE that requires a 30 amp circuit is the EVSEUpgrade which is a popular option as it's the cheapest way for a LEAF owner to get a 240 volt EVSE.

You are correct that for say a 30/32 amp EVSE such as the ClipperCreek HCS-40 a 40 amp circuit is required which would need at a minimum #8 wire.

 

[QueenBee]

I did have the electrician pull 10 gauge wire though; I like the idea of overbuilding a circuit that's going to be pulling continuous high current. If nothing else, the reduced resistance will eventually pay for the cost of the heavier wire. :lol:

I'd really like to see some studies on the heavy loads in homes and the economics of increasing the wire gauge for those circuits above the minimum required. Especially as homes have gotten bigger and the average wire run has increased. I also suspect that we are building houses where voltage drop is not properly being considered.