Wiring gauge for 30A L2 EVSE? Electrician used #10?

[Valdemar]

Interesting, what might be the purpose of this feature then if not installing the unit on a "weaker" circuit?

I reckon that is the purpose of the feature as per the engineer's design, and then the manual writer or lawyer got nervous and added the contradictory language.

Cheers, Wayne

I suspect the unit is labeled as 30A and wouldn't pass an inspection on anything less than a 40A circuit. I wouldn't try to prove the unit is set to a lower setting to a picky city inspector and safe to operate on a 30A circuit or less unless my sole intention was to annoy him. Could be the manufacturer is trying to save customers from inspection headaches and at the same time attract some "savvy" buyers opting for an installation without pulling a permit on an existing 30A dryer circuits.

 

[MikeD]

Valdemar: Further text from the same VersiCharge manual is

"3.5 Amperage Adjustment:
The Siemens VersiCharge has the option to set the maximum amperage/power that can be delivered to the car using the Amperage adjustment switch. Note that Versicharge cannot control the power draw to the EV, it can only communicate the current capacity of the device to the EV.
Note: The EV controls the power draw. the VersiCharge only communicates the maximum available power to EV.
Dial Settings:
§ Amperage adjustment dial is for use by a qualified technician only
§ Purpose of the amperage adjustment dial is to limit the max power that can be delivered by the charging station.
§ The dial has 10 settings
o 0-4 are for amperage adjustments
o Settings 5-9 are for factory use only. These settings will result in a fault if used.
§ Verify that the VersiCharge is disconnected from power when changing the amperage adjustment dial"

and

"Section 3: Installation
3.1 Building Survey
• Available voltage, current and frequency:
§ VersiCharge EV charging stations can draw up to 30A at 240 VAC, 50/60 Hz (7.2kW of power). The complete electrical structure of the building must be adequately sized to handle the entire building energy load, under peak conditions, as well as the charging station load under operation.
§ Checking for adequate power includes all the connections from the utility through the entire circuit structure to the branch circuit position and connected wiring.
§ Utility connection and transformer capacity - check with utility service provider to ensure enough power is available for the building and the VersiCharge under full loading.
• Available breaker positions and amperage
§ Verify the panel has an open position for a two pole breaker.
§ Verify that the additional 30 A draw from the VersiCharge will not exceed the total loading for the Main Breaker of the structure.
• Breaker selection
§ A 2-pole, 40 A dedicated branch breaker is required for both cord-and-plug installation and hard wired installations. Siemens Part numbers: Q240 (plug-in type), B240 (bolt-on type).
§ The VersiCharge must be wired on a dedicated circuit, with no other loads wired on that circuit."

So the only thing that I can think of is if in the future "brownouts" were to become a continuing problem one could react by limiting the maximum power used by this EVSE. Also useful if the owner sees some advantage to the EV's battery pack by charging at a lesser rate. And finally perhaps Siemens foresees some future change in the NEC that would allow, for example, multiple EVSEs for charging multiple EVs but at a total power rate within the residence's power capacity.

Scanning thru this manual I also noticed the following interesting info

"§ Nuisance fault: As a leader in electrical technology, Siemens has made the decision to install 5 mA grounding protection in all VersiCharge devices. This is the same level of protection that is required in kitchens and bathrooms of residential dwellings. Some other manufacturers (EVSE and Auto manufacturers) have selected 20 mA protection levels. Because Siemens units measure to a more sensitive level, occasional charging interruption may occur under certain circumstances. See section 4.3 for reset instructions."

Note: This "ground fault" type of protection only protects a user from shock "downstream" from the EVSE, not at the EVSE's outlet (if a "cord and plug" installation is used instead of "hardwired"). Note this EVSE provides for hiding the outlet behind the EVSE to provide some additional measure of protection.

One last comment: When the VersiCharge first became available, I recall that the early edition of its installation manual recommended the use of a GFCI type breaker for "cord and plug" installation. At some point this recommendation was dropped. I think from a safety standpoint it is a good idea to use a GFCI for a "cord and plug" installation, but not if there are "nuisance tripping" problems -- and this may be what led Siemens to drop this recommendation.

 

[davewill]

I suspect the unit is labeled as 30A and wouldn't pass an inspection on anything less than a 40A circuit. I wouldn't try to prove the unit is set to a lower setting to a picky city inspector and safe to operate on a 30A circuit or less unless my sole intention was to annoy him. Could be the manufacturer is trying to save customers from inspection headaches and at the same time attract some "savvy" buyers opting for an installation without pulling a permit on an existing 30A dryer circuits.

As long as the settings are internal and the installation instructions state that it can be installed on lower amperage circuits, I don't see why it wouldn't pass inspection. Certainly lots of Tesla owners have installed their HPWCs on less than 100a circuits without issue.

 

[CharlesinGA]

The $399 GE unit is a hardwire only and has a jumper that can be installed inside on the circuit board to tell the car it is less than 30 amp, It has a couple of different settings, so you can match it to the available circuit.

If you have to run wires, run the right stuff. If its your property take the time to do it and do it for max power. If a rental, you compromise and utilize what is there.

 

[BoulderLeaf]

Thanks all, I see this turned into a lively discussion.

As an update:

1. I got a permit. (Philosophically, I have strong reservations about this.)
2. The electrician came back out and re-wired using #8 copper (actually stranded #8/3, 90 deg C insulation - but only used two conductors). Curiously, the electrician was also unaware of any necessary derating required with 4+ conductors in the conduit by the panel.
3. Inspection performed and all should be good. There was a lingering question about the derating required by the number of conductors (4; two 120V outlets and the EVSE) in the conduit leading to the panel, but the inspector said I'm good since it's a 24" section with open ends on either side.

A side note, the electrician I used is not green, and does a lot of commercial work. I'm wondering why he chose to use #10 to begin with as he should have been aware of the derating required for continuous loads. I should have pressed him harder at the time of previous install.

In any case, we're good now. Thanks again for all of your input!

 

[joelb]

There is some mis-nformation in this thread I would like to clarify. Single conductor #10 copper wire with modern insulation installed in conduit is actually rated at 36 amps, and this includes a hefty safety margin. This is the number you derate from, not the 30 amp number being thrown around. Which means a continuous load of up to 28.8 amps is allowed.
Additionally, while the thermal trip curves on circuit breakers do vary by manufacturer, they are only required to trip at 125% or greater of their nameplate rating, and it may take literally hours at 125% to do so. At anything less than 125%, they may never trip. This is normal and legal. So a 30A breaker will probably never trip until it sees more than 37.5 amps, and it may have to see that for several hours before tripping. For a 40A breaker that number would be 50 amps.
As a customer you should get want you want and are willing to pay for. But in the electricians defense I do not believe his initial install was illegal or endangered you or your property. (I put my own level 2 EVSE on #10 and a 30A breaker and have no concerns about it.)

 

[wwhitney]

Single conductor #10 copper wire with modern insulation installed in conduit is actually rated at 36 amps

Not sure where you got 36 amps, but it's not from the National Electrical Code. Per 2014 NEC Table 310.15(B)(16), its ampacity is 30, 35 or 40 amps, depending on the temperature rating of the insulation (60C, 75C, or 90C). 240.4(D) stills limits the maximum breaker size to 30 amps for most applications.

Additionally, while the thermal trip curves on circuit breakers do vary by manufacturer, they are only required to trip at 125% or greater of their nameplate rating, and it may take literally hours at 125% to do so. At anything less than 125%, they may never trip. This is normal and legal.

Agreed in principle. I'm trusting you on the 125% figure, certainly is above 100%

So a 30A breaker will probably never trip until it sees more than 37.5 amps

I have to disagree with that. To say "probably" you'd have to test the multitude of breakers out there and come up with some statistics. The point of upsizing the breaker (and wiring) is that the same standard that allows the 30A circuit breaker to hold at 37.5 amps indefinitely also allows it to trip at 24 amps after 3 hours.

But in the electricians defense I do not believe his initial install was illegal or endangered you or your property. (I put my own level 2 EVSE on #10 and a 30A breaker and have no concerns about it.)

Illegal is a little strong, it is however, not compliant with the NEC. I agree there is no danger, the only downside is nuisance tripping. Which is not something you want for an EVSE.

Cheers, Wayne

 

[Valdemar]

I put my own level 2 EVSE on #10 and a 30A breaker and have no concerns about it.

I hope because you had an existing circuit, and not to save $5 in materials...

 

[CharlesinGA]

There is some mis-nformation in this thread I would like to clarify. Single conductor #10 copper wire with modern insulation installed in conduit is actually rated at 36 amps, and this includes a hefty safety margin. This is the number you derate from, not the 30 amp number being thrown around. Which means a continuous load of up to 28.8 amps is allowed.
Additionally, while the thermal trip curves on circuit breakers do vary by manufacturer, they are only required to trip at 125% or greater of their nameplate rating, and it may take literally hours at 125% to do so. At anything less than 125%, they may never trip. This is normal and legal. So a 30A breaker will probably never trip until it sees more than 37.5 amps, and it may have to see that for several hours before tripping. For a 40A breaker that number would be 50 amps.
As a customer you should get want you want and are willing to pay for. But in the electricians defense I do not believe his initial install was illegal or endangered you or your property. (I put my own level 2 EVSE on #10 and a 30A breaker and have no concerns about it.)

"single conductor" refers to individual wires that would need to be installed in conduit, ie. THHN is most commonly. The 90°C column in Table 310.15(B)(16) may only be used for de-rating, which is done due to temperature of area where the wire is run, or for number of conductors in a raceway. The 80% rule is not de-rating, but rather simply a limit on the use of the circuit, to be established after other correction factors are applied. In addition, NEC 240.4(D) restricts #10 wire to 30 amps, so in order to get a 40 amp circuit, you are going to need to go up to #8, so you can meet the 80% rule.

Most home installations will use a jacketed multi-conductor cable (ie. NM or non-metallic cable) typically known as Romex® (which is a registered trademark of the Southwire Corporation.) Current production NM-B cable, while having a 90°C temp rating, is limited by NEC 334.80 to the ampere ratings given in the 60°C column of table 310.15(B)(16).

Charles