100 amp service not enough for 48 amp charging

[JeffADK]

My ca. 1960 house has 100A service, and a full panel.

New garage will be built before rivian arrives. it will either get separate 200A service or I’ll move the service entrance to the garage, upgrade my service, and feed the house from there.

Several years ago I planned to pursue your latter option because my new garage was located next to the transformer pole, but found out that having the service entrance on my detached garage would cause the entire service to be metered as a commercial rather than residential service according to the tariffs in effect at that time where I live. I ended up with the meter on the garage, running the feed underground to the house to the main panel, then running a 60A circuit back to the garage to a sub-panel. I wasn't happy about the extra conduit and copper, but I got rid of the aerial service and got the meter off the side of the house.

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[toade]

I just had my electrician install a plug for my soon to be delivered Rivian. He recommended a 30 amp plug rather than the 50 amp one because my house only has 100 amp service. I think the gist is that if I run the oven, dryer and charge the R1T at the same time as other regular stuff I could pop my main breaker. Upgrading the service/panel to 200 amps is thousands of dollars.
Looks like now I will have to get a different portable charger as the Rivian one only does 50 amp outlets.
I can charge overnight with the 30 amp no problem so that is not much of an issue.
The 30 amp outlet does not qualify for the Evergy install rebate of $500 but I don't qualify anyway because I have net metering for my solar, and I probably don't want to go to the Time of Use plan anyway.

Are there a lot of people with these issues?

You could get something like the Charepoint HomeFlex or the Juicebox where you can set the charger to only deliver 30A. Install it on a 60A circuit, that way you at least have the option to charge higher if needed. Just make sure it's not at a time that you are not running AC, oven, etc. Nice to at least have the option.

 

[timesinks]

Question for all, I’m in same boat. Shouldn’t the electrician install 14-50 which is 50 amps and use the truck software to limit to 30 amps?

There's no guarantee you or a future owner will actually configure your vehicle to consume less, and based on the load calcs, your panel would be oversubscribed.

They will allow an EVSE with hardware config under a service door or protected behind an installer software interface to be de-rated, since that requires a certain degree of being deliberate in reconfiguration. But being able to accidentally forget to throttle down the car is asking for a fire.

 

[Forager]

My 1965 house has 60-amp service ?

In the next 12-18 months I’ll be upgrading to 400a, which is the maximum I can request without paying a surcharge. Since my current service is under the minimum for a new connection (100a), I *think* my upgrade from the utility is free.

 

[timesinks]

https://learnmetrics.com/60-amp-wire-size/#:~:text=60 amp wire size is,size for 60 amp 220V.

Uhh... I only play an armchair electrician on the internet, but this article does not know how to calculate voltage drop.

Southwire is an electrical manufacturer with good calculators: https://www.southwire.com/calculator-vdrop

If I punch in 60A on 6AWG copper wire for a 200-foot run (100-feet out and back), I get a 4.42% drop. The article claims you would experience 20% after bumping up to 4AWG. It's just... wrong.

For sizing the breaker (and the minimum wire size), you use the 125% rule: a 48A continuous load goes on 60A wire and a 60A breaker. Good so far.

You may also notice the ampacity tables have 3 temperature columns. The THHN that tends to be pulled in conduit for this kind of application is good for the 90C column (though breakers are typically rated with 75C terminals, so after you've sized your wire for the number of circuits in the conduit, you need to make sure you're still at or under the 75C ampacity for the size you're running). 6AWG THHN is rated up to 75A; 6AWG can land on a breaker up to 65A due to the 75C terminals. So a 60A breaker protecting wire rated for 75A expecting a 48A continuous load is all within spec here.

For voltage drop, you use the 48A number (the actual nameplate load expected at the end of the wire), not the breaker size. Punching 48A into the southwire calculator (still 200' of 6AWG copper), I get 3.53% voltage drop. This is perfectly acceptable.

Bumping up to 4AWG wire triggers some additional rules about the sizes of any boxes along the run and the distances between entering conduits and stuff. And 6AWG is hard enough to work with (though, the saving grace for a hardwire EVSE is you probably don't need to pull the neutral). Also remember that a 6AWG circuit can have an 8AWG equipment grounding conductor (the green one).

 

[crashmtb]

Several years ago I planned to pursue your latter option because my new garage was located next to the transformer pole, but found out that having the service entrance on my detached garage would cause the entire service to be metered as a commercial rather than residential service according to the tariffs in effect at that time where I live. I ended up with the meter on the garage, running the feed underground to the house to the main panel, then running a 60A circuit back to the garage to a sub-panel. I wasn't happy about the extra conduit and copper, but I got rid of the aerial service and got the meter off the side of the house.

the commercial metering thing is pretty silly!
I wouldn’t be surprised to find a similar rule here.
My garage is also detached - on the back lane. I wouldn’t mind having one less overhead cable. Too bad the nearest pole is at the opposite side of my yard. Then again it would only be another 20’ of trenching….. hmmmm

 

[crashmtb]

My 1965 house has 60-amp service ?

my house was changed from a fuse box to breakers in the 70s or 80s from the looks of the panel…and The index cards I found with old circuit listings. Probably whenever central air conditioning was added.
Was quite likely 65a or so originally.

 

[SANZC02]

I just had my electrician install a plug for my soon to be delivered Rivian. He recommended a 30 amp plug rather than the 50 amp one because my house only has 100 amp service. I think the gist is that if I run the oven, dryer and charge the R1T at the same time as other regular stuff I could pop my main breaker. Upgrading the service/panel to 200 amps is thousands of dollars.
Looks like now I will have to get a different portable charger as the Rivian one only does 50 amp outlets.
I can charge overnight with the 30 amp no problem so that is not much of an issue.
The 30 amp outlet does not qualify for the Evergy install rebate of $500 but I don't qualify anyway because I have net metering for my solar, and I probably don't want to go to the Time of Use plan anyway.

Are there a lot of people with these issues?

Did you have them quote an upgrade? When I had solar installed last year I had the service upgraded from 100 amp to 200 amp. It was 2500 for the new box, all new breakers, and all permits.

I thought the cost was reasonable.

 

[Riviot]

My 1965 house has 60-amp service ?

In the next 12-18 months I’ll be upgrading to 400a, which is the maximum I can request without paying a surcharge. Since my current service is under the minimum for a new connection (100a), I *think* my upgrade from the utility is free.

Was city or county are you in? You've got me thinking about our cabin plans...

 

[Forager]

North King County, but my power is through Seattle City Light.

 

[NW Brah]

I just had my electrician install a plug for my soon to be delivered Rivian. He recommended a 30 amp plug rather than the 50 amp one because my house only has 100 amp service. I think the gist is that if I run the oven, dryer and charge the R1T at the same time as other regular stuff I could pop my main breaker. Upgrading the service/panel to 200 amps is thousands of dollars.
Looks like now I will have to get a different portable charger as the Rivian one only does 50 amp outlets.
I can charge overnight with the 30 amp no problem so that is not much of an issue.
The 30 amp outlet does not qualify for the Evergy install rebate of $500 but I don't qualify anyway because I have net metering for my solar, and I probably don't want to go to the Time of Use plan anyway.

Are there a lot of people with these issues?

You should definitely install the 50a receptacle. If you are using your portable charging cable, the max current draw will be 32 amps (even though the outlet is rated at 50 amps and a 40amp breaker). If you plan on putting the rivian wall mounted charging station in, inside the unit there are selectable Dip switches you can set current limits to 6a, 12a, 16a, 20a, 32a ... all the way up to 48 amps. You can also limit the charge settings from the vehicle too. Someday in the future, your home electrical service will be swapped to a 200a service. Putting in the larger receptacle and wire will future proof your setup, so you wont need to redo the whole thing if you ever want to upgrade. And in my experience, unless you have some crazy electrical loads in your house it is highly unlikely your total load will be high enough to trip the main. You should be just fine.

 

[NY_Rob]

Our 1963 built house had 100amp service, when we went with solar (43 panels) 3yrs ago we upgraded to 200amp service at that same time so were were able to deduct 30% of the panel upgrade as part of the solar install. IIRC the 100 to 200amp upgrade was $2,500.

 

[blturner]

Did you have them quote an upgrade? When I had solar installed last year I had the service upgraded from 100 amp to 200 amp. It was 2500 for the new box, all new breakers, and all permits.

I thought the cost was reasonable.

I think they are working on a quote. Thanks for that price. I was just guessing that it would be at least $1500 to $2000 and I would do it. But if it was going to be $4000 then no. I really need to settle my thoughts on what it is worth too me. But this is my first electric vehicle so I kinda want to spend some time with it before I make the investment. If I find myself sitting at the local level 3 charging much then I will definitely do it.

 

[LaunchGreen]

I think they are working on a quote. Thanks for that price. I was just guessing that it would be at least $1500 to $2000 and I would do it. But if it was going to be $4000 then no. I really need to settle my thoughts on what it is worth too me. But this is my first electric vehicle so I kinda want to spend some time with it before I make the investment. If I find myself sitting at the local level 3 charging much then I will definitely do it.

My 2 cents: average home ownership tenure is around 8 years and you won't recoup your investment. If it's expensive and you can make it work without it being a pain in the butt, let the next owner deal with the upgrade.

 

[MikeySea]

I just had my electrician install a plug for my soon to be delivered Rivian. He recommended a 30 amp plug rather than the 50 amp one because my house only has 100 amp service. I think the gist is that if I run the oven, dryer and charge the R1T at the same time as other regular stuff I could pop my main breaker. Upgrading the service/panel to 200 amps is thousands of dollars.
Looks like now I will have to get a different portable charger as the Rivian one only does 50 amp outlets.
I can charge overnight with the 30 amp no problem so that is not much of an issue.
The 30 amp outlet does not qualify for the Evergy install rebate of $500 but I don't qualify anyway because I have net metering for my solar, and I probably don't want to go to the Time of Use plan anyway.

Are there a lot of people with these issues?

You might check out this product which splits the power before it hits your panel and therefore doesn't count against your load calcs. It's a way to add a large 60amp EVSE circuit without upgrading your panel but it is expensive... though likely still cheaper than upgrading to a 200amp service and qualifies for the Evergy rebate. They also make an indoor version which is slightly less.


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