Single family dwelling load calc.

[ritelec]

Hi
I'm planning on installing a ev charger. The house currently has a 150 amp single phase service.
I would rather not upgrade their service to 200 amp.
I did a load calculation plugging in the numbers from the code book.

Please check that I did this correctly and and my load calculation is truly 138.5 amps. ( my square footage is actually greater than the true house footage)
And I'm wondering, how close to the service size is that number allowed to be. For instance, can the calculation be 149 and 150 would be good?
Could the number be 150 and 150 be good?

Thank you

 

[Buck Parrish]

If my recollection is correct. Your calculation has already figured in your demand factors. So you could go with a150A on a SFD

 

[ritelec]

My bust. I didn't include my attachment.

Here it is.

What is a SFD?

 

[retirede]

What is a SFD?

Single Family Dwelling

 

[wwhitney]

Here it is.

While conservative and perhaps prudent to include the EVSE at 100% in the load calc, the language of 220.82/220.83 does not require that. So absent a local amendment, it could go in the upper portion of the calculation. I expect some building departments may be attempting to use their discretion to require the EVSE at 100% even without an amendment, but IMO that would be an overreach.

Cheers, Wayne

 

[charlie b]

Yes you can use a 150 amp panel if the (properly) calculated (meaning that all permitted demand factors and any required x125% were included) gave you a result of 150 amps. Some clients may require you to include a "load growth factor," typically 20% or so. But the NEC does not require that.

 

[nizak]

While conservative and perhaps prudent to include the EVSE at 100% in the load calc, the language of 220.82/220.83 does not require that. So absent a local amendment, it could go in the upper portion of the calculation. I expect some building departments may be attempting to use their discretion to require the EVSE at 100% even without an amendment, but IMO that would be an overreach.

Cheers, Wayne

So the EV charger is considered a fastened in place appliance and is not subject to the 100% rating of the nameplate?

Wouldn’t the fact that it could operate at maximum draw for much longer than 3 hours require it to be figured at 100%?

I’m getting so many requests for residential chargers that it would be nice to know exactly how the code sees it.

Thanks

 

[wwhitney]

So the EV charger is considered a fastened in place appliance and is not subject to the 100% rating of the nameplate?

I find no language in 220.82/220.83 or 625 that says otherwise, so yes.

Wouldn’t the fact that it could operate at maximum draw for much longer than 3 hours require it to be figured at 100%?

There have been proposals to modify 220.82/220.83 along those lines, as that may better reflect reality, but none have been accepted as yet. So absent a local amendment, or a building official who takes it upon themselves to fix this "flaw" in the NEC, no.

Of course, this position should be tempered by reality. If an existing residential load calcs out to 65A under 220.83, and the residence has a 125A service, then the 40% factor would let you add 150A of EVSEs to that service. That seems unwise.

Cheers, Wayne

 

[tortuga]

Item​	qty​	VA​	subtotal VA​
General Lighting​	3402​	3​	10206​
Small Appliance​	2​	1500​	3000​
Laundry​	1​	1500​	1500​
Microwave​	1​	1550​	1550​
Dishwaher​	1​	1200​	1200​
Ejector​	1​	1176​	1176​
Disposal​	1​	1440​	1440​
EV Charger​	1​	11520​	11520​
​	​	​	31592​
​	​	​	​
First 10kVA​	​	​	10000​
Remainder VA​	​	​	21592​
40% Of remainder​	​	​	8636.8​
​	​	​	​
HVAC​	1​	7680​	7680​
​	​	​	​
​	​	​	​
Total ​	​	​	26316.8​
Amps​	​	​	110​

 

[nizak]

I find no language in 220.82/220.83 or 625 that says otherwise, so yes.


There have been proposals to modify 220.82/220.83 along those lines, as that may better reflect reality, but none have been accepted as yet. So absent a local amendment, or a building official who takes it upon themselves to fix this "flaw" in the NEC, no.

Of course, this position should be tempered by reality. If an existing residential load calcs out to 65A under 220.83, and the residence has a 125A service, then the 40% factor would let you add 150A of EVSEs to that service. That seems unwise.

Cheers, Wayne

I understand that common sense goes just as far in electrical installations as it does anywhere else.

It just seems that many times ( for me at least) the EVSE puts the calculated load on paper right at the point of a service upgrade.

Knowing what else is in the house as far as power consumption many times will tell you that what’s on paper and what in reality will actually be drawn through the meter are two different things.

I like to sell upgrades but sometimes the income realized as a contractor isn’t worth the headaches that the Utility puts upon us to accomplish it.

Unless there is supplemental electric heat strip for instance or some other ridiculously high amp draw it’s hard to overload a 200 amp service with a house 3,000 or so Sq ft.

 

[ritelec]

Thank you all .