Two feeders, one breaker.

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lukestickney75

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First off, I want to say thank you to all the people that have contributed to this forum. It has been my "go to" spot for quick answers over the years. Thank you. :thumbsup:

Question: Can you feed two separate 100 amp loads with two separate feeders and combine those feeders at the main breaker 100 amp breaker and still be code compliant?

Situation: I have a customer that lives in a condo building and wants to install a Tesla high power wall charger in his parking space. This is a 20 unit building with CH EZ Meter Stacks with 100 amp feeds going to each condo in the building. His panel is two floors up, both floors are post tension and getting to the panel in his unit is impossible without major work, opening common area walls, xraying, core drilling, etc. The meter stacks and main breaker that feeds his unit is less than 50 feet from his parking space so it would be really easy to simply pipe to the breaker in the meter stacks instead of getting to the distribution panel in his unit.

We did a one month recording of his power usage in his space to confirm the existing connected load and determined that his power consumption never exceeds 31.5 amps during dinnertime/weekends (his peak consumption times) and falls below 5 amps at night. We don't know what the actual usage is at night because the CTs don't record anything below 5 amps, so lets just assume 5 amps.

Additionally, I am aware that this additional connected load does not calc out and even using Section 220.87(2) doesn't work. But the Tesla high power wall chargers as well as the car can be set to never draw about a certain amperage. For example, even though the wall charger is fed by a 100 amp breaker, it would be set to never draw about 60 amps and will only be charging at night to take advantage of off peak rates.

Thoughts? Questions? Advise?

Thank you in advance.
 
I don?t think you can do what you suggest unless in the very unlikely event that the breaker is rated to accept two conductors. What you can do, however, is to intercept the feeder to his unit a short distance from the meter, install an enclosure, and create a tap within the enclosure. I would be happier if the enclosure had two breakers, one to feed his unit and the other to feed the car charger. But I don?t think that is a requirement, so long as you follow the tap rules of 240.21(B).

Welcome to the forum.
 
I think Charlie is right although I am not convinced that you would in compliance with the load calculation rules, even if you will never overload the feeder.
 
Thanks Charlie.

I wasn't actually thinking of terminating two feeders in a single breaker lug, but rather using a polaris to splice the feeders at the breaker.

I thought of the panel idea but the space around the meter sockets is maxed. I guess we could mount a panel in the parking space next to the charging station and pipe from the meter socket to the new panel and then from the panel to the panel in the unit. Seems like a lot of extra work for the same result.
 
If you do this, then the feeder to the dwelling is no longer carrying 100% of the load and and may be too small if 310.15(B)(7) (NEC 2014) or the equivalent table on older editions was used to size it.

I'm not sure if calculated/measured max load can override full size feeder requirement that would be triggered?

I understand this is completely counterintuitive but it's the Code.
 
fmtjfw said:
If you do this, then the feeder to the dwelling is no longer carrying 100% of the load and and may be too small if 310.15(B)(7) (NEC 2014) or the equivalent table on older editions was used to size it.

I'm not sure if calculated/measured max load can override full size feeder requirement that would be triggered?

I understand this is completely counterintuitive but it's the Code.
Click to expand...

I looked it up because it seemed odd to me and it actually does say that.

I think you could get around it by supplying another PB with just two breakers in it. One feeding the apartment and the other the charger.

I still do not see how you get past the load calcs though.
 
Are there any spare meter spaces? Whats the maximum amperage of the meter socket disconnect, ie can you fit a 125 amp or 150 amp breaker inside?


Im leaning toward adding a larger breaker with a sub near the meter, 100 amp for the unit and another for the charger.


I do admit the others are bringing up good questions regarding the dwelling table calculations. IMO, since the car charger is out of the dwelling space the table no longer applies. And in reality, 35 amps plus 60= 95 amps. You would be running the feed above the 75 degree column while the breaker lugs are only 75*C. Granted the overload is not likely, but down the road it could happen.
 
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