Subfeed Lug Block on 200a buss meter/main panel to feed Span Smart Panel with 225a buss

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kb2014

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I have a 200a meter/main panel outside. I want to move all circuits to a Span Smart Panel mounted inside, opposite the outside panel. The meter/main will have no branch breakers.

A Subfeed Lug Block and 4 wire run would feed the Span panel 200a main breaker. The Span panel has a 225a buss. If we land the 70a solar breaker in the Span panel, which complies with the 120% rule, is the 200a busbar in the old meter/main an issue or does that busbar also have to be rated at 225a?
 
My first question would be, is there a listed sub feed lug feed for this meter/main of 200 amps? Second, this is now a feeder and your calcs would be based on 200 amp. Also the solar limit is based on the invertor output, not the breaker size.
 
kb2014 said:
I have a 200a meter/main panel outside. I want to move all circuits to a Span Smart Panel mounted inside, opposite the outside panel. The meter/main will have no branch breakers.

A Subfeed Lug Block and 4 wire run would feed the Span panel 200a main breaker. The Span panel has a 225a buss. If we land the 70a solar breaker in the Span panel, which complies with the 120% rule, is the 200a busbar in the old meter/main an issue or does that busbar also have to be rated at 225a?
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The main panel is still an 'issue" but you can qualify it using the other 'sum of all breakers' rule. It comes right after the 120% rule in the book.
 
texie said:
My first question would be, is there a listed sub feed lug feed for this meter/main of 200 amps? Second, this is now a feeder and your calcs would be based on 200 amp. Also the solar limit is based on the invertor output, not the breaker size.
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Yes, the panel is the MBE2040B200BTF and the BRPSF225 is the listed subfeed lug block according to Eaton.
The AC rating on the system is 10.958 KW 30 400w panels and 30 Enphase IQ8M inverters...Just under 46 amps output?
When I mentioned a 70a breaker, I was referring to the maximum size for the 225a buss based on 120%.

If the Span panel has a 200a main breaker fed by the subfeed lug block, and the solar breaker is on the opposites end of the Span 225a busbar, wouldn't the 200a main breaker on the Span panel limit the current on the main panel busbar to 200a?
 
kb2014 said:
If the Span panel has a 200a main breaker fed by the subfeed lug block, and the solar breaker is on the opposites end of the Span 225a busbar, wouldn't the 200a main breaker on the Span panel limit the current on the main panel busbar to 200a?
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Yes, as long as no other loads are in the main, like you said. Importantly it also follow the rule I mentioned above.
 
jaggedben said:
Yes, as long as no other loads are in the main, like you said. Importantly it also follow the rule I mentioned above.
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I'm finding some opinions that all upstream panels must comply with the 120% rule of a subpanel with solar. I'm having trouble understanding how the solar backfeed on the Span panel bus would pass upstream to the main panel busbar. Wouldn't the 200a Span panel main breaker only contribute up to a maximum of 200a current to the Span panel bus and therefore only load the Main panel bus up to 200a current?
 
kb2014 said:
I'm finding some opinions that all upstream panels must comply with the 120% rule of a subpanel with solar.
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For the third time...
There's another rule.

If you have 200A or less of overcurrent devices in the main panel, you're okay.
Read 705.12 in its entirety. Tell us which code cycle you're on and I can give a specific reference. (Numbering keeps changing.)

It is correct that all upstream panels need to comply with the rules. But the 120% rule is not the only option.
 
Sorry. I had already ruled out option (3), the sum of all devices.

So, per code I do have to apply the 120% rule to the main panel.

For my understanding, why wouldn't the 200a Span panel main breaker only contribute up to a maximum of 200a current to the Span panel bus and therefore only load the main panel bus up to 200a current?

I understand the bus with a primary source and power source having current of greater than 200a, but I don't see how the main panel bus would ever have more than 200a since it only can contribute up to 200a to the subpanel.

Thanks
 
kb2014 said:
Sorry. I had already ruled out option (3), the sum of all devices.
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Why?
kb2014 said:
So, per code I do have to apply the 120% rule to the main panel.
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No, you don't. You can use a different rule for each panel.

kb2014 said:
For my understanding, why wouldn't the 200a Span panel main breaker only contribute up to a maximum of 200a current to the Span panel bus and therefore only load the main panel bus up to 200a current?

I understand the bus with a primary source and power source having current of greater than 200a, but I don't see how the main panel bus would ever have more than 200a since it only can contribute up to 200a to the subpanel.
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Already said this was correct in post #10.
 
Ah! didn't realize you could try all three rules for each panel.

The only load on the main panel bus is from the subfeed lug block which feeds the 200a main breaker in the Span panel. Is it correct then, that because it feeds that breaker, you don't have to consider any individual devices downstream of that breaker on the subpanel?
 
Yes.
The code has been a little vague about the treatment of subfeed lugs, but since you have the main breaker in the Span panel, it is essentially the same as having a single 200A feeder breaker in the main panel. So it meets the rule.
 
Excellent! I appreciate you taking this time to help me understand this.
I assume we should install a placard on the deadfront stating something like, "DO NOT INSTALL LOADS"
 
One more question on the Subfeed Lug Block.
Since the load is limited to 200a, does it matter where the block is located on the bus? Located nearer the top of the bus means a shorter wire run to the Span panel.
 
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