resi 400 amp service

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kwired

kwired

Electron manager
Location
NE Nebraska
I am seeing inaccuracies in size of feeder conductors in this thread.

If an aluminum SE cable is used I believe it needs to be 300Kcmil, If an aluminum conductor in a raceway is used it is likely to be allowed to be 4/0

If a copper SE cable is used it should need to be 4/0, if a copper conductor in a raceway 3/0 should be allowed.

I am sure someone will correct me if I am wrong.

Another thing that has not been mentioned is the fact that if the two panels mentioned are 200 amp panels fed by 200 amp breakers they will not require a main breaker in the panels. If I were the OP and decided to use the owner supplied meter because he got such a good deal he will probably get main lug panels at the price of the main breaker panels on the original bid, or else the fact that he is trying to cut expenses by providing these materials makes the original bid no longer valid and who knows what happens next.
 
infinity

infinity

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Location
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kwired said:
If an aluminum SE cable is used I believe it needs to be 300Kcmil, If an aluminum conductor in a raceway is used it is likely to be allowed to be 4/0

If a copper SE cable is used it should need to be 4/0, if a copper conductor in a raceway 3/0 should be allowed.

I am sure someone will correct me if I am wrong.
Click to expand...

Actually you're correct on all counts. IMO if we must have it then the stupid 60 degree SE cable rule should only apply to smaller conductors. Needing #4/0 cu conductors in SE cable but only #3/0 cu in conduit is silly.
 
K

KWH

Senior Member
I need a little help on this

I need a little help on this

Are you guys referring to 230.42 (b) concerning the SEU / SER also the table in 310.15(b)6 refers to the feeder between the main disconnect and the panelboard. Table 310.16 rates #300al for 190amps is this the correct wire based on the 800amp and under rule. I am new to this board and a great example of it's value, I mainly do commercial installation's but try to keep up on the housing side , this would be a time consuming/profit eating mistake in the field. Thanks
 
infinity

infinity

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KWH said:
Are you guys referring to 230.42 (b) concerning the SEU / SER also the table in 310.15(b)6 refers to the feeder between the main disconnect and the panelboard. Table 310.16 rates #300al for 190amps is this the correct wire based on the 800amp and under rule. I am new to this board and a great example of it's value, I mainly do commercial installation's but try to keep up on the housing side , this would be a time consuming/profit eating mistake in the field. Thanks
Click to expand...


There are a few different issues being discussed in this thread. One is the issues being that the 2008 NEC says is that the interior use of SE cable is now required to be sized according to its 60 degree C ampacity. This is a change from previous codes that allowed it to be sized from the 75 degree C column of 310.16. There also is a clarification in the 2008 NEC that requires that the SE cable must carry the entire load when applying table 310.15(B)(6).
 
LarryFine

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Points in no particular order:

1. Do we know that the OP is under the '08 NEC?

2. With the panels back-to-back with the meter/mains, is the feeder really interior wiring?

3. He could just nipple them together, eliminating cable, and use individual wires.

4. Can't the old size wire still be used as long as each panel's calculated load is within the wire's rating?

5. He could trade a meter for the meter/main, and use main-breaker panels originally planned.

6. How about using 150a breakers instead of 200a ones?
 
ceb58

ceb58

Senior Member
Location
Raeford, NC
ceb58 said:
No problem, done all the time. But the only reason to use the meter combo would be if the panels were to be located elsewhere violating the closest point of entry rule. Your only problem now is you will need 250mcm Al SER (4) wire to feed the panels (if under 2008) or 3/0 Cu. The panels inside are now sub panels. His heck of a deal may go out the window now that the wire type has changed.
Click to expand...

As to wire size I did post wrong. I was thinking Al and looking at the Cu table. 250 mcm Cu SER cable 300 mcm Al SER. But, As Larry said, we haven't heard back from the OP to even know if he is under 2008.
 
K

KWH

Senior Member
Still Confused

Still Confused

I am still having trouble understanding this, 310.15(6) states for this application the feeder shall be the feeder between the main d/c and the panelboard that supplies all loads for the dwelling unit, where does it say this cannot be a main lug panel or this cannot be applied to interior wiring when your still dealing with a feeder. The picture in the handbook 310.9 shows a typical apartment sub fed panel and says 310.15(6) applies and makes no note of interior or exterior . I am taking most of what is being said here as applying to seu or ser being installed for other purposes inside a dwelling unit
 
ceb58

ceb58

Senior Member
Location
Raeford, NC
KWH said:
I am still having trouble understanding this, 310.15(6) states for this application the feeder shall be the feeder between the main d/c and the panelboard that supplies all loads for the dwelling unit, where does it say this cannot be a main lug panel or this cannot be applied to interior wiring when your still dealing with a feeder. The picture in the handbook 310.9 shows a typical apartment sub fed panel and says 310.15(6) applies and makes no note of interior or exterior . I am taking most of what is being said here as applying to seu or ser being installed for other purposes inside a dwelling unit
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Lets confuse you some more:D For the situation in the OP he is installing a 400amp meter combo with 2- 200amp breakers. From these breakers he will feed two 200amp sub panels. That is what throws 310.15 B 6 out. The wording " the panel board that supplies ALL loads" With his situation he will have two sub panel boards supplying the load and size it to 310.16 60 deg.
When dealing with interior wireing it would be the same. If you ran a feeder from one of the sub panels to another sub panel located somewhere else in the building you could not use 310.15 B 6 because it doesn't supply ALL loads and it would have to be sized to 310.16 60 deg.

Now if it were a 200 amp meter combo or standard meter base to 1 200amp panel that supplies ALL the load then you can size it by 310.15 B 6. But again if you feed a sub panel from this panel the ser would be sized by 310.16 60 deg .

And yes, the OP could use main lug panels since he has the 2- 200amp breakers in the combo.
 
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K

KWH

Senior Member
OK I think that clears things up

OK I think that clears things up

The fact that you have 2 panels, not because there is a MLO being used or there is interior wiring, would there be any case to be made even with 2 feeders this is still one service and you are serving the required load.

Thanks
 
infinity

infinity

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Location
New Jersey
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ActionDave said:
Besides code rules and perhaps some temperature issues is there any real reason for this?
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The code change was to bring SE cable in line with NM cable which already had the 60 degree C ampacity requirement. Other than that I don't recall there being any other substantiation such as the use of SE cable at 75 degrees being unsafe. Someone said well SE and NM look kind of the same so lets make them have the same 60 degree C ampacity. A very poor reason IMO.
 
ceb58

ceb58

Senior Member
Location
Raeford, NC
infinity said:
The code change was to bring SE cable in line with NM cable which already had the 60 degree C ampacity requirement. Other than that I don't recall there being any other substantiation such as the use of SE cable at 75 degrees being unsafe. Someone said well SE and NM look kind of the same so lets make them have the same 60 degree C ampacity. A very poor reason IMO.
Click to expand...

I have read that a certain wire company tested 4/0 SE cable in a wall packed with insulation. They loaded the wire to 200amps for several hours and it failed. This gave them ammo to go to the CMP with there test results, that no one can get there hands on, and with some persuasion got the code changed. Could it be just to sell more expensive wire????

Let me throw this into the mix. I was in a code class with many inspectors and the SE cable issue came up. They gave a situation that they did not agree with but were requried to follow.

A 200 amp meter combo mounted on the house back to back with a 200 amp sub panel. Under normal situation you could use 310.15 B 6 and feed the sub with 4/0Al.
Now if say the outside condensing unit or heat pump, well pump, outside recp. or any thing associated with the dwelling were fed from the branch circ. panel in the combo then you could not use 310.15 B 6 to size the wire. The wire would have to be sized to 310.16. The reason was that now the panel inside did not feed ALL loads.
There dumbfound response to this scenario was now you have reduced the load on the feeder so you must increase the size of the wire :confused::confused::confused:
 
iwire

iwire

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ceb58 said:
I have read that a certain wire company tested 4/0 SE cable in a wall packed with insulation. They loaded the wire to 200amps for several hours and it failed. This gave them ammo to go to the CMP with there test results, that no one can get there hands on, and with some persuasion got the code changed. Could it be just to sell more expensive wire????
Click to expand...

There is nothing in the ROPs or ROCs to back that up.

The comments I have read in the ROP address the issue Rob mentioned directly.
 
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