400 amp resi service

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jjhoward

jjhoward

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Northern NJ
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Owner TJ Electric
Suggestions please:
I am putting together a bid for a 4K sq ft new residence with an overabundance of lighting. This house will be mostly an art gallery. GC wants a 400 amp UG service. (Load analysis TBD, still looking at the plans.)
For the 400 amp, 240V single phase UG service, should I run parallell 2/0 Cu lines or do I pull 4/0 CU through this 85' of 3" PVC?
If I run the parallel conductors, am I OK to run them all in the same conduit?
Never installed any service gear > 200 amp, single phase.

Thank you.
 
Re: 400 amp resi service

jjhoward said:
Suggestions please:
For the 400 amp, 240V single phase UG service, should I run parallell 2/0 Cu lines or do I pull 4/0 CU through this 85' of 3" PVC?
Click to expand...

The smallest single conductors for 400 amp would be 400 Kcmil CU or 600 Kcmil AL.

The above is based on Table 310.15(B)(6).

IMO you can not use Table 310.15(B)(6) for paralleling conductors.

For a full 400 amps with parallels in one raceway you looking at two - 4/0 cu or two - 300 cu
 
So, if I derate for multiple conductors (table 310.15(B)(2)(a)) this 400 amp service drops to 320 amps.
Ok, but what temp column should be used from table 310.16?

The only things these wires are attached to are the lines in the street (POCO secondary) and the lugs on the meter socket. Sounds like 90 degrees to me. Is there a reason to use a lower temp?
 
BTW, Bob I am not sure where I came up with the 4/0 Cu for 400 amps.
:roll:

You are correct, the smallest cu conductor for 400 amps is 400 kcmil.
 
BTW, Bob I am not sure where I came up with the 4/0 Cu for 400 amps
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Since the raceway will contain 2 parallel sets of conductors, you would end up with 4-6 CCC's so you must derate their ampacity to 80%.

(2)(260 amps)=520(80%)= 416 amps or as Bob said you may use table 310.15(B)(6) which would allow one set of 400 Cu.
 
You should check with your POCO and find out what their requirements are for 400 amp UG services. The last one I installed required a CT cabinet installed in the garage and I installed a 4" PVC stubbed out 10' from the house. The POCO came in and ran 2 sets of their own 4" PVC's (1 spare) ran the wire from the transformer pad to the CT cabinet and I believe they used 350 kcmills as feeders (but that's the POCO - they do whatever they please) in one 4" PVC. Out of the CT cabinet I installed a 1 1/4" galvanized conduit to an electronic meter cabinet (POCO installed and wired the meter).

I also had to provide load calcs to the POCO. If after you do your load calcs if you find out that your house doesn't warrant a 400 amp service the POCO may not arbitrarily install one for you ( just because you want one) at their expense.
 
goldstar said:
You should check with your POCO and find out what their requirements are for 400 amp UG services.
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That is probably the best advice right there. 8)

All the POCOs are different you should not make any plans until you talk to your power company. You can probably download their "Green Book" from their web site which will give you some info but still talk to someone at the POCO before you purchase any material.
 
Around here (Virginia) it's the "Blue Book" and it is available online from the PoCo. Definately the best place to start. Our PoCo would install the laterals and we would do the service entry wires.

Mark
 
Thank you all for the input.

The POCO at this site (JCP&L) considers 320 amp service as the next one up from 200 amp. Whenver I have done 200 amp UG installs with JCP&L, the HO is responsble for the lateral. I will cofirm with them that holds true for larger installs.

The load analysis for this residence will be a little different since the entire 1st floor will be an art gallery. I will be calculating the lighting load as continuous. Most likely the finished basement will be the same.

Not sure if this extra lighting will get me to 320 amps.

I have downloaded their info guide last year, it was dated 2003. I will check for an update.

Thanks again, I will let you all know how this shakes out.
 
Joe,
You may want to look at NEC 110.14(C) Temperature Limitations. This will probably limit you to the 75 degree C column of 310.16. Other than as a staring point in the process of derating, you will rarely be able to use the 90 degree column.
 
jjhoward said:
So, if I derate for multiple conductors (table 310.15(B)(2)(a)) this 400 amp service drops to 320 amps.
Click to expand...
No it doesn't. If the load is 400 amps, then you need a service panel rated for 400 amps, and the service is, by definition, a "400 amp service." What gets derated is the ampacity of the service conductors, not the rating of the service itself. It just means that you need to use larger conductors to serve the 400 amp service.
 
Hi Charlie,

Yes you are correct. I am working backwards here.
The load analysis has not been done yet.
The GC said let's install a 320 amp service.
The POCO here will allow a 320 amp service without a CT.
The meter pan is rated at 400 amps max, 320 amps continuous.
I am assuming that the load will come in over 200 amps. The plans are still changing so I don't have accurate info yet. Lots of lights...this is a house with the first two floors set up as an art gallery with an extraordinary amount of lights. (Continuous load...)

I would like to work the numbers for a 320 amp service lateral and
2 200 amp MB panels inside.
Not sure what the neatest way is to connect my two MB panels to the meter pan.
Any suggestions? Should I hang a trough inside??
 
jjhoward said:
Not sure what the neatest way is to connect my two MB panels to the meter pan.
Any suggestions? Should I hang a trough inside??
Click to expand...

Are the MBs going to be back to back with the meter? If so then 1 conduit out of each MB to the meter.
If the MBs are in a different location you should check with the AHJ to find the max distance that unfused conductors are allowed to enter a dwelling. Code says the AHJ shall determine this distance. In my county he says it is FIVE feet. This usually means that these service conduits are under the slab. If you have the 2005 NEC Handbook there is some discussion of this after 230.70 (A)
I personally think a cable tray in a residence is ugly. My 2 cents 8)
 
Thank you Tincan.
I agree, a trough in a house just looks too commercial.
That was what I was wondering, should I put 2 pipes through the wall from the meter pan.
You have answered my question, thank you.
Yes, the MB panels are grouped right on the interior wall behind the meter pan.
 
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