400 amp residential service

[JustWork]

I have one overhead 400 amp residential single phase service figured to be fed from overhead with paralleled 4/0 cu in 2.5" pvc to the service head. Both panels will be located approximately 20 feet from the meter location the meter will be located on the exterior of the dwelling and the panels will be located on the interior. We are Looking to install two 200 amp disconnects one on each side of the meter pan which we will be each disconnect with 3/0 cu from double lug's on the load side of the meter. We would then use 4/0 aluminum SER from the load side of the disconnect to their respective panels. I would use a #2 grounding electrode conductor. I have installed 400 amp underground services back to back this would be my first 400 amp overhead sub feed and wondering if there were any other input. Thank you

 

[jumper]

1. Why two 4/0 CU? 3/0 CU is good for 200A or one set of 500kcmil CU is good for 380A.

2. The SER 4/0 AL is good for 180A, unless it is run in insulation to the interior panels, then it is 150A. 338.10(B)(4)
So you would be limited to 150A disconnects. This will affect the size of the service conductors needed to the meter.

3. What electrodes are available/present? Need to know that before I can comment.

 

[Dennis Alwon]

There are issues with your install. The use of the residential table for service conductors is not allowed since you have 2 panels. As Derek was stating what is the situation of your ser cable. Look at 338.10(B)(4).

Also what code cycle are you using?

 

[augie47]

Unless money is no object, first I would take a step back and look at my load, total and on each panel. In some cases your plan may have inadequate conductors, in some cases, overkill.
First off, since your show using AL SER, AL must be acceptable. So, from a cost standpoint, I;'d look at AL throughout (Unless POCO won't accept it as a riser).
Since you have multiple disconnects, your riser only need to be rated for the total calculated load. Your 4/0 Cu
with derating for a shared conduit is good for 416 amps, 3/0 would be good for 360 amps which is most likely higher than your calculated load.
AS others have mentioned, unless your AHJ accepts using the "service Table" for two panels, you 4/0 SER may be undersized.
Also as mentioned, the grounding electrode conductor depends on what electrodes and what connection point.
FOr a proper diagnosis, we need details.

 

[suemarkp]

With paralleled 4/0 copper in your riser, you'll need a 1/0 copper GEC or water bonding wire if using a single conductor. But as others have said, depending on the electrodes, some max out at #6 and #4 copper. And if the water pipes are plastic, then you'll skate on that one too.

 

[JustWork]

1. Why two 4/0 CU? 3/0 CU is good for 200A or one set of 500kcmil CU is good for 380A.

1A. This was a purely a brain freeze on my part my notes are 3/0 cu why I typed 4/0?

2. The SER 4/0 AL is good for 180A, unless it is run in insulation to the interior panels, then it is 150A. 338.10(B)(4)
So you would be limited to 150A disconnects. This will affect the size of the service conductors needed to the meter.

2A. We are not sure of the construction of the surrounding finished walls for which the SER will be installed currently it will be attached to concrete walls

3. What electrodes are available/present? Need to know that before I can comment.

3A. As for the electrodes there is nothing available at this moment and it is still up in the air for several reasons. The dwelling was damaged by the storm which has taken out the whole lower section. We are looking to quote this to restore the service to the dwelling. If they restore the concrete walls and footings I would be using a #4 cu to the concrete encased rebar and just walk away with that being my GEC.
I believe the water main is plastic up to the meter and discussions were made to use poly pipe to replace all waterlines in the lower level that have been compromised. Which now brings up another thought since the whole lower level is in poly pipe but copper piping is retained in the top floor will I be required to run the GEC to those pipes?

I propose to install parallel service conductors which I have to add their cross-sections together to determine the minimum size of grounding electrode conductor.

This place is located on the beach and relying on the ground rods is not always the best option in my opinion.

If I was to use 4/0 ser as my largest conductor x2 since in parallel I would have to use the size required from 250 thru 500 kcmil which would be a #2 copper GEC.

My other option would be to eliminate the SER install a trough from the back of the disconnects to the underside of the panels and then use individual conductors but at a higher cost.

As for Alu on the whole service it is right on the beach.

Since the storm the state (NJ) inspectors have been taking care of a lot of these inspections and the local inspectors are just overwhelmed themselves so having detailed discussions with them has not been easy. As mentioned I have not performed this type of install before and I would like to know that I am giving the customer the correct install for his project as well as me being a professional and making sure that my install will be code compliant therefore allowing me to sleep at night.

I will say it is amazing how the mind and body gets so comfortable doing the same thing every day, that you forget some of the important things that you did use every day to get to that comfortable position. :slaphead:

 

[augie47]

Since the NEC allows a 400 kcmil Cu for a 400 amp service (assuming requirements are met), you 3/0 parallel Cu should definitely be O.K. for your riser as well as feeding you disconnects.
Unless you run into a situation where 338.10 and your AHJ require you to use the 60? rating on your SER, the 180 amp 75? rating should be good for your 200 amp OCP, although you could, of course, be asked to supply load calculations.
To me your GEC would be based on your parallel 3/0 Ci service conductors (not your 4/0 AL feeder) but the numbers would be the same as yours for the combined 335.6 kcmil Cu.
Sounds like you are good to go.

 

[Dennis Alwon]

To me your GEC would be based on your parallel 3/0 Ci service conductors (not your 4/0 AL feeder) but the numbers would be the same as yours for the combined 335.6 kcmil Cu.
Sounds like you are good to go.

Why would that be? The riser wires are service conductors so you would have to use the largest ungrounded service conductor according to 250.66. IMO, you would need to use the 4/0 size in the calculation not 3/0

 

[augie47]

Why would that be? The riser wires are service conductors so you would have to use the largest ungrounded service conductor according to 250.66. IMO, you would need to use the 4/0 size in the calculation not 3/0

In post #6, I thought he said the 4/0 was a typo and he used 3/0. Perhaps I am in error.

 

[Dennis Alwon]

In post #6, I thought he said the 4/0 was a typo and he used 3/0. Perhaps I am in error.

You are correct. I saw your statement of 3/0 not 4/0 but you were talking about the feeder.. My turn to shut up...

 

[kwired]

If parallel conductors are in same raceway then 310.15(B)(3) (OP did not mention specifically if this is a single raceway or multiple raceways) could come into play if a full 400 amps of ampacity is needed. Paralleled 3/0 with 90C insulation would only be good for 360 amps in this case.

I don't think 310.15(B)(7) applies to any paralleled conductors, so that section does not matter for line or load side of disconnects.