Help with 400 amp resi pedestal install

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augie47

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Location
Tennessee
Occupation
State Electrical Inspector (Retired)
so...after our mudling through..

If we have house, garages & shops all attached..
and we install a 400 amp meter pan at a point between the house and the pole
and we bring (2) sets of service conductors from the pan to (2) M/B
panels located adjacent to each other
and we feed the new loads from the new panel
we have a Code compliant situation
but
the service conductors from the meter would have to be sized 310.16
since neither are "full load" conductors.
The conductors to the meter could be sized 310.15(B)(6), so it would probably be more economical to keep the meter as close to the house as possible.

Do I have it correct ?
 

jjhoward

Senior Member
Location
Northern NJ
Occupation
Owner TJ Electric
Yes you have it correct sir!

The conductors from the pedestal to the house need to be sized per 310.16.

I also need to find a 400 amp meter pedestal that does not have a disconnect in it + has double lugs on the load side. Maybe this is not an odd thing to find.
 

jjhoward

Senior Member
Location
Northern NJ
Occupation
Owner TJ Electric
I must find out what conductors are in the ground now.

I may choose to re-assign the existing lines for the new panel, and pull new conductors for the existing panel.
 

augie47

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Location
Tennessee
Occupation
State Electrical Inspector (Retired)
So, it's okay to use two runs of 4/0 AL without overcurrent protection but not okay to run two runs of 350 AL each with overcurrent protection?

I'm not sure I follow you.
He could use 4/0 AL for his service conductors to each panel, but not with one having a calculated load of 190 amps. He would have to limit the load to 180 amps.
 

wirebender

Senior Member
I probably wasn't very clear, the wire size didn't really enter into it. My point was it seems odd that we can run the two runs to the house without overcurrent protection but we can't run them if each has overcurrent protection.
 

Dennis Alwon

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Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
I probably wasn't very clear, the wire size didn't really enter into it. My point was it seems odd that we can run the two runs to the house without overcurrent protection but we can't run them if each has overcurrent protection.

Odd but true. If there is a service disconnect at the meter then the wires to the house would be feeders and 225.30 would not allow 2 feeders to a structure. If there is no disconnect then you can have two sets of service cables. Odd huh-- I think that's what threw me off.
 

Dennis Alwon

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Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
4/0 can be used as long as the calculated load for each panel isn't greater than 180 amps. The wire must also be a UE that is dual rated to enter the house.
 

jjhoward

Senior Member
Location
Northern NJ
Occupation
Owner TJ Electric
Hi Dennis;
I was thinking of mounting a R3 splitter box on the house so the underground feeders terminate in the box and I bring SEU from the splitter/trough box into the house.
 

Dennis Alwon

Moderator
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Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Hi Dennis;
I was thinking of mounting a R3 splitter box on the house so the underground feeders terminate in the box and I bring SEU from the splitter/trough box into the house.

Now you may have a problem as se cable is rated 60C. This means, if aluminum, you would need 300 kcm and a calculated load under 190 amps. This would only be for the se cable. Problem is the lugs are not rated for 300 kcm.
 

jjhoward

Senior Member
Location
Northern NJ
Occupation
Owner TJ Electric
The meter pedestal will be by the utility pole which is 100' from the house.

I think I need 500kcm alum from the meter to the pole for the POCO to hook up.

From the pedestal to the house: 2 separate conduits, one is existing (need to do some rework at the pole, since this existing conduit goes up to the POCO secondary lines.) Rework this existing 2" conduit to terminate in the pedestal. These existing conductors will be on the load side of this meter.

2nd conduit is new: probably same size conductors as the existing (assuming 4/0 alum on the load side of the meter) from the new meter to the house.

At the house, remove the existing meter pan and install an enclosure where I can attach the 2 sets of conduit and tie the 2 sets of underground conductors to separate 200 amp SEU cables. Go through the wall of the house with the SEU and terminate in separate 200 amp main breaker panels in the house. I would like to install a splitter box that has lugs mounted on insulated standoffs. If not I will hook these wires with bugs and tape.

Not sure what lugs will be a problem for me?
 

Dennis Alwon

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Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Joe, again this may be a problem. The calculated load on panel that is existing is 190 amps and 4/0 alum is only good for 180 amps. When you convert to se cable what size will you use there? Can you not just pipe out of a long trough into the panels????
 

jjhoward

Senior Member
Location
Northern NJ
Occupation
Owner TJ Electric
I was planning to use 4/0 compact aluminum conductors from the meter pedestal to the trough. I think that cable is XHHW.

The existing underground cables presently terminate in the meter pan on the outside of the house.
I need to splice something to those wires to feed power into the panel in the basement.

So since I must have an enclosure on the outside of the house I was thinking to splitter box or bugs to SEU cable.
 

jjhoward

Senior Member
Location
Northern NJ
Occupation
Owner TJ Electric
Actually the compact alum conductors are rated XHHW-2. So, I could run them into the building.

If I am able to mount the new panel in a reasonable location relative to the outside enclosure I could pipe these new conductors directly into the panel.

But those existing conductors that were terminated on the top of the 200 amp meter lugs are not long enough to get into the the building. So, I need bugs or something to connect al SEU cable from the existing panel to these existing underground conductors.
 

wirebender

Senior Member
As usual, I'm confused.
Would this not be more than one set of service entrance conductors since the meter is located at another structure?
I have a similar installation coming up is why I am so interested in this thread.
 

jjhoward

Senior Member
Location
Northern NJ
Occupation
Owner TJ Electric
Hi Tony;
Right off the bat, the POCO suggested installing a meter pedestal at the pole and running another underground feed over the shop (other side of the house from the existing underground feed).

So, it is OK with the POCO.

See 230.40 exception #2, looks like it is ok if the panels are grouped together.
The suggestion from our POCO would not had the two panels placed near each other.

No disconnect at the meter, else it is a problem.
 

iwire

Moderator
Staff member
Location
Massachusetts
Assuming it is part of a dwelling unit.

230.40 Exception No. 3: A single-family dwelling unit and a separate
structure shall be permitted to have one set of service entrance
conductors run to each from a single service drop
or lateral.
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
Actually the compact alum conductors are rated XHHW-2. So, I could run them into the building.

If I am able to mount the new panel in a reasonable location relative to the outside enclosure I could pipe these new conductors directly into the panel.

But those existing conductors that were terminated on the top of the 200 amp meter lugs are not long enough to get into the the building. So, I need bugs or something to connect al SEU cable from the existing panel to these existing underground conductors.

I still see the possibility of a couple of problems. Keep in mind 4/0 AL @ 75? is 180 amps so your original load most not remain at the 190 you calculated for that wire.
Secondly, if you convert to SE cable, your ampacity drops to 150 amps.

As usual, I'm confused.
Would this not be more than one set of service entrance conductors since the meter is located at another structure?
I have a similar installation coming up is why I am so interested in this thread.
There is one service to the meter then split into two sets of service condcutors to the service disconnects. As such, IMO, it is Code compliant.
 
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