Are these Feeder Sizes right?

[LA-Sean]

Doing a Main Panel Upgrade for an Apartment Building. It has 6 Apartment Units, 1 House Panel, and 3 Spare Meters. The Utility has approved us for One Drop of 400Amp. Its not much but we want to over size the Unit for future electrical deployment. As you can see from Each of the Single-Line Diagram the Sub-Panels will have a 200A Bus. The Feeder Schedule doesn't make sense to me. I believe all the Feeders from the Main to the Main Panel to the Sub-Panels should be set to (1) 2"C - 3#1 +1#8 GND. What are you thoughts? If you need additional information to form an opinion. please feel free to ask.

 

[infinity]

I believe all the Feeders from the Main to the Main Panel to the Sub-Panels should be set to (1) 2"C - 3#1 +1#8 GND. What are you thoughts?

How did you come up with those wire sizes? It shows a 200 amp OCPD ahead of those panel feeders.

 

[LA-Sean]

Hi Infinity. Are you speaking about the Feeder Schedule Keynotes? Those were provided on the Drawing by the Electrical Engineer. I believe they are wrong. I have tried connecting him to discuss but he has since dropped-off the face of the Earth. That is why I am reaching out on this forum to see if I can get some help. From past experience I believe the feeder size 2"Conduit - 3 of the #1 Wire +1 of the #8 Wire for GND from the Main Panel to all the Sub-Panels. But I could be wrong.

 

[infinity]

From past experience I believe the feeder size 2"Conduit - 3 of the #1 Wire +1 of the #8 Wire for GND from the Main Panel to all the Sub-Panels. But I could be wrong.

From what's is shown on the drawing you are incorrect. Each meter has a 200 amp OCPD after it with a feeder to the sub-panel. That feeder needs to be rated for 200 amps so for Cu #3/0 is required.

 

[Elect117]

For MLO, 200A is a minimum of 3/0 copper thhn/thwn with a #6 ground. I cant tell from the drawing which feeder applies to what on the single line. My guess is they are all E6.

Please refer to the table 310.16 for conductor ampacity.

Infinity beat me to it.

 

[infinity]

I cant tell from the drawing which feeder applies to what on the single line. My guess is they are all E6.

Yes it does appear that they left out the E6 designation for each panel feeder.

 

[LA-Sean]

E6 on the Feeder Schedule Keynotes says: "(1) 2"C - 3#3/0 + 1#6 GND. I don't see E6 on the Single-Line Diagram. Only on the Keynotes. So, I should be good with running that to all the Sub-Panels?

 

[Elect117]

E6 on the Feeder Schedule Keynotes says: "(1) 2"C - 3#3/0 + 1#6 GND. I don't see E6 on the Single-Line Diagram. Only on the Keynotes. So, I should be good with running that to all the Sub-Panels?

The plans look incomplete. I would suggest asking a different engineer to review the plans or your electrical contractor. There is no voltage drop number near the ":" on the plans. The footages for each panel are also identical which is odd. Your electrical contractor should be able to verify this as well.

Normally 3/0 is the minimum wire size but there are times when you need a larger wire size by code. For example, voltage drop.

 

[LA-Sean]

Thanks for the Heads up. Elect117. I will definitely follow-up with our Electrical Sub-Contractor.

 

[augie47]

Another oddity (IMO) is the wording mentions a MCB but the drawing doesn't show one and that many 200 amp panels from a 400 amp buss is unusual to say the least, A load calculation would be interesting.

 

[infinity]

Another oddity (IMO) is the wording mentions a MCB but the drawing doesn't show one and that many 200 amp panels from a 400 amp buss is unusual to say the least, A load calculation would be interesting.

Seems like a 3Ø service with 1Ø panel feeders would be more inline with 7-200 amp panels on a 400 amp service. And where is the service disconnect?

 

[curt swartz]

This drawing needs to get dropped into the paper shredder.

Using 3/0 for the feeders is common sense but the drawing should show that.

As Augie stated you should have a main breaker. You have 10 service disconnects.

The drawing also shows the utility ISC of 30K with 27K at the unit panels. The meter center and unit panels are spec'd as 22K.

 

[jaggedben]

Since you said these are apartments, 310.12 probably applies and you can use 2/0 cu from each 200A breaker to each panel.

I agree the 400A service disconnect seems to be missing from drawing: the note refers to a 400A MCB but it's not shown.

The Feeder Schedule keynotes don't seem to me to actually refer to anything in the drawing. Seems like a copy/paste from something else.

 

[CoolWill]

Apparently, the available fault current gets higher the further you are away from the transformer. You might have some sort of free energy device on your hands here

 

[LA-Sean]

From what's is shown on the drawing you are incorrect. Each meter has a 200 amp OCPD after it with a feeder to the sub-panel. That feeder needs to be rated for 200 amps so for Cu #3/0 is required.

Hello Infinity. I have a Follow-up Question. The Feeder Size for the Connection to the Utility is also not marked. I have a approved for 300 AMP overhead Connection (400AMP Connection De-rated for 70%). Please see attached Single Line Diagram and Feeder Schedule. There are 2 Feeder Size that might apply. I am not sure which one to choose:

(1) E3 (1) 2 1/2"C - 4#4/0 + 1#6 GNG

(2) E2 (1) 2 1/2"C - 4#250KCMIL + 1#4GNG.

I am planning to use copper thhn/thwn. But I am not sure which Feeder Size to Choose. When I look at the Ampacity Chart both could potentially apply.

 

[infinity]

Both E2 and E3 would be code compliant for 200 amps but you might have to check the size of the EGC since the ungrounded conductors have been increased in size.

Not sure what you mean about the 300 amp overhead. If that is before the service point then the size is not covered by the NEC. Is there an OCPD in the 400 amp disconnect? If so the service conductors are sized based on the OCPD size.

 

[LA-Sean]

Overhead is referring to "Overhead Utility Service" of the 300 to 330 AMPS (70% Rated of a 400 AMP Service). There will be a 2-1/2" Conduit going up from the Disconnect to the Overhead Utility Service Connection that will house the Feeders. Need help figuring out which feeder size to use for the raceway between 400A Disconnect and the Overhead Utility Service Connection Point:
(1) E3 (1) 2 1/2"C - 4#4/0 + 1#6 GNG

(2) E2 (1) 2 1/2"C - 4#250KCMIL + 1#4GNG.

 

[Elect117]

300A of load, neither of those conductor sizes from E3 or E2 work. And neither of those sizes are protected by 400A OCPD. Same for if the load is 330A. Use the 75°C column for conductor sizing when landing them in switchgear/panelboards.

Ask your electrical contractor or engineer. It sounds like you need design help for your project.

The answers you get on this forum are only going to be as good as the question being asked and I am concerned that you need someone to help finish the design.

 

[infinity]

Overhead is referring to "Overhead Utility Service" of the 300 to 330 AMPS (70% Rated of a 400 AMP Service). There will be a 2-1/2" Conduit going up from the Disconnect to the Overhead Utility Service Connection that will house the Feeders. Need help figuring out which feeder size to use for the raceway between 400A Disconnect and the Overhead Utility Service Connection Point:
(1) E3 (1) 2 1/2"C - 4#4/0 + 1#6 GNG

(2) E2 (1) 2 1/2"C - 4#250KCMIL + 1#4GNG.

What size is the OCPD in the disconnect?

 

[curt swartz]

The drawing shows bussing to the meter stacks which is typical. The main device is normally connected directly to the buss so no cables are needed. For an overhead service the main device can serve as the termination point for the customer installed service risers. Underground services require a separate EUSERC approved underground pull section.

There are still other issues with the design that need to be addressed. Short circuit current and series ratings is a big one.

Not to be an ass but it seems link you are planning to DIY this project instead of bringing a qualified EC and possibly engineer. We are not supposed to help not electrical professionals on this forum. If you are not planning to DIY this let the EC and engineer you higher deal with the details.