Three Service Panel Residence Correctly Grounded?

[david]

This is an excellent suggestion, and is much appreciated!

My question is, can what's going to become a 400 A service panel now have two sub-panels (a 100 A sub-panel, and a 200 A load center converted to a sub-panel) connected to it (assuming appropriately sized connecting conductors, with separate ground and neutral wires, with no ground-to-neutral bonding anywhere, and with ground and neutral circuit wires properly connected)?

Many thanks! Best regards, Bill

You suggested at one point to move the 200 amp panel inside, by that suggestion i would think you have room to group a 200 amp service disconnect besides the 400 amp and sub-feed the exterior panel from that disconnect. I am thinking this would be a less expensive solution in time and material cost.

 

[Smart $]

...

Another possibility is subfeed lugs to install in the 400 amp panel, if feeder tap rules can be met for supplying the other panels.

Feeding the 200A panel outside via feedthrough lugs in the 400A (if viable) may well be the least expensive option as no additional disconnect or OCPD would be necessary.

SE conductors will have to be sized for 400A main (the greater of calculated load or 351A as the minimum ampacity). The feeder taps to the 200A subpanel will have to be sized for the full 200A.

 

[a0128958]

Thank you for the many suggestions. I have revisited the customer site with the suggestions in mind, and have visited with the customer.

Here is an updated 'as is:'



One big correction is that the inside garage panel is a 200 A service entrance load center, not a 400 A. Thus, the 2/0 svc feed is now the correct AWG.

In the document shown it lists 6 violations:

1. No disconnect noting outside svc main & inside svc main (grouping)
2. Ground conductors exist from meter socket to svc entrance load centers
3. No GEC present for outside 200 A svc entrance load center
4. Ground-to-neutral bonding exists in what?s used as sub-panel (inside upstairs 100 A load center)
5. 14 tandem breakers exist in upstairs 100 A load center. Model BR3030BC100 allows for zero.
6. Not enough space between A/C units and outside panels

I will be installing an energy monitoring & logging system into this residence, and, a dedicated automated processor for all home functions including advanced lighting control. As a result of the audit, I will ask the customer to at minimum fix the violations related to surge and noise, specifically 2, 3 and 4. The actions I have asked for include:

2. Remove ground conductor from meter socket to 200 A outside svc entrance load center and from meter socket to 200 A inside garage svc entrance load center.
3. Install grounding rod just below outside 200 A svc entrance load center and add GEC to neutral bus.
4. Remove all ground-to-neutral bonding in inside upstairs 100 A load center (neutral & ground circuit wires are already 'pure')

Later this evening I'll have some more time to illustrate with existing images.

Many thanks for comments! I'm a lot more appreciative of the complexities of this particular site thanks to the assistance here.

Best regards,

Bill

American Energy Efficiencies Inc.

 

[a0128958]

Outside meter socket:


Outside 200 A svc entrance load center for water heaters (six 40 A 2 pole circuits), two 60 A A/C condenser circuits, and one 30 A A/C condenser circuit:


Outside 200 A svc entrance load center, showing interior wiring:


And inside garage 200 A svc entrance load center (what I thought was 400 A):


Thank you.

Best regards,

Bill

American Energy Efficiencies Inc.

 

[kwired]

Thank you for the many suggestions. I have revisited the customer site with the suggestions in mind, and have visited with the customer.

Here is an updated 'as is:'

View attachment 9460

One big correction is that the inside garage panel is a 200 A service entrance load center, not a 400 A. Thus, the 2/0 svc feed is now the correct AWG.

In the document shown it lists 6 violations:

1. No disconnect noting outside svc main & inside svc main (grouping)
2. Ground conductors exist from meter socket to svc entrance load centers
3. No GEC present for outside 200 A svc entrance load center
4. Ground-to-neutral bonding exists in what?s used as sub-panel (inside upstairs 100 A load center)
5. 14 tandem breakers exist in upstairs 100 A load center. Model BR3030BC100 allows for zero.
6. Not enough space between A/C units and outside panels

I will be installing an energy monitoring & logging system into this residence, and, a dedicated automated processor for all home functions including advanced lighting control. As a result of the audit, I will ask the customer to at minimum fix the violations related to surge and noise, specifically 2, 3 and 4. The actions I have asked for include:

2. Remove ground conductor from meter socket to 200 A outside svc entrance load center and from meter socket to 200 A inside garage svc entrance load center.
3. Install grounding rod just below outside 200 A svc entrance load center and add GEC to neutral bus.
4. Remove all ground-to-neutral bonding in inside upstairs 100 A load center (neutral & ground circuit wires are already 'pure')

Later this evening I'll have some more time to illustrate with existing images.

Many thanks for comments! I'm a lot more appreciative of the complexities of this particular site thanks to the assistance here.

Best regards,

Bill

American Energy Efficiencies Inc.

2/0 (copper) is only acceptable for 200 amps when allowed by 310.15(B)(7). Your installation does not meet all the requirements of (B)(7), primarily the fact that those conductors are not feeding the entire dwelling load is what doesn't comply. They would need to be 3/0 copper or 4/0 aluminum conductors minimum @ 75 deg C. And if the calculated load is more than 180 amps the aluminum conductor would need to be 250Kcmil minimum.

 

[a0128958]

2/0 (copper) is only acceptable for 200 amps when allowed by 310.15(B)(7). Your installation does not meet all the requirements of (B)(7), primarily the fact that those conductors are not feeding the entire dwelling load is what doesn't comply. ...

Oh my! This detail I was unaware of. Much appreciate bringing this forward. This one I think I can get fixed.

I've added to the violations list:

7. 2/0 copper conductors are too small for inside garage 200 A svc entrance load center panel because these conductors are not feeding the entire structure.

Many thanks!

Best regards,

Bill

 

[a0128958]

Update ('as is' picture (existing conditions) above):

After a number of meetings with the customer and his electrician, agreement has been reached to do the following:

1. Install a double-lugged 400A disconnect (fireman's) switch between the 320A meter socket and any load centers. Switch has neutral-to-ground bonding in place. New ground rod and GEC installed for the switch.

2. No 4 AWG ground conductor from meter socket to disconnect (existing conductor will be removed).

3. Move termination point for (both) 4 AWG cold water pipe grounding conductors from inside garage 200A load center's ground bus to 400A disconnect's neutral bus.

4. 'Clean up' outside 200A load center such that circuit ground wires go exclusively to ground bus and likewise neutral wires to neutral bus. All neutral-to-grounding (strap, screw) to be removed. 4 AWG existing grounding conductor from load center's ground bus to disconnect's ground bus stays.

5. 'Clean up' likewise for inside 200A load center. 4 AWG existing grounding conductor from load center's ground bus to disconnect's ground bus stays.

6. 'Clean up' likewise for upstairs 100A sub-panel. Bare copper existing grounding conductor from sub-panel's ground bus to inside garage 200A load center ground bus stays.

6. Increase conductor size appropriately for feed from disconnect to garage 200A load center (change from 2/0 to probably 3/0).

7. Upstairs 100A sub-panel (Cutler Hammer BR3030BC100) is not rated for any tandem breakers, yet 14 exist. Correct by adding a 125A max 24 1-pole spaces MLO sub-panel next to existing 100A sub-panel. Appropriately change feed conductor sizing to accommodate 2 sub-panels. Lastly move 14 circuits from existing 100A to new 125A sub-panel.

I have appreciated the counsel here very much. Thanks!

Best regards,

Bill