Three Service Panel Residence Correctly Grounded?

[a0128958]

I'm preparing to install energy monitoring h/w and lighting automation into a large residence in the Dallas area. During an inspection of the existing wiring, shown here:



I've noted a number of things the structure owner I believe needs to correct. Here's my list. Is it complete, and compliant with 2014 Code? And, have I missed something?


1. Make connection from DCW pipe, within 5' of entering residence, to meter panel ground bus (1/0 wire?).

2. Remove insulated wire from meter ground bus to 200 A ground bus.

3. Remove insulated wire from meter ground bus to 400 A ground bus.

4. Add earth rod and connect to 200 A neutral bus.

5. Move foundation concrete rebar ground connecting insulated wire from 400 A ground bus to 400 A neutral bus; verify wire is #4.

6. Verify size of 3 wires from 400 A meter base to 400 A service panel (should be 400 kcmil?).

7. Remove 100 A svc panel ground bus to neutral bus strap (or replace svc panel with w/ subpanel).

8. Insulate 100 A svc panel neutral bus from panel case (or replace svc panel with subpanel).

9. In 100 A svc panel, make sure all circuit grounds go to ground bus. Same for circuit neutrals - make sure, with no exceptions, that neutrals only go to
neutral bus.

Many thanks.

Best regards,

Bill

 

[iwire]

Unless there is a disconect at the meter you have an issue with grouping.

It looks like there there are two service disconnects, one inside, one outside. That is a violtion.

 

[augie47]

My first thought was what iwire noted.
I also don't see the need for your #4 on the list.

 

[a0128958]

... Unless there is a disconect at the meter you have an issue with grouping.

It looks like there there are two service disconnects, one inside, one outside. That is a violtion.

Indeed, there is no disconnect at the meter.

Here is an image of what's outside, panel with meter only, and panel with 200 A main breaker and circuit breakers for outside A/C condenser units and inside hot water heaters:



Looks like the outside 200 A service panel needs to be moved inside. Thank you.

I have added to the list at beginning of thread:

10. The outside 200 A service panel and the inside 400 A service panel is a violation. The outside 200 A panel needs to be moved inside near the 400 A panel (garage).

Much appreciate the comment.

Best regards,

Bill

 

[iwire]

I would leave the panel outside but swap the meter socket out with one that has a either a single main or multiple mains.

I also would suggest a load calculation to make sure the service conductors are large enough.

 

[a0128958]

... I also don't see the need for your #4 on the list.

Thank you. I have deleted #4 from the list. Here it is, updated:

1. Make connection from DCW pipe to meter panel ground bus. Connection at pipe needs to be within 5' of pipe entering residence. Wire needs to be 1/0.
2. Remove insulated wire from meter panel ground bus to 200 A service panel ground bus.
3. Remove insulated wire from meter panel ground bus to 400 A service panel ground bus.
4. (removed from list) Add earth rod and connect to 200 A service panel neutral bus.
5. Move foundation concrete rebar ground connecting insulated wire from 400 A service panel's ground bus to neutral bus; verify wire is #4.
6. Verify size of service wires from meter panel to 400 A service panel (should be 400 kcmil?).
7. Remove 100 A service panel's ground-bus-to-neutral-bus-strap (or replace service panel with w/ a 100 A subpanel).
8. Insulate 100 A service panel's neutral bus from case (or replace service panel with a 100 A subpanel).
9. In 100 A service panel make sure all circuit ground wires go to ground bus. Same for circuit neutral wires only to neutral bus.
10. Outside 200 A service panel and inside (garage) 400 A service panel is a violation. The outside panel needs to be moved inside near the inside panel (garage).

Much appreciate the correction.

Best regards,

Bill

 

[a0128958]

I would leave the panel outside but swap the meter socket out with one that has a either a single main or multiple mains.

I also would suggest a load calculation to make sure the service conductors are large enough.

I feel foolish for not thinking of changing the meter socket to correct the grouping violation (versus moving the outside 200 A service panel to next to the inside garage 400 A service panel). Far better correction, by a long shot. Thank you!

I've learned I can't go back and edit a prior post. Next time I publish the updated list I'll show #10's corrective action to be 'appropriate change at the meter socket.'

I'm also going to change #6 (Verify size of service wires from meter panel to 400 A service panel (should be 400 kcmil?)) to be as you recommend (load calculation to ensure service conductors are adequately sized). The service wire to the 400 A service panel just looks awfully small to my eye.

Much appreciate the comments.

Best regards.

Bill

 

[jim dungar]

I'm also going to change #6 (Verify size of service wires from meter panel to 400 A service panel (should be 400 kcmil?)) to be as you recommend (load calculation to ensure service conductors are adequately sized). The service wire to the 400 A service panel just looks awfully small to my eye.

If you put a disconnect at the meter, the conductors to the 200A and 400A are no longer service entrance conductors, they are now feeders. Any neutral-ground bonding in the existing panels will need to be removed.

 

[a0128958]

If you put a disconnect at the meter, the conductors to the 200A and 400A are no longer service entrance conductors, they are now feeders. Any neutral-ground bonding in the existing panels will need to be removed.

Yep, forgot to note that. I remain of the belief that putting in disconnect at meter is less expensive alternative to fix problem (versus moving 200 A load center from outside to inside next to 400 A load center). Thus, will add to list to have all neutral-ground bonding removed in the existing 2 load centers and sub-panel (see below).

I had opportunity to return to the customer site and relook at current implementation. I've updated the existing diagram:



Items noticed and changes to the diagram include:
1. I found two #4 insulated wires from 200 A load center ground bus to DCW pipe.
2. The 3 service/feeder wires from meter socket panel to 400 A Load Center are each 2/0 AWG MTW/THWN-2/THHN, along with a #4 insulated ground.
3. 200 A and 400 A load centers have neutral-to-ground bonding (straps) in place; 100 A sub panel has neutral and ground isolated.
4. Only the 200 A load center has circuit neutral and ground wires mixed on the neutral and ground busses. The 400 A load center and the 100 A sub panel neutral and ground busses are 'pure.'
5. Concrete foundation rebar #4 insulated ground wire is tapped onto #6 bare wire from meter socket neutral to ground rod (tap is outside of meter socket panel).

I think the action item list is now reduced, thanks to help here and the second inspection this morning:

1. Outside 200 A Load Center combined with inside (garage) 400 A Load Center is a violation. Change Meter Socket Panel to include disconnect means.

2. Neutral-to-ground bonding in 400 A and 200 A Load Centers becomes a violation after Meter Socket Panel is changed to include disconnect means. Fix by removing all neutral-to-ground bonding in these 2 load centers (remove strap in each).

3. Mixing of circuit neutral and ground wires in 400 A Load Center on neutral and ground busses becomes a violation after Meter Socket Panel is changed to include disconnect means. Fix by changing circuit neutral and ground wire connections such that neutral and ground busses are 'pure.'

4. Feeder wire size (2/0 AWG MTW/THWN-2/THHN is a violation for 400 A Load Center that has an existing 400 A main breaker. Fix by doing a load analysis to determine if main breaker size can be reduced, or, if feeder wire needs to be increased to 400 kcmil.

5. Verify wires from DCW pipe are connected to an acceptable point (currently connected to 400 A Load Center's ground bus).


Best regards,

Bill

 

[mwm1752]

There's probably a bigger list to be done to make anything current

 

[Smart $]

For the current configuration, the grounding conductors between meter socket and each panelboard are a violation. They create an objectionable current path and a parallel path for neutral current. They should be removed and one of the grounding conductors to the DCW copper pipe should be connected to the 200A panelboard neutral (or ground bus if MBJ adequately sized).

Upon changing out meter to meter/main, all depicted grounding conductors must terminate at or before the meter/main, then as stated there can be no load side grounding to grounded connections.

 

[a0128958]

For the current configuration:

the grounding conductors between meter socket and each panelboard are a violation. (They create an objectionable current path and a parallel path for neutral current.) They should be removed ... one of the grounding conductors to the DCW copper pipe should be connected to the 200A panelboard neutral (or ground bus if MBJ adequately sized).

Upon changing out meter to meter/main:

all depicted grounding conductors must terminate at or before the meter/main, then as stated there can be no load side grounding to grounded connections.

Yep, I messed up on the DCW copper pipe connection. I should have added an action to move both grounding conductors to the DCW copper pipe to the meter socket's neutral bus, joining where the ground rod grounding conductor and foundation rebar grounding conductor both connect to the meter socket's neutral base.

Revised action list is:

1. Outside 200 A Load Center combined with inside (garage) 400 A Load Center is a violation. Change Meter Socket Panel to include disconnect means.

2. Neutral-to-ground bonding in 400 A and 200 A Load Centers becomes a violation after Meter Socket Panel is changed to include disconnect means. Fix by removing all neutral-to-ground bonding in these 2 load centers (remove strap in each).

3. Mixing of circuit neutral and ground wires in 400 A Load Center on neutral and ground busses becomes a violation. Fix by moving circuit neutral and ground wires such that neutral and ground busses are 'pure.'

4. Connection of DCW copper pipe grounding conductors to 400 A load center's ground bus becomes a violation. Move both grounding wires to meter socket neutral bus.

5. Feeder wire size (2/0 AWG MTW/THWN-2/THHN is a violation for 400 A Load Center that has an existing 400 A main breaker. Fix by doing a load analysis to determine if main breaker size can be reduced, or, if feeder conductors needs to be increased in size to 400 kcmil.


I also agree that if the meter socket panel is not changed right away to include a disconnect, then, at minimum the grounding wires from the meter socket panel to each load center should be removed, and, one each of the DCW copper pipe grounding conductors should attach to each load center's neutral bus. The mixed connections of circuit neutrals and grounds can continue at the 200 A load center.

Have much appreciated the comments!

Best regards

 

[kwired]

As you can see from comments so far, there is no specific correct list of actions to be taken. For each current violation that has been pointed out there is often more than one possible solution, and each possible solution will have different related actions that go with it.

As has been said, if you put a main disconnect for all of it outside in or at the meter, you now have established a new service disconnect, and all the grounding electrodes need to run to that point as well as the equipment grounding conductor originates there and must be isolated from the grounded conductor from that point on. If you move the 200 amp panel so it is next to the 400 amp panel, they are both still service equipment and must have common connection to the grounding electrode conductor.

Since you have a CEE and a water pipe grounding electrode, you have no requirement for any ground rods at all, but is not prohibited to install any either. A ground rod is typically only necessary when there is no other qualifying electrodes present or no others to supplement the water pipe as is required.

Size of GEC to water pipe is dependent on the size of the service entrance conductors. Just because you have a 200 and a 400 amp main breakers does not mean 600 amp service conductors is necessary for this application. With multiple service disconnects the service conductors only need to be sized to the load calculations.

 

[Smart $]

... With multiple service disconnects the service conductors only need to be sized to the load calculations.

True up... or should I say down... to the point where they split.

As it is now, the taps to the 200A and 400A mains need to be sized such that they are protected by their respective main OCPD rating.

If a single main is installed ahead of the panels, the feeders or feeder taps to each panel must be protected by the main (if feeder) or load-end OCPD (if feeder tap)... or corrected so that they are.

 

[kwired]

True up... or should I say down... to the point where they split.

As it is now, the taps to the 200A and 400A mains need to be sized such that they are protected by their respective main OCPD rating.

If a single main is installed ahead of the panels, the feeders or feeder taps to each panel must be protected by the main (if feeder) or load-end OCPD (if feeder tap)... or corrected so that they are.

I agree with that.

 

[novemberaudi]

Once the correct size conductors are installed in the 400 amp panel. If the load is appropriate it may be less expensive to feed the outdoor panel from the panel in the garage and not change the meter setup.

 

[Smart $]

Once the correct size conductors are installed in the 400 amp panel. If the load is appropriate it may be less expensive to feed the outdoor panel from the panel in the garage and not change the meter setup.

That's a good point. Cost will include an additional OCPD in the 400A panel and rerouting conduit and conductors, as you cannot route feeders back through the meter enclosure.

 

[a0128958]

Once the correct size conductors are installed in the 400 amp panel. If the load is appropriate it may be less expensive to feed the outdoor panel from the panel in the garage and not change the meter setup.

This is an excellent suggestion, and is much appreciated!

I was not looking forward to visiting with the customer next week to outline corrective actions needed, noting the high expense of changing out the 400 A double-lug meter socket panel for one that includes a switch disconnect means. The above suggestion is much more doable.

This suggestion makes the 400 A load center the structure's 400 A service panel, with a 400 A main breaker already in place.

There's an existing inside, upstairs 100 A sub-panel with a feeder from the 400 A load center (with an in-line 100 A OCPD in the 400 A load center). The 100 A sub-panel is an actual sub-panel with no ground-to-neutral bonding present anywhere) and is properly wired as a sub-panel (with appropriately sized feed conductors, with separate ground and neutral wires, and with ground and neutral circuit wires properly connected to the appropriate bus).

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

 

[novemberaudi]

I don't think you are going to be able to install a 200 amp breaker in the garage panel, I'm guessing a 125 would be the biggest you could put in. But yes you can have both panels fed off the garage panel. What load is connected to the exterior panel, just the A/C condensors?

 

[kwired]

I don't think you are going to be able to install a 200 amp breaker in the garage panel, I'm guessing a 125 would be the biggest you could put in. But yes you can have both panels fed off the garage panel. What load is connected to the exterior panel, just the A/C condensors?

When you get into the 400 amp series panels the chances of it being able to accept a breaker larger than 125 amps increases. Such breakers will usually take up two slots per pole, but part of the reason they maybe don't list them to be installed in a smaller panel is because there is not enough wire bending space in the smaller cabinet. Get a commercial grade panel and you probably can install them.


Now if the OP can install a 200 amp breaker, next thing will be just how much will the breaker cost? Sometimes those kind of items are much better priced with a bill of materials that includes the panelboard than as stand alone purchases.

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