Service question

[SCBO1]

Existing residential single family home with a 200A service and a 100A service next to each other. The two services SE cables go to the service meter can. Water pipe ground and ground rod ground is connected to the 200A service and the 100amp service ground was brought over to the 200A panel grounding bar.

I have never seen this, most of time I see the 100A as a sub-panel. This is existing and was approved in 1978, all electric home.

Is this a common set-up when needing additional service , for an all electric home?

pc1

 

[steveray]

E3501.2 Number of services.

A dwelling unit shall be supplied by only one service.

 

[fatboy]

Agree with steveray.....

 

[steveray]

Might be one service with multiple panelboards which would be allowable, but it sounds like the grounding is wrong....

 

[Dennis]

I believe there is only one service. Are there 2 meter bases or just one? 2 meter bases does not make it 2 services. If there is one service lateral (underground) or one service drop (overhead) then there is one service.

So how many meter bases are there?

 

[gbhammer]

Existing residential single family home with a 200A service and a 100A service next to each other. The two services SE cables go to the service meter can. Water pipe ground and ground rod ground is connected to the 200A service and the 100amp service ground was brought over to the 200A panel grounding bar. I have never seen this, most of time I see the 100A as a sub-panel. This is existing and was approved in 1978, all electric home.

Is this a common set-up when needing additional service , for an all electric home?

pc1

Confusing is the way, OP you have made.

 

[SCBO1]

Sorry, my mistake, only one meter (service) socket.

One 200AMP house breaker panel with a 100AMP panel installed within 3" of the 200amp panel.

Two Service entrance cables (multi-wire) from the meter service, down through the house wall to the breaker panels in the basement.

Two grounding sources, one ground rod and one water pipe ground both entering the 200amp panel. Grounding wire from the 100Amp to the 200Amp panels grounding bar. The 100Amp panel is not set up as a sub-panel.

Steveray is correct, one service, two panels, I too do not believe the grounding is correct.

 

[SCBO1]

Dennis, there is one meter for two panels. Underground service to the meter socket from the POCO.

 

[Dennis]

Then you have a 300 amp service and the gec must be sized based on the combined size of your service entrance cables. Thus is you have copper service wire then one would usually have 3/0 copper for the 200 amp box and #3 for the 100 amp box. You need to go back to chapter 9 and look up Table 8 for conductor properties. Thus 3/0 = 167800 cir. mils and #3 = 52620 cir. mil. add them together and then look up the equivalent wire size in Table 250.66. 167800+52620= 335600 cir mil. From the same table that is equivalent to 350KCM conductor. T. 250.66 states a #2 copper gec is required.

Same thing for aluminum. Now be careful the contractor cannot use T. 310.15(B)(6) to size these conductors. He/she must use T310.16.

Once the #2 is run to the first panel then the contractor can tap off that conductor with #8 copper to the 100 amp panel assuming that is size for the conductors used. Remember t.250.66 is based on wire size not breaker size so even if you increase to a larger conductor then you would typically need then you must base the GEC on that larger conductor.

Hope that isn't too confusing. Now if they ran the GEC into the meter base sized with #2 then that's all she wrote. Some poco's do not allow it.

This graphic has two meters but it the same idea.

 

[Francis Vineyard]

Here the POCO does not allow GEC in their meter can and unless each GEC are independent to the common GES; my understanding when applying 250.64© and (D) the GEC tap from the 100 amp has to be outside of the 200 amp panel to maintain a continuous connection should one of any panels be removed. In addition should the #8 GEC tap onto another GEC at that point shall be a "common" GEC sized to the overhead or underground SE cable; not the SE combined to each panel. In this case still works out to be #2 copper.

Had a contractor last week asking if the electrician could do something similar but I've yet to see a residential single meter can that is listed for more than one set without a gutter to the panelboards.

Francis

 

[SCBO1]

Update, the meter socket was installed in the 70's and has two double lugs for two panels for an all electric house. The POCO said they did'nt want the panel GEC in the meter base like Francis sez. Verified it's not in their meter base, all is good.

Sometimes you see something you've never seen before!

pc1