Questions re Efficient placement of main and subpanel

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Paul Blakely

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New construction. Based on location of utility pole, main service will come in on North side of house. Was planning to bring in 200 amps to a main service panel in the single story laundry room. Main draws in that area are clothes dryer, small water heater, guest bath and just a couple bedrooms.
On the South and central sides of the house, there will be range, HVAC unit, garage workshop, "solar-ready" breaker in panel (maybe?), Mbrm and Bath, another small water heater. Also thinking of putting an electric vehicle circuit in the garage. (There is a 46" unvented, conditioned crawl space with concrete floor under the single story house that will contain the HVAC unit centrally located and the two stubby hot water tanks placed to minimize the wait time North and South. Didn't want recirc pump).

So my questions revolve around how most efficiently to arrange the service. Most of the power will be drawn on the South and Central sides of the house. (56 ft North to South). The city will only take the service to the North side of house. It looks too costly to run #2 gauge wire inside the house through a 3" conduit to get that main panel to the garage. So I was thinking I would put the 200 amp panel in the North side and then run a 4 guage wire to connect to a 100 amp subpanel in the garage.

Does it make sense to do it this way?
Can I do that run to a 100 amp subpanel with a 60 amp breaker, 4 gauge wire from the 200 amp main service?
Do I have to have a copper ground rod connected to the subpanel or just the main service panel?
Would I need 40 amp breaker for solar panels and 50 amp breaker at 240 volts for future electric vehicle?
If I have to have those two large circuit breakers in addition to a 50 amp 240v circuit for the range, is that too much for a 100 amp subpanel?
If I install some solar panels, do I have to send wire from the south facing roof to the main panel on the North side and what size would that wire be?

Thanks for any assistance.
 

wwhitney

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A few comments:

- A diagram would be a lot easier to follow than your narrative description.
- Presumably your service panel in the laundry room will be on an exterior wall.
- I agree that it makes sense to put in a subpanel at the other end of the house for loads there. Aluminum wire is cheaper than copper wires, a larger Aluminum SER cable would be the typical choice.
- To size the subpanel and the feeder, you need to do a load calculation for the loads supplied by the panel. Or since you have a 200A service, you could just put in a 200A subpanel and run 4/0 Al SER cable. Your service panel would need to be able to accept a 200A branch breaker.
- No grounding electrodes at the subpanel, that all happens at the service panel.
- A PV inverter can connect up in the subpanel. That will require that the feeder breaker in the service panel be at the opposite end of the bus as the service conductors. And if you want to allow for a 40A breaker for a 7.6 kW inverter, you'll either need to use a 200A subpanel, or you could use a subpanel with a 125A rated bus supplied via a 110A or smaller breaker in the service panel.

Cheers, Wayne
 

Paul Blakely

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A few comments:

- A diagram would be a lot easier to follow than your narrative description.
- Presumably your service panel in the laundry room will be on an exterior wall.
- I agree that it makes sense to put in a subpanel at the other end of the house for loads there. Aluminum wire is cheaper than copper wires, a larger Aluminum SER cable would be the typical choice.
- To size the subpanel and the feeder, you need to do a load calculation for the loads supplied by the panel. Or since you have a 200A service, you could just put in a 200A subpanel and run 4/0 Al SER cable. Your service panel would need to be able to accept a 200A branch breaker.
- No grounding electrodes at the subpanel, that all happens at the service panel.
- A PV inverter can connect up in the subpanel. That will require that the feeder breaker in the service panel be at the opposite end of the bus as the service conductors. And if you want to allow for a 40A breaker for a 7.6 kW inverter, you'll either need to use a 200A subpanel, or you could use a subpanel with a 125A rated bus supplied via a 110A or smaller breaker in the service panel.

Cheers, Wayne
Thanks Wayne, for the suggestion to use Aluminum SER cable as the typical choice. While trying to find whether a GE 200 amp main service panel would accept a 200 amp branch breaker, I came across another forum that suggested a subfeed lug kit would avoid the need for a 200 amp breaker. So I would have to research how that would be wired at the main to the subpanel.

Not sure what you mean in your last paragraph after saying the PV inverter can connect up in the subpanel. As you suggested to me, a diagram would be a lot easier to follow than the narrative. I will try to upload a diagram in the next day.
Thanks again.
 

Paul Blakely

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Thanks Wayne, for the suggestion to use Aluminum SER cable as the typical choice. While trying to find whether a GE 200 amp main service panel would accept a 200 amp branch breaker, I came across another forum that suggested a subfeed lug kit would avoid the need for a 200 amp breaker. So I would have to research how that would be wired at the main to the subpanel.

Not sure what you mean in your last paragraph after saying the PV inverter can connect up in the subpanel. As you suggested to me, a diagram would be a lot easier to follow than the narrative. I will try to upload a diagram in the next day.
Thanks again.
Thanks Wayne, for the suggestion to use Aluminum SER cable as the typical choice. While trying to find whether a GE 200 amp main service panel would accept a 200 amp branch breaker, I came across another forum that suggested a subfeed lug kit would avoid the need for a 200 amp breaker. So I would have to research how that would be wired at the main to the subpanel.

Not sure what you mean in your last paragraph after saying the PV inverter can connect up in the subpanel. As you suggested to me, a diagram would be a lot easier to follow than the narrative. I will try to upload a diagram in the next day.
Thanks again.
I've attached a blueprint of the house to better convey the layout. I was intending to bring the main service into the house on the right side in the laundry room. But the bigger electrical load would be on the left side of the house, where the proposed subpanel would accommodate solar panels from the roof on the far left, the electric range in the kitchen, hot water heater#1, as well as several 240 outlets in the garage. That subpanel would be located in the garage.

The main panel would accommodate dryer, hot water tank#2. HVAC could be served from either main or subpanel since it will be located near the center of the house, though it would be a shorter run from the proposed subpanel.

The city will take the service to the nearest point, which is why I located the main panel on the right side. But I think I would be better off if I could somehow get the main panel into the garage.

Since there is a 4' crawl space, is it possible to have #2/0 copper or #4/0 aluminum enter the crawl space through the rim joist on the right side (since I didn't place a penetration in the concrete wall ) and then run that over to the panel in the garage? If that is possible, would the cable have to be within 3" conduit?
Would the garage be a more efficient placement of the main service panel rather than running a 200 amp subpanel to the garage?

Thanks.
 

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wwhitney

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The electrical service needs to have a disconnect on the exterior of the house or immediately on the inside of where it enters. The only way you could get the electrical service to the garage would be bury (or encase) the service under (with) at least 2" of concrete where it crosses under (through) the footprint of the building. That would mean that the service is considered to "enter" where it rises up above the concrete in the garage.

You are better off putting your service disconnect on the outside of the house by the laundry, or on the exterior wall of the laundry room. The wires the electric company runs are typically smaller diameter that what the NEC requires (i.e. they won't be 2/0 Cu or 4/0 Al), so you will have less voltage drop at the garage subpanel if the laundry to garage feeder is sized per the NEC rather than by the utility. If the GE service equipment you mentioned won't take a 200A branch breaker, then use a different piece of equipment that would. Or run a smaller feeder to a smaller garage subpanel, but plan to take the PV to the service panel if its breaker is bigger than 20% of the subpanel's rating.

Cheers, Wayne
 
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