Solar Panel System

Pettrix · Jan 9, 2017

I might be installing a ground mounted solar panel system in a year or two. I am building a house/garage now and pulling power to the site. It will be a 400 amp service with an exterior panel mounted on the garage exterior.

What should I do to prepare for the future solar panel system install? My garage will have a concrete wall so if I need to sleeve a hole, now is the time to do it.

RNeumann · Jan 9, 2017

400a is a lot of power. If it is after the meter (sub panel) you will need 3 wires plus the ground. The 3 main wires in copper THHN (about the smallest wire you can use) will be 500 which is nearly an inch in size! Plus a ground which can be smaller. With all that you are going to need to put conduit in the ground that is 3-4". I'd use sch. 40 pvc with LONG sweeps. You will also need to put a ground in the concrete before you pour. 20' of rebar in the base of the footing that sticks out of the slab/footing near your panel will work- it's called a ufer ground.

If it's a new service with a meter call your utility as they typically want to see what's up and will tell you what they want.

That's a lot of power! In the post meter/sub panel scenario-- Most homeowners could get away with 100-200a and if needed would add a second 200a panel- the wire alone for 400a will come on spools that are truck mounted and will take a winch to pull.

Good luck and google "wire amp chart" and "conduit fill calculator" also look at panels that can have a 400a breaker. That is going to cost a lot as well.

It may be easier to have the utility put a service at your shop and pay for 2 meters- house and shop.

EddieWalker · Jan 9, 2017

I have two 200 amp panels to my house. One panel is in my garage, which feed the garage and all the outlets in the house. The other panel is in my utility room that powers my HVAC system, my electric water heater, and then runs out to my hot tub, RV pad and everything else outside. I forget what sized conduit I used to run the wires up through my slab and walls, but since the walls are 2x4's, it was 3 inches or less.

RNeumann · Jan 9, 2017

Yep 200a is 4/0 THHN aluminum wire (smaller if copper) and with my conduit calculator you would need 2 1/2" PVC. Still use long sweeps.
This is much more reasonable!

nikdfish · Jan 9, 2017

Are you planning on a strictly grid-tied system, battery based or a hybrid? Grid tied could pretty much all be done externally, as that is where you are planning for the main utility breaker location, although it would probably need a weather proof cabinet or shed. Battery or hybrid would mean you need a location for battery installation & conduit for the feeds. Lead acid batteries are typically happier in an area that stays reasonably climate controlled (they lose efficiency when cold) & may require separate ventilation for safety if not sealed.

Nick

techman · Jan 9, 2017

Besides your spool for a feedthrough, the only other prep on a grid tie is to leave a 2-pole breaker space open at the bottom of the panel (furthest from the supply end of the panel).

paul

Pettrix · Jan 9, 2017

RNeumann said:
400a is a lot of power

That's a lot of power! In the post meter/sub panel scenario-- Most homeowners could get away with 100-200a and if needed would add a second 200a panel- the wire alone for 400a will come on spools that are truck mounted and will take a winch to pull.

Good luck and google "wire amp chart" and "conduit fill calculator" also look at panels that can have a 400a breaker. That is going to cost a lot as well.

It may be easier to have the utility put a service at your shop and pay for 2 meters- house and shop.

I am having 400 amps pulled so that my guest house will have 200 amps and then my future main house will have the other 200 amps. That's why I am having 400 amps brought to the house as it will serve 2 homes.

Will 3" PVC conduit be large enough for the wire pulls?

Can the ground mounted solar system be connected/installed from the OUTSIDE of the garage where the main line feed comes in? Or will I have to gain access to the inside of the garage?

Pettrix · Jan 9, 2017

nikdfish said:
Are you planning on a strictly grid-tied system, battery based or a hybrid?

It will be grid tied/hybrid but I will NOT be sending power back to the utility company. I will be using the Tesla battery to store power.

prichard · Jan 9, 2017

3" would be absolute minimum. I wouldn't want to pull it. If I had to do 400A I'd pull parallel 250MCM in 3". But I'd go for 2 200A services as suggested previously. 200A meter, breakers, wire, etc are all going to be much cheaper. Around here 200A is max residential meter size. 400 is considered a business service and the monthly charges are even more.

Pettrix · Jan 9, 2017

The utility company will provide the power cable. I have to provide the trenching and conduit. They said 2" conduit up to the house site and then there will be a transformer about 80' from the house and then it goes to a 4" conduit to the house.

The utility company will pull the cable up to the home.

RNeumann · Jan 9, 2017

Ok perfect you have a lot of your info. The utility will pull 1 smallish wire to the transformer and then 3 large wires to your panel. You can do grounds outside. In that case it's 2 rods 8' long and 10'apart (verify distance). Those can be added later. I suggested the ufer as it's easier for most to just bury the rebar before you pour the concrete.

I want to make sure to provide good info here so let's make sure we all understand. The utility will install a transformer and then pull wires to the meter which is on the house? You are then wanting to take 200a to a guest house and 200a to the shop? Is this correct? The 3" you are asking about is the 200a leg to the shop? If that is the case 3" would work fine. You could run copper or aluminum THHN wire in that. In fact you could run smaller conduit if you wanted.
Interesting to note the utility is wanting 4"'conduit for the wires they are running....way oversized! They have much lower wire size standards and don't have to run 4 wires like you would.

Pettrix · Jan 10, 2017

RNeumann said:
Ok perfect you have a lot of your info. The utility will pull 1 smallish wire to the transformer and then 3 large wires to your panel. You can do grounds outside. In that case it's 2 rods 8' long and 10'apart (verify distance). Those can be added later. I suggested the ufer as it's easier for most to just bury the rebar before you pour the concrete.

I want to make sure to provide good info here so let's make sure we all understand. The utility will install a transformer and then pull wires to the meter which is on the house? You are then wanting to take 200a to a guest house and 200a to the shop? Is this correct? The 3" you are asking about is the 200a leg to the shop? If that is the case 3" would work fine. You could run copper or aluminum THHN wire in that. In fact you could run smaller conduit if you wanted.
Interesting to note the utility is wanting 4"'conduit for the wires they are running....way oversized! They have much lower wire size standards and don't have to run 4 wires like you would.

I already did the Ufer Ground in my rebar footing.

Yes, the utility will install a transformer about 80' from the house and then pull the wires to the meter on the outside of the garage. I will then take 200 amps to the guest house and the remaining 200 amps will be pulled to the future main house about 150' away.

The 3" conduit will be used for the 200 amps going to the future main house.

RNeumann · Jan 10, 2017

You are in good shape with 3" with either aluminum or copper.

prichard · Jan 10, 2017

I thought you were asking what you needed for the 400A. As RN said, you're good to go.

prichard · Jan 10, 2017

BTW, it's very common for utilities to require oversized conduit. Telephone companies used to require 2" conduit for a cable that was less than 1/2".

RNeumann · Jan 10, 2017

prichard said:
BTW, it's very common for utilities to require oversized conduit. Telephone companies used to require 2" conduit for a cable that was less than 1/2".

Yep in my current location the phone company requires 3" conduit to their box. Our work around is to have the phone company put their box near the property line and then we run 1" or 1 1/4" conduit to the house. It's only one cat5/6 line normally- which is good up to about 350'

Pettrix · Jan 10, 2017

So I can install a solar panel system later on by tying into the outside meter connection. I just wanted to make sure I don't need to leave an open sleeve in the concrete wall for future access.

Pettrix · Jan 10, 2017

Another ridiculous thing is the utility company wants me to put 6" of 1" minus shading over the SCH 40 conduit. That's completely unnecessary. I've buried SCH 40 PVC pipe with native soil that had large rocks in it. One just has to push the soil back on top and not DROP it from a high height. SCH40 is tough pipe and a large rock sitting on top of it will not puncture it. A large boulder dropped from 10 feet might crack it.

RNeumann · Jan 10, 2017

Pettrix said:
So I can install a solar panel system later on by tying into the outside meter connection. I just wanted to make sure I don't need to leave an open sleeve in the concrete wall for future access.

I read up on Tesla's system a year or two ago so I'm going off memory- from what I recall they mount a large lithium battery to a wall (like in your garage) that is 480v DC. From their they transform that to AC and lower the voltage to match the utility. When I looked at it a lot of the details were not worked out.

I'm assuming Tesla will provide some specs for what they want.

As far as the solar I would add a 3" conduit about 4' -6' from the utility conduit on the same wall. That will allow the the solar to enter the structure and tie in as needed to either the Tesla setup or the main panel- depending on how Tesla wants it setup- I'm guessing it's into the Tesla side.

Are you doing the electrical? Is the main panel going on the outside with a sub-panel on the inside? Or is the main with all your breakers going on the outside? I'm guessing if you want conduit in the concrete something is going on the inside?

As far as the utility conduit- they have their ways...shaking my head. Not much you can do other than say OK.