GRID-TIE wiring from Inverter to grid plans

[Borderline]

Been lurking, thought I'd join up.

We're in the initial planning stages of a DIY Grid-Tie project. The Solar Array will be installed on a machine shed roof. The attached sketch should show this but,

1) The main power from utility first goes from power pole/transformer to the "House" Breaker Box.

2) Power from the "House" box goes underground to the "Shed" Breaker Box (please note, Shed boxes main breaker is located in "House" box)

3) From what I understand, I can run the A/C from Inverter to "Shed" box, which in turn takes the solar generated power to the "House" Box (we utilize the same underground wiring), in which we tie in to a reverse meter

4) of course there is a bit more to it, just wanted to keep it simple for an explanation

Are we on the right track? Please review attached Wiring Plan and Breaker Box photos. THANKS!

[heimdm]

Welcome. If I am following correctly, you are looking at 14,000 watts / 14 kw ac capacity. That would put you near 60 amps. When connecting load-side (in a breaker box), with dual power sources (utility & solar), you can only be at 120% of the bus bar rating. Based on the photos you would be probably installing a new 200 amp breaker box. If you get a 225 amp bus bar box, 120% of that would get you to 270 amps, What size breaker is protecting that leg to the shed? Edit: noticed based on the picture, you have 70 amps feeding the shed over 4 awg wire.

One thing you have to watch is voltage rise. As the electricity travels from the inverter to the utility, the voltage rises, basically its voltage drop in reverse. So the thinner the way, the longer the run is, the more voltage rise you will get. Recommendations is to keep voltage rise to within 2%. What brand inverter are you looking at? Here is the calculator I use: https://unboundsolar.com/blog/voltage-drop. Going 140' over 4 awg wire, I would plan on pulling thicker wire. What size conduit is running betwee the shed and the houes? To the wire to pull, Bruce always says the most expensive wire you can afford is what you should use.

[Mike90250]

A long cable run like this, would suggest the use of Aluminum wire, properly secured at each end, should be less expensive than copper - if your conduit has enough room for the aluminum, which is 2 sizes larger than the copper size ( for the same amps )

[SunEagle]

A long cable run like this, would suggest the use of Aluminum wire, properly secured at each end, should be less expensive than copper - if your conduit has enough room for the aluminum, which is 2 sizes larger than the copper size ( for the same amps )

That picture looks like the Shed main power cable is in the same conduit as the pump power cable. I don't see how a 14kw system can be back fed into the main through the 70 amp shed panel.

So the OP would have to run a new cable from the solar inverter to the main panel and make a legal connection to the grid either via a bigger panel or splice into the feed to the main panel.

[Borderline]

Hi folks. YES, 14,000 Watts (not kW). The cable running from main (house) breaker is outdoor rated and doesn't run through a conduit.

If we can't connect the AC from Inverter to shed breaker, I'd have to trench in a new line to run cable to the house breaker

[solarix]

I tell people frequently that they ought to replace their electric service every 50 years - whether it needs it or not. If you are thinking about a large (>10kW) solar array, you should put in a "solar ready" type 200A panel with a 225A buss. If you had a 70A main breaker out at the shed subpanel, then you could inject the solar power upstream of this breaker and save the trenching. However the code is not real clear on this strategy and will depend on your local AHJ to approve it. Also, as stated in other posts, your inverter might not like being so far from the service because of the voltage drop. Good luck....

[heimdm]

When I added my panel box for my solar install, I ended up using Leviton's panel boxes, which were actually pretty nice. They are 225A bus bar, and I liked the fact that the wire landed on the bus bars (hot & neutral) instead of physically to each breaker. I did not go with the smart breakers.

In my setup we ran a single feed (4/0) from the meter to just below the Solar AC combiner box. There we had a junction of polaris connectors. From there one feed went to the Solar AC combiner, and the other feed went to a regular panel box to feed the outdoor patio.

If you are pulling thick wire, Southwire makes some really pulling heads (Simpull head), makes the job a lot easier. One thing I don't think your drawing had on it, that is probably required is going to be a fusible disconnect with the big red handle an ability to tag out/lock out. Most utility companies require that where the solar connects in to your electric.