Solar question on detached garage

[vrinner]

Totally amateur question here...

So I am putting solar on my new detached garage, new 100 amp sub panel on garage is about 100' run to my house 200 amp panel.

The solar is going to be hooked up on the roof of the garage and into the 100 amp sub panel in the garage that will also feed all my garage electrical.

Question...there doesn't need to be two sets of wires going between the garage and the house? I just want to make sure I'm not missing something with this magic solar stuff.

 

[wyliesdiesels]

nope

have you done load calcs?

 

[mm08822]

The house feeder connection at the sub-panel buss must be on the opposite end of the buss from the inverter inputs.
The sum of 125% of the inverter output(s) plus the supply feeder OCP value shall not exceed 120% of the buss bar rating.

What is the panel buss rating?
What is the feeder OCP value?
What is each inverter(s) max output?

Worst case - you may need to replace the panel (for a higher buss rating) or lower the OCPD rating supplying the feeder.
Best case - it all within the above requirements.

You also need to do this calculation for the main panel. Feeder breaker needs to move to the opposite end of the buss from the main OCPD location.

 

[99LeCouch]

So the inverter is going in the garage? And it's a grid tie system without storage? That won't need a second set of wires. Whenever the solar is making power, it will help supply the garage panel. The garage will use whatever power it uses, then the remainder of the power, if any, will go to the house panel. The house will use whatever it uses, and any excess will go out into the grid. When the solar isn't making power, everything will draw from the grid as before the solar was installed.

 

[walta]

Some utilities/ states require a second meter for the solar. Some fire departments require the solar disconnect be within a few feet of the power meter.

After you make the regulators happy you then need to make it safe in that no wire of panel can be overloaded.


Walta

 

[Git]

mm08822 is spot on. I am also in SoCal (SCE) and when they installed the breaker in my main panel for the solar - it had to be at the opposite end of the panel (in my case the very bottom of the panel which required them to move some breakers around)

Also, the derated my main panel from 225 amps down to 200 (replaced the main breaker)

 

[vrinner]

Load calcs for the new garage were done with the solar panels factored in so we should be good there.
I recently upgraded my main house panel from a 100amp to a 200amp panel. All the other technical talk is beyond me but I'm assuming my solar company when submitting the plans will take all that into consideration.

I do have four open breaker spots at the bottom of my new panel.

For the solar inverters I'm thinking it's the "Solar Edge 11.4-H" listed as a line item...yes it's going in the garage. It is also a grid tie in system without storage.

Thanks for the input...although I still think it's magical that electricity comes and goes as needed!

 

[Git]

For the solar inverters I'm thinking it's the "Solar Edge 11.4-H" listed as a line item...yes it's going in the garage.

Sounds like a slightly newer version than mine. I have the 11400A which appears to be now discontinued (and looks to be quite a bit bigger) and the 11400H is the replacement

https://www.wholesalesolar.com/9900118/solaredge/inverters/solaredge-se11400a-inverter

Something to keep in mind. SolarEdge Inverters usually come with a 12-year warranty but they offer an extended warranty out to 25 years. My installer included the cost of the extended warranty in the initial cost - but you can also buy it yourself.

Here is a link with more info. I think it's $745 for 25 years of coverage
https://www.renvu.com/Learn/SolarEdge-Extended-Warranty-SolarEdge-Inverter

 

[Ray-CA]

Also, the derated my main panel from 225 amps down to 200 (replaced the main breaker)

Same here (200 down to 175) Anyone know why?

Ray

 

[wyliesdiesels]

Same here (200 down to 175) Anyone know why?

Ray

MM explained it in comment #3.

The sum of 125% of the inverter output and the OCP rating cannot exceed 120% of the bus bar rating.

If that sum does exceed that, then the OCP rating needs to be lowered.

 

[dcg9381]

If you've got an installer that deals with your geography, that's good. I'd also caution you (really, the installer) - some jurisdictions require external disconnects for both the AC and DC sides. Newer inverters have automatic disconnects for the DC array, but not all areas recognize them, even if they are NEC compliant.


How big is your array?

 

[99LeCouch]

SolarEdge monitoring is decent for checking in quickly. It goes down to panel level, which is nice in case of infant mortality. The installer knows exactly which panel to replace, and the logs will help get warranty coverage.

Are you hardwiring the monitoring card, or getting the Zigbee? The downside of the Zigbee is it only updates every 5 minutes. Not that big a deal. The SolarEdge monitoring website is also faster than the phone app, but has the same functionality for the end user.

Enjoy your new system!

 

[vrinner]

I'm getting 36 LG Neon series panels...11.52KW system size.

The proposal doesn't say hardwiring the monitoring card but it does say "Web monitoring" I will be running internet to the new garage as well.

 

[Ray-CA]

MM explained it in comment #3.

The sum of 125% of the inverter output and the OCP rating cannot exceed 120% of the bus bar rating.

If that sum does exceed that, then the OCP rating needs to be lowered.

Thanks

I read that but I don’t understand it. Would someone explain it me please?

Ray

 

[Git]

Basically, if you have a 200 amp panel and your solar installation can add another 60 amps you have the *potential* of pulling 260 amps across the main busbars of the panel and they were not designed to handle that much load. There is a built-in safety factor of 120% which would be 240 amps, but with the solar adding 60 amps, you would be over the 120%/240 amps by 20 amps. So to reduce the potential, they reduce the main breaker which is the simplest/easiest solution

This explains it better:
https://www.civicsolar.com/support/installer/articles/what-panelboard-sizing-120-rule

 

[mm08822]

Basically, if you have a 200 amp panel and your solar installation can add another 60 amps you have the *potential* of pulling 260 amps across the main busbars of the panel and they were not designed to handle that much load. There is a built-in safety factor of 120% which would be 240 amps, but with the solar adding 60 amps, you would be over the 120%/240 amps by 20 amps. So to reduce the potential, they reduce the main breaker which is the simplest/easiest solution

This explains it better:
https://www.civicsolar.com/support/installer/articles/what-panelboard-sizing-120-rule

^^^This^^^ but so many stars have to line up for this to be a real concern. It is however, what the code specifies.

Same goes for the inverter input cb on opposite end of buss that the main feed cb is on. Assumption is load circuits are consuming in between the 2 feed points and the buss will never see full or higher than rated current.

 

[Ray-CA]

Thanks for the explanation.

Makes it very clear now

Ray

 

[Orionrising]

Realize thought if you are feeding a sub panel, the systems has to turn off when grid power comes down, you could have a transfer switch but only for things on that Sub panel.

Sent from my Moto G (5) Plus using Tapatalk