Grid-tie into Subpanel Question

IronMan_74

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Mar 17, 2022
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Hello everyone! I recently started looking into and researching all things solar as I'm thinking about adding a solar system to my house. I've been reading/watching everything I can find for the past week and am starting to put the pieces together. One thing I'm not clear on though is the Grid-tie hook-up and more specifically how it would work in my situation. So wanted to ask for some help/feedback here before I go digging much further to make sure I can accomplish what I want to.

First a little background. My main goal is not to go completely off grid or even size the system to replace most of our usage, just looking to offset some electricity costs with solar. I have a shed that we built last year for our pool equipment. My wife doesn't want solar panels on the roof of our house but might be OK with them on the pool shed roof. the side of shed roof facing south is about 34 feet long and 11 feet tall. I estimate I could fit anywhere from 10 to 12 ~350 to ~430 watt panels on it or somewhere around 4kw of solar production. When we installed all of the equipment and everything for the pool we ran a subpanel out to the shed that's hooked up to a 50 amp breaker in the main panel. Inside the subpanel there are a few different breakers for the pool equipment as well as LED lighting around the shed. I also recently installed 2 20 amp breakers for crypto mining equipment but am only using 1 of the 20 amp breakers currently (and its maxed at 80% load 24/7).

So knowing that's the space I have to work with and that I would want to keep all solar related equipment installed in/on the shed, would I even be able to tie into the grid at that subpanel? And if not, is there anything i could "upgrade" to make that possible?

Thanks for the help!
 

BentleyJ

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You would absolutely be able to tie into the shed subpanel directly with a grid-tie system, microinverters are a good choice, but you would need to install a 2 pole breaker. This would meet your goal of offsetting some electricity usage but there would be no batteries or back up in a grid down situation.
 

Brett V

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Are you planning this as a DIY? Feeding that much power back in to the grid might attract unwanted attention from your power company. You should have the proper permits and inspections done.
 

BentleyJ

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If you did wish to go further and install a combination system where it is grid-tied but also can provide some back-up, then it sounds like you would really need to install a critical loads panel and separate hybrid Inverter that is capable of AC Coupling to the grid-tie system on the shed. These items would be installed near the main panel and then move some breakers for your refrigerator, lights, computers Etc.
 

IronMan_74

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You would absolutely be able to tie into the shed subpanel directly with a grid-tie system, microinverters are a good choice, but you would need to install a 2 pole breaker. This would meet your goal of offsetting some electricity usage but there would be no batteries or back up in a grid down situation.
If you did wish to go further and install a combination system where it is grid-tied but also can provide some back-up, then it sounds like you would really need to install a critical loads panel and separate hybrid Inverter that is capable of AC Coupling to the grid-tie system on the shed. These items would be installed near the main panel and then move some breakers for your refrigerator, lights, computers Etc.

Thanks for the reply! I just wasn't sure if the subpanel being fed by a 50 amp breaker would limit/impact how many watts/amps i'd be generating and feeding into the panel. things might change down the road but with where prices stand right now i don't see myself adding batteries for backup/off grid use any time soon. so mainly just offsetting some electricity costs (like the pool equipment and crypto miners :) )
 

IronMan_74

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Are you planning this as a DIY? Feeding that much power back in to the grid might attract unwanted attention from your power company. You should have the proper permits and inspections done.

my thought right now is that I would be DIY as much as I possibly could. That being said I would plan to do proper permits and inspections and make sure i was setup properly with net metering with the utility company. Actually doing the install and wiring i feel confident doing, i've done enough electrical and other building work around my house i think i can do this too. The hard part will be figuring out what all items i need to buy and how it will all wire together.
 

BentleyJ

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I just wasn't sure if the subpanel being fed by a 50 amp breaker would limit/impact how many watts/amps i'd be generating and feeding into the panel.
Sorry, I didn't answer this question previously. Usually you have to use the 120% rule, so on your 50A subpanel you would be limited to 10 Amps. Since 15A may be the smallest breaker you could get for a standard subpanel. It would be up to your local building dept if they would allow you to install a 10Amp fuse or generic breaker in a J box in front of the subpanel to limit the input power per the rule. You would still get 2.4KW which roughly translates to 12KWh per day.
 
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