Residential Solar Generator – Mini Shed (insulated with AC)

[will_fish]

Over the past 2 years, I have read countless articles on this forum and watched most of Will’s videos (yeah, I’ve watched a lot of videos). The information and feedback was invaluable and made this project possible. The process to complete this project was educational (to say the least) and a lot of fun! Thanks to everyone for making this forum such a collaborative environment!

Here were the main objectives for this project:

• Create a system that could safely and easily connect and disconnect from the house electrical
• Create a system that could provide partial house backup and support limited house circuits (ongoing if needed)
• Create a waterproof/climate-controlled space to store inverter/batteries (outside the house and near the main panel)
• Install the solar panels on a shed (anchored) that sits about 20 feet back from the house

Here are the key components (most are detailed on the attached diagram):

• Inverter (Growatt SPF 3000TL)
• Battery (Lion Energy UT 1300) x 4
• Battery (EG4 LifePower4)
• Transfer Switch (Reliance R510A)
• Solar Panels (Rec Alpha REC365AA) x 8
• Solar Combiner (MidNite Solar MNPV6)
• Solar Panel Rails (IronRidge XR1000) x 4
• Mini Shed (Keter 17209457)

Diagram (Pic1): System diagram with component and wiring details.

Sheds (Pic2): Keter mini shed (29” x 55” x 67”) which holds inverter & batteries and large custom shed (8’ x 12’ x 8’) where the solar panels are installed. The Keter mini shed is framed inside to provide structure for the air conditioner install, inverter install, and the exterior AC electrical boxes. The Keter mini shed is primarily insulated with ¾” foam board (double layer for ceiling). Also, cement board was used as a mounting surface for the inverter and fuse holder.

AC Boxes (Pic3): AC input/output (AC4/AC5) from solar inverter and AC input/output (AC3/AC2) from house panel. Mainly used RV-style input/output boxes (GE & Midwest) except for the input to the house which uses a transfer switch (from Reliance).

Inverter & Batteries (Pic4): Using the Growatt inverter (IN1) with the WiFi stick. Also, using communication between the EG4 battery (B2) and the Growatt inverter. After initial setup, the information from the WiFi stick has been very stable along with the battery to inverter communication. Initially started with just 4 Lion Energy batteries (B1) and then added the EG4 battery after a few months.

DC Wiring (Pic5): Used the Victron fuse holder with included busbar (DC2) so that a separate busbar would not be needed. Also, placed both negatives directly on the Victron shunt (DC3) given the bulk of the connector. Created custom brackets to install the MidNite Solar breaker (DC1). NOTE: MidNite Solar recommends only using their breakers in their breaker boxes. Lastly, created a custom device (large red button) to pre-charge the inverter capacitors. My understanding is the EG4 battery has a pre-charge so my custom device should not be needed when the EG4 battery is connected (and turned on first).

Combiner (Pic6): Used a solar combiner box from MidNite Solar (DC5) along with four 20A breakers and one 63A GFP breaker. Also, installed a surge protector from MidNite Solar. The diagram also shows four 25A inline fuses (for each pair of solar panels) which are installed under the solar panels.

Solar Panels (Pic7): Installed 8 Rec Alpha 365W solar panels (SP1) on the shed using IronRidge rails and footings. The shed is anchored using 6 ground anchors buried ~3 feet deep and bolted to the shed skids with wire rope.

Aerial (Pic8): The solar panels on the large shed are attached to the inverter in the mini shed using ~40 feet of 6-AWG THWN-2. The solar panels are facing east and west since that was the original orientation of the large shed. The solar panels have a clear view of the southern sky throughout the day.

Solar Production (Pic9): The complete system has been running for about 1 year and has generated more than 3,100 kWh.

 

[400bird]

Wow, that is quite the impressively complex set up you have there!

 

[OffGridInTheCity]

Really nice! Thank you for sharing
I'm guessing you're next issue is... how to expand! Solar is soooo cool it can leave you wanting more.

 

[will_fish]

Really nice! Thank you for sharing
I'm guessing you're next issue is... how to expand! Solar is soooo cool it can leave you wanting more.

You guessed it, I’ve resisted the temptation so far but definitely looked at options to add more ?

 

[will_fish]

Wow, that is quite the impressively complex set up you have there!

Yeah, it did get more complex than initially planned. I’d definitely keep it simpler if I was to build it again.

 

[x98myers7]

Good stuff!

note to all the residential owners out there.... this is a nice way to bypass many of the issues related to panels on the roof of a home and the corresponding NEC requirements. only thing i would suggest changing is moving everything out to the detached shed instead of the "attached" mini-container, then run your AC line into the home!

 

[will_fish]

thanks for the comment...I debated putting the inverter/batteries in the large shed but opted for the mini shed so I would not need to run an AC line from the house (grid) to the large shed. My logic for using the mini shed was to minimize electricity flowing between the large shed and the house. With the mini shed, electricity is only flowing from the large shed when the solar panels are active which is only a few hours per day. If the inverter/batteries were in the large shed then electricity would be flowing from the house (grid) to the large shed for most of the day (when the panels are inactive) and electricity would be flowing from the main shed to house all hours of the day. Hopefully that makes sense.

But I'm guessing your point was mainly around potential code issues and having the inverter/batteries away from the house would be better. Please let me know if I missed your main point.

 

[x98myers7]

yes, and for simplicity's sake overall. additionally, it keeps all fire hazards away from the residence. your line runs are shorter than the DC line I ran from my roof junction box down to the basement, haha. so no worries about power "flowing".

I'm curious... why the AC unit in the mini-shed? do you also have a heater on the batteries to keep them warm in winter?

 

[will_fish]

Thanks for the response, makes sense from a fire hazard perspective.

Regarding the AC in the mini shed, we live in Texas and even today ("Fall") it is 95 degrees and 100 heat index. During the summer, it can reach 110+ heat index and inside a shed/attic it will reach 120+. From my experience and research, heat degrades batteries (of all types) at a pretty substantial pace. My solar batteries cost about $5,000 and the cost for the AC and insulation was less than $300. I figure the AC will provide extended battery usability which should more than cover the additional expense for the AC/insulation/operation.

There are quite a few papers that discuss how battery life is impacted by heat. This report has a couple models related to temperature impact on batteries. These are the results from the more conservative model:

 

[solar_trees]

First of all, thanks for posting, this looks really nice!

Do I understand correctly that you have grid power feeding in to the Growatt and then when battery is low, the grid power is routed back into the house via the transfer switch? This is something I wanted to do, but wasn't sure if it was safe.

 

[solar_trees]

only thing i would suggest changing is moving everything out to the detached shed instead of the "attached" mini-container, then run your AC line into the home!

I did not realize this would be an option. Are there any other pros/cons to doing this besides simplicity and safety?

 

[x98myers7]

I did not realize this would be an option. Are there any other pros/cons to doing this besides simplicity and safety?

it's totally an option. the main benefit is being able to have a true off-grid system that does not have to be NEC compliant.

some will argue that RSD and AFCI residential requirements still apply, however that's still up for debate and interpretation. I don't think they do, especially if you don't bring DC circuits into the house. keep all the "nasty" DC away from the house and you'll never raise an eyebrow. IMO, this is the ONLY route if you want to install batteries for off-grid in a residential setting because there are no affordable "listed" lifepo4 battery options.

 

[x98myers7]

This is something I wanted to do, but wasn't sure if it was safe.

completely.

and in fact, just about every outbuilding that has power has an AC circuit fed from the home. as long as you install THWN (90degC wet UL rated) strands of appropriate size for amperage, you can run whatever you like to and/or from the house. AC is AC whether it comes from the grid or an inverter, in or out of a building.

the issues you'll run into are installing on "plastic" sheds/outbuildings. that's a no-no. you need a "stick built" wood construction shed that is properly secured for local requirements. get that shed/outbuilding AHJ reviewed, approved and installed before you think about adding solar to it. some jurisdictions have strict requirements for outbuildings (like mine) and some have none.

 

[solar_trees]

Ok, the part I wasn't sure about was feeding power from the grid back into the transfer switch.

 

[x98myers7]

Ok, the part I wasn't sure about was feeding power from the grid back into the transfer switch.

what's the use case?

 

[will_fish]

First of all, thanks for posting, this looks really nice!

Do I understand correctly that you have grid power feeding in to the Growatt and then when battery is low, the grid power is routed back into the house via the transfer switch? This is something I wanted to do, but wasn't sure if it was safe.

Correct, grid power is fed into the inverter (AC input) and the inverter (AC output) goes into the transfer switch. The inverter determines whether solar/batteries are sufficient to power loads or whether grid power is needed. The inverter settings will determine when to switch to grid power (when solar is not available, when batteries reach a certain point, etc.). My inverter settings wait until the batteries are down to 30% before switching to grid power. I prefer to leave some battery capacity over night in case there is an outage.

 

[z_zk_z]

Hello, Can you please post the part number for the Frigidaire window air conditioner, also is the Frigidaire plugged into the grid? I am in the hot & humid Florida and trying to figure out how to keep the electronics (batteries & inverter) comfortable ?. My air conditioner will be another load on my solar system (i.e., not fed from the grid) and I like the idea of a mini shed since it will not be a big load on the solar system. Thanks in advance for your reply...

 

[will_fish]

Hi, here's the link for the AC: https://www.homedepot.com/p/Frigida...ted-Room-Air-Conditioner-FFRE053WAE/312546094

The AC is plugged into an outlet that is fed from the inverter AC output. So the AC is powered by solar/batteries for 70-80% of its electricity usage. The inverter switches to grid each night when the batteries are depleted to 30%. But during those hours the AC usage should be low since it is after dark and it is a bit cooler outside.

The mini shed has also been good from an isolation standpoint. In the bigger shed we store lawnmower and many other things which a few people access. With the mini shed, it just stores the solar equipment and can stay locked without someone having an access issue or accidentally bumping the solar stuff.