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diy solar

Help needed designing workshop solar

No.15

That's my number
Joined
Jun 29, 2020
Messages
123
Could I get some help designing my workshop solar setup?
I have a 40x60 shop being built that I want to put solar on. I have the panels I purchased at surplus but I need everything else. I do have some 24v batteries and some lifepo cells.

I need everything else. This system will not sell to the grid. I would like a controller that will start my generator if needed and also tie in with grid power. I have 2 items that will use 230v (compressor and lift) otherwise it's pretty standard.

I would like recommendations for
Controller for gen, grid, batteries.
Mounting system for panels (metal roof)

I have an electrician who is going to put everything in
I would like something that is perhaps expandable in the future because if all works well I will use this to supplement my guest house. Current grid line in powers the 1200sq ft house and the separate 2400sq ft workshop (being built)
 
If you are in the US and you're putting panels on the roof of a building, you need Rapid Shutdown devices on each panel to comply with NEC 2017 or newer.
There are only a few inverters that are NEC-compliant for putting panels on a building. Of them, the easiest to install and have everything safely in one unit is the Sol-Ark, 12k or 15k. Then all the solar strings, Grid input, and AC output to the main panel are all in one unit. You don't need a lot of extra breakers, fuses, and stuff hanging on the wall.

As for batteries, EG4 has the best price, but the Homegrid Stacked & Combined series are designed to work with Sol-Ark and make setting up the batteries safe and easy while being code compliant.

Feel free to msg me for more details.
 
It is best to design the entire system before buying anything.
Now that you have panels, need to ensure Voc of a string (adjusted for record cold day) doesn't exceed max allowed SCC/MPPT input, also Isc.

I use SMA, Sunny Island battery inverters AC coupled to Sunny Boy GT PV inverters. This can work entirely off grid, with grid input (optionally backfeeding for net metering), or zero export, also auto generator start.

Up to 18kW 3-phase battery and 36kW PV inverter, or 24kW split-phase battery and 48kW PV inverter. I would over-panel the PV inverter to about 150% of rating with SE and SW oriented PV strings.

You have to define kW starting surge and continuous loads, and kW & kWh night time loads, to determine inverter, PV, battery capacity needed.
You say "shop" but not many 240V loads. Catalog 120V and 240V loads (including how many 120V on each phase.) Most inverters either have a max kW per phase, or max kW 240V and limit to imbalance between phases.
 
If you are in the US and you're putting panels on the roof of a building, you need Rapid Shutdown devices on each panel to comply with NEC 2017 or newer.
There are only a few inverters that are NEC-compliant for putting panels on a building. Of them, the easiest to install and have everything safely in one unit is the Sol-Ark, 12k or 15k. Then all the solar strings, Grid input, and AC output to the main panel are all in one unit. You don't need a lot of extra breakers, fuses, and stuff hanging on the wall.

As for batteries, EG4 has the best price, but the Homegrid Stacked & Combined series are designed to work with Sol-Ark and make setting up the batteries safe and easy while being code compliant.

Feel free to msg me for more details.
Rapid shutdown only applies for businesses and residences. A home shop or shed does not require rapid shutdown… but note, if it doesn’t, the fire department will not provide rescue or structure protection.
 
I have a similar set up but started on Solar two years ago, I will let you know what I learned:
I have a 3000sqft shop and a guest house -originally these had their own 200Amp 240vac service.
My home is a separate 200A 240 vac service.

Two years ago I started work towards moving the shop/guest house off grid.
The shop is divided into two parts, woodworking on one side, and metal working/welding/automotive on the other.
Since I already had a utility connection, i designed and implemented the change is stages. This reduced the immediate upfront costs, allowed me time to do it all myself, and to learn what the system could (and couldn't) do at each stage.
I chose to go with the MPP Solar 6048 model Inverters, which output 120-240 even with just ONE inverter, and comes with Ground-L1-L2-N terminals reducing the complexity of dealing with ground-N bonds. These inverters are 6kw output and can be set in parallel to get 6-12-18 etc kw peak output. I started with just one 6048, and one Signature solar 100A 48 vdc rack battery. I set up a subpanel beside the existing panel, and this allowed me to move loads over one by one as I learned.
Since then, I have moved on to the next stage, and now have two MPP 6048's in parallel (with space for a third one) I have 480Ah of 48 volt rack batteries (and plan to add 560Ah more), and I have 16 CS 440 PV panels on the shop roof (and space to add 16 more). I have disconnected the original shop service from the utility, and now have twin buried lines to my home. The twin lines are for: 30A 240vac charge power from the house panel to the shop in case I need to charge the batteries during winter/cloudy week; a dedicated 30A 240vac line to the house to a CLP (critical loads panel) to run my well pump, furance fan, fridge and freezers if the utility goes down, or just to use excess power when that is available.

The shop:
In the shop I have many large motors, and the heating system (pellet furnace with propane backup) small HWT for wash-up area/washroom, and the biggest single start up load is a 6Hp air compressor.
By calculation, the compressor was going to be boarderline to start up with the two MPP 6048's plus other normal loads (lights etc) and I could have needed three units. Each MPP caps out at 27.3A 240vac each, for a total of 54.6A The compressor being 240 volts puts an equal load on both L1 and L2 legs of the panel and inverters and this is very important. If you have (or buy) a large compressor do not go 120VAC: first off, the 120volt will mean double the inrush amperage (for the same Hp), and secondly, it will be unbalanced (higher amperage on L1 or L2 compared to the other). Unbalanced loads can trip the inverters if they difference is too high. I was fortunate that my compressor motor is high enough classification that the inrush amperage remains below the limits of the two inverters working together even with other shop loads, but I was prepared to need three inverters.
A number of readers are now screaming at this post "use the LVX 6048 for motors" but that option comes at a price, and I don't mean the money.
A low frequency inverter like the LVX 6048 or EG model that is very similar, has a down side, for me this was the standby current running 24/7 was going to need 3kw per day just to feed that standby idle power. MPP LVX 6048 units can not be paralleled with the PIP LV6048 so I had to chose, go with the Low frequency inverters or go with the high frequency and perhaps need three units. And yes, if I ended up with three 6048's the standby consumption would be about the same as two low frequency inverters, so this was a risk. My thought at the time was if I ended up needing three 6048's I could turn off one when not needed. It turned out for me, that two units run everything including my well pump.

What would I do if I were you. You don't have years of data on what your shop power use will be, your just building. You likely do know the guest house use, and the shop will only add to this.
Make a spreadsheet of all the loads you plan for the shop, than add a section of wish list items that Could be added to the shop over the years ahead. I can say over 21 years in my current shop, I am always adding. Most items add to the total loads, with the exception of my shop lights, since the LED's cut my power consumption, but then I immediately added more equipment that took their place LOL.
Be sure to capture Every load, it is easy to miss furnace fan or bathroom exhaust fan/sump pit pump or a small shop fridge/HWT that you figure 'doesn't use much power' but in fact may use nearly the same as a full sized fridge/HWT.

If I was starting from scratch: I would consider high end equipment like Victron/SMA/Fronius and weigh out the initial costs against long term performance. The better quality equipment is more expensive (x2, x3 and more ish) but comes with more features, and much lower standby current draw. If you have the space for more PV solar panels than you really need, due to the size and orientation of your roof, you could do (as I did) and just figure on additional panels to offset the standby consumption of the inverters. This is not an easy choice and will depen on budget, roof space cost of PV panels, winter solar potential etc. Although I am very happy with the way my system operates & what is cost, I am not sure if I made the best long-term choice or not on the equpment, time will tell.
I recommend you have at least 30A utility supply to your shop to allow battery charge/by-pass if you have a long string of cloudy days. I recommend you consider running a line to supply your home with a CLP (critical loads panel) so in a utility power outage you can run your essential loads of your home from the batteries - without stringing out extension cords. Be sure you understand the insurance and electrical code requirements going in, if it turns out you need RSD (rapid shut down) this limits your options, and if you already purchased equipment that doesn't facilitate the RSD your going to be disappointed.
Good luck with your shop project, and hope this post helps you (and others) to plan a great system that works for you.
 
Rapid shutdown only applies for businesses and residences. A home shop or shed does not require rapid shutdown… but note, if it doesn’t, the fire department will not provide rescue or structure protection.
I only see one Exception in the code, and that's not it. That may be a local ordinance.

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