Off-grid house with a shop

[Troubleshooter]

Please bear with me as I figure this out. We're making a move to a property that will be completely off-grid (the cost of running power line is roughly $20k), so I am 99% decided to just go with a solar system. I understand the principles, however my only experience with off-grid power is running a 4kW generator to my travel trailer. Our requirements for the house are fairly simple and besides a well pump I don't anticipate any large load on the system. Here's the twist, currently I have a few fabrication tools in the shop that I'd like to find a way to use. I want to size my inverters to be able to run my 220v welder, 220v plasma cutter and a large 80 gallon air compressor (Everything is single phase 240v). Plasma cutter and the air compressor would need to be able to run simultaneously. This is not a full time production operation, most of my work is small custom fabrication for offroad vehicles.

My plan is to get a 48v system, with about 5kW of panels, 8kW inverter and 200Ah of batteries, and a backup generator, that I would just turn on manually prior to running anything in the shop. Would my plan work? I specifically need recommendations for all-in-one inverter/controllers.

 

[alcook62]

Before you spend a dime, do a thorough energy audit. Plan out a worst-case scenario (2+ days with minimal sun) and then plan from there. Go in with a plan and the money spent will be well spent.

 

[Steve_S]

OK, You already have an issue which will cause problems. PRECISION ! 220VAC is Europe ! IF you are in North America say 240V which is Split Phase @ 60Hz and NOT the same as European 220VAC Single Phase @ 50Hz! This is a VERY IMPORTANT key bit of info, otherwise you will get info that is confused. People here have actually bought the Wrong equipment, plugged it all together to only make very expensive Magic Smoke !

The size of your battery bank which is determined by A) Your Daily Consumption + B) Number of days or reserve power without generation you wish to have available.

The Solar Controller is sized relative to the size of the Battery Bank and how many Amps it will take to charge within a Given Time. That "Given Time" is usually based off the Lowest Sun Hours available in a day (North America that is end of December). If you have 3 hours of Sun on December 21st to recharge your daily use, you will need enough Solar Controller to deliver the power + enough solar panel to deliver what the SCC requires.

The number of solar panels is determined by what the SCC (Solar Charge Controller(s) ) need to deliver the required amperage to the battery bank. Each SCC has a limitation as to maximum input Voltage & Amps it can accept from Solar.

 

[Troubleshooter]

Thanks steve, I am from Russia, but now live in the US, so kinda used to just saying "220", but yes, my system will be split phase 240v/60Hz. Since the shop is a hobby/side business, I can totally go without using any of the high load equipment in case of bad weather/low charge. All I want is for it to be able to handle occasional use, or use with a generator turned on. Otherwise, the system will power fairly simple 2000 sq. ft. optimized for passive solar. My current home uses average 1.5kWh, peaking at 3kWh, but that also runs a big hot tub which will not be moved to the new house. I don't expect to exceed 25kW in daily use in the new house.

From looking at the numbers, to be able to handle the shop load I would need inverter in a 12kW range. But I do want the ability to just flip the generator on while I'm running a welder or plasma, as to not deplete the stored battery power. Looking at 14kW generators.

Should I be considering something like MPP or Growatt 12000 units, or run a pair of 6000 units?
Would I regret these seemingly cheaper units? Should I with a pair of more expensive inverters? Any suggestions? I have been looking at Sol-ark 12000 as well, but i would actually need a pair of 8k units to get my desired output, plus I don't need grid-tie functionality they provide.

This is the kit I've been looking at as the starting point. https://unboundsolar.com/1892453/un....76-kw-18-panel-heliene-off-grid-solar-system. They have it configured with Schneider or Magnum inverters. Is either of those better than the other?

 

[MichaelK]

That Unbound "kit" looks very much like my own system, which started out as a Renogy "cabin kit".

That being said, I would no longer advise anyone to buy a kit which includes panels. What I've discovered is that purchasing local Craigslist panels is far cheaper (and higher quality) than the panels you buy online that get shipped to you. Buy panels locally and drive them home in your own truck. I can get 5000W of grid-tie panels locally for about 1100$.

The Schneider XW+6848 is an excellent choice. It has very large surge capacity, which you will want to have for your power tools, like the air compressor. AiO units will be a complete disappointment there. They do not have meaningful surge capacity.

I also like Midnight charge controllers. For 5000+W of panels though you might need two of them.

A 200Ah battery is tiny for a system of this size. I would triple it. The owner's manual for the 6848 specifies that you need at least a 440Ah battery bank for it. Besides the surge, the larger battery reduces ripple-current, which in general is hard on the inverter's components.

I have performed welding with my XW, but was always scared about it. I've heard reports from other solar enthusists that happen to be electrical engineers that welding is very hard on inverters in general. I've always felt safer welding off of my backup generator. I could replace a fried generator in hours. A fried inverter might take days to weeks to replace. Hence I tend to be very conservative.

 

[Troubleshooter]

So, it sounds like I should just scale down my solar system down to what my house actually needs and just up-size my generator, which would be used for any heavy duty equipment and for backup to the solar system when needed. Would it be possible to wire in a such way to manually switch it on to power a 240v subpanel and also have it auto switch on by inverter/charge controller when solar storage goes below certain level?

 

[MichaelK]

Schneider inverters have a designed 240V ACin circuit for the direct connection of a generator. It can be used for generator assist, or for charging the batteries in cloudy weather. It does have an automatic generator start function I believe, though I've never used it as such. I've always manually started my generator manually whenever I wanted to charge batteries, which is infrequent. They have this feature in both the XW, and also their somewhat smaller Conext series. I use both.

I would keep the scale of your system about the same except for a larger battery bank. Then the XW could power almost everything, except when you want to do some serious welding, or plasma cutting. It will help if you document the power needs of each component you want to power, but I can tell you that my XW has powered a 240V well pump, and cement mixer, and a 1hp saw, all at the same time, with no power blinking. Each of those has high surge starting loads.

 

[Steve_S]

Thanks steve, I am from Russia, but now live in the US, so kinda used to just saying "220", but yes, my system will be split phase 240v/60Hz. Since the shop is a hobby/side business, I can totally go without using any of the high load equipment in case of bad weather/low charge. All I want is for it to be able to handle occasional use, or use with a generator turned on. Otherwise, the system will power fairly simple 2000 sq. ft. optimized for passive solar. My current home uses average 1.5kWh, peaking at 3kWh, but that also runs a big hot tub which will not be moved to the new house. I don't expect to exceed 25kW in daily use in the new house.

From looking at the numbers, to be able to handle the shop load I would need inverter in a 12kW range. But I do want the ability to just flip the generator on while I'm running a welder or plasma, as to not deplete the stored battery power. Looking at 14kW generators.

Should I be considering something like MPP or Growatt 12000 units, or run a pair of 6000 units?
Would I regret these seemingly cheaper units? Should I with a pair of more expensive inverters? Any suggestions? I have been looking at Sol-ark 12000 as well, but i would actually need a pair of 8k units to get my desired output, plus I don't need grid-tie functionality they provide.

This is the kit I've been looking at as the starting point. https://unboundsolar.com/1892453/un....76-kw-18-panel-heliene-off-grid-solar-system. They have it configured with Schneider or Magnum inverters. Is either of those better than the other?

The AIO Systems I would consider would be Victron, SolArk or Growatt and certainly nothing lower scale than that.
"KITS" Can be handy such as complete kit's from Alt-E or Major Vendors which provide all the essential pieces which are generally good quality brand components. I would Absolutely & Totally Avoid kits from RENOGY or any off-shore bundled kits. Mess with that junk and you'll get frustrated & angry FAST !

Modular Systems with separate Solar Controllers & Inverter/Chargers are more complicated due to the componentry and do require more planning & design considerations. This method is more flexible and so can be tailored for specific use cases & applications as a result.

With your intentions to run Heavies as well as normal "general" use I strongly urge you to avoid anything below Tier-2 Grade Equipment.
In any case, with your system it would be prudent to ensure the Inverter/Charger system has an AGS (Auto-Gen-Start) Port which can use a GCSM (Generator Control Start Module) to auto start & stop a Genset for recharging batteries when required. NOT ALL GENSETS ARE COMPATIBLE WITH GCSM'S !!!
Please see here for a Typical GCSM, Link to the main PDF included, so you can search to see if your GenSet is on that list. If it is not, then most likely NO Brand of GCSM will support it.
The Atkinson GCSM: http://atkinsonelectronics.com/gscm-mini-60hz-usa-canada/
The GCSM Manual/List (Search this for Genset compat.) http://atkinsonelectronics.com/content/product_pdfs/All Hookup Diagrams Merged.pdf

 

[Troubleshooter]

Kohler 14RESA generator , that i've been looking at, is on the list.

 

[Troubleshooter]

I decided to go with Sol-ark 12k, and a pair of Fortress eFlex 5.4 batteries. Planning to add more down the road, if needed. I am planning to just run my heavy use 240v equipment off a generator directly when needed.

 

[JMc]

Will any of the workshop equipment require 3-phase power? If that’s the case then spending the $20K for a grid tie might be worth it considering the expenses of over-sized generators and the electronics needed to produce clean three phase power. I know a lot of the newer machines with inverters can use 240 single phase, but the output power of the motors is reduced significantly when they are wired like that.

 

[Troubleshooter]

No 3-phase here. Compressor and the plasma are the only ones that absolutely must be able to run at the same time. It looks like compressor draws 22 amps and plasma 44 amps, that's over 60amps, but even with lights on and other things running I've never tripped the 60A breaker at the main panel (60Amp at the main, wired to a garage sub-panel, with dedicated 240v 50A circuits to welder, plasma, air compressor and 2-post lift).

Electrical is the only grid connection I would have at the property, so if I could I'd love to avoid it. Solar is in the plans regardless, so I'd prefer not to spend $25k on a grid connection in addition to spending $25k on solar power.

 

[MichaelK]

No 3-phase here. Compressor and the plasma are the only ones that absolutely must be able to run at the same time. It looks like compressor draws 22 amps and plasma 44 amps, that's over 60amps, but even with lights on and other things running I've never tripped the 60A breaker at the main panel (60Amp at the main, wired to a garage sub-panel, with dedicated 240v 50A circuits to welder, plasma, air compressor and 2-post lift).

OK, this isn't a standard 15A wall socket. These are powered with 22 and 44 amps at 120, or 240V? This would be a VERY serious off-grid system.

 

[Troubleshooter]

What about running a second dedicated inverter (something that can handle a big surge) connected to the same battery pack, and wired to a dedicated 240v panel for garage (and well pump) use?

 

[MichaelK]

What about running a second dedicated inverter (something that can handle a big surge) connected to the same battery pack, and wired to a dedicated 240v panel for garage (and well pump) use?

Well, if you want to buy a real inverter in addition to the toy inverter, then what's the point of buying both? Just get an Outback Radian or a Schneider XW, and be happy.

 

[Azsolarshop]

No 3-phase here. Compressor and the plasma are the only ones that absolutely must be able to run at the same time. It looks like compressor draws 22 amps and plasma 44 amps, that's over 60amps, but even with lights on and other things running I've never tripped the 60A breaker at the main panel (60Amp at the main, wired to a garage sub-panel, with dedicated 240v 50A circuits to welder, plasma, air compressor and 2-post lift).

Electrical is the only grid connection I would have at the property, so if I could I'd love to avoid it. Solar is in the plans regardless, so I'd prefer not to spend $25k on a grid connection in addition to spending $25k on solar power.

Hey I am looking to do the same as you are planning. We are planning on building a 2300sqft house with modern appliances (electric stove/microwave/kurig coffee/fridge/standard freezer/washer dryer/dishwasher/thankless water heater/etc) I plan on having an independent solar well pump and pressure pump from rps solar. My shop is similar to yours, I hobby build all sorts of things with a lathe, mill, welder, plasma cutter, air compressor, common power tools, the angle grinder and metal saw are my biggest concerns. My belt grinder is the only three phase item but ran off a vfd.

Please keep this up to date on your experience, I would greatly appreciate it. I plan on doing solar for the house and shop minus the heavy items like welder, plasma, air compressor. I would like to keep grinders, mill and lathe on the solar. Like you the cost to run electric is close to the cost of my solar system. And it would be awesome to say we live off grid.

 

[12VoltInstalls]

planning to just run my heavy use 240v equipment off a generator directly when needed.

That is the best plan imho.
The only ‘exception’ might be a 120V Lincoln welder which, if set up Mig, can do a bunch of stuff well or tack hold before firing up the generator and actually penetrating on thick stock.

A 200Ah battery is tiny for a system of this size. I would triple it.

This - even if just for the house and NOT the 220 stuff. I run on ~300Ah useable from lead acid batteries; for a more normal cabin or house that might not even be barely bare minimum. 200Ah won’t make you happy, and lighter-cycled batteries of any kind can last longer. Not really a ‘’rule’’, but for small systems sometimes it’s a useful thought exercise to think of 100Ah usable as needing solar input of 100W in good sun or 200W+ in poor sun to stay healthy. So 5kW of panels suggests a lot more battery. However, 5kW isn’t really a small system either. Again, not a rule, there are no rules:
Your consumption is the rule.

 

[Porch]

I have the same setup with a small home shop. Inverters are 2 Outback 3648 so 7.2kw total at 240v. I have a Miller 215 welder, Hypertherm PowerMax30 cutter, and an 80 gallon air compressor. Along with all the other assorted metal working tools.

My only issue was with the air compressor. At the 80PSI turn on point, the startup surge of the 5HP motor was about 20kw for about half a second. If the tank was empty or the batteries full, it was not an issue. But on a partly full tank of air, or low batteries, it had a real hard time starting and would often overload the inverters and they would turn off.
I solved the issue by switching out the motor for a 3 phase unit, and installed a cheap ebay VFD on it. I set the ramp up speed to happen over 4 seconds. The startup surge went away and it has zero problem starting now. I also lowered the frequency from 60Hz to 42Hz as it still gives me the air flow I need, but the noise level is greatly reduced. I can always set it to 60Hz or higher if I need the airflow for something.

The VFD worked so well, I did the same 3 phase conversion to a 3HP well pump also running off the same size Outback system. It's also worked wonderfully and solved the massive startup surge issue they where having every few minutes due to the trees they water.

 

[12VoltInstalls]

3 phase conversion to a 3HP well pump

So revealing my idiot department qualifications- as I’m not versed much past 120VAC- are there not VFDs for 230-240V? Or was the point of the three phase to lower amps per leg? I can’t remember exactly how the VFDs do their thing. 120VAC and under is my thing; I can barely install 220 welders, stoves, and compressors without thinking a minute

 

[Porch]

I was not clear. Most 3 phase things are 230-240v. You can also find 208 and other strange voltages in industrial applications. I am talking about converting any big single/split phase 240v motor loads to 3 phase 240v.

So one of the main befits of 3 phase is you are making all 3 legs do work, so you get smaller wire sizes, or higher HP motors for their size. The 3HP 3 phase well pump I installed was about 2/3 the size of the 3HP split phase motor.
Normally you just connect up your 3 phase motor to the 3 phase you get from the grid and the motor spins. Change some wires around, and the motor spins the other way. No startup cap, nothing complicated. It just works and is simple and is efficient. It was one of the big inventions of Nikola Tesla.

The side benefit of this, is if you very the frequently and what leg gets power first, you can very the speed and direction of the motor. Modern VFD drives take advantage of this. They take normal 3 phase power, convert it to DC, then back into 3 phase AC at any frequency you want and you get easy variable speed. Industrial applications have been doing this for 20 years to start big motors and AC units.

The great thing is in the past 5 years or so, is the flood of cheap Chinese VFDs on ebay, that support one new feature. In addition to 3 phase in, they will take normal 240v split phase in (what is in every US house hold). You don't need 3 phase at your home to run a 3 phase motor now. The VFD will convert single/split phase 240v to 3 phase 240v with no issues.

Combine this with the slow start of a VFD, turns this into a killer feature for a well pump. Normal well pumps, you don't want to cycle off and on too often. The startup surge is not good on the motor, there is often starting caps and relays in the pump controller that are stressed. And in an off-grid application, the startup surge is not good for the inverters. So you put several big pressure tanks and use a 40-60 pressure switch so the pump does not cycle often in attempt to make everything last longer.

But with a VFD programmed for a slow ramp up, all those pain points go away. No startup surge, no relays or caps to wear out. Shoot, the pressure switch is carrying logic level power now (5v), so the contacts will last forever. So the pump can cycle once every 5 minutes, or once every 5 seconds. It makes no difference to anything.