Mountain cabin off-grid

softdown · October 2016

I would suggest talking to a couple folks, if possible, about solar energy in the area. Between clouds and heavy snowfall, it may be possible that panels would remain covered for quite some time. I never seem to have covered panels for very long here but deep snowfalls are quite rare.

It seems to be folks way up north advocating for vertical panels. It would be of interest to determine when that becomes a necessity. I might even consider a separate panel that is hooked up during the winter. I would also study the energy created by a 90 degree panel. I tried to input Telluride into pvwatts.nrel.gov data. It substituted Grand Junction saying it is 91 miles away.

90 degree panels would appear to perform well during the winter months. This idea has more merit that I may have thought. I'm pretty sure that a single 90 degree panel would keep the batteries charged. The batteries will be very cold. Self draining will be minimal. Running the inverter will be the largest energy consumer by far.

You communicate clearly. That makes helping a lot more fun.

Horsefly · October 2016

BB. said:

A suggestion or two... Get a sheet of plywood sub floor (or something like 3/4 inch ply--depending on how heavy the stuff you will hanging), and build/wire your system at home--And test. Disconnect the battery+panel wiring, and take the whole assembled unit up to the place in the spring.

Another suggestion--possibly, if you use exposed wiring (instead of metal conduit)--You might want to sheath the face of the plywood with sheet rock or cement board--And put some cement board (or ceramic tile, etc.) at the base of the e-panel installation. I am always a bit concerned about fire--And keeping the equipment/wiring mounted in such away to avoid spreading flames is not a bad idea.

Lastly--E-panels... Pre-wired panels that are available for some models/brands of equipment. Can save a bunch of work getting all of the parts together.

https://www.solar-electric.com/catalogsearch/result/?q=schneider+epanels

Have fun!
-Bill

Thanks Bill! I was already planning on some level of bench assembly and test, although I hadn't thought through exactly if I would test everything. I can't test stuff with the generator until we get to the generator, but I suppose I can do most everything else. I had also assumed I would mount everything on plywood for assembly, but hadn't thought of putting some non-flammable surface on top of the plywood. Good thought, so I'll include that in my plan.

I had looked at the pre-fab panels. It seems MidNite Solar does sell one that connects to the SW4024 from Schneider, but it comes with their Classic 150 CC, where I plan to use the Schneider CC.

Thanks again.

Steve

Dave Angelini · October 2016

I think you will find that moving around a plywood equipment rack with particle board a messy affair. It just won't hold-up
Home Depot sells a fire retardent paint that could go on the plywood. The SW below has an AC panel on the bottom that you may not need if you have a panel already. Then again it gets you an inverter bypass that you can run the home off the genny if the inverter were to fail. It might save you buying an AC load center as there are 10 spaces for breakers, I think. I PM'd you BTW. Good Luck!

Image: https://us.v-cdn.net/6024911/uploads/editor/j0/u3gke56cwy2u.png

softdown · October 2016

Home Depot/Lowes ought to carry sheets of tin that could cover the plywood/OSB (oriented strand board). There is also a 5/8" firewall that I use almost exclusively instead of 1/2" drywall. It is heavy but not near as bad as particle board.

You are being steered towards a rather deluxe set-up. Nice if you can folks afford it (sounds like you can). However....I would then take a hard look at something like the Outback FLEXPower...Outback FLEXpower One FP1 VFXR3524A 3,500 Watts 24 Volts for Off-Grid and Grid-Tie...where everything is already professionally done for you. Then you just need four sturdy lag screws to drive the ~1/8" steel sheet into a wall. It is kind of heavy. I did it myself but I was voted "Jolly Green Giant" in school.

Horsefly · October 2016

softdown said:

Home Depot/Lowes ought to carry sheets of tin that could cover the plywood/OSB (oriented strand board). There is also a 5/8" firewall that I use almost exclusively instead of 1/2" drywall. It is heavy but not near as bad as particle board.

You are being steered towards a rather deluxe set-up. Nice if you can folks afford it (sounds like you can). However....I would then take a hard look at something like the Outback FLEXPower...Outback FLEXpower One FP1 VFXR3524A 3,500 Watts 24 Volts for Off-Grid and Grid-Tie...where everything is already professionally done for you. Then you just need four sturdy lag screws to drive the ~1/8" steel sheet into a wall. It is kind of heavy. I did it myself but I was voted "Jolly Green Giant" in school.

softdown - I may be getting confused by your "deluxe set-up" comment. It seems like the Schneider SW4024 is cheaper than the Outback VXFR3524A (almost $300) and the Schneider MPPT60-150 CC is only about $80 more than the Outback FlexMax60, and the Schneider control panel is about $70 more than the Outback MATE. In total, it seemed to me the Schenider set-up was actually a little cheaper than the equivalent Outback one. Am I missing something? I know I am a rookie at all this, so it wouldn't surprise me if I missed something. Everything I have found got me really turned on to the all-Schneider set-up, but if it turns out I got the wrong parts picked out, I'll step back.

As for the pre-assembled set-ups: I couldn't find one for Schneider, but depending on your answer to the previous paragraph, I may be looking back at Outback!

Steve

softdown · October 2016

It appears to me that you are being pointed towards building something akin to a FLEXPower system where multiple points of safety, convenience, and technology coincide. With your background, you may enjoy the challenge. Then again...you may prefer to watch the Broncos march to another Super Bowl with your free time.

Building a real solar system is a daunting task. I would not encourage anyone to do it unless they were both reasonably tech savvy and a good handyman with a great deal of time to spend on it. But then...you have an ideal background to tackle it.

With many users, there is something to be said about an instruction manual and a "Do Not Touch" sign. If something goes wrong, the finger is more inclined to escape your direction.

The FLEXPower is indeed pretty simple to set up. I left the wires dangling fearing a small mistake and a big loss. With a pro to finalize the connections, we were done in 1-2 hours. It does weigh 98 pounds...be ready for that.

I just returned my set-up to its default values. The old pros would toss me to the crocodiles for that. But then....outsmarting factory settings may be best left to the old pros.

My set up works perfectly. However....I should have used true deep cycle batteries. Instead I listened to a self styled old pro and used large truck batteries. Don't be like softdown. Use true deep cycle batteries. Not even marine deep cycle batteries cut the solar mustard.

The Outback FLEXpower system comes fully assembled and tested from the Outback factory. The units are built to meet National Electric Code (NEC) standards and designed for ease of installation. FLEXpower FXR systems can be used for both off-grid and grid-tie configurations. The systems have been outfitted with all the necessary wiring, circuit breakers, communications, battery monitoring and PV ground fault protection. All equipment is ETL listed. The FLEXpower ONE FX-R Series is perfect for nearly any type of application: residential and commercial applications including cabins, vacation homes, farm buildings, remote communications sites and back-up power systems, with all necessary components integrated into a compact hang-on-the-wall system with a minimal footprint. The FLEXpower systems are designed for fast installation which cuts down on time and cost. The system comes with a mounting bracket that attaches to your wall, which then allows you to hang the FLEXpower system. This allows you to get up and running very quickly; simply connect the PV input, AC output, and battery connection.

Specifications:

3,500 Watts
24 Volts DC
VFXR3524A Pure Sine Wave Inverter with Advanced Charging
250 Amp DC Inverter Breaker/Disconnect
MATE3 System Controller and Display
FLEXnet DC Battery Monitor
FLEXmax 80 Amp Charge Controller With Remote Temp. Sensor
HUB 10.3 Communications Manager
FLEXware Surge Protector
One Standard Electrical Outlet
120VAC Bypass Assembly
AC and DC Electrical Enclosures
Mounting Plate and Mounting Bracket

Warranty: 5 Years....Outback will be here in 5 years (my words)

Horsefly · November 2016

Hello again, it's me the OP. I'm back with a somewhat silly question.

My original design was going to use 3 relatively large panels in series. We had a requirement change, so now I've got to move up to four panels. I can't put them all in series else I would exceed the charge controllers input limit, so I will have to go with two parallel strings of two.

Here's the silly question: Is there any reason at all to use a combiner box for just two small strings? Up to this point I had been focused on just one string, so I don't know anything about combiner boxes. I was assuming I would just wiring them together at the panels and run one pair of wires (probably bigger gauge now) to the charge controller. However, I thought I should check in with you experts as to whether this is some requirement to have a box, or if there was some other advantage.

Any thoughts?

Thanks in advance!

Steve

mike95490 · November 2016

A fused / breaker combiner box is not needed for only 2 parallel strings, but having breakers handy to flip things off, or compare panel production is nice

softdown · November 2016

Good to see you back. Was recently wondering about your whereabouts.

There are folks here who have likely forgotten more than I can still remember. Bear that in mind. It isn't a *requirement* to my knowledge but it would be prudent to use a combiner box with fuses or breakers with four panels. Yes....larger wire from the combiner box is a good idea. Southwire has a nice, easy wire sizing chart that was recently referenced when I made a thread looking for a nice, easy wire chart. You will likely use THHN inside of conduit. USE-2/solar wire is rated for outdoor conditions but it seems quite rare in sizes larger than 10awg. THHN/THWN if you expect water on the wires.

You will also want to ground most everything: neg. of battery, charge controller, panels, circuit breaker box, inverter. Dry, sandy soil sometimes needs two grounding rods. MidNite makes some nice ac/dc lightning arrestors.

How long is the planned run from the panels to the charge controller? I think most medium arrays can use 8awg or 6awg unless the run is very long. You know all this, I talk to myself here at times....

Remember that rodents sometimes like to chew on exposed wires.

Horsefly · November 2016

Thanks @mike95490 and @softdown. Good inputs.

I guess I'll go ahead and put a box at the array. The idea of being able to compare one of the two strings by shutting off the other is compelling. I had spec'd a MidNite Solar SPD on the PV side in my E-Panel inside, but maybe I'll move it to the combiner box.

As for wire: I had already done some math, using a wire resistance table I found on net. Based on that, I had come up with 10AWG would let me go up to 92ft with the panels I'm using (SunWorld 295W), with a 2% voltage drop. I'm pretty sure we will be somewhere between 50ft and 75ft, so I hope that will be good.

Edit to add: We will be using some type of conduit (probably PVC) from the combiner box to the cabin. We have previously had marmots chewing threw almost anything they can find.

Back to the parts list!

softdown · November 2016

You did the math but consider this. There is a decent chance that your new power plant will have over $12,000 invested. 2% of that is $240. You could spend maybe $40 more and lose ~.05% (very rough guess with 6awg). But then....I buy my wire in bulk rolls. I also tend to overdue things. Murphy? Guy was an optimist.

I'm not a huge Home Depot fan but their copper wire costs less than Lowe's.

Marmots? I always seen them in very high elevations. You will get a lot of solar production if very high.

softdown · November 2016

Another thing. Panels pointing to the east and the west do pretty darned well except during the Nov-Feb season. You may want to take a closer look at using your roof. Since you don't use the place from Nov-Feb...

I am running a large freezer from panels oriented to the east. Will add a smaller freezer and fridge when i get the west panels operational. They are happily mounted.

I live in Colorado /solar paradise/alpine desert. Why not take advantage?

Horsefly · November 2016

Thanks @softdown. I'm actually planning on a pole-mount for our panels, so no roof mount. The front of the cabin faces the beautiful mountains almost due south, so the roof lines are tilted to the east and west. Better to do the pole mount. My brother-in-law is the mechanical genius (I just do electrical / math stuff), and will doing all the rack / mounting stuff. We will be tilting due South, including taking into account an almost 10° magnetic declination.

I agree we should do well at almost 9000ft harvesting solar power. Add to that the fact that it is almost never cloudy, and it is a pretty ideal spot for solar. That may be why you have to pass 4 other homes with solar on the little 3 mile dirt road to get to our place.

Steve

kamchuka · November 2016

Horse fly, your cabin sounds bad ass!

mike95490 · November 2016

> The front of the cabin faces the beautiful mountains almost due south, so the roof lines are tilted to the east and west. Better to do the pole mount.

If you wanted to, you could likely split your array on E & W faces of the roof, and have virtual tracking. Although pole mounts work too (My arrays are on 2 poles)

softdown · November 2016

Marmots are big, tough looking hombres. Think I might use rigid PVC, maybe steel EMT and bury it some. They might take a liking to flex conduit....

Horsefly · November 2016

Good point @softdown. We'll have to consider something strong. They mostly leave stuff alone, but we have had some hydraulic hoses chewed up. I guess they think the hydraulic fluid will taste good, but it was probably the last thought they had. My guess is they will not be attracted to the PV wire, but better to be safe.

Mountain Don · November 2016

Marmots like rubber. We had one chewing on a Jeep tire some ten years ago. A friend had a radiator hose shewed through

BB. · November 2016

Assume that the wiring will be chewed on if you have problems with animals. Placing in conduit/metal boxes will be a big help. Here are a couple of products that have been used on cars (some manufacturers seem to be using Soy based insulation which may also attract mice/rats):

https://www.amazon.com/Honda-4019-2317-Rodent-Tape/dp/B00AJTG3N0 (Believe it--Honda heat shrink paper tape)
https://www.amazon.com/Transtar-4423-Amber-Rustproofing-oz/dp/B00H2W3YZW (waxy film seems to discourage chewing)

-Bill

softdown · November 2016

^^^You may not have seen Colorado marmots. This may be like trying to stop .50 cal with a vest designed for handguns. Plus you have the high country sun. I'd use steel EMT after thinking about it.....maybe 1" PVC.

https://www.nps.gov/seki/planyourvisit/marmots.htm

You Are Entering Marmot Country.

Each spring and early summer until mid-July, the marmots of Mineral King have been known to dine on radiator hoses and car wiring. They can disable a vehicle. On several occasions, marmots have not escaped the engine compartment quickly enough and unsuspecting drivers have given them rides to other parts of the parks; several have ridden as far as southern California!

How can you protect your vehicle and marmots?

-Wash the outside, undercarriage, and engine compartment of your vehicle before visiting.

-Physically block marmots by driving over a tarp and then wrapping it around your entire vehicle. Cover the wheel wells and leave your hood up. Wrapping chicken wire around the vehicle is no longer advised, as marmots have learned to get around the wire

BB. · November 2016

Not a Hoax?!?!?!?!? From Softdown's link:

Car covered by tarp

Rangers recommend using tarps that cover the wheel wells from early Spring to mid-July.

NPS/Jennifer Swacina

-Bill

mike95490 · November 2016

I've got the problem with mice in the tractor engine bay, leave it idle for a week, and there's a nest.
But it's way easier for a rodent to chew through a tarp, then to defeat chicken wire.

Dave Angelini · November 2016

I think all of this is why some really smart people use a garage or barn for equipment

Horsefly · November 2016

Not withstanding the marmot issue (which we know we have, but are confident we can deal with - we've had a detente with them for many years!), I wanted to update you guys on what I've come up with. I didn't know much when I started posting here, but feel like I've learned lots just by reading. You guys are awesome. Anyway, I hope you won't all poke too many holes in the design that I've attached here, since I already ordered most of it from NAWS. We still have to order the panels and the batteries, so I'm keen to hear thoughts about those. Of course if there are issues with the other stuff in the design, I'm game to hear them, but be gentle: That's money already spent! I'm anxious for spring time so we can start pulling this together. The intent is to wire it mostly together in my sister's driveway and test things out, then cart it up to the mountains and plug it in.

A couple of items worth noting that are not specific in the drawing: We're going to pole-mount the four panels, and - per the help I got here - I'll put a simple combiner box up on the pole. Also, the generator is not auto-start. We are starting out with the generator as our best buddy, since we are used to starting it all the time whenever we need power. I'll need to experiment some to determine the low-voltage shut-down to set the Inverter to, as I want to shut down the inverter way before we get to 50% DoD on the batteries, and force people to become more conscious of our kWh usage.

westbranch · November 2016

Hfly, how did you come up with 60A breakers in the Combiner box? ( you will have to give us the specs for those PV's)
Same question (60A CB's)for the MN Epanel?
And I do not see a GFI breaker ~ 1Amp(?) or does the CC have one built-in like the MidNite Classic?

Horsefly · November 2016

westbranch said:

Hfly, how did you come up with 60A breakers in the Combiner box? ( you will have to give us the specs for those PV's)
Same question (60A CB's)for the MN Epanel?
And I do not see a GFI breaker ~ 1Amp(?) or does the CC have one built-in like the MidNite Classic?

@westbranch it probably says something that I don't really know that I understand your questions.

As for the combiner box, I don't know that there was lots of conscious thought about the breaker size. Per some other things I've read here, I decided the breakers were just to let me test / verify the two parallel strings. Putting the SPD at the combo box gave me the feeling I was protected from surges (pun intended). The panels I'm looking at are tagged in the diagram. They are the SunWorld 340W 72 cell panels, Voc of 47.6V, Isc of 9.7A. I'm putting them in a 2x2 array of 2 parallel strings of 2 panels in series.

The 60 circuit breaker on the PV line thru the E-Panel was also just a WAG. With Isc combined on the line of less than 20A, I was really just seeing that breaker as a cut off, more than protection.

I don't know what the GFI comment is about. Ground fault was not something I was considering on the DC side of things. What exactly do you mean?

Either way, thanks for checking it out and commenting.

Steve

westbranch · November 2016

the spec's plate on the back of those panels should give a fuse rating and that is the appropriate size
They are the SunWorld 340W 72 cell panels, Voc of 47.6V, Isc of 9.7A.

For this part you should be using Imp x 1.25 x1.25 will give you the minimum number, in amps, you need , then round up to next CB size... probably about 15A.

The CODE requires GFI now and it is a good thing to have, there is an 80 amp plus GFI all in one block, as shown in the midddle left of this diagram, labeled MNDC-GFI 80-

http://www.midnitesolar.com/pdfs/MNSW4024-KID-B-REVI.pdf (link fixed. -Bill B.)

hth

mcgivor · November 2016

Just on the sideline reading, one question for Horesfly, is your well a deep or shallow as the pump demand is pretty high. What I've done is use a deep well pump powered by a generator to 3000 liter(800 gallons) holding tank then use a smaller demand pump to provide running water. The smaller pump can be used in shallow wells up to 8 meters (around 26 feet) suction head. Have a float switch which cuts the feed to the demand pump when the tank is low, work like a charm and the demand pump is only 100W with a small holding reservoir to maintain pressure. Have to pump about once per week with the generator, two people using, there are larger models available, not sure if these are available in the U.S but there must be something similar. See picture attached.

softdown · November 2016

Shutting down the inverter that early would mean about a 12.2/24.4 shutoff point. There exists no really great reason to do that with deep cycle batteries. I would urge an 11.5/23 volt shutoff. Many here claim that is still too high. Inverters will let you run below the shutoff point for a specific time. Usually enough time to run a microwave or power tool. Certainly enough time to meet the surge needs of high amp motors.

I might consider buying a spare panel in case one goes down. Panels work best when they are perfectly matched. But then, I may get carried away with the old "Be Prepared" idea.

I'd like to see this cabin paradise someday. If you folks require a strong back just let me know. I could bring a backhoe but bad experiences with Colorado passes. Cheaper to rent...

Horsefly · November 2016

westbranch said:

the spec's plate on the back of those panels should give a fuse rating and that is the appropriate size
They are the SunWorld 340W 72 cell panels, Voc of 47.6V, Isc of 9.7A.

For this part you should be using Imp x 1.25 x1.25 will give you the minimum number, in amps, you need , then round up to next CB size... probably about 15A.

The CODE requires GFI now and it is a good thing to have, there is an 80 amp plus GFI all in one block, as shown in the midddle left of this diagram, labeled MNDC-GFI 80-

http://www.midnitesolar.com/pdfs/MNSW4024-KID-B-REVI.pdf (link fixed. -Bill B.)

hth

@westbranch - I'll take a look at the breaker sizes. Like I said, I wasn't even going to put a combo box in, but was persuaded that it would be useful to disconnect one string at a time. Hence my thinking that the breaker isn't really to be a breaker.

On the GFI: Your link is broken, but looking at the title of the document you were pointing to it looks similar to the one I was going from, which is on the same product page as the E-Panel I bought:

http://www.midnitesolar.com/pdfs/MNSW2524-4024or4048-CL150-REVE.pdf

As far as I can tell there's no GFI anywhere. Ground Fault just sounds like a strange thing in an ungrounded DC. I guess I'll go look at the NEC.

Mountain cabin off-grid

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