Off grid design check

Ocean · September 2017

Just going to say again - Solar Water Heater. It doesn't have to be complex.

Get a propane water heater as your primary. Get a "batch style" solar water heater - and run the output of the Batch heater into the input of the Propane heater. This way the propane heater always sees hot water coming in... greatly reducing - or eliminating - it's need to use propane to maintain temperature. The output of a properly oriented batch style heater can be scalding , so be careful.

A batch style heater is basically an insulated Stainless Steel Tank (typically about 20 gallons per unit) laid horizontally (within an enclosure) with a parabolic reflector behind it.... facing South, optimized for winter. Insulate the lines - and locate it as close to your propane heater as possible. Can be roof mounted or ground mounted.

This will offset your water heating bill in a major way, while not sacrificing hot water on a cloudy day. I have seen them mounted incorrectly - they must be laid horizontally - in line with the path of the sun.

Plenty of other types of systems exist, but this is the most basic, and in my opinion, reliable. A bypass valve located at the propane heater would let you use Solar heated water directly, if for example you were to run out of propane. I have a system like this. It's flawless. I don't use any propane to heat water 8 months of the year... and I love showers. For your size of family, put two or three in series.

Raj174 · September 2017

@chsdiyer,
The variable speed compressor is not only nice, it's very likely necessary if you want to start it with the XW 6848.
A 2600 sq. ft. house would normally take at least 4 tons, so 28000 BTUs is quite a savings in heating and cooling. With a variable speed system you would need the next size up from 28000, which is 3 tons. The unit only draws as much power as is required to handle the heating or cooling load at the time. Could ramp up to 3000 watts in a warm house and then reduce power to maintain a set point. Depends on thermostat setting and the heat load. Take a look at the attached PDF below. Sheds a lot of light on how it works.

Rick

BB. · September 2017

www.homepower.com magazine is a fun read, and you can get some good ideas from it for home design too. A fair number of free articles on-line to get an idea of their product.

-Bill

Mangas · September 2017

Good to hear you're acquiring the tractor. Off grid in our environment they are indispensable. Contracting them at $80 + an hour gets expensive and inconvenient over time. Kubota makes some very reliable medium duty TLB M units and smaller tractors.

Our LG propane dryer leaves no residual drying odor.

I think most of the guys here prefer sizing the genset for less support than we do. With family off grid in very remote situations such as ours, I prefer having 100% standby behind us. With our new HVAC system, yes the genset is running even less than before which I have to acknowledge. But when you need it, you need it! The larger gensets in the 15 kw to 22 kw range are getting cheaper and cheaper. Having that on demand genset supporting everything we may need was driven more by peace of mind than economics. I guess I'm built that way especially with family in mind. I don't like running out the clock on the solar hardware either. When I approach 85% useful life, I replace.

We have a late model atmospheric 55 gal propane water heater. Surprisingly, it uses very little propane. I had a tankless water heater years ago and it worked fine. Might compare the prevailing unit cost differentials.

As posted, we have two three ton variable speed high efficiency HVAC compressor units. IMO only way to go in a larger system. Our new Trane installation has more than proven itself in an off grid application. I think our units are rated at 22 SEER.

Anticipate potential future expansion in your site plan too including utility location runs. Given your background you probably have thought that through.

chsdiyer · September 2017

Ocean - interesting on the batch water heater. I've often thought about just running a garden hose line laid out just before the water heater. That get's pretty hot it's self, just doesn't last very long once you start running the water. I'll definitely keep solar water heating in mind but i'll probably start off simple to start.

Rick - Thanks for the pdf. We had an old 13 SEER unit at our old house and the air wouldn't come out lower than 70 degrees. Put in a 14 SEER AirEase system and the air came out in the 50's but oddly enough our power bill went up after that install. Perhaps the older unit wasn't drawing much power since it wasn't working well to start with. Variable speed certainly seems the way to go with conventional heat pumps.

The XW6848 says max dc input voltage is 60V. Is it more ideal to run two panels in series and parallel the rest and feed into the Inverter, or more series connections with the solar and do a DC-DC from solar to inverter to give the inverter a more consistent input voltage. Oops sorry, not thinking. That's the battery input to the inverter. Solar inverter would be for the charge controller.

Bill - thanks for the link. I've already found a few pages to read on there.

Mangas - We have Kubota, Massey and John Deere dealers in town. I was looking for a used Kubota for a while but even used, they're pricey. I think I've set my mind on an LS XG3025H. They seem to outperform every other tractor in their class and some of the next class up. 1600lb lift capacity on the front loader. Most people have never heard of them, but they are owned by LG group and also make some lines of New Holland. From the people i've talked with in tractorybynet.com they seem to be solid tractors with great performance and thousands less than the other brands mentioned. We have one acre cleared and I asked someone how much to cut the overgrown grass...$350. Time to buy.

We had a tankless natural gas water heater in our old house. It did great and our gas bill was negligible each month...about the cost of going out for lunch.

Do you know how much energy you're 3 ton unit uses on a given day?

Yeah, I forget where I heard or read it, but someone said, when you lay conduit, run a second one at the same time for future use. You may never use it, but it'll make things a whole lot easier if you do.

Thanks so much for all the input! I'm going to try and get my design finished up and will post it when I'm done.

Edit: for question about inverter
Edit again: recover from dumb question

Mangas · September 2017

Good choice. That looks like a very nice tractor with a Tier 4 diesel. Like my Kubota M59 it has Hydrostatic which is contemporary. Front loader 1,600 pounds should be fine for most homeowner applications. Might inquire if they offer a backhoe and PTO quick attach kit.

I keep on hand extra fuel, air main and precleaners filters, thermostat, UDT fluid filters and fan belts. My experience, I would definitely buy a new unit and forgo a used one. After 7 years, my Kubota has only 450 hours on it and is barely broken in. Couldn't live without it saving time, money and my back! Helps keep the homestead safer too.

The 3 ton Trane XV 20i variable speed units are very stingy powerwise with low surge ratings. I never have recorded daily A/C consumption but believe when the Comfort Link II thermostats are showing compressor speeds running at say 67% in the summer late afternoon the inverters show about 1,700 watts for each A/C compressor and air handler. Normally, A/C compressor speeds idle only around 25% to 35% when running on and off during the day. Ceiling fans help keep the system idling most of the time. We set the house thermostats at 82 degrees. Not sure if this helps with your question.

Yes, I would lay in extra conduit. We shade our underground tanks and buried conduit with crusherfines.

Anawa · September 2017

chsdiyer, a 10 acre home site with oaks, pine, and sweet gum, sounds like you're somewhere in the South East? If so, that's a mixed blessing; lots of sun, mild temps, but, designing for comfortable/affordable AC (think, small kids growing into teens) will be one of your off-grid challenges. Some thoughts as you prepare your final design for an off-grid journey.

First, I'm a realtive newby at off-grid living, but I've spent a lot of time out-of-the-city, on the land and I always anticipated living in the "country". I thought about it a lot both in the short term and, especially, the long term. My planning revolved around retirement, but it appears you have a young family that brings into play different long term considerations. You may want to think about stuff at least 10 years (or more) in the future.

Is it your plan to do a DIY installation? If so, when you're traveling or simply unavailable, who's going to keep the solar equipment up-and-running? Will it be your wife, next door neighbor, brother-in-law, or.... ? For the time being, I'm able to keep things up because I'm not leaving daily to go to work, but that will probably be different for you. I will admit that it's fun and energizing to do your own installation and it definitely saves you money in the short term, but is this your primary goal? I'm not advocating that you engage a professional solar installer, even if you did, you'll probably experience some degree of inconvenience. Just something to think about.

Off-grid living can be challenging and those of us that do so decide for a variety of reasons. I guess my off-grid decision was a bit pragmatic and not focused on "saving the planet". Personally, when I look around my immediate environment and examine the totality of the short term global disaster predictions, the scientists seem fixated on a political ideology rather than a factual analysis. Around here, we call that putting a square-peg into a round-hole. So much for that mess and back to our off-grid decision, my wife and I were facing a binary situation: spend $30k for utility power or spend $20k (less 30% tax credit) for solar. At the time, it was a no-brainer, but after experiencing an outage from a defective inverter part, anxiety with sufficient PV to both charge batteries and run the AC, installing more PV, and forever measuring battery SG and tweaking the settings, that $10k left-on-the-table didn't seem so bad. So, maybe negotiating with your neighbor with a little "financial juice" may not be a bad idea. The "juice" would be somewhere in that $40k you intend to spend on the solar. Just saying and not making any judgement calls

I do not want to hijack your thread with my ramblings, but here's a few things you may want to consider.

Mini-splits are the way to go with AC in the SE. They're a bit pricey on the front-end, but their efficiency and overall flexibility is very good. Wi-fi control capability is nice, too.
Grundfos SQ well pump and holding tank is a solid and stable system. Add booster pump to pressurize.
Wood stove as your primary heat source. You'll be surprised how easy and efficient the stoves are. Hey, the kids will even enjoy contributing to the family comfort and well being.
Plan your equipment room for easy accessibility, adequate space, and maintenance. You'll be spending more time in there than you think, make it easy on yourself. Believe it or not, but my batteries and equipment are right outside my entrance door. Rain or shine I always have covered access.
Design your house now! And think in terms of openness, heating and cooling efficiency, and off-grid living.

Hope it all goes well for you.

chsdiyer · September 2017

Mangas - it does have a backhoe option, but not something we can afford. Originally I was looking at the GC1710 by Massey or the BX25 by Kubota to get the backhoe. People praise those two as being able to handle a lot more than they look like they can. And perhaps after the house is built, that's all we'll need, but to get the house built and land cleaned up, we'll need something bigger. Definitely be a much needed back saver. We initially started clearing the land by hand with a pick axe, trying to uproot all the trees. It's mostly over grown with small gum trees and wax myrtle bushes. We finally got some sense and got a bull dozer to do an acre one weekend. Pretty impressive on the HVAC system.

Paul - good point in thinking long term, I can tend to get caught up in the now. We are in the south east...coastal South Carolina. Our old house was built in 1839 so we're used to not being able to have the house the exact temperature we'd like, though it did get better after our renovation. We redid the whole house (living in it the whole time). A good bit of it was done before we had our first child. Looks like number three will be here right when we're getting things started. One of the reasons we're moving out there is to try and get our kids more of a naturey lifestyle. You go out to eat these days and all you see is kids with their faces in tablets. It's sad. People are always shocked that we can take 12 hour car rides and don't have a dvd player or any electronics for the kids to play with. We hope to just have a simpler life with some farm animals and grow some food. Maybe start up a small nursery.

I do plan to do my own install. I couldn't afford someone else anyway the rates they charge around here. And none of the solar installers offer off grid options or even battery back up options. We're doing most the build ourselves to save money and it's just so hard to find good help around here. I also enjoy doing the work, and hope some way to get more experience and maybe get to finally use my PE license some day. I work from home two days a week and my wife is home with the kids. I assumed if you go away on a trip and aren't using much energy, the system would be fine on it's own. Do you (off grid homes) need to have someone monitor things while you're gone?

I don't think offering $40k for a utility easement is practical. I'd be better off buying the one acre lot on the other side of the trouble neighbor for $50k. We've though about this as we'd be on grid and about 400feet from our land, however, we'd be in an HOA of 10 lots on 15 acres and we've already had issues with the neighbor we'd have next door. We still think about it as a last minute back up but it seems like off grid can work for us and we'd like to be own our land.

Thanks for the tips!

Photowhit · September 2017

chsdiyer said:

. We finally got some sense and got a bull dozer to do an acre one weekend.

Aren't they amazing! A friend had one out to do a half day's work at his place, a huge D9 he cleared and packed a 800 foot drive, cleared a spot for a Double wide and garden and made a low water bridge so they could bring it in. I think he was drinking beer before noon! We have a track hoe that has a harder time with trees, anything less than 10" didn't seem to even slow him down!

Estragon · September 2017

I also did the solar system on my own. Partly for cost, but more because I thought designing and installing it would help me understand it better. On balance, I think it was the right choice.

In my case, the remote location means no permits, which is a mixed blessing. I did what works for me, but there is no inspector to point out mistakes in design or execution.

Leaving the system unattended needn't require a babysitter, but some planning may needed depending on the time unattended. For short periods, a properly designed system should work fine on its own. For more than a few days, you have to make some choices. For example, are you ok with an automatic generator start system, and comfortable with the consequences of its failure? I'm not, so I would empty the fridge and leave the system to essentially float with few or no loads. Some people are ok with AGS and do fine though.

Mangas · September 2017

I would definitely incur the expense to have the land cleared and excavated by a contractor using larger equipment leaving time to manage the project's civil lay out. Faster and less stressful.

Backhoe can wait but I would have a tractor with loader and pallet forks (your own or rented) on site 24/7 while building the project. Important piece of equipment to keep a project moving forward, minimizing construction delays with potential related costs. You might initially rent the one your looking at from your nearby dealer to see if it meets your expectations. To close a future sale it would be in their best interests.

I've had very good success with Kubota tractors. Little more money but very reliable and durable.

Full scope off grid projects are initially more work and investment getting them on line but once completed the independence is very rewarding.

BB. · September 2017

One suggestion on the easement... It is possible that the value of the land will be increased by that amount (and more as time goes on). Having power to the property is worth a lot to many people. Off grid power systems--They are hard to sell for much to most buyers down the road.

And the issues of off grid power and maintenance (vs, for example, utility power + backup genset) as you age.

Batteries will last, typically 5-8 years (fork lift batteries can last 10+ years). Electronics--After 10+ years, generally replacements (getting parts for older electronics and custom parts gets difficult after 5+ years).

And, more than a few of us have killed our first battery bank or two getting system operations right (getting "cheap" batteries for the first "training" bank can be helpful for the bank account).

-Bill

cow_rancher · September 2017

I found this on another forum and this guy has 8 tons of geothermal. When his 5 ton unit is running, I think it's only pulling about 3.5kW. That seemed pretty good to me. That's my only gauge on understanding how much energy geothermal would pull. We would do ground loops and not from our well. Dave, how else are mini splits used other than wall hanging? I'm not sure what the Schneider system is illustrated relevant to mini-splits, is that the wrong attachment?

OK I have:
8.4KW Grid tie, never seen more than 7.9, without the geothermal cooling my elec bill is $25-$50, with the geothermal cooling it's $250.
Unless you can use pump and dump, I would never recommend geothermal, I have a field 50'X50' 1/4" copper ground loop manifold grid loops 10' underground (I own a backhoe) connected to the compressor with 1" and 3/4" copper. Problem with a ground loop/field is in the winter, especially with your high ground water, it will freeze, think of it as an typical heat pump where the coils freeze up, you don't get heat exchange. That said we heat with an outside air combustion fireplace, I would recommend a name, but I completely re-built it my self as the original one burnt thru. Plus we have a pellet furnace, thermostatically controlled, the best heat source I have ever seen, 1 ton of pellets last me 2-3 years (1 ton=1 pallet buy on sale), it's an Englander, bad design for the glow starter, it stays on until the combustion cycle ends (count on one glow plug per year). Plus we have solar hydronic heating in the slab, I used polybutalene, as it was available at the time, now use PEX with a vapor barrier now, it's aluminum tube in the PEX for some reason... I have 8 each 4'X10' panels, combination of Gobi and Sunpower, storage is 1300 gallons of RO water, that will provide 90% of all heat needs for a 3,500' house on sunny days. Insulate the slab on the ground and between the slab and stem walls, which is the type of building we do in Arizona, I probably have 10-20 nights below freezing, some down in the teens, which is when you use the fireplace and call in sick to work.

Rancher

chsdiyer · September 2017

Bill - I fully expect the land price to go up regardless. The 15 acres on the other side of the problem neighbor's property sold at the peak of the market for 590k. We didn't pay near that amount for our 10 acres, though considering this issues, we still over paid. But long term we'll be ok. The property to our North is owned by problem neighbor's brother (we're surrounded by various members of this family, though it's marsh to the South). I asked him about an easement and after several months he finally said, no way! The problem lady has for a year, and even before we bought the land, told us she would help us out. That's what has me so annoyed, but in reality, she's never going to sign it. She tried to get me to buy 10 acres she owns further up the road, but she wanted 700k for it. That should give you an idea of how realistic it would be to pay her to give the utility company an easement.

Long term, I expect the neighbor to the North or West to want to do something with their properties. Once that happens the power company will provide us power. Right now it's all vacant parcels around us and none have or want power on it.

Rancher - Interesting about your geothermal. A neighbor's coworker said he installed it and his power bill went from $300/month to $75/month. I think I've pretty much ruled out doing geothermal considering all people have said about conventional and mini-split heat pumps. We'll probably go with one of those options or a combination. We pay about $250 in the summer in our rental, but it's very inefficient, 2000sqft and the heat pump unit outside sounds like a car crash every time it kicks on...pretty old. Our old house was roughly the same size but our bill in the summer was near $400/month. Much older house (single pane windows killed us)

Anawa · September 2017

Given what you've shared about your current land situation, a $40k "negotiation stash" appears woefully inadequate. I can, however, relate to your situation. We successfully negotiated an access/utility easement many years ago after agreeing to a few unpalatable terms. For us, our property is 1.25 miles "off the paved road".

I'm not sure how, or even if, other off-grid folks monitor their systems while they're away, For us, we use Outback's OpticsRE to monitor the battery SOC and assess the power consumption to determine if we forgot to turn something off. These are my primary concerns. I've had to use the remote generator start a couple of times just to be sure my battery was fully charged. So far this has been adequate to meet our needs.

Similarily, when traveling we monitor the indoor temps and the mini-split operation. The mini-splits wield the power consumption around our place and pretty much demand our respect. Our system permits remote start/stop capabilities (wi-fi) which is very nice. A couple of times in a haste to get out the door, we've discovered that we forgot to turn off the unit, but were able to do so remotely. The system also has e-mail alerts to advise of high or low inside temps. We've turned on a unit a time or two to raise the inside temp above freezing.

For us, that's about all the monitoring we do.

Dave Angelini · September 2017

It is nice Paul to remote monitor. And you can have someone else do it for you by giving them the access for while you are too busy to
care

Schneider has their version "Insight" and I often go between both web apps for other people. Very safe and all the data you could want.

Image: https://us.v-cdn.net/6024911/uploads/editor/4i/6tsm9kf1xlkc.png

chsdiyer · September 2017

I was reading the inverter installation manual and it calls for the battery to be within 10 feet. However, it also requires the inverter to be away from any combustible gasses such as those from vented lead acid batteries. So my question is, if the inverter is together with the battery, how does one typically have a large lead acid battery bank and properly vent it to keep the Hydrogen release away from the inverter? Do you build your own batter cabinet and have a vent pipe to it, or wall it in separately in a small room and vent that room or if the room is big enough and vented will the hydrogen gas naturally not build up?

Estragon · September 2017

I have my batteries on one side of a wall, and inverters etc on the other. The batteries live in a box that will someday be vented, but in the meantime just have a loose lid. Both in a crawlspace averaging 4' high, roughly 25x50.

chsdiyer · October 2017

Ok, I've been going through the 2017 NEC and trying to figure out specs. Still can't quite peg the HVAC, but i'm assuming 12 hours run time worst case. At that estimation I'm looking at roughly 20-25kWh of total usage a day. Of that, maybe 10kWh/night.

Looking at 23 SEER (lennox) conventional heat pump - variable speed (3-3.5 ton).
(32) 330W LG panels
(6) 8-CS-25PS Surrette batteries 820Ah ----48V/39kWh ~$8500(alternatively considering buying a DEKA industrial battery locally, need to see what's available or Surrette AGM battery of similar size but way less cycles. I've also considered getting a cheaper battery but that means multiple parallel strings and less cycles and I'm not sure it's worth it for the added maintenance. unless I went with a 20kWh battery to start off with)
(1) XW+6848 inverter
(2) XW-MPPT80-600 charge controllers
Probably going to hold off on the generator until we've moved in
(4) pole mounts of 8 series connected panels (though probably less forgiving for future expansion - charge controller still has room for more series connection but pole mount couldn't take any more panels. I suppose I could get larger pole mounts, but from the dimensions, they get pretty big, 8 seemed a nice size)
-In our current house we use about 135 gallons of water/day. Plan to have grundfos DC deep well pump feed to cistern holding tank. Will have second pump at tank to supply water to house.
-Still looking at propane tankless for water heater. Our old house had gas tankless, current rental has gas tank. According to our old bills, neither uses that much gas but the tankless we used about half of what the tank uses.

-Housing the PV equipment in it's own building probably made out of cinder blocks.
-Each charge controller will have two solar arrays feeding them. Voc = 41 per panel. 8 in series corrected by Table 690.7(A) gives Rated Voltage of 387.04Vdc
-Max Circuit Current: short circuit current of panel = 10.49A, no parallel strings, corrected by 690.8(A)(1) max circuit current of 13.1Adc. Charge controller can handle 35A (to my knowledge this is with the 125% factored in 28A otherwise). 2 array strings input gives me 26.2A.
-PV conductor ampacity with 690.8(B)(1) = 16.39
Need to figure my distance and calculate the voltage drop but I'm planning to use 10awg PV wire from pole to charge controller.
-Each array will have a disconnect at the utility shed with proper labeling,
-According to 690.15(A) looks like I need another disconnect at the pole (to be within 10ft of equipment)
-I'll have a disconnect between the inverter and the battery
-I'll have an AC disconnect after the inverter but will also have main breaker at the panel board in the house.

Thinking of switching to outback equipment since they have the GS8048A 8000W inverter, but I'm not sure they're charge controller will work for my solar set up. The Schneider inverter should be big enough, though I might need a second one if I get my work shop going.

mike95490 · October 2017

Off-Grid
It's not "bad" but it's a major time sink. Water lines to check. Pond level to check. Batteries. Generators. pumps, filters
I run the water plant. The electric plant. The heating plant (firewood & masonry heater) Hang a picture up for me please. Don't mow the lawn there. Mow this over here. Feed the sheep, move pasture fences. Order seed for pasture. Seed pasture. chase turkeys eating the seed. Hose froze, water tanks drained. It goes on.

mcgivor · October 2017

Sounds something like my day, but it is rewarding none the less.

Off grid design check

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