diy solar

diy solar

Complete rebuild of a house - how would you power and heat/cool ?

The head units of the mini splits require 120/240AC their control circuity creates PWM/DC/VFD to alter the output to compressors as needed.

I’m not aware of any just DC powered mini splits.

Hotspot Energy DC 48v mini-split. Check out my Post #40 above...

Engineer755 video shows it in action.


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Adding same 'Hotspot Energy DC 48v mini-split' links from other post here:

For DC on the mini-split, Hotspot Energy is the main player in town... https://www.hotspotenergy.com/solar-DC-air-conditioners/

Engineer775 goes over these as well (has has a couple other videos on them too):
 
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I liked this guy's videos on the geothermal implementation (not mini-split style though, but a lot of good info there):
This is one of the very videos I have watched. This system will work fine for the animals. I don't know yet if I can do this for the house. if we go geothermal, I will dig extra deep and do the house and then put others like he shows in various levels above it.

Thanks for the feedback on the minisplit longevity. That is encouraging.

I plan to consult with Scott at Engineer775 once I have enough together to make it worth his time and my $.
 
I would never recommend mini-splits for heating. Cooling for sure, and they'll work for heating, but that's not their strong suit. If they're supplanting a more traditional heating method, be it gas, wood, or electric, they're fine. But their strength is really for cooling where you enjoy the drafty nature, and because you don't have the cost of duct work.

Since most mini splits are dual cool/heat, they are intended to be a backup. if I can get cool only, I will do a cost-benefit analysis to determine which way to go. One is none, two is one.
12V DC is never going to be as efficient as 120, or even 240.

what about 48V? we get 20% efficiency off PV panels. About a 30% efficiency in the grid energy production when using natural gas or coal. if I go PV and then through an inverter, I get the PV efficiency and then 85-93% efficiency with the inverter. So which uses the provided energy more efficiently?
 
Get a quote to spray foam an entire 100 year old construction house, let me know when it’s under 10-15k. That’s also after you gut the walls to studs. Even then your talking about 2x4 construction not 2x6 or even Uber double 2x6 construction of our brothers to the north.

I’d love a DIY spray foam system but it’s not quite obtainable.
That price just knocked me out of my chair! You can buy the kits at Lowe's but for a whole house, hiring it is more economical. A contractor buddy has not had to remove everything to studs to do this install - just slits near the bottom of the wall and the company just used poles to get it everywhere. Still cheaper than gutting and replacing all that plaster!
 
Since most mini splits are dual cool/heat, they are intended to be a backup. if I can get cool only, I will do a cost-benefit analysis to determine which way to go. One is none, two is one.


what about 48V? we get 20% efficiency off PV panels. About a 30% efficiency in the grid energy production when using natural gas or coal. if I go PV and then through an inverter, I get the PV efficiency and then 85-93% efficiency with the inverter. So which uses the provided energy more efficiently?

One thing I might add about using mini-splits. On the 4-head I installed for my brother in law, they have 2 heads upstairs in the bedrooms, and 2 heads downstairs (kitchen and living room). One thing I learned, is if I did it again, I would instead go with two smaller outdoor units, each with 2-head (a pair for upstairs, and a pair for downstairs).

Because we had gone with one single large outdoor unit of 36000 BTU, but all 4 heads (2x 9000btu, 2x 12000btu) have to share it (which is totally fine, except they can only do heating, or cooling mode whenever they want, on the fly, but not at same time)...

In certain seasons, the 2 head upstairs needs cooling, while the 2 heads downstairs may want heating, so in auto-switching mode, the ones calling for heat have to wait until the ones calling for cooling are done using it, since it can't run in both modes at same time.

Most of the time this is not a real issue (especially on a well insulated house), but say one person what to cool down a single room, but the other 3 units are heating 3 other rooms, the cooling will have to wait until the 3 heads take a break, to switch over and cool the one room.

Or the other way I might do it, is to just install 1-outdoor to 1-head unit for each room... Or do the 1-outdoor to 2-head units (for each floor), since the rooms on a floor were more likely to stay on same mode together.

My Mother's system doesn't have a problem with this since her house is insulated really well (more modern) and both floors tended to stay more constant temperature.

However it was a little more obvious at my brother in law's place because he had a 100-year old house with poor insulation so I could tell there was more tendency for it to be cooler downstairs and hotter upstairs, so the upstairs tended to want cooling more, and the downstairs tended to want heating more. So it would work on cooling upstairs for awhile, then it would switch and work on cooling downstairs for awhile, like round-robin...
 
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I am more than open to suggestions on a good HVAC engineer.

I will get some solar to expand my current system to take advantage of the rebates. Can go grid-ties for not too much.

Why off grid? Did you see Texas? Mad rolling blackouts out West? A good ice storm here and the power can be out for a couple of weeks. Not only do I need to keep the family safe, but the animals still require care. Never mind the product in freezers. Just because I CAN does not mean I will at the moment. But having the plan enables setting the foundation for it.
I recommend you go on hvac-talk.com in the AOP section you can present your home plans, and there are experts there that will help you formulate a thorough plan for improvements, hvac, electrical etc.
Free.
I would be focusing on insulation. It is FAR better to reduce the load than to build big enough to cover it.
If you are truly getting the place beware of lead paint dust and children.
Air sealing is critical to efficiency. Insulationproperly installed adds to that, without air sealing, insulation is useless.
Home style dictates types of hvac equipment. Basement, main floor and attic renovated 2nd story... lots to unpack here.
Prepare before purchase. Way more economical.
 
I would never recommend mini-splits for heating.
Why not?

Cooling for sure, and they'll work for heating, but that's not their strong suit. If they're supplanting a more traditional heating method, be it gas, wood, or electric, they're fine. But their strength is really for cooling where you enjoy the drafty nature, and because you don't have the cost of duct work.
The newer gen mini-splits are supposed to work even better for heating in temps down to, and even below -10 degrees F. Even my parents older last-gen Daikin in PNW Washington works fine for heating in the PNW, that's all they use in Winter (they haven't fired up their pellet stove in years)...

My brother-in-law in Michigan does fine with his mini-split using it all Winter, and his isn't even the latest-gen style which are supposed to operate better below 10 degrees F.

I Iived in the PNW for 35 years and it's not horribly cold, but a airtight wood stove was really the ticket for comfort. Good firewood is easy to source - there's a ton of alder trees that get cut down every year and once seasoned burn hot and clean. Air conditional isn't needed - it rarely gets over 75 there. Central air furnace either natural gas or electric are the norm. Older cheaper homes got electric baseboard heaters which were horribly inefficient. The deluxe setup is still a heatpump type central system.
My parents in the PNW do have to use their mini-split for AC in the Summer since their skylights tend to let a lot of Sun in it gets warm there (especially with the last several drought Summers). They live like 10 minutes from the bay...

They do have a pellet stove they previously used to use frequently in the Winter, but since around 15 years ago when they had the Daikin 4-head mini-split installed they only used that for 100% of heating and cooling now, and don't use their central heating anymore. It's a huge house, and they only have the 4-heads in the key areas and it keeps the house perfect temp all year round.
 
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Why not?
The newer gen mini-splits are supposed to work even better for heating in temps down to, and even below -10 degrees F.

They surely do, and I use mine that way as well, even though it doesn't get as cold here. I'm just saying they are better coolers than they are heaters. That's just my humble opinion. For heating I prefer LPG or NG - instant heat. That's my story and I'm sticking to it. :giggle: YMMV

All of your friends and relatives can do whatever they want. I'm good with that!
 
A lot of bad information in this thread. Most suggestions are cool but not a good use of dollars.

Correct information : don't bother with anything else but high SEER 9000 btu single head mini splits. The 38 SEER rebranded Gree models on signature_solar are the cheapest but if you don't trust that brand you can get Fujitsu models over 30 SEER. You will need 2-3 depending on layout. Small rooms get a vent.

Insulation is good, especially important for split heating is to seal air leaks to prevent drafts.

Radiant heat in floor is a huge cost unless the plumbing is already installed. If it is obviously the way to go is a condensing boiler that burns gas or propane.

If the tubing isn't installed use electric for the radiant heating, less efficient but it's just to make the bathroom floor warn.

For solar a ground mount array using bifacial panels is the obvious way to go. For the batteries obviously server rack lithium iron phosphate at 48v. Will seems to like the MPP brand (from watts247) more than growatts.

You probably will need about 10 kilowatts of bifacial panels, 5k on signature solar. 3 server rack batteries, $4500-$5k. A large all in one inverter, $2400 for the 12k growatts. And probably about $1k in wire and subpanel and breakers and building materials for the rack.

Wire it so that your loads are on a subpanel that has 2 breakers, one 60 amp from your main grid powered panel and one from your inverters. Use an interlock kit. This way you can just switch back to the grid if your cheap inverter fails.

Don't forget to have this in a separate building than your main dwelling. And mount your solar power board on cement board.

For hot water either takagi tankless condensing outdoor units, fed by gas or propane, or a hybrid heat pump water heater. Some advantages either way.

For your laundry there are heat pump dryers if you want to solar power them, or you can use fuel burning. Same for your dishwasher, the highest rated models use heat pumps to heat the water.
 
What about 48V? we get 20% efficiency off PV panels. About a 30% efficiency in the grid energy production when using natural gas or coal. if I go PV and then through an inverter, I get the PV efficiency and then 85-93% efficiency with the inverter. So which uses the provided energy more efficiently?

I have no idea. Not even sure what you mean by a percentage of efficiency.
What I do know is that PV systems are expensive, and the ROI verses modern traditional equipment on the grid, is a long payback.

I intend to build an off-grid system to assist with power needs on my next place. Lots of good information here on how to do this.
And I like mini-splits verses paying an HVAC pro to design and install a system. But that's a whole 'nother story. :p
 
Yeah the simplest and laziest way to set it up:

If the grid power is of reasonable cost, just do 2-3 mini splits you install yourself on exterior walls. (speaking from experience use exterior walls only and mount the outside unit on a wall bracket on the thick rubber mounts).

You can do each install in a couple hours once you learn how on the first one.

Don't over spend on insulation just seal leaks. Energy star appliances, condensing type for the fossil fuel burning ones. Gas dryers instead of electric. Countertop convection/air fryers instead of conventional ovens. Shower stall instead of tub with curtain and a 1 gpm head. And of course all LED bulbs.

No reason to bother with solar if grid power is cheap. Just install a generator inlet on an exterior wall and an interlock kit to let it back feed the electrical panel. All of $100 in materials. (Electricians will gouge to install). And have a small generator for backup that can use propane or gas.
 
They surely do, and I use mine that way as well, even though it doesn't get as cold here. I'm just saying they are better coolers than they are heaters. That's just my humble opinion. For heating I prefer LPG or NG - instant heat. That's my story and I'm sticking to it. :giggle: YMMV

All of your friends and relatives can do whatever they want. I'm good with that!

I see what you're saying and respect your humble opinion. ✌️

My biggest beef with LPG and NG (especially in my case for my upcoming off-grid homestead build), is its reliance to an ongoing service from a 3rd party. First off my ranch property doesn't have NG option out there, and propane is a pain to truck out there, even if I did want to pay ongoing monthly fees for energy.

My personal goal in energy is always a solution that is as close to free in the end (passive home tech a plus here). Once all your solar panels have earned their keep, the Sun is essentially providing you your mini-split's needs for any additional supplemental energy needs where the passive home strategy may fall short and you never need to buy propane or wood again.

To each his own I guess. I know some places they like wood a lot too (like PNW where the trees grow thick), but out in the desert where I am at, are not a lot of trees in comparison. A person has to look at their local area and decide what are the abundant resources. Here in the desert where I'm at, Sun is free and abundant so anything using electricity is more versatile to me. Or just harnessing the Sun's energy directly with passive home tech.

Peace bro...
 
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I see what you're saying and respect your humble opinion. ✌️

My biggest beef with LPG and NG (especially in my case for my upcoming off-grid homestead build), is its reliance to an ongoing service from a 3rd party. First off my ranch property doesn't have NG option out there, and propane is a pain to truck out there, even if I did want to pay ongoing monthly fees for energy.

My personal goal in energy is always a solution that is as close to free in the end (passive home tech a plus here).
Peace bro...
This is an understandable goal but this is not how you should work out the math. You should assume the inverter will die every 10-15 years (lower number for a cheaper brand) and that the solar panels will need replacement at 25 years. Yes some equipment will last longer but a lot of equipment will fail prematurely. Panels will delaminate and corrode, or get broken by wind blown debris, etc.

So this is just a monthly cost of the equipment cost divided by months of life. If the current prices for energy service are not much more money just stay with it.

You are dependent on someone sending a truck to deliver replacement parts and the things you cannot make yourself at all times. Thats just how the world works. Hope you have diversified financial assets.
 
Yeah the simplest and laziest way to set it up:

If the grid power is of reasonable cost, just do 2-3 mini splits you install yourself on exterior walls. (speaking from experience use exterior walls only and mount the outside unit on a wall bracket on the thick rubber mounts).

You can do each install in a couple hours once you learn how on the first one.

Don't over spend on insulation just seal leaks. Energy star appliances, condensing type for the fossil fuel burning ones. Gas dryers instead of electric. Countertop convection/air fryers instead of conventional ovens. Shower stall instead of tub with curtain and a 1 gpm head. And of course all LED bulbs.

No reason to bother with solar if grid power is cheap. Just install a generator inlet on an exterior wall and an interlock kit to let it back feed the electrical panel. All of $100 in materials. (Electricians will gouge to install). And have a small generator for backup that can use propane or gas.

Much more helpful than "A lot of bad information on this thread."

Mounting a compressor unit (outdoor split unit) on a slab also works. It is WAY simpler, especially if the slab is already there.
I tend to agree with not running lineset through a house. I had one leak at a welded connection fitting and had to replace it. I wouldn't want it buried in a studwall or floor/ceiling joists.

I've installed a couple of these now and they are pretty easy, and they work just killer. Silent and efficient. (y)

My house was built without insulation in the walls. The stucco is nearly 2" thick, but the cavities are bare. On the north walls I did completely remove the plasterboard and apply fiberglass insulation, re-sheet-rocked. It makes a huge difference! But the doors and windows are open nearly six months out of the year. The house has 3 windows and 6 sliding glass doors, all one level.


@Samsonite801 - when I built a giant place in the PNW the natural gas main had not been run that far out in the county. We rented two 10,000 gallon propane tanks (5 acre property) and the local gas dealer filled up what we used a time or two a year. They charged us $60/year for the tanks, and prorated the annual usage by the month. We had a 95% efficient 'pulse' gas central furnace, two gas ovens, and two gas waterheaters. Gas jets in appliances are a little different for LPG, but we didn't have any trouble sourcing them at the time.

Since we were sitting on an alder grove there was an air-tight wood stove that passed through from family room to living room, with gold-plated doors so they didn't tarnish, and a furnace return duct in the ceiling above it so you could turn on the furnace fan and circulate the stove heat throughout the house. We finished one of the two 3000 sq ft floors in the place. It was pretty cool, and super efficient.

Things may have changed some now, that was thirty years ago.
I agree though, best to utilize what you have local to you.
 
Much more helpful than "A lot of bad information on this thread."
Sure but people are suggesting things like geothermal. You can't diy install one unless you own heavy equipment and they are $20,000 to install. 3 mini splits from signature solar are 1200 each and a few hundred bucks in materials to install. Yeah they probably fail sooner but when that happens you can replace a mini split in an hour, most of the work is running the wire and installing the mounts.

Other people are saying waste 10k on spray foam. Dumb, it's the same problem, it will never ever pay for itself.

Same with solar thermal. Total waste of money (because the solar thermal panels are so little used they are far more expensive than PV panels now for the same energy input)

You are right a ground pad is an option but now you gotta deal with the line set, greater issues with grass or flooding, easy to ram it with the mower. I think it's more work to install and not as good. I have done both.

For a 2000 square foot house with 3 mini splits I am hitting peaks of 120 a month for the total electric bill in Texas. Or about 500 a year in total energy costs for heating and cooling in Houston Texas. This climate needs extreme amounts of air conditioning. So geothermal or spray foam will never pay for itself. I have an attic cellulose fill, did it myself for $400. And new windows. But the walls are the old style with the usual fiberglas that tends to settle to the bottom of the wall cavities, nothing special.
 
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This is an understandable goal but this is not how you should work out the math. You should assume the inverter will die every 10-15 years (lower number for a cheaper brand) and that the solar panels will need replacement at 25 years. Yes some equipment will last longer but a lot of equipment will fail prematurely. Panels will delaminate and corrode, or get broken by wind blown debris, etc.

So this is just a monthly cost of the equipment cost divided by months of life. If the current prices for energy service are not much more money just stay with it.

You are dependent on someone sending a truck to deliver replacement parts and the things you cannot make yourself at all times. Thats just how the world works. Hope you have diversified financial assets.

Well my actual goal is to rely less and less on electricity altogether. The folks in our co-op community are designing houses that don't need any furnace or HVAC altogether. I am only thinking if my design falls short somehow then I 'could' use a mini-split to fine tune the last couple degrees, but really hoping my design will be foolproof and won't require any mini-split or HVAC anything.

A lot of my system will be built around 48v native DC operation, like LED lighting and pumps that operate on DC power directly. My goal is to have my LV6548 inverters for bare minimum use. I'd like to be able to just shut them off most of the time (or just run them on energy saver standby mode), maybe use them mainly for the shop equipment and things like that.

I'm not a very picky guy and don't need a lot of bells and whistles to operate happily. I have power redundancy up the yin yang already. I just want to build a world where I don't have to pay much for services just to basically live.

I can get out of most of the bills, except I still haven't figured out how to get free internet or cell phone, so those will likely be there forever, as long as taxes...
 
I can get out of most of the bills, except I still haven't figured out how to get free internet or cell phone, so those will likely be there forever, as long as taxes...
A laudable goal. Just don't miss the forest for the trees. You can't get out of paying to keep your car running, food, rent to the government (property tax), tribute to the healthcare system so they keep you alive longer, internet, and paying for replacements to stuff that breaks especially your cheap Chinese solar parts.

I bet those costs are way more than what the power company charges.
 
@Samsonite801 - when I built a giant place in the PNW the natural gas main had not been run that far out in the county. We rented two 10,000 gallon propane tanks (5 acre property) and the local gas dealer filled up what we used a time or two a year. They charged us $60/year for the tanks, and prorated the annual usage by the month. We had a 95% efficient 'pulse' gas central furnace, two gas ovens, and two gas waterheaters. Gas jets in appliances are a little different for LPG, but we didn't have any trouble sourcing them at the time.

Since we were sitting on an alder grove there was an air-tight wood stove that passed through from family room to living room, with gold-plated doors so they didn't tarnish, and a furnace return duct in the ceiling above it so you could turn on the furnace fan and circulate the stove heat throughout the house. We finished one of the two 3000 sq ft floors in the place. It was pretty cool, and super efficient.

Things may have changed some now, that was thirty years ago.
I agree though, best to utilize what you have local to you.

Yeah my parents in the PNW have a big giant propane tank on their property too, and I always would hear them gripe about how much it costs to fill it every so many months hehe...

That's where I grew up over there too in the PNW, when I was a kid, we had the air tight stove, with the hot water pipes on it to heat the hot water heater, we cut our own firewood off of our 7 acres forest, I would split it and stack it as my chores every year. No thanks, got tired of it, besides wood stinks up the house (unless you're into that cabin fireplace smell thing hehe)...

My grandparents next door to us, they had a wood furnace that was in the garage, built siamesed onto the central heating system, theirs was a little better since it was in the garage it didn't stink up the house, but you still had to go out, cut down trees and cut/stack the wood.

Pellet stoves are handy, my parents newer place has one and I would fire it up sometimes when I go visit over there, but pellets are expensive, don't really see how you save anything there...
 
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We rented two 10,000 gallon propane tanks (5 acre property) and the local gas dealer filled up what we used a time or two a year. They charged us $60/year for the tanks, and prorated the annual usage by the month. We had a 95% efficient 'pulse' gas central furnace, two gas ovens, and two gas waterheaters. Gas jets in appliances are a little different for LPG, but we didn't have any trouble sourcing them at the time.
Presumably you meant 1000 gallons, or a total of about 1600 gallons usable. Or $3200 - $6400 of just propane. Hope that it lasted longer than a year, though why did you need 2 tanks?
 
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