diy solar

diy solar

Recommendations for Mini-Split Heat Pump System

Dave Poz has a video about installing one.

It’s linked in this thread:

 
Earlier this summer, my girlfriend and I installed a Mr Cool Model DIY-12-HP-WMAH-115B, DIY-12-HP-C 12000 btu minisplit heat pump (heats/cools) in my 780 sf, well insulated off-grid cabin in the Ouachita Mountains of western Arkansas.

lit was a fun project and although I have only used it in the heating mode, it has worked very well so far.

Since it has a variable speed compressor, the amperage draw has varied. So far, I’ve seen the amperage draw range from 3 to 11 amps on my Trace SW4024 inverter. This may also include, at times, other items on the system.

My solar array size is 3,725 watts and I have 18 Duracell 105 Ah AGM batteries for storage.

The battery bank is new and so far, all is well. I was a bit concerned about my system drawing too many amps and shutting down, but that has happened only once - today. Murphy’s Law!

In addition to the inverter and battery bank mentioned, I have a Trace T-220 transformer connected to the output of the inverter allowing me to run my well pump and GE GeoSpring 50 gallon water heater.

The job of installing the minisplit was fairly challenging, but certainly doable. The hardest part for me was adding the additional circuit and mounting the holding bracket for the unit.

I’ll try and send a photo of it in a moment. By the way, making the connections with the pre-charged coolant lines was easy.

The unit really seems to do a great job cooling my cabin. So far, I’ve mostly run it during the day and shut it off at night. The cabin stays comfortably cool. I’m glad that I did it. It is super quiet.
 
Does anyone have experience with installing and running a 120V mini-split system in a small cabin or RV setup? I'd like some real-world data on energy usage, efficiency, reliability and ease of self-installation (I know it voids warranty for some systems). I'm interested in systems with high SEER ratings but not ridiculous price.
Thanks for posting your question: I too, need this information. I'm only trying to heat and cool an 800 sqft living area comprised of two small bedrooms and a kitchen/living room area/dining room area. I've heard good things about these mini-split systems but since I'm 100% off-grid I have to take everything electrical into consideration in this building project. Plenty of room for solar panels (already have 4kw of 100 watt panels to install) but everything else is still in the planning stages.
 
You are correct, many people incorrectly call any mini-split system a heat pump - I've seen many listed that way but are actually only AC units.
WOW, that is one heck of a system you've listed in your signature. I'm still in the planning stages of my off-grid system and I'm guessing you did some serious research before forking out the kilo-dollars for all that you have. Any regrets or things you'd do differently? I'm still learning how everything works and how to design the system for the barn/house that we'll begin building in a month or so. I was particularly interested in knowing if the generator controller will work on any generator? I have a couple of gas generators and one that is dual fuel, gas or propane, and was wondering if I could use them where they automatically start when the battery bank gets low?
 
WOW, that is one heck of a system you've listed in your signature. I'm still in the planning stages of my off-grid system and I'm guessing you did some serious research before forking out the kilo-dollars for all that you have. Any regrets or things you'd do differently? I'm still learning how everything works and how to design the system for the barn/house that we'll begin building in a month or so. I was particularly interested in knowing if the generator controller will work on any generator? I have a couple of gas generators and one that is dual fuel, gas or propane, and was wondering if I could use them where they automatically start when the battery bank gets low?
Yes, I'd have done the system in my signature first.

Unfortunately, I assumed that our off the grid experience would be short-lived, that as soon as I had a new pole, service entrance, meter box, distribution boxes, cabling etc and passed both my (expensive) electrical inspection and an inspection by the power company I'd have power again. So my first 4 systems were 'temporary.' At first we just had a propane-powered generator that ran 24/7 more or less. Then I added a Heart Interface Inverter/charger and 16 T-105a golf cart batteries (wired to be 12V) so we could shut the generator off at night. Then we went to a better generator (our first Onan) sill propane. Then we added a 2nd inverter/charger (Xantrex) and another 16 batteries. Next, we went to diesel generation as we could get diesel delivered, but not propane, and it cost less to run and was believed to last longer. Then it dawned on us (the county said NO) that this wasn't temporary - that is when I got serious and stopped buying used stuff. We went to 48V with the big forklift battery in our signature, and the SMA Sunny Island, and two new generators - that was great we could run all day on 2 hours of generator time. As we've added more solar that number got smaller and smaller, now the generator seldom cranks - just for an equalization charge, or after 3 days of no sun. Of the system I have now I have no regrets, but the first 4 systems were a waste of time.

Atkinson makes several different generator start modules - this one has seen me through 4 different Onan generators. It is set up to start the generator (and stop it) from commands from my SMA Sunny Island Inverter/Charger (I think most quality inverter/chargers are probably capable of this, as are my charge controllers), and also senses the voltage of my main battery and if for some reason my Inverter let my battery languish, will crank up and charge them.

Even an older used Onan or Kohler is light-years better than the Chinese junque most generators sold today are.
 
I have a 12k BTU Mr. Cool DIY heat pump but I don't have enough use to tell you how much it uses over time. I loved the DIY setup, as it's almost impossible to get an HVAC guy to work in a home off the grid (or even drive here) and I didn't want to have to buy a whole bunch of HVAC tools I'd only use once. It came precharged and all I had to do was make the connections.
 
Here’s the photo of the Mr Cool Minisplit heat pump that my girlfriend and I installed. So far, it’s working fine and is so quiet that sometimes I have to step outside to see if the compressor is running.
 
I self-installed a 120V 12000BTU Pioneer mini-split about 4 years ago and have run it every year here in western Washington and it's awesome. At the time is was about $650. Can't even tell its running on the electric bill. It both heats and cools and has a 'dehumidify' setting where it first cools, then heats and repeats the cycle. VERY easy to install. It basically cools the whole 1800 sq foot house and we move the cooled air back to the bedrooms by running the furnace fan. It can keep the whole house cool but struggles to cool it down if its gotten hot inside first. We've used it in up to 90 degree weather which is hot as hades around here.
Here is the newest version, costs $750.
 
I came across a very useful spreadsheet for comparing SEER, EET and other A/C specifications, I think I found it through the forum, but I can't seem to find it now. Does anyone recall what I'm referring to and have the link handy?
 
This unit has an alleged SEER or 38:
7ACBB223-A36A-407A-8628-07823A99049B.jpeg
 
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Any idea of energy consumption for various conditions (do you get varying conditions in south Florida even?)
i have recently installed a classic america 120v 22 seer mini split in my camper.
the area in the graph over 14 oct is the heat pump running, the spike over 16 october is running a small ceramic space heater
approx 500w vs 1000w w a base load around 150-200w
my batteries wont make it through the night running the heat pump, im relying on propane.
this was in missouri w temps going down to 40 degrees
 

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also fyi you can borrow the ac install tools from orielly for free (w deposit)
 
Here’s the photo of the Mr Cool Minisplit heat pump that my girlfriend and I installed. So far, it’s working fine and is so quiet that sometimes I have to step outside to see if the compressor is running.
My girlfriend and I installed another Mr Cool heat pump a few weeks ago. This time, we installed a larger DIY unit - a 220 volt model
23000 btu. The installation went well and it heats nicely. Overall, the instructions are helpful and everything arrived in good shape. This was not a solar installation, but I thought it would be helpful to the readers to know that the quality, at least in this case
- consistent.
 
Earlier this summer, my girlfriend and I installed a Mr Cool Model DIY-12-HP-WMAH-115B, DIY-12-HP-C 12000 btu minisplit heat pump (heats/cools) in my 780 sf, well insulated off-grid cabin in the Ouachita Mountains of western Arkansas.

lit was a fun project and although I have only used it in the heating mode, it has worked very well so far.

Since it has a variable speed compressor, the amperage draw has varied. So far, I’ve seen the amperage draw range from 3 to 11 amps on my Trace SW4024 inverter. This may also include, at times, other items on the system.

My solar array size is 3,725 watts and I have 18 Duracell 105 Ah AGM batteries for storage.

The battery bank is new and so far, all is well. I was a bit concerned about my system drawing too many amps and shutting down, but that has happened only once - today. Murphy’s Law!

In addition to the inverter and battery bank mentioned, I have a Trace T-220 transformer connected to the output of the inverter allowing me to run my well pump and GE GeoSpring 50 gallon water heater.

The job of installing the minisplit was fairly challenging, but certainly doable. The hardest part for me was adding the additional circuit and mounting the holding bracket for the unit.

I’ll try and send a photo of it in a moment. By the way, making the connections with the pre-charged coolant lines was easy.

The unit really seems to do a great job cooling my cabin. So far, I’ve mostly run it during the day and shut it off at night. The cabin stays comfortably cool. I’m glad that I did it. It is super quiet.
Update on my Mr Cool 12000 btu DIY minisplit heat pump.

I’m now using it in heat mode at my off- grid cabin. On cold and sunny days, when I’m producing more solar power than my batteries can accept, I run the heat pump in heat mode all day long.

At first, I was shutting it down at night, to save battery power, but found out that it really didn’t draw much
power at night - as long as it wasn’t particularly cold.

So, it appears that, at least during sunny fall and winter weather, the heat pump is doing its job efficiently and I’m using less propane than before to heat our well-insulated 700 sf cabin.
 
I have seen people use a separate 240V dedicated inverter to run the heat pump. Generally the 240V versions can handle multiple zones...
Good point. I was actually thinking about installing a 240V Mr Cool heat pump, but when I did the estimated load calculation on my 700 sf cabin, it seemed like the unit would have been too big.

Its really rewarding at times to try new projects in an effort to push a solar powered off-grid system to its’ limits. I believe that as the technology continues to evolve, it’ll get even easier and more fun to go off-grid, without giving up many of the luxuries of a conventional home.

I’d like to hear from other members who have “pushed the envelope” too. They may be doing a fun project that I need to try!
 
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