Hi all! Last year I finished up the solar and batteries project. Switched the tank water heater out for an electric one. This year's project is to minimize propane usage in the furnace for heating! So I'm hoping you can help point me in the right direction. First off, either way I'm going to DIY as much of it as possible. I like to understand completely and be able to adjust/repair my own systems as much as possible. Second, this is for our cottage in Northern Michigan. The 1st goal is to add air conditioning for hotter summer days. Second goal is to electrify heating in the spring and fall. We are rarely ever here in the harshest winter months, but I'll leave the propane furnace and tank in place just in case. The home is about 1200 sq ft. Poorly insulated. Built in 1870s?. The furnace feeds into duct work that is probably a bit leaky. I'm looking at an open loop geothermal system for the simplicity. Although we have about 10 acres, and it's sandy soil with a fairly high water table here. So I figured I'd start out with open loop and then drill bore holes and convert to closed loop if the open loop becomes and issue. Currently looking at the water furnace 500r11 ndz026. Any idea on price there? Although I need to confirm manual J calculations. I used Coolcalc.com and input info in as best as I could. I don't know much about mini splits. Not sure if there would be any cost savings there with the 26% tax credit and the fact that I'm DIYing. I do like the idea of skipping the duct work altogether and that I can put an indoor unit in different sections of the house and run them independently. Anyone still with me? Too long winded? 😂 I appreciate any input from folks with more experience then me.

Ground-source heat pump systems (often mistakenly called Geothermal) are nearly always a losing proposition in the lower 48 States for a residence less than about 10,000 sf...negative Return on Investment (ROI). So I would recommend a ductless minisplit air-source system for your situation. You should also improve your insulation and sealing, and you should then accomplish an accurate Manual J so as to properly size system.

I agree with above.....I had a unit go bad after 3 years of use. There just aren't enough sales in geo units to get them perfected in my mind and may components to go bad. Minisplits are high volume sellers around the world.

My focus was more on the negative ROI. But I fully agree that complexity and poor design is a problem too. There is no shortage of stories about people spending a fortune on these ground-source heat pump systems and never getting them to operate properly or even at all.

Isnt there a limitation on the mini splits or heat pumps? As they wont work in colder regions? We installed geothermal (thats what everyone calls it, even if it is a ground source heat pump) and have been very happy with it. We live in NY and the mini splits, or air to air heat pumps, whatever they are called, wouldn't suffice for our cold temps (or so I was told).

I think on the very cold days I myself would just burn some wood to help out. I am in the process of adding a couple mini splits because I have excess solar to burn and they size good to work with my inverter.

Mini splits (an air-source heat pump system) will "work" at all temps, but their heating efficiency decreases as the outdoor air temp decreases. Ground-source heat pump systems behave exactly the same way except ground temp doesn't vary as much or get as cold as outdoor temp so they tend to be more efficient.

Yes, mini splits are air-source to air heat pumps. You can also get air-source to water heat pumps for hydronic radiant floor heating. So called Geothermal are ground-source heat pumps. Real Geothermal are just simple pumps that source existing natural hot water from a hot spring like you find in Yellowstone.

At what point can mini splits work for the normal house?

I've been looking for a house in TN and was surprised that they still use propane and natural gas. I'd have thougt that was far south enough.

PS is "mini-split" still the proper tern for these? even if they dont use the wall mounted air handler? And rather are a central unit supplying ductwork?

"At what point can mini splits work for the normal house?" Not sure exactly what you are referring to? Mini splits can cool and heat buildings at any location if sized properly. Again, efficiency varies with temp and should be considered too.

Air-source to air heat pump systems use compressor, condenser, expansion valve and evaporator components and can either utilize duct work or be ductless.

Ductless air-source to air heat pump systems "split" their system components into two types of installed units that are connected by refrigerant lines. Ductless air-source to air heat pump systems use an outdoor compressor/condenser unit and also use "mini" indoor air-handling evaporator unit(s). Hence they are called mini splits.

I have 2 questions basically.... Do Air to Air heat pumps, and Ductless mini-splits use the same technology to create heat and AC? I know the distribution system is different. And why does no one where I am from in NY, or where I am moving to in East TN, use these all electric heat pumps? In NY I have been told it gets too cold for them to work rihgt. In TN I expected to see them, but people still use Nat Gas and Propane to heat, even with much less heating loads and warmer temps.

"Do Air to Air heat pumps, and Ductless mini-splits use the same technology to create heat and AC?" Yes, exactly the same technology...a refrigeration cycle using a compressor, a condenser, an expansion valve and an evaporator. A reversing valve is also used to allow moving heat either into or out of the living space as required for either heating or cooling the living space. Ground-source heat pump systems add the complexity and expense of also needing to pump water in long lengths of pipe buried in the ground. This explains this subject fairly well:

https://home.howstuffworks.com/home-improvement/heating-and-cooling/heat-pump.htm

"And why does no one where I am from in NY, or where I am moving to in East TN, use these all electric heat pumps?" It is difficult to know why anyone does what they do... Like most things, many people lack the critical thinking skills necessary to make the best decisions. And then there are also people happy to use this deficiency for their personal agenda advantage via propaganda and other miss-information. The intelligent thing to do when selecting a heat source is to carefully consider ROI by determining and accounting for acquisition cost and operational cost at your location as I previously explained in great detail here:

https://www.greenbuildingtalk.com/Forums/tabid/53/aff/12/aft/86467/afv/topic/Default.aspx

We use a low acquisition cost electric boiler (100% conversion efficiency but only a 1.0 COP compared to say mini split at 3.5 COP) expressly designed for hydronic radiant floor heating for most of our heating BTUs which costs us about $30 per month to heat our 4000 sf. We also use a wood-fired masonry heater as desired or when it is very cold outside...we have an ACCA Manual J 26F 99% Outdoor Design Temp. But we also have an energy efficient passive solar cooled/heated home...which is always the best first step in this design process. Again, all of this was previously explained in great detail.

Thank you for taking the time not only respond to me, but to the whole forum at large. its truly a help for those novices like me, who truly do want to make educated decisions, but struggle to find expert info. So my existing house for example, we installed "geothermal". I was told the Manual J calculation is 54,600 Btuh heat loss @ -9 degrees OAT. Would an air-to-air or air-to-water (we have in floor heat) truly have worked in this scenario?!?!? The geothermal was expensive, but after tax credits it was similar in cost to buying a propane powered system. NY has/had very good credits on top of federal credits. We have been very happy with the system. Our bill has never been more than $250 for a month and we heat 4000sf (including walk out basement)

You are most welcome! Always happy to help...or at least try to help...

How well a mini split will operate in extremely cold climates really depends on the brand and model of mini split. Here's one that operates at a decent COP down to -15F.

https://www.fujitsu-general.com/us/residential/benefits/year-round-comfort.html#:~:text=Fujitsu%20General's%20line%20of%20mini,down%20to%20%2D15%C2%B0F.

Most mini splits will operate down to any temp because they turn on an electric heater, but this drops the COP to 1.0 (100% conversion efficiency) instead of say the much higher 3.5 COP it may have performed when the temp was 40F. It is important to determine the COP range of the specific mini split in regard to your local climate.

Also keep in mind that most of the time the temp won't be this cold and the mini split will perform very well.

Have you heard much about these units? https://www.arcticheatpumps.com/cold-climate-heat-pump-overview.html

Also, with your Masonry Heater, do you have a hydronic heating loop installed? I'd love to have a setup like that, where running a wood stove or similar. heats a storage tank of water, then heats your slab lots or mass and long reload times.

Yes, I am aware of that unit but we don't have any first-hand experience with it. We also tend to avoid recommending one brand over another. I recommend taking the time to research and seeing how actual users rate them...so basically what you are doing!

No, we don't heat water with our masonry heater. We have found that just firing it for about 60 minutes every other day heats all the interior thermal mass including our hydronic radiant concrete slab floors very nicely for about 48 hours. This works very well for us because we have lots of interior thermal mass, we have a very energy efficient building envelope and our masonry heater is in the center of an open space floor plan. Since masonry heaters are only fired for a very short time, I don't think they would work very well as a heat source for hydronic radiant floor heating. I think a wood-fired boiler in an out-building might be a better solution. However, we do have an acquaintance who did use their masonry heater to heat water in a storage tank below their home to reduce domestic hot water energy requirements:

http://mbryner.fatcow.com/docbryner/mossy_hollow/Thermal_Storage.html

I hope you find this useful.