Alternative heat source, minisplits for real?

DBoon

Minister of Fire
Jan 14, 2009
1,162
Central NY
Just checked electric usage since beginning of October. It looks like the mini splits have probably consumed about 200 to 250 kWh of electricity to heat 1200 square feet of space through 600 degree days. That's about $25 to $30 or so of electricity. My old basic gas service charge was $20/month and I probably would have consumed about 30 therms of gas at about $1/therm, so I'm looking at about half the heating cost so far during these moderate, fall temperatures.
 
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Brian26

Feeling the Heat
Sep 20, 2013
473
Branford, CT
Here is a good graph on how good a mini split can maintain an exact perfect temperature. The air was bone dry (outside dewpoint of 9) here so I switched over to oil to run the whole house humidifier.

Notice the perfectly maintained 67 degrees overnight and then the wild swings of the furnace when it went on around 8am

These things are amazing for running super quiet at only the btus required for the heat loss.
Screenshot_20191201-104041_My AcuRite.jpg
 
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begreen

Mooderator
Staff member
Nov 18, 2005
81,123
South Puget Sound, WA
That hysteresis is pretty normal when taking a space up 5+ degrees, even for a mini-split. The oil burner heated up the place quickly and shut off as the thermostat was satisfied. But the actual room mass and contents had not warmed up fully, just the air. Once all the chairs, sofas, walls, floors, etc. are up to temp, those temperature swings should be much less, even with the oil burner running, depending on the swing setting of the thermostat.
 

Brian26

Feeling the Heat
Sep 20, 2013
473
Branford, CT
I ran both my mini splits for pretty much the entire month of November set to 70. The results were impressive considering Nov was a really cold month here. I did have a fire or two but have been finding that mini splits do very little to indoor winter humidity so I have been having less fires. Every time I have a good hot fire its crazy how fast my indoor humidity drops. My wife is very sensitive to dry air.

I monitored the electric consumption of both my 12k splits. They average around 6 kwhs a day it seems and combined consumption was 448 kwhs. I have solar panels but at CTs electric rates of .20 a kWh it would have cost $89.60 for the month. The national average is like half that so many would cut that in half. Seems like a bargain for leaving the tstat at 70 for the month.

Screenshot_20191211-102754_Monitor.jpg
 
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Alexx

New Member
Dec 31, 2019
8
Linwood KS
Mini split does not have to be a ceiling cassette or a head high on the wall. They make indoor sections that sit near the floor-makes sense to me if the primary objective is heat and they aren’t in my line of sight.

2 ton conventional ACs or Heat pumps use 12 gage wire circuits too.
 

Brian26

Feeling the Heat
Sep 20, 2013
473
Branford, CT
Mini split does not have to be a ceiling cassette or a head high on the wall. They make indoor sections that sit near the floor-makes sense to me if the primary objective is heat and they aren’t in my line of sight.

2 ton conventional ACs or Heat pumps use 12 gage wire circuits too.
I have a floor console unit. Its superior to my wall unit downstairs in heating. The big advantage is the return air sensor is measuring the air a foot or 2 above the floor. Wall units are measuring the much warmer air temperature just below the ceiling height. The floor console units are also drawing the air in from the floor. The performance is stunning. The air outlet can be set for top or bottom or both. It puts out great warmth across the floor. Here is a flir shot of the unit in operation.

2nd one is the air sensor located just above the string on the door.
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maple1

Minister of Fire
Sep 15, 2011
10,351
Nova Scotia
Yup. Another +1 here for floor mount units, one of our 2 Daikins is floor mount. I think our high mounted wall mount unit certainly works well, but it makes more slight air currents that you might sometimes end up sitting in and can feel a bit chilly even if they really aren't.

Some also have mounted their wall units down low for better heating feel.
 

Brian26

Feeling the Heat
Sep 20, 2013
473
Branford, CT
Yup. Another +1 here for floor mount units, one of our 2 Daikins is floor mount. I think our high mounted wall mount unit certainly works well, but it makes more slight air currents that you might sometimes end up sitting in and can feel a bit chilly even if they really aren't.

Some also have mounted their wall units down low for better heating feel.
Its also pretty amazing how good they can regulate a constant near perfect temp. I have a return air and supply temp sensor on mine. It just locks right on the setpoint and maintains it perfectly.

Here is the supply/return temps when I had the unit turn on at midnight set to 69 degrees.

Screenshot_20200207-030556_My AcuRite.jpg Screenshot_20200207-030556_My AcuRite.jpg Screenshot_20200207-094008_My AcuRite.jpg Screenshot_20200207-094008_My AcuRite.jpg
 
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Seasoned Oak

Minister of Fire
Oct 17, 2008
6,748
Eastern Central PA

peakbagger

Minister of Fire
Jul 11, 2008
5,009
Northern NH
One thing for folks with pets to consider. A floor mount is far more likely to collect per hair and also for some reason is also a popular spot for cats to perch on (No clue why but then again we are talking about cats ;) ). The units have filters that can be cleaned so it just means upping the maintenance. I expect the recessed ceiling unit is probably the safest option from a pet hair perspective. Somewhere I ran into a comment that a cat had decided that the top of standard high mounted wall unit was a perfect perch to survey its domain. The system was not working well so a tech was called. The tech found a unit that barely would flow any air. He opened up the case and the filters were packed solid with fur.

For those who are tenants of a house owned by a cat, they may want to consider making the top of these units per unfriendly ( Pigeon Spikes ?) and keep an eye on the fllters.
 

Brian26

Feeling the Heat
Sep 20, 2013
473
Branford, CT
The floor units are 10 times easier to clean and take apart. The coil is completely exposed. The coil can also be easily be moved out of the way to access the fan. The refrigerant lines dont need to be removed. Wall units require special cleaning hoods and the flong fan wheel can be a nightmare to acess and clean. The floor units use an actual round fan blade.

A ceiling unit would be great for cooling but in heating mode it would be drawing in the hottest air at the ceiling level. All the cold air is going to sink to floor level. The colder the air intake the efficiency goes way up. I have a wall unit as well and the floor unit blows it away in heating mode. The floor level is way warmer than where the wall unit is.

On my house central air all the returns were at the floor level. I installed new inlets with dampers at the top of the wall. The difference in cooling was staggering as I was now drawing in the hottest air. In heating mode I use the floor returns. The results were impressive.

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Seasoned Oak

Minister of Fire
Oct 17, 2008
6,748
Eastern Central PA
I agree efficiency wise the floor units would work better for heat , but i go out of my way to keep from cluttering the walls with appliances if possible The best case scenario (for me)is a heating and cooling system you cant easily see. For hydronic systems i like the cabinet kick panel heat exchanger.
 

peakbagger

Minister of Fire
Jul 11, 2008
5,009
Northern NH
Off on a tangent are John Siegenthaler's radiant heating and cooling walls and ceilings where there is no evidence of any heating or cooling system. They line up well with the cold climate air to water units (if and when any of the big boys decide to start selling existing product into the US market). I will gladly run glycol around but far less comfortable moving refrigerant. I will agree the cooling aspect is scary as dewpoint issues can cause mold but many commercial studies show that if its a tight building with no vapor sources, radiant cooling can work. The cooling aspect is definitely "bleeding edge" for a home system but perfect for wood systems with storage as the supply temps for heating are about as low as anyone can get meaning far more effective storage capacity.
 

Highbeam

Minister of Fire
Dec 28, 2006
16,835
Mt. Rainier Foothills, WA
Warning, opinions to follow! This is highly subjective stuff.

Those ceiling cassettes look just like the ceiling mounted AC units in RV trailers. Like actual trailer trash. Further, their efficiency was way lower and cost much higher than the wall units.

The "best" looking units are the ducted ones. They can be hidden in a closet, attic, or below the floor and all that you see is a conventional HVAC grill.
 

Alexx

New Member
Dec 31, 2019
8
Linwood KS
The ceiling units can look good, but i think if you check the efficiancys the different head units have differences. Any sort of duct work changes things quickly. Might not matter much but those wall units are the most efficient and one outdoor unit to one head is the most efficient set up. Those multi head systems also leave some things to be desired, redundancy, efficieny, simplicity, sound.
 
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Ashful

Minister of Fire
Mar 7, 2012
15,404
Philadelphia
It used to be those Mitsubishi ceiling units were cooling only, no heat. Have they changed them to also do heating?
 

peakbagger

Minister of Fire
Jul 11, 2008
5,009
Northern NH
I review various proposals for VRF (Variable Refrigerant Flow) based systems on occasion. The household multihead systems are usually a simple VRF design. On the commercial systems, the air handlers have a coil and drain in them so they can go either heating or cooling and are sold in lots of different configurations including the low mounts, the high mounts, inline duct mounts and other configurations. They typically are custom systems and need to be engineered. The original high ceiling mounts were optimized for predominantly cooling as they came out of Japan where the population is concentrated in warmer regions of the country. A typical Japanese home is cramped so a high mount is a better fit than a low mount.

An engineered system typically means its going to be higher cost to install and for most people on a budget mini splits are already too expensive. Sure if someone is building or remodeling a new expensive home where cost is less of an object, there probably are a lot of alternatives but to someone with a 100K home that have a tough time scraping up money to replace a window unit so they dont broil in the summer, a 3 K minisplit is already a tough sell. My guess is there is premium for even the low mount unit and definitely an install premium for a ceiling unit. There is lot of competition starting to pop up on commodity minisplit installs so I expect some dealers are differentiating themselves by selling premium offerings like multiheads and alternative indoor heads. They make most of their money on manpower so a complex install requires more manpower and makes more profit. I expect if you look at $ per BTU produced the cost per BTU for complex system is higher on unit basis.
 

Brian26

Feeling the Heat
Sep 20, 2013
473
Branford, CT
If you know how to install one a single head unit is pretty much a cheap disposable appliance in my opinion and its like that in most of the world. Costco and Walmart sell them for a couple hundred bucks in Mexico. I read it cost $50-100 there to have one installed.

My Midea 12k Hyperheat was $1k shipped to my house and it came in a Midea Carrier North America box with both Carrier and Midea stickers you put on yourself. If it blows up I can still buy 3 more and be ahead of a professional install.

I have noticed alot of off brand names around here so I suspect someone is doing these on the side for cheap.
 
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peakbagger

Minister of Fire
Jul 11, 2008
5,009
Northern NH
If and when EPA gets serious again abut HFCs I expect they will tighten up on who can sell and install. Ozone depleting chemicals were tracking downwards for quite few years but have bumped up of late as there is lot or third world use and abuse so CFCs and HCFCs. I expect most folks just vent the gas when they remove them compated to recycling it.

Odds are the next generations of these will use propane for refrigerant.