18k or 24k mini split

[ching0n]

I totally agree with you. The point I like to make is that not all mini-spits have the same heating efficiency.
And your unit cools 24K BTU. I didn't look up the curve, but how much does it heat at 0F? It's never been that cold here, but mine would not do very well. (Daikin)

So now we've got to size units for the cooling of our building and then the heating of our building at <whatever traditional low> temps are in the area. That probably makes sense in the midwest, but when I did my install I didn't even think about it.

I learned the hard way. My 2 x 24k units cool 2400 sqft fine in Texas when it's 100 degrees out, but when we hit 25 degrees F, they don't have a chance to keep up, building temps drop into the 50s... Maybe colder, that's as cold as I let it get.

Course, we get about 12 days per year at 32 degrees on average. It's been 7 years since we hit 23 degrees.

Should I have installed 4 units instead to keep up with the <10 days we get below 30 F every year? I think I would still make the same choice.. I just found that I had to add portable propane heaters.

Do your units have a automatic defrost mode when running it in heat mode? I don't know how much frost plays a part in the efficiency rating or if it's all compressor/refrigerant pressure based but it may be possible to improve things installing a drain pan heater.

I suspect (don't quote me) that some of these units are derated because they lack some of these options (defrost, pan heater) so the unit may just shut down to avoid frost blockage.

What other options you have? I'm guessing nat. gas is a no go? Propane can get pricey. I've seen some chicom diesel heaters that vent outside that don't seem too bad cost wise. Even better if you run them on fuel oil.

 

[dcg9381]

Do your units have a automatic defrost mode when running it in heat mode? I don't know how much frost plays a part in the efficiency rating or if it's all compressor/refrigerant pressure based but it may be possible to improve things installing a drain pan heater.

I didn't know drain pan heater was a thing. That's a great idea. Yes,they go into defrost mode (you can tell because they stop producing heat at all) but in the last "great freeze" the defrost mode didn't produce enough heat or wasn't long enough to sufficiently de-ice the unit outside.

What other options you have? I'm guessing nat. gas is a no go? Propane can get pricey. I've seen some chicom diesel heaters that vent outside that don't seem too bad cost wise. Even better if you run them on fuel oil.

We're rural. No utilities at all except for electrical. I added propane space heaters (portable) and they take care of the problem, but as they are ventless you do get moisture. I actually designed the house to have drops for portable propane heaters too and I've been able to heat the entire house on a 30K BTU unit.. Nice option if we have another one of Texas' famous week long power outages.

 

[dcg9381]

you'd be surprised. I dunno what your budget is but I've kind of put all import inverter units in the same basket (except mitsu & fujitsu). Customer/tech support will likely be better for "mr. cool" and they have precharged lines but I'm fairly certain they all come from the same x nubmer of places. Even the Daikin units look the same and are priced as if no longer Japanese (which I suspect they're not).

Family has hyper-heat units in Michigan where it's much colder.. All I know is that those units work a lot better in the cold. This was my first implementation and frankly I really didn't consider heating efficiency. I want people to learn from my mistake.

 

[ching0n]

I didn't know drain pan heater was a thing. That's a great idea. Yes,they go into defrost mode (you can tell because they stop producing heat at all) but in the last "great freeze" the defrost mode didn't produce enough heat or wasn't long enough to sufficiently de-ice the unit outside.

We're rural. No utilities at all except for electrical. I added propane space heaters (portable) and they take care of the problem, but as they are ventless you do get moisture. I actually designed the house to have drops for portable propane heaters too and I've been able to heat the entire house on a 30K BTU unit.. Nice option if we have another one of Texas' famous week long power outages.

They sell drain pan heater kits that may fit a number of units. You'll have to check if your unit's board has the provision for it (sometimes the manual helps here)....If it's going into defrost mode it may be likely that it puts voltage across that output so I'd check that by forcing it into defrost if it allows it.

Also, I don't know where in Texas you are but if you have very dry winters defrost/pan heater may not help at all. This is to literally remove frozen water from the coils and pan so the unit operates in very cold weather. If you never saw water dripping out during defrost mode (you'll hear the refrigerant flow backwards too) then this may be of no help.

 

[FL Guy]

I picked up my "ductless aire" 24k 21 seer for 1450$ from home depot

How big of an area are you cooling with this unit?

 

[racecougar]

How big of an area are you cooling with this unit?

I can't answer for ching0n, but I run a Gree 24K unit in my 1800 sq ft shop (just over 21,500 cubic feet) in climate zone 4A (near St. Louis, MO). The building is very well insulated though.

 

[Highbeam]

I didn't know drain pan heater was a thing. That's a great idea. Yes,they go into defrost mode (you can tell because they stop producing heat at all) but in the last "great freeze" the defrost mode didn't produce enough heat or wasn't long enough to sufficiently de-ice the unit outside.

My Mrcool 24K outside unit has a drain pan heater. It may also have a crankcase heater. Something comes on and makes a small noise(hiss/hum) when it's below freezing if the unit is powered up. I use wood heat mostly so the minisplit is on standby and the engineers decided that it should be somewhat warm while on stand by. Kind of like a block heater on a big diesel genset.

For the defrost cycle the thing just runs backwards and heats the coils with hot compressed refrigerant to melt all of the ice off of the actual coil but the pan heater keeps that melted coil water from freezing back up and allows it to drain away.

The bigger problem is sucking snow into the unit when it's humid out and below freezing. The system has to defrost more often. It senses the need to defrost vs. the old fashioned timed defrost cycle. Despite all of the defrosting, the delivered "Total capacity" is still very good and more efficient than straight electric to very low temperatures.

 

[pcmeiners]

In your case, in Canada SEER ( air conditioning) rating is NOT important, the HSPF (heat rating) is. Due to heavy snow you better get it installed off the ground as are mine in Pennsylvania, also protect against rodents using it as a home. Elevating posts are from Home depot, 4x4 wood post composite covers, filled with concrete ( cut from 24" pieces); this composite post cover is not PVC, which is not strong. Height depends on high level snow height, your minsplit may need to be higher (unless you like digging out your mini during blizzards for exercise ).
For any units your thinking of buying lookup the AHRI certificate, hopefully it gives heat and efficiency rating at multiple temperature.