Split air-conditioner in shop...

[Chris09]

Looking on Amazon there is a Senville brand 18,000 single zone mini split for $1,300.00 wondering if anyone has used that brand. A lot cheaper than anything I can get locally.
[added] Senville Manual shows that it can control to 8C in some sort of low limit mode so maybe that's the 8C that I was guessing around. It seems to say you can leave it off, and if it senses 8C, it will start up.
Charts appear to show that for R410A, in an outdoor air condition of -8.33C DB, and -10.56 WB, Port Pressure [which I have to assume is Suction Pressure] will be 302, 339 and 362 psi at in indoor [air entering the coil] at 55, 65 and 75F respectively. Assuming zero pressure drop those pressures translate to about 34C, 38.5C and 41.35C SST or mean evaporator temperatures. The chart, I assume is a COP chart, which indicates a COP ratings of 1.95, 2.25 and 2.35 at 55, 65 and 75F.
Similar COP with their R32 charts. And not much reduction in performance at -17C DB and -19WB.
Two kilowatts [or more] for the price of one down to about -10C outside is pretty good.

 

[Chris09]

Looking further into the Senville manual, there are similar performance charts for R22 which I guess might have been used in these units before 410A.
Jumping right down to the corresponding COP chart for that refrigerant, you have 1.25 to 1.40 for the same [-8.33C or 17F] drybulb outdoor air temperature.
That is remarkable. I had no idea how R410A changed the heat pump world [for colder climates].
Fully reviewing the 190 pages, I'll say this of it, it's like a lot of boiler manuals, lots of good information combined with brilliant obfuscation or outright absence of what you really need or want to know; the units of pressure and temperature are convoluted. The charts below the tables must be COP charts, but are not specifically labelled as such [I guess they're COP charts], and there are no corresponding heating values [what a surprise, how many times have I not seen that].
I seem to recall in one separate document that this or another heat pump brand had a nominal 18,000 btu/hr rating [which is cooling mode] but in heating mode had a 16,000 to 4,000 btu/hr heating capacity. What I'm unable to find in google land, is a simple direct comparison of heat pump output in btu/hr for various manufacturers. [Lie, I just did it now, but I knew it would dazzle me with stupid distracting bs].
So it appears that at 17F outdoor air temperature, a nominally rated 18,000 btu/hr heat pump will run the outdoor fan at high speed, run the compressor at high speed [to achieve maximum pressure and SDT] and then trim the indoor fan motor speed to achieve a warm discharge air temperature. Could be wrong, but I'm guessing you're only getting about 4,000 btu/hr.
...which is like a kilowatt

 

[ST1100Y]

I had no idea how R410A changed the heat pump world [for colder climates].

With R32 you can transfer more energy with even less charge then R410A...
Sure, from a pure technical POV were R12 & R22 brilliant, stable, reliable "safety refrigerants"... seen environmentally not...
R410A cranked the COP noticeable, R32 even more... lower charges, smaller HEX volumes, narrower piping diameters, lower energy consumption... and lower losses at long pipe runs...
(one can build VRF systems for office and hotel buildings with a total pipe run of up to 1000 meters and a head/elevation of up to 90 meters... and no worries about oil transport, the lubricants have foam additives, enabling safe oil retrieval even during minimum compressor revolutions & gas flow, thus no "oil siphons" needed...)

To stay with your 18,000 BTU single unit, I attached the performance chart of a Toshiba Seiya R32 series residential split type air2air model (of course in kW and °C...)
Mind that they all are Inverters, variable speed rotary type compressors with PMV expansion valves... thus operating in part-load the majority of the time, so EER & COP increase even more after the first cooling down or heating up of the space due to the then quasi "oversized" heat-exchangers...

Over here, with our brick/concrete build houses, radiators and floor heating systems, with constant raising energy costs and amplified by the never-ending CO² propaganda/debate, air2water heat-pumps are a big thing now... the outdoor units absorbs energy from the ambient air (+ the absorbed electrical energy) and warms your heating system as well as your domestic hot water tank...

 

[Chris09]

That must translate to some of these new refrigerants having a greater NRE, better miscibility or maybe just higher velocities sweeping the oil back, and greater vapor density, things I haven't given much thought to in almost forty years.
Will have to look up R32.

 

[ST1100Y]

...better miscibility or maybe just higher velocities sweeping the oil back...

Those thick, almost honey like refrigeration oils came with the Inverter rotary compressors (requiring higher viscosity) appearing on the market... (80ies, still R22...)
At first I cursed over the bubbling oil spills every time when detaching my gauge manifold hoses, but soon realized the why and simply got me quick couplings for the check valves...
Those oils saturate with refrigerant and change of pressure will cause them to foam like a carbonated drink...
On fix speed machines the oil-film is dragged along the pipe walls by the refrigerant flow-speed (minimum 4m/sec or 787ft/minute), requiring an oil trap about every 2.5m/8ft vertical...
In an Inverter systems such flow speeds are simply not given, hence the solution with the "oil foam column" in the lines...

 

[Chris09]

So the Toshiba unit in heating mode, at -10C / 17F using the nominal capacity columns, the compressor will use 1.15 kW and transfer 3.20 kW [2.05 from the cold air plus 1.15 from the compressor] into the indoor coil. COP is 2.79
That's just about 11,000 btu/hr which is very good.
I've got a 68,000 btu/hr furnace for my upstairs and I clocked the run time during a -10C period and it runs 33% of the time on low speed, which according to the rating plate 36,000 btu/hr.
... So it still wouldn't work...

 

[ST1100Y]

So the Toshiba unit in heating mode, at -10C / 17F using the nominal capacity columns, the compressor will use 1.15 kW and transfer 3.20 kW [2.05 from the cold air plus 1.15 from the compressor] into the indoor coil. COP is 2.79
That's just about 11,000 btu/hr which is very good.
I've got a 68,000 btu/hr furnace for my upstairs and I clocked the run time during a -10C period and it runs 33% of the time on low speed, which according to the rating plate 36,000 btu/hr.
... So it still wouldn't work...

So your home is requiring 10kW @ -10°C ... seems quite high but I've no idea about the actual living space nor the thermal insulation class there...
Here most residential homes get along with 6~8kW air-to-water heat-pump models, up to 16kW are avail... (beyond that are commercial models... outrageous price range for home owners)

For my small shop (~35m²/380sq ft) the mini split does its job, that 8°C/46°F frost protect is a genius feature and way more efficient then trying to achieve such with standard electric panels (even the highly advertised infra-red panels are just electric heaters with ~98% efficiency...), the utility bills would kill me...

 

[Chris09]

Actually, it's only my upstairs that requires the 10kW, I've also got a furnace that serves the basement, so, it just gets worse.
To your second point, there is no living space we're hoarders.
And don't get me started on R values, every time I look in a wall [still, after 22 years] I find more construction waste that has to go into the trailer.
But the good thing is pretty soon we're all gonna be Americans and everything will work out.
400 sq ft for a ton and a half suggests to me that Vienna not only doesn't wait for me, but is not the place I thought it was; I haven't used an A/C rule of thumb since the space shuttle exploded, but I guess the world has warmed up.
Back then, the rule of thumb was 1 ton for every four hundred square feet, and even that in practice was too much for everything from about Calgary up.
I see the proportionate increase once you get into domestic water; I'm gonna throw a dart and say you don't have evil natural gas there.
When demand heaters became sexy over here, the firing rates drove changes from the meter in the form of either building code changes or 2 psi regs; I could never get my head around the BC Safety Authority here allowing gas supplies to these idiodic demand heaters [let alone fireplaces and ranges] fireplaces going to concealled regs... and concealed regs with pressure limiting orifices. The thing about pressure limiting orifices is that when the diaphram eventually leaks, the rate of leakage into the concealed space would be limited.
So, I guess.. the fire is... delayed?
What do I know... I'm just a dumb tin basher

 

[SupraSabre]

I was talking to one of my neighbors today about them. He has one in his garage and keeps the garage at 60F, during the winter. And makes it comfortable in Summer.

Chris often complains about her sewing room being too cold during the winter and too hot during the summer. And anytime the boys spend a night, they are always too hot in the spare room, so they grab all the fans and have them running at full blast! I think I would need two double units. One for Chris's sewing room and the guest room and I think a double unit for my 1,100 st garage. With it so long, one unit at each end would keep the garage comfy year round.

It'll be late this spring for me to look into them.

 

[Chris09]

... and the wheels on the bus, go round and round.

 

[Larry Fine]

... and the wheels on the bus, go round and round.

Or: ... and the green grass grows all around, all around, ...

 

[Chris09]

... and the foaming, scrapes the oil off the walls and brings it back.

 

[Chris09]

Cooling is a big deal now, in the US some of these condensing temperatures and performances are consequential, if I might say. At my old age, I hate being involved in imaginging that AC and everything else might be life safety systems. But they are.

 

[Chris09]

[deleted] Getting back on thread topic.
Looking at how practical are some and maybe not other air source heat pumps could be in colder regions.
My opinion is generally poor and unconvinced of their practicality from seeing the disappointment of owners who learn that they're substantially relying on electric heat because the units can only run for a sliver of time, saving them about as much energy as the compressor crankcase heater uses to keep the oil from migrating into the compressor during the long and cold off cycle.
But that was a long time ago, reciprocating compressors, R22 and I'm pretty sure [in Alberta at least] expensive electricity relative to natural gas.
A little digression but relative, I put an electric make up air unit in a restaurant in Grande Prarie and they couldn't afford to run it. Couldn't justify the power. They also didn't pay us, sometimes it's good to be an employee.
There's absolutely no doubt in my mind that these things are terrific, here in the lower mainland. I work in buildings where many of these now old R410A systems have been running trouble free for fifteen years. Whole different world. Before the even newer systems as pointed out.
So, before believing [again], how much heat is out there in the cold, and how much can I get.
I did a bit of math off of the psychrometric chart. The chart only goes down to -10F drybulb, where at dewpoint, it indicates zero enthalpy, essentially no practicable heat. At least mine does, I'm sure there must be new ones now.
I've measured a few temperature differences across some outdoor units and I like 10F, some higher, some lower but will keep surveying.
Going by the chart, and we're at sea level, I picked our 17F [-8.33C] entering air at 50% as a first example. Air leaving drops to 7F, about 80% in the absence of any latent cooling, goes from 5 btu/lb to about 2.5 btu/lb, and the density drops from 12.05 to about 11.75 cfm/lb.
This works out to be about 78.33 cfm of outdoor airflow to pick up 1,000 btu, or 940 cfm per ton.
Going right to the bitter end of the chart, and assuming the same 2.5 btu/lb, the air would be entering the coil, at 7F[-14C] and 50% RH [selected], air would be leaving at -2F, about 40%RH, and the density would drop to maybe 11.5 cfm/lb.
This works out to about 76.67 cfm of flow to pick up 1,000 btu, or 920 cfm/ton.
If these numbers are right, there's a lot of heat out there it just becomes a matter of knowing which pumps can bring it in and which are more like air conditioners.

 

[Chris09]

Looking at the Toshiba Seiya RAS-18E2KVG-E in heating mode at nominal operation from the chart attached.
Close to a linear 4.1 to 3.5 kw from 5.5C down to - 8C, then 3.5kw to 2.5kw linear from -8C down to -15C.

The Samsung Windfree 3.0e AR18CSFCMWKXCV in heating mode [from the chart].
All values are for 72F Indoor Temperature, which I presume is air entering.
OAT 23F / 18.0 MBTU / 2.2 kW; OAT 14F / 16.3 MBTU / 2.1 kW; OAT 5F 13.8 MBTU / 2.0 kW; OAT 0F / 12.0 MBTU / 1.9 kW; OAT -5F / 9.8 MBTU / 1.7 kW.

Getting back to the Toshiba heating chart, the coldest outdoor air temperature listed is -15C [5F], which indicates a capacity of 2.48 kW[8,469 BTU/HR], 1.05 kW of power, and a COP of 2.35

To compare, it looks like this particular Samsung, which is not their Max Heat model, is rated lower for heating than the Toshiba, -5F compared to +5F.

Could be some errors in here, lots of flipping between screens and converting units [the BB gets stuck, sometimes for days...], and it doesn't seem right, but it appears that.

At 5F Outdoor Air Temperature, The Toshiba [with the R32 Refrigerant] will provide 8,460 BTU/HR of heating for 2.0 kW of power input,
while the Samsung [with R410A Refrigerant] will provide 13,800 BTU/HR of heating for 2.1 kW

The toshiba document is 44Meg and probably too large to upload here but it is at RAC+for+North+America+(R410A+60Hz+HP)_Ver.3.1_231121A