DC powered Mini Split Air Conditioning system

[RichP]

Hello,

I picked up a used (barely used) generic brand Mini Split air conditioning system for cheap (1 ton cooling), that takes DC input.

The label on Compressor portion of the Air Conditioning Unit says:
Rated Volatge: DC 48V
Cooling Capacity 12000 (2000-13500) BTU
Rated Input Power (Cooling) 850 (100-13000) W

I have some Kyocera KC158G PV Modules. The specs on these are:

Max Power: 158W
Max Power Voltage: 23.2 Volts
Max Power Current: 6.82 Amps
Open Circuit Voltage: 28.9 Volts
Short-Circuit Current: 7.58 Amps

I’m interesting in powering this unit with the PV modules directly.

It seems like I would have a 2S3P arrangement: 2 in series (23.2VX2=46.4V), and 3 in parallel (850W input power required / (158 W X 2 ) = 2.7)

I realize I'm falling short of the input voltage by 1.6 (48-46.4 ), but I'm guessing that might be negligible as it is 97% (46.4/48) of the input voltage.

Would love to hear your thoughts about this project. I have never hooked up anything solar before, but have a background in EE /physics in college classes with lab work, so understand enough to possibly know if I am going to kill myself, and of coarse the home repair projects wiring things up.

Would love to have your opinions here on this project.

Thanks in advance.

 

[MisterSandals]

I’m interesting in powering this unit with the PV modules directly.

Not a chance. That kind of load put on the panels will drop the voltage by a LOT. And, the surge current that would require would put all but a beastly battery bank on its knees if not face.

 

[MisterSandals]

Please don't misunderstand my previous post, I've been banging the drums for DC split mini systems for the folks that have been pursuing this for RV's, vans, storage containers... have not seen many good installs, most are AC run thru an inverter.

I'd love to see you get a DC system going. I'm just pretty certain it would require a 48v battery bank, and not of the wimpy variety.

 

[RichP]

Not a chance. That kind of load put on the panels will drop the voltage by a LOT. And, the surge current that would require would put all but a beastly battery bank on its knees if not face.

Thanks for the response. I can add panels in parallel ( have quite a few). I have read that the DC Inverter Air Conditioning units have substantially less surge current then standards Air conditioning compressors.

 

[gnubie]

Any chance of posting the model of the aircon? As MisterSandals already said the unit will likely pull the panels too far off Vmp . With the model of the unit we could at least work out if it's just a dumb hard start compressor style or a soft start with the compressor actually being a small 3 phase motor run off a VFD-like controller.

never mind, thought that 2nd image was the specs for the panels

 

[MisterSandals]

We have an HVAC professional and solar expert for such things:

Summoning the spirit and wisdom of @Supervstech

 

[RichP]

I added the Panel Spec to this post if that helps.
The generic Airconditioner is KFR-35W/BPDC48V-A1

 

[gnubie]

That AC pops up on alibaba when I Google it. Consumption tops out at around 1500 watts when heating, but nothing about how it drives the compressor unfortunately but it is touted as a 'solar powered air conditioner' so you'd hope it's soft start. The catch with running off panels alone is that you must always be able to produce at least as much electricity as the unit demands. That means potentially at least 1500 watts when running. Most of the time your panels will not be producing their paper ratings, 158 watts so you are reasonably going to need more than 10, likely 15 when the sun is perpendicular to them just to cover 1500 watts. As the sun moves off angle, the number of panels increases.

Now maybe I've misread things when you said off PV modules directly and you really plan on having a battery in there. If that's the case and given the AC won't always be running full tilt you could store enough power in the battery to cover the peak demand of the unit.

This still doesn't consider starting current, that's still to be answered.

 

[Dzl]

Why do you want to power it from the panels directly? What is your goal? It may or may not be possible and/or practical to do so (I'm strongly leanign towards not practical/possible), but it may be possible to accomplish the same goal in a different way.

 

[Supervstech]

Minisplit tech is great, there are several models out there that run with PV in mind, 1300 summer peak wattage, and 1500 winter peak wattage needed... I would want a battery bank, 200Ah to be certain the unit can perform... plus, running at night is kinda needed.

could you run it from panels directly? Yes. Especially if you have tracking panels. But without tracking, you are going to need 3 or 4KW of panels to get there.
another thing you dont know is max voltage... 46 is your VMP... of 28.9 gives you a max of 57.8V, and that may be outside the winding voltage, not to mention what voltage in cold weather with the system idle could get.

 

[RichP]

That AC pops up on alibaba when I Google it. Consumption tops out at around 1500 watts when heating, but nothing about how it drives the compressor unfortunately but it is touted as a 'solar powered air conditioner' so you'd hope it's soft start. The catch with running off panels alone is that you must always be able to produce at least as much electricity as the unit demands. That means potentially at least 1500 watts when running. Most of the time your panels will not be producing their paper ratings, 158 watts so you are reasonably going to need more than 10, likely 15 when the sun is perpendicular to them just to cover 1500 watts. As the sun moves off angle, the number of panels increases.

Now maybe I've misread things when you said off PV modules directly and you really plan on having a battery in there. If that's the case and given the AC won't always be running full tilt you could store enough power in the battery to cover the peak demand of the unit.

This still doesn't consider starting current, that's still to be answered.

Thanks for your input. I like to try to use what I have on hand, and I don't have batteries, but have about 40 unused Kyocera 158 Watt panels. My first attempt at this would be to do this without batteries. I live in the Phoenix, Arizona area, so most of the electrical need in the summer is for cooling. I like the idea of positioning the panels such that they receive the greatest solar radiation during the greatest cooling demand (late afternoon). Appreciate the input.

 

[RichP]

That AC pops up on alibaba when I Google it. Consumption tops out at around 1500 watts when heating, but nothing about how it drives the compressor unfortunately but it is touted as a 'solar powered air conditioner' so you'd hope it's soft start. The catch with running off panels alone is that you must always be able to produce at least as much electricity as the unit demands. That means potentially at least 1500 watts when running. Most of the time your panels will not be producing their paper ratings, 158 watts so you are reasonably going to need more than 10, likely 15 when the sun is perpendicular to them just to cover 1500 watts. As the sun moves off angle, the number of panels increases.

Now maybe I've misread things when you said off PV modules directly and you really plan on having a battery in there. If that's the case and given the AC won't always be running full tilt you could store enough power in the battery to cover the peak demand of the unit.

This still doesn't consider starting current, that's still to be answered.

Thanks for looking that up. I just did that for the first time last night, and learned that it can accept between 48 and 60 volts. The power input says 850(190-1250). I don't know if this is the right interpretation, but is it right to interpret 850(190-1250) as average (min-max). Therefore, the average power consumption is 850W, minimum 190W, and max 1250W. I'm wondering if 1250W is the surge power needed to kick the compressor on. I'm wondering what the unit does when its power requirements are not met by the input. Is it designed to operate on the max power input, or will it blow a fuse? Not sure. And I can't find a manual online. I might trying to email the manufacturer, I'm sure they'll be interested in corresponding, as they would love to sell more of these units.

 

[RichP]

Please don't misunderstand my previous post, I've been banging the drums for DC split mini systems for the folks that have been pursuing this for RV's, vans, storage containers... have not seen many good installs, most are AC run thru an inverter.

I'd love to see you get a DC system going. I'm just pretty certain it would require a 48v battery bank, and not of the wimpy variety.

I love people being blunt! I would love to see if I can make this work. I have a bunch of panels in the garage, no batteries, and this Mini split. Trying to see if I can save some electricity this summer in hellish Phoenix Arizona. I also like the idea of seeing what is the minimum panels you need to run a credible mini split system. This might be a good thing for people on a tight budget in the Phoenix, AZ areawhere I'm sure they would love to have solar powered AC during the peak temperature of the day. You might break even on the costs compared to the electricity you would pay for.

 

[Supervstech]

Thanks for looking that up. I just did that for the first time last night, and learned that it can accept between 48 and 60 volts. The power input says 850(190-1250). I don't know if this is the right interpretation, but is it right to interpret 850(190-1250) as average (min-max). Therefore, the average power consumption is 850W, minimum 190W, and max 1250W. I'm wondering if 1250W is the surge power needed to kick the compressor on. I'm wondering what the unit does when its power requirements are not met by the input. Is it designed to operate on the max power input, or will it blow a fuse? Not sure. And I can't find a manual online. I might trying to email the manufacturer, I'm sure they'll be interested in corresponding, as they would love to sell more of these units.

Minisplit units have a variable speed compressor. They start out low wattage demand, then ramp up to maximum 120% ish over speed for max demand heating or cooling.
There is negligible surge wattage startup.
You need to size the array to output the full 1500W in full sun. I would recommend the battery bank to keep comfort between peak sun times.

 

[RichP]

Why do you want to power it from the panels directly? What is your goal? It may or may not be possible and/or practical to do so (I'm strongly leanign towards not practical/possible), but it may be possible to accomplish the same goal in a different way.

Hi Dzl. I'm trying to use panels directly because that's the equipment I have on hand (no batteries). Thanks for the response. I'm on-grid in Phoenix, but looking for ways to see if I can save some electricity not having to run my Frigidaire Window Unit so often.

 

[RichP]

Minisplit tech is great, there are several models out there that run with PV in mind, 1300 summer peak wattage, and 1500 winter peak wattage needed... I would want a battery bank, 200Ah to be certain the unit can perform... plus, running at night is kinda needed.

could you run it from panels directly? Yes. Especially if you have tracking panels. But without tracking, you are going to need 3 or 4KW of panels to get there.
another thing you dont know is max voltage... 46 is your VMP... of 28.9 gives you a max of 57.8V, and that may be outside the winding voltage, not to mention what voltage in cold weather with the system idle could get.

Thank-you! When I googled the unit and pulled off data from Alibaba.com, the input range was listed at 48-60 Volts. If this is true, it looks like 57.8 Volts is within range. I'm wondering what the unit does when it's power requirements exceed that of the input? Will it still run or shut down? I'm thinking that depends on how the internal circuitry was designed. The cooling demands are proportional to the Suns Energy, e.g. the bright sun is likely going to be the hottest, and also, positioning the panels so that max received radiation is at max energy demands would also probably be ideal. Kind of an interesting experiment.

 

[DASH]

 

[gnubie]

Minisplit units have a variable speed compressor. They start out low wattage demand, then ramp up to maximum 120% ish over speed for max demand heating or cooling.
There is negligible surge wattage startup.
You need to size the array to output the full 1500W in full sun. I would recommend the battery bank to keep comfort between peak sun times.

Earlier smaller splits may not be inverter types but pretty much everything on sale these days is apart from the bargain basement options out of China.

*edit*
Surprisingly Panasonic seems to have a couple of smallish non-inverter types too.

 

[grizzzman]

Perhaps this will help

 

[Supervstech]

Perhaps this will help

Actually, that is for the AC couples option equipped system.
This will be an all dc 48V unit.

Solar & DC Air Conditioners | 48v DC Solar & Telecom Air Conditioner Heat Pump | Off-Grid Air Conditioning