diy solar

diy solar

Why hybrid solar air conditioners but not the 48vdc ones?

Zwy said:
Hope it works out better than the experience here. https://diysolarforum.com/threads/hot-spot-energy-acdc-solar-mini-split-total-failure.63239/

I don't blame the condenser failures on the manufacturer, it is pretty clear the proximity to the ocean would cause the failures.

Energy usage might be another matter.
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I am in the land of mini splits in a very small country surrounded by ocean on three sides. A good chunk of the population is by the ocean given that Seoul-Incheon and Busan are the two biggest cities and both are ports.

I noticing more and more Gree and Midea clones here along with Carrier (Midea). LG (followed by Samsung) is still by far the most numerous, but others are creeping in.

The Toshiba compressors were designed by a company that is native to a chain of islands.

I guess my point is, they should be able to withstand it but apparently can’t.
 
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Still think the compressors are DC motors, and the variable speed is achieved by varying the frequency of the electronic commutation of DC voltage to the stator coils, which apparently are in fact arranged like 3 phase motors, frequently in multiples of 3 - leading to more assumptions and confusion :)

Here's the compressor from my minisplit:
1684802106270.png
 
Yes I probably should have pointed out mine is from a super-duper Deye / Solar mini split.

I am curious on LG and such, I have their 2022 model inverter washer. (?)

So, maybe everyone is right about the motor they had in mind ? :)
 
SilverbackMP said:
I am in the land of mini splits in a very small country surrounded by ocean on three sides. A good chunk of the population is by the ocean given that Seoul-Incheon and Busan are the two biggest cities and both are ports.

I noticing more and more Gree and Midea clones here along with Carrier (Midea). LG (followed by Samsung) is still by far the most numerous, but others are creeping in.

The Toshiba compressors were designed by a company that is native to a chain of islands.

I guess my point is, they should be able to withstand it but apparently can’t.
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I have a coil coating that is designed for harsh environments that corrode condensing coils. It works, I've put it to the test on some heavy duty equipment that would see failures of condensers and evaporators within 2 years without the coating. Coating will extend the lifespan easily by double.

It is called Duracoil, my supplier makes me buy it by the case as they don't sell much of it.
 
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timselectric said:
I didn't buy the solar mini split.
I bought the 48v unit.
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Maybe uses the same compressor as the solar mini split. Could be an inverter type newer than what he posted about.

I'm starting to get leery of any products marketed as solar, DC powered which normally was AC powered and especially the latest and greatest.

Got burns to prove it, I'm still smarting over the 6500EX problems.

timselectric said:
I'm no where near the ocean. (That's where hurricanes happen)
Click to expand...

In his case, I'd blame the condenser failures on the salty air. Which can be treated to prolong life of the coil.


timselectric said:
It's drawing 300 to 500 watts, when it's running.
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I'll have my Pioneer up and running soon. I know my window air in the kitchen window draws about 1,000 watts.
 
Zwy said:
I'll have my Pioneer up and running soon. I know my window air in the kitchen window draws about 1,000 watts.
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The window AC that mine replaced used 2kw when running. And was powered through the inverter system. This was a major improvement for me.
 
Captain Rick of Sailing Sophisticated Lady (YouTube) just install one on his sail boat with the condenser on deck. Video is recent, but I think he said he'd installed it 6 months ago.
 
This conversation is getting more and more pertinent to my use case, but I posted my own thread on considerations with a SMA (US) system(s).

diysolarforum.com

Dumb question: Do more panels and Sunny Boys offer more amps in offgrid SMA installation

Based on 4x SI and AC coupled SBs. I tried to search the forum, but didn't get a definitive result. I am pretty sure the answer to the question is yes based on that slightly older post of the guy building out a big SMA powered crypto miner system and also the post a couple of months ago where...
diysolarforum.com diysolarforum.com
 
Think someone (signature solar) is ever going to import the 48v direct units?
 
I asked Solaracdc.com.au some questions about their products and they also stated:

"We will soon be launching our full range of Solar ACDC products that we have developed with Deye to our standards in the US. "

They sell the 48V unit as well as a Concealed Duct unit also.
 
The difference between a PWM sinewave inverter and a PWM variable speed motor inverter is the PWM chopping frequency is typically lower on motor driver and most of the PWM current averaging is done by the motor winding inductance so little to no external PWM filtering is used on three phase variable speed AC motor.

There is really no such thing as a 'DC' motor. When a motor is called 'DC' it just means it is internally commutated so outside applied power is DC.

Many of the variable speed compressors are not induction motors with induced rotor current to create rotor magnetic field. They use permanent magnet rotors which is more efficient (and a bit more expensive).

Hermetic compressors get their cooling by return refrigerant gas. If the three-phase inverter motor driver is integral or attached to compressor base, the three-phase compressor inverter cooling can also be done by return refrigerant. This eliminates the need for additional air-cooled heat sinks for inverter.

To make a 48vdc mini-split, only need to take the frontend battery to HV DC converter from a HF inverter and put it as the HV DC power supply for the three-phase compressor PWM inverter, along with some power management controls. No need to develop a low voltage compressor which would be expensive, lacking the high-volume manufacturing cost benefits of standard mini-split compressors.

Heat pumps btu output drops as inside to outside temperature delta increases. This means compressor compression ratio must increase to compensate for low density return refrigerant gas. Inverter three phase variable speed compressors run up to 144 hz of drive frequency running the compressor motor rpm's up to very high level of about 8,000 rpm's. They scream at full heat mode capacity.
 
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I believe AC mini-splits use a full wave bridge rectifier to convert AC into ripple DC. Then they try to flatten out the ripple DC using a capacitor. A few years ago I posted about the much-improved power factor, derived by plugging my Midea U-shaped inverter window AC into a square wave output UPS. PF from .58 to. 90. Has anyone thought about converting an AC sine wave into a square wave(555 timer 50% load factor to make a square wave pulse train, just for mini-splits) then plugging a mini split into the AC square wave? There are other methods of doing this. (Schmitt trigger?). The ripple correcting capacitor (heat generator?) that flattens the bridge rectifier ripple DC output, might be unnecessary because flipping the square wave produces a flat horizontal voltage line (with legs to zero). All this to improve the efficiency of AC mini-splits.
 
I believe Midea for U.S. market only adds a low frequency choke inductor between bridge rectifier and HV DC filter capacitor. This yields a typical PF improvement to an average of about 0.8 which is similar PF for most conventional PSC AC motor compressors.

Mini Split AC PF choke.jpg

When variable speed air conditioner backs down to lower output power the power factor improves as the current pulse peaks are less.

Full Wave rectified Power Factor diagram.png
 
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