Air Conditioning - AC or DC?

[marklg]

@marklg, you mention in that linked thread that you were in contact with Espar regarding the Breezetronic. I saw some physical dims/drawings but didn't see a data sheet. Not seeing it on their website either.

Seems this is AC powered. Anyone know if it is DC Inverter tech? I'm gonna guess "no" as I read references to soft start and that should not be needed if it were.

If this Espar isn't DC Inverter tech, what's the perceived benefit? Name and reputation? Some innovation I'm not picking up on?

It is an inverter unit. It ramps the power up and down as needed. They sent me some advance info with the dimensions I asked for. They said they are working on updating the datasheets. It does need updated controllers / thermostats, but it includes many controls on the unit, as well as offering multiple options including an app.

They have a big presence in that city in Indiana and I think they will be aggressively competing.

Regards,

Mark

 

[3Play]

@marklg, you mention in that linked thread that you were in contact with Espar regarding the Breezetronic. I saw some physical dims/drawings but didn't see a data sheet. Not seeing it on their website either.

Seems this is AC powered. Anyone know if it is DC Inverter tech? I'm gonna guess "no" as I read references to soft start and that should not be needed if it were.

If this Espar isn't DC Inverter tech, what's the perceived benefit? Name and reputation? Some innovation I'm not picking up on?

I don't know the specifics for this one, but most mini splits are running native 48vdc and use a transformer from the 120AC side.
This is why solar minisplits are possible, they just inserted the panels voltage in between the AC power supply and added a circuit to regulate VDC, or to swith to AC when power is too low on the solar side.

 

[Dax Travels]

I don't know the specifics for this one, but most mini splits are running native 48vdc and use a transformer from the 120AC side.
This is why solar minisplits are possible, they just inserted the panels voltage in between the AC power supply and added a circuit to regulate VDC, or to swith to AC when power is too low on the solar side.

Same as my Midea U. DC inverter AC is amazingly efficient compared to the old style still so common in RVs.

 

[blutow]

Conversion from Australian pricing is more like $1400 - $1700. That wouldn't be so bad. That might be without the interior part. It looks like they sell them and ducted versions separately

Regards,

Mark

If they sell them in the US market for ~$1500, I suspect it will be a popular option. And if they are going after the OEM space, I suspect they would need to be under ~$500/unit at big committed OEM volumes. Both of those price points should provide enough margin to make sense for Espar if the volume is there, but the EU retail pricing I saw was 3600 Euro for the bigger unit (with controls). Espar doesn't do any favors in the US market with their fuel heater pricing, but maybe they will price the A/C units aggressively since it's a new market for them.

 

[blutow]

And if anyone is interested, here are the specs for the 230v EU version of that Espar A/C unit. It's basically a 12k BTU unit. I assume the "current average cooling A" is amps at a given exterior temp/humidity and hopefully max compressor speed. 6.38A at 230v works out to over 1400 watts, so not particularly efficient. And from what I see on other units, these inverter driven variable speed compressors are not that much more efficient than a single speed induction motor setup when both are running maxed out (not uncommon in a van). That midea window unit that everyone points to for efficiency still tops out at ~12A at 115v (so almost 1400 watts). And my 13.5k BTU houghton "old school" rooftop A/C maxes out at 1,550 watts (ignoring the startup surge), so similar efficiency to those others at max cooling. And to be fair, none of these units will hit those "worst case" wattages in typical use. I don't think I've ever seen higher than 1300 watts from mine and it's usually running around 1100w on a hot day and under 1000w at night. From what I can tell, the biggest advantages of the variable speed inverter systems is the efficiency at partial cooling and they also don't have a big startup surge.

 

[Midwestdrifter]

I don't know the specifics for this one, but most mini splits are running native 48vdc and use a transformer from the 120AC side.
This is why solar minisplits are possible, they just inserted the panels voltage in between the AC power supply and added a circuit to regulate VDC, or to swith to AC when power is too low on the solar side.

Most mini splits use brushless DC motors. These take three phase AC input (controlled by a motor driver/inverter). These are permanent magnet motors, with the magnets on the rotor, and the stator being the active component. The voltage of these motors varies. The Midea U unit uses around 300V to drive its motors. This is produced by using a peak conversion circuit to turn 120VAC into about 300VDC. This DC power is then fed to the motor controllers. The actual voltage and frequency fed to the motors depends on load and desired motor speed, and thus can be highly optimized. More specifically these motors are sensorless, (no position sensor for the stator coils). Instead the controller uses back EMF to determine where the magnets are relative to the stator coils, and thus varies the polarity and voltage of each phase accordingly.

The logic is typically 5V and 12V, and has its own DCDC power supply fed from the main DC bus. Mini splits are fairly similar topology.

While these motors are called brushless DC, they don't actually accept DC power themselves. Instead the motor controller requires DC input, so it can chop it up to the right frequency for each phase.

 

[3Play]

Most mini splits use brushless DC motors. These take three phase AC input (controlled by a motor driver/inverter). These are permanent magnet motors, with the magnets on the rotor, and the stator being the active component. The voltage of these motors varies. The Midea U unit uses around 300V to drive its motors. This is produced by using a peak conversion circuit to turn 120VAC into about 300VDC. This DC power is then fed to the motor controllers. The actual voltage and frequency fed to the motors depends on load and desired motor speed, and thus can be highly optimized. More specifically these motors are sensorless, (no position sensor for the stator coils). Instead the controller uses back EMF to determine where the magnets are relative to the stator coils, and thus varies the polarity and voltage of each phase accordingly.

The logic is typically 5V and 12V, and has its own DCDC power supply fed from the main DC bus. Mini splits are fairly similar topology.

While these motors are called brushless DC, they don't actually accept DC power themselves. Instead the motor controller requires DC input, so it can chop it up to the right frequency for each phase.

A friend of mine was taking apart mini splits about 6 or 7 years ago and we were actually trying to come up with the solar mini split.
All the units we encountered could have the 120VAC power supply completely divorced from the unit and could be fed 48 to 60VDC directly to the board after the power supply and it would feed through to the ESC. (Electronic Speed Controller).
I don't know if it was using an inverter after that point to give the ESC 300VDC. I just know it wanted over 48VDC after the 120VAC power supply, and there was a something after the 120VAC that was transforming the power to about 48VDC.
A couple companies came out with the product and we dropped the project. I don't know where it has gone since, but the solar units want at least 3 panels in series to ensure no less than about 54VDC.
I am sure higher voltage and frequency would be more efficient, Tesla told us these things in the late 1800's......

Are you saying they are now inverting to 300VDC directly from the 120VAC power supply?
If so, this is different than what we encountered and I am very curious.....

 

[Midwestdrifter]

Are you saying they are now inverting to 300VDC directly from the 120VAC power supply?
If so, this is different than what we encountered and I am very curious.....

There are a few different topologies. Early units (and "solar" units) used more common 48V BLDC motors for the blowers, and sometimes the compressor. Newer split units use high voltage compressors and motors, especially when running over 10k BTU. Here is an example from a 36k BTU replacement compressor. This unit is a 3 phase BLDC motor with 300V rated input. 300V is approximately the peak-peak voltage of a 120VAC sine wave (120V is the RMS value, not the peak value).

A power factor corrected peak rectifier can be very efficiency and simple, making ~300VDC from a 120 or 240VAC input. Which is then typically switched directly by the motor controller/inverter.

 

[Franny]

Veering off course, but another option is 24v. In Europe the parking air coolers are typically 24v.

24V air conditioner. Under $500. https://a.co/d/h32IMGs

Rest of system like this:

4000W 110v / 24V inverter/charger 140A MPPT (Easun, Powmr, Vevor, etc). Under $400. https://ebay.us/m/srRSz1

24v Yixiang diy battery box. Under $400. https://yixiangpower.com/products/u...ype-without-cells?_pos=1&_sid=496faf6fa&_ss=r

8 cells for above. Under $800. (Last year they were $55/unit). EVE MB31 314Ah Double hole studs.

2 residential solar panels. Under $300. Sometimes you can find 440w units for $100.

 

[3Play]

There are a few different topologies. Early units (and "solar" units) used more common 48V BLDC motors for the blowers, and sometimes the compressor. Newer split units use high voltage compressors and motors, especially when running over 10k BTU. Here is an example from a 36k BTU replacement compressor. This unit is a 3 phase BLDC motor with 300V rated input. 300V is approximately the peak-peak voltage of a 120VAC sine wave (120V is the RMS value, not the peak value).

A power factor corrected peak rectifier can be very efficiency and simple, making ~300VDC from a 120 or 240VAC input. Which is then typically switched directly by the motor controller/inverter.

View attachment 393442

View attachment 393441

This is new to me, how are they getting 170v out of the 120 phase of the wave?
Why isn't it 240v peak to peak?

 

[3Play]

Veering off course, but another option is 24v. In Europe the parking air coolers are typically 24v.

24V air conditioner. Under $500. https://a.co/d/h32IMGs

Rest of system like this:

4000W 110v / 24V inverter/charger 140A MPPT (Easun, Powmr, Vevor, etc). Under $400. https://ebay.us/m/srRSz1

24v Yixiang diy battery box. Under $400. https://yixiangpower.com/products/u...ype-without-cells?_pos=1&_sid=496faf6fa&_ss=r

8 cells for above. Under $800. (Last year they were $55/unit). EVE MB31 314Ah Double hole studs.

2 residential solar panels. Under $300. Sometimes you can find 440w units for $100.

You can get the EG4 24v rack mount for about $1400 , it has all the protection circuits, I think building your own battery is not worth it...

 

[Midwestdrifter]

This is new to me, how are they getting 170v out of the 120 phase of the wave?
Why isn't it 240v peak to peak?

I don't want to clog the thread too much, but have a look at the graph I posted. 120VAC is the average voltage over time. You need to use the average (RMS) voltage to calculate power etc, so that is what is generally used. Since the voltage oscillates (60 times a second) the actual peak is about 170V above/below neutral. Since the voltage oscillates between positive and negative 170V, a peak rectifier can actually achieve about double that in DC voltage. If you compare the difference between the positive and negative peaks, its >300V. Instantaneously its never greater than 170V, but the rectifier can store charge between peaks, and thus obtains a higher DC voltage.

 

[3Play]

I don't want to clog the thread too much, but have a look at the graph I posted. 120VAC is the average voltage over time. You need to use the average (RMS) voltage to calculate power etc, so that is what is generally used. Since the voltage oscillates (60 times a second) the actual peak is about 170V above/below neutral. Since the voltage oscillates between positive and negative 170V, a peak rectifier can actually achieve about double that in DC voltage. If you compare the difference between the positive and negative peaks, its >300V. Instantaneously its never greater than 170V, but the rectifier can store charge between peaks, and thus obtains a higher DC voltage.

I never knew the peaks were that high. Is it a special rectifier?
Interestingly, I built some rectifier circuits to clean up the brushless 3 phase motor's output into DC +/- 75 to 50vdc.
They make extremely efficient alternators......

 

[rollerbearing]

Is it a special rectifier?

Yes, in the sense that it is not your typical full wave rectifier. Properly configured, you can get twice the peak voltage with a voltage doubler circuit.

Delon circuit​

Figure 4. Bridge (Delon) voltage doubler
The Delon circuit uses a bridge topology for voltage doubling;[p 6] consequently it is also called a full-wave voltage doubler.[2]

 

[Midwestdrifter]

I never knew the peaks were that high. Is it a special rectifier?
Interestingly, I built some rectifier circuits to clean up the brushless 3 phase motor's output into DC +/- 75 to 50vdc.
They make extremely efficient alternators......

Yeah, just like how BLDC motor is more efficient than a separately excited DC or induction motor, a permanent magnet alternator is more efficient than a conventional alternator. For example the high output 48V alternators I am looking at for my new build are permanent magnet type. Between the higher voltage and PM design, they can output about 5kw from a package the size of a 2.5kw conventional alternator.

 

[alexk243]

Is there any concern with the weight of the midea u-shaped AC on the back door?

As much as I dislike the bulkiness and how it would block the bike rack, it's hard to beat the low power draw, low cost, and ease of install.

 

[3Play]

Is there any concern with the weight of the midea u-shaped AC on the back door?

As much as I dislike the bulkiness and how it would block the bike rack, it's hard to beat the low power draw, low cost, and ease of install.

It's only 60lbs. people hang a lot more than that on doors.
I made an acetyl wedge under the door, so it is supported when closed.

 

[Midwestdrifter]

The unit needs to be properly attached and supported. Otherwise it should be fine.