Built your own split system?

[jeff5may]

I finished up the install today (for now). I also heated and cooled the outdoors a little to get an idea of how this control functions.

It looks like this now:

I stuck the control panel and a piece of coroplas to the metal cover plate that now covers the new guts. I stuck the remote control to the coroplas with a piece of velcro. Now it is ready to live another lifetime in a new window or wall.

I played around with the remote control, and figured out it doesn't sync with the main unit until you change modes. It has 5 modes: cool, dehumidify, auto, fan, and heat. In heat mode, you have to use the remote to disable or enable aux heat vs. heat pump. In auto mode, you have to set the temperature on the control panel. Changing the temperature with the remote does nothing in auto.

I figured out the unit also has a predictive temperature control loop of some kind built into it. I originally had the thermometer (black plastic covered sensor) fastened to the indoor coil with romex nail clips like most of the window units do. The heating or cooling of the coil would throw off the temperature a little due to the close proximity. Rigged this way, when I set the unit close to the outdoor temperature, the unit did not shut off exactly when the setpoint was reached. The unit would run for a minute or two and overshoot the target temperature a bit. When the compressor cut off, the blower ran for a minute or more. After a couple of these cycles, the sensor was very close to the setpoint by the time the fan shut off.

[iamgeo]

Originally Posted by jeff5may

Iamgeo,

I believe the main, original intention of the manufacturer was to provide an inexpensive solution for window and mini-split owners whose units have suffered a control board failure, keypad failure, struck by lightning, etc. Original, factory control boards are very expensive to replace. Complete system replacement even more not cheap.

Xringer experienced one of these failures recently, and the cheapest, refurbished control board available for his unit is around 300 to 400 dollars (depending on the source). A whole new system is in 4 figure territory. This line of controls will not work with his system, because he has a variable-speed compressor. These controls will only work with single-speed compressors. I'm really glad he shared the link, as this type of control is perfect for the hacked heat pumps I tinker with.

Ok. Now I understand.

[jeff5may]

I was looking through qunda's website and found this:

Model no. QD30
Inverter air conditioner control panel

[Xringer]

Seems smallish. Maybe for a 9,000 BTUh system?

Group of QD30 inverter air conditioner control panel general purpose inverter inverter air conditioning control system modification



Not seeing where the IDU connects up.. Or even how that could work..?.

[jeff5may]

From the description page, this is a versatile control that ccould be rigged a number of ways. It is a slave module that seems to be able to use a number of control modules as an input. It can take a common on/off command or who knows what kind of speed signal. I wish i could read Chinese.

Whatever input signal it takes, it responds by supervising the compressor. It has some thermistor thermometers that I imagine you would fasten to the rig to tell the control board what is reacting how. The chip next to the bridge rectifier looks a lot like the one inside the sanyo that died...high voltage and pwm signal goes in, 3 phase drive signal goes out.

[Xringer]

CN2 looks like it's got frequency step input controls. 5 or 10 Hz up or down. And a common / ground?
Still not seeing the comm line to the IDU.
So maybe those Up & down lines get bumped by a controller that runs the IDU? fed by IR remote..
Or maybe the IDU runs as a Stand-alone, using Fan-mode? (Sanyo IDU works in Fan, without anything but 230vac)..

Is CN3 the 4way-valve control line??

Maybe I can get someone to translate some of this for us. I'll post if I get any info.

[Xringer]

New link: https://www.aliexpress.com/item/32956162411.html

They are making some interesting pcbs these days.. Inverter support!

Universal DC Inverter control system for split air conditioner QD82 Drive strong DC compressor/outdoor/indoor DC fan motor/electronic expansion valve

Scroll down the page to the wiring details...


Amazon has the QD81B version.. https://www.amazon.com/CHUNGHOP-Univ.../dp/B07S89QC4S

[ThomSjay]

I was just snooping around, and found this thread because it looked interesting.

Maybe I don't know what I'm talking about but, this link https://www.amazon.com/CHUNGHOP-Universal-Controller-Conditioner-Conditioning/dp/B07S89QC4S states that the controller is at a fixed frequency, and therefore no longer an inverter A/C unit. (for Xringer)

[Xringer]

Because of the DC motor design, the boards have to be 'inverter' type controllers.
But, the frequency of the controlling clocks (which controls the RPMs of the motors) will become fixed. The OEM boards vary the RPMs, thus control the amount of power being used.
My Living room Unit will use 1200w when it starts and then drop down to 470w after the room starts to cool. Then will drop to just a few watts when the room is at target temp.

Buying one of these 24k BTUh replacement boards is risky, because it might run the old Sanyo at a full 24k BTUh, sucking down full power until the thermostat shuts it off. Meaning it would work a lot like Old-Tech USA HVAC.
Not really desirable, but maybe better than nothing.
What would be great, if one could manually adjust the Fixed frequency. Make it run at RPMs in a lower power range. Like 400 to 800 watts.
Which would never deliver the full 36k BTUh heating or 24k BTUh cooling the Sanyo hardware is capable of, but it would be satisfactory for the average day.

Running this old Sanyo at full RPMs, would work. But, because it can produce almost instant cooling or heat in a large area. It might easily over-heat or cool rooms real fast. Blasting out 36,000 BTUh of heat when only 12,000 are really needed.. LOL!
(Spec on 24k Sanyo is 24k cooling and 36k BTUh heating)..

Cheers,
Rich

[ThomSjay]

Thanks.
I wish that I understood the systems. In my mind it should be easy to configure an Arduino or RPi to receive the clock signal and vary an output to drive an SSR (or several) all whilst watching a temp sensor. Anyway, I will back out now before making a mess of the situation.