Minisplit Inverter communication standard

[cadillackid]

I am currently working on designing and building a system that can replace the wired thermostats on the Grunaire HX series 20 SEER inverter mini-split heat pumps...

I am interested in any input that someone can give as far as the hardware / protocol standard that this and other inverters use to communicate over 1 signal wire...

my first thought was 2 wire RS-485 however there is only one signal wire..

My next thought was CAN but again requires 2 wires...

looking at the indoor board and the wired thermostat board it appears the indoor board provides a "high" at 5 volts constantly in waiting.. and then if the thermostat needs to send something it pulls that "high" down and the microcontroller goes into a receive mode...

the indoor board uses a simple ATMEG16 microcontroller and the T-stat board uses a PIC16F73 controller...

the tstat board receives data from the indoor board as the room temp is displayed on it.. however only 1 pin on the PIC is used... how do they do that?

anyone who can give me any pointers on the cntrol circuitry of minisplits in general is greatly appreciated...

like I say my eventual goal is to be able to create an interface whereas these units can be controlled by a PC or home automation system... there is a lot of interest...

so im looking to be able to set mode, set fan, set temp, and also0 be able to read what mode, current room temp etc...

I have no need or want to control the inverter itself... the unit can better handle what it needs to do to maintain the temp than I do...


and to those who may respond... simple IR commands via the IR remote port are not an option as I have no way of knowing what mode a unit is currently in...

I realize these things are not like a daikin or other commercial units that have networking capabilities built it... however thats why im writing on this forum as it seems to be more technical than the other boards on the internet....
-Christopher

[Brian_UK]

Welcome Christopher, I think that your ideas have already been thought about and on the market.

Here's one as an example...
http://www.x10.com/activehomepro/activehome-pro.html

[cadillackid]

im not sure how x-10 type standards apply to minisplits.. I have a home automation system that runs partially on X-10 as well as other protocols.. and i have several zone controllers by companies made for use in central HVAC systems but nothing that is used to control AND monitor minisplits...

sure i can output temperature up and down commands via IR blasters but i need a way to monitor what current setpoints are, current operating parameters as well as current room temps and of course any error codes the units may issue...

or are you telling me that the protocol that minisplits use to communicate with their components is powerline X-10 style based?

help me out here if theres something I missed in your message..

im just hiong to find some info about the comm standard used in the wired Tstat or tstat receiver board uses to communicate to the main indoor unit control board.. as well as indoor to outdoor communications...

since there is a separate signal wire on most of the modern units that is not the power line im guessing its not a powerline communication bus....

activehome, homeseer, mister house and other automation software works off of already established hardware standards such as serial to X-10 adapter.. or serial to Z-wave adapter, or USB to dallas 1-wire interface etc...

im not looking for the SOFTWARE im looking to build a HARDWARE interface such as serial to minisplit adapter or similar.. then write my own software to talk to it... however I need to first decipher what they are doing hardware-wise and then decipher what they are doing protocol wise to achieve this....

-Christopher

[Yuri B.]

Hello C.

I realize these things are not like a daikin or other commercial units that have networking capabilities

But still why not to have a look at Daikin hardware ?

[cadillackid]

I love daikin hardware... except for the price tag.. I can get the 1 ton 20 SEER Grunaire or Americaire minisplits for under $900.. plus I understand with Daikin I would also have to sell a customer on a BACNET adapter or such as well.. so in short few words in this economy people just dont have the dough to spend for high end equipment.. at least not from what i am seeing..

granted I really dont want to sell units, i merely want to design an interface... more or less i wanted to design and build the interface for my own home... however lots of people seem to have an interest in communicating with various minisplits... esp users in europe / australia where they are more common...

I retired from the HVAC industry full time and am now much more into the control side of things as opposed to field service or systems design....

for a high end home or a business i think daikin is a great choice... but many people here in the states are still not warmed up to the idea of full blown minisplit zoning.. so often i find here minisplits will be used for an attic room, a garage, a finished basement.. an addition.. make a 3 season room into a 4 season room etc... mostly single zone applications...

the communications protocol more than likely is very similar amongst the manufacturers since it seems like many of them have just 1 wire as "signal" or "comms" or however they call it in their documentation..

granted I cant begin to design an interface to communicate to all mini's but id like to try with one or two and see what happens...

-Christopher

[Yuri B.]

Unfortunately I lack your knowledge of interfaces per se, leave alone those applied in ACs.

I see the final product as a wonderful diagnostic instrument: you connect to outside pcb and look how the unit its doing (may even give command to compressor to turn a little and stop, etc, name it). Then the same for the inside units's pcb. (We are often so ignorent and helpless at the whole issue as to which pcb blame in a non-operating AC)

Sorry if dissapointed you and let's hope for comments of others. I am very interested too.

Signal is being transmitted relative to an other wire between units.

[cadillackid]

well signal appears to be an inverted serial comm between ground and signal.. however in most comm circuits there is a send wire and a receive wire....

in the circuit between the indoor and outdoor boards I can kind of see that they are using a "latched" high... basicilly both boards remain in a receive state until one of them pulls the line low and sends data...

in that case there is a seaprate rx and tx pin on each of the micro controllers.. going through opto-isolaters for surge suppression and then using a transistor as the "latch" for which line is in rx and which is in tx....

I havent tried to hack that protocol as I really dont need to interfere with the comms between the indoor and outdoor units..

I am interested in the comms between the wired controller and the indoor board... this is where I could be able to create my own interface for the unit...

without access to the code in the unit's indoor board micro (ATMEG16) I wouldnt be able to offer what you are looking for which is direct control f compressor, fan, etc...

the interface i am looking to build offers only the ability to set temperature, indoor fan speed, mode, etc... basicilly the functions available on its thermostat.

I talked to one manufacturer of units and they indicated that china will not disclose any info on how the comms works.. I guess its a highly guarded secret for some odd reason...

I know for a fact amcoaire and Grunaire are identical units except for cosmetics.. others may also be identical in operation as well...

-Christopher

[Brian_UK]

I think that you will find different methods employed by each manufacturer.

[cadillackid]

I definately believe that each manufacturer uses different methods... although im finding that the latest units coming out are all going to a single wire standard... even samsung who used to use stadard RS-485 has gone to the single wire 5 volt standard.... granted im sure everyone's protocol is a bit different but it seems hardware wise they are going to a similar standard... now to just find out what that is and ill be able t get started hacking the protocols...
-Christopher

[cadillackid]

if a moderator sees this thread can you please move it to technical refrigeration / new technologies i think it better fits there than in this forum
thanks
-Christopher

Edit: As you've asked nicely we'll move it for you.

[cadillackid]

just a little more FYI... it is appearing more and more like the communications link between the wired controllers and the indoor board is an 8192 baud serial link very very similar to the 80's and early 90's automobile ECM comms employed by several manufacturers... makes sense since the ATMEGA16 micro is designed for automotive...

a 5 volt open drain circuit is employed by the indoor board.. oscilloscope testing shows that the indoor board first pulls the line low for 100 milliseconds, then goes back high and sends its data.. high is 0 low is a 1... when done it leaves the line high for about 200 milliseconds.. at which time the T-stat can pull it low and begin transmitting if needbe... the indoor board after the 200 millisecond wait will always resume and send a string of data through over and over.. the Tstat appears to only send when a change is made from its control panel...

I also found another OEM that is using these exact units..
so now we have Grunaire , AmcorGroup, and TurboAir.. and these units are manufactured for these companies by ChigoGroup out of China.. they all use the same Boardset, however have different packaging...

-Christopher

[cadillackid]

just another update to this project... the communications between the indoor unit and the WIRED remote follows very closely the communications between the IR remote and the unit...

the unit uses a 5 volt TTL level signal.. and uses Pulse distance encoding....

the wired Tstat sends a 5 byte data stream with one start bit and one stop bit to the unit... the unit then responds with a 4 byte data stream with one start and one stop bit... these are done over 1 wire...

the wired thermostat looks for this 4 byte stream to come across. if it doesnt see it then it will generate an FA code across the wired control....

the unit itself does not require any data from the wired control to operate as it can operate with or without the wired control in place...

the data stream does not use a Checksum or CRC for error checking... the data bytes are sent and then sent again inverted.. so if the original and the inverted do not match the unit or controller will ignore that byte...

I have not yet deciphered yet which part of which byte does what and whether it is send LSB or MSB first, however that will be the next part of the project and will just be trial and error sending different combinations of settings across the pipe, catching and decoding them..

if I have a hunch it is that they are sent LSB first as that is what follows most IR remote standards.... and this protocol seems to hold close to the IR standard..
-Christopher

[cadillackid]

just another update... the comm standard has been SOLVED.. i can successfully communicate with a chigo-group Minisplit inverter using a micro-controller... I can set any mode, setpoint, fan speed, swing, etc and also read back from the unit all of its parameters including its current room temperature...

this communication is done using an ATMEGA328P Micro-controller device.....

the unit can still be controlled using its wireless remote as well...

so if anyone is interested let me know.. this opens up the possibilities of using minisplits in home or business automation systems.. where an energy management system can control them.

-Christopher

[Yuri B.]

Congratulations!
Which programming software do you use ?

[cadillackid]

I am using right now the "Zbasic" programming langauge for the ATMEL micro-controllers...

I run the Native mode devices which means the compiler creates native ATMEL code for the micro...

my current application is completely custom for my home.. the boardset I have designed was created to adapt minisplits into my zoned and ducted HVAC system.... in effect with 3 minisplits running... each adapted for ducting.. i have the capacity of 5500 BTU all the way up to 42,000 BTU of cooling and similar for heating...

the efficiency is incredible.. these units most always are running at very low speed and also with soft start have longer run times and much closer temperature swing in the house...
I notice FAR LESS electricity usage with the new system vs the old which was a standard Trane condenser unit which I had retrofitted with a txV... in zoning applications the system load varies greatly and a standard or even 2 stage unit just runs in vain and wastes energy or freezes up.

zoning in the USA is beginning to gain popularity as people finally become more energy conscious..

a side benefit of this project is that people are interested in minisplit control remotely esp in offices and schools... so i may end up developing that into a product.. however I doubt anyone in the general population will have much interest in my advanced zoning system at home.. its design first and foremost had comfort in mind - just so turns out that it saves a lot of energy too...
-Christopher

[minisplituser]

Hey Chris,
Is it possible for you to send me the service manual for Grunaire units to rounderatwn@yahoo.com . My service guy came this AM and the baord with the two large black capacitors had a hole and split in one end of the capacitors. So they are supposed to be sending me a new board. I am interested in the zoing approach to residences as I think this would be much more comfortable than traditional systems. I remember sweating in the kitchen in my parents house, while you could hang meat in the bedroom.

Didn't mean to hijack, but these units are of interest to me.

Thanks,
Chad

[cadillackid]

just an update now.. i hyave all 3 of my individual zone controllers up and running... using onboard temperature sensors to measure.. liquid , suction, and supply air temps.. and then talking through the mini's wired interface to control setpoint, mode ,etc..this also allows me to read back and log any error codes that a unit may set... which is great.. because often a unit will pop an error code for just a second or two.. or a unit will act erratically yet the customer sees no error codes... I would be able to plug my test board into a unit for a few days (between the wired controller and the unit) or if they arent using the wired controller just plug into that port.. and have it log any error codes it might incur... possibility of a great diagnostic tool here... granted this only works with the Chigo inverters... however chigo is expanding their inverters into north america rapidly....

since these are ducted into my main system, their onboard blowers are gone and my central blower moves air across the coil and varies the dampers..

I find these units respond to me very well.. in fact if I reduce the airflow across the coil, the unit will reduce its compressor speed and vice versa.. so that gives me yet another area of control over them...

another way of control is by the onboard digital pot on my control board that effectively "fakes" the unit's temperature sensor... that way I can match my on-wall thermostat temperature with what the unit "sees".. and also progmatically narrow the minisplit tendency to allow Large temperature swings....

so all in all this project is a great success.. and these inverter units pull so much less energy than I expected even.

the next step will be to take my prototype breadboards and layout real PCB's and have them made.. i will probably add the capability for more temp sensors and maybe a general I/O or two just so the board has more uses or could control other types of units as well.... I will be posting a video of my system on youtube.. ill post the link once it is ready
-Christopher

[TonySYS]

Hi

I am also searching for this information. Can you send me specifications you have (protocol) and variables if possible.
Thanks

[cadillackid]

you looking for thje protocol between the indoor board and the user controller or the indoor board and the outdoor board? what kind of units are you working on?
-Christopher

[TonySYS]

I am looking for Carrier Xpower. They have Toshiba inverter compressors and probably electronic board too.

[cadillackid]

as far as I know the Chigo units use the Sanyo compressors and the boards are manufactured by 'Strong' PCB company I believe..

although chigo wont cough up the info on their suppliers... from what i can tell though many of these units use similar protocols but I dont have a carrier unit in my hands to work the protocol.... if I had one i might be able to see what they use....
-Christopher

[Nick Johnson]

CADILLACKID,

I am very interested in the product you are developing to control minisplits. Our church is considering them as an option but due to service issues will probably use Daikin or Mitsubishi. Do you plan on offering control of those mini-splits?

I found a part number for a board for Mitsubishi mini-splits but could never get a price. The residential division doesn't sell it apprently and the commercial division has little incentive since they charge about 3 times as much for VRF systems where these might displace sales.

[cadillackid]

for mitsi i think you can put their minis into a city multi network and run them that way...

my board is still working and working well, however albeit still not out of the prototype stage as I have added a couple "safeties" into it and such.. I have planned to run my boards a year for a complete heating and cooling season before I think of releasing them... im about 6 months in of good solid testing.. im running them in my own home on my home-built minis... and for those skeptics my home built "ducted" splits in a hybrid environment ran beautiful over the heating season without issue... other than a cracked evaporator coil pipe.. (I shouldve caught it at install becausew there was very little nitrogen charge when I pulled the caps to pipe it up).. typical bad braze joint on one of the tubes from the chinese factory...

id like to add some more functionality to my boards too like time-based setbacks and such directly on board the circuit instead of a central processor to do it.. so ive got to write the software for that... im using an ATMEGA328 processor and have Plenty of codespace and cpu cycles left to add some more to it...
-Christopher

[airefresco]

Wow Christopher, I am suitably impressed by this. Is the processor you are using the same as what is used in the arduino modules? Is it actually possible to do something like this with the Arduino?

[cadillackid]

the processor I am using is the same one used in the arduino.. I dont know the arduino well enough to know if this could be done with it or not... I also use the ATMEGA1280n processor as well as that is going to be the main brain that controls the central fans , etc..

here is a link to a post I made in another thread with some pics of an experiment i did in my own house with ducting my minisplits and custom building them as a prototype experiment...

http://www.refrigeration-engineer.co...5&postcount=13

-Christopher

[airefresco]

So how does your controller integrate with in a/c pcb? Does it just connect on the terminals or have you actually soldered directly on to the board? It´s quite a fascinating project. I have been looking at the Arduinos as a way in to microprocessors et al. They same fairly simply to learn the basics on and quite robust, so a good learning tool.

[cadillackid]

the Chigo mini's I work with actually have provisions for a Wired "remote" controller built onto their indoor Main PCB.. its a 1 wire communication (bi directional).. so that is where I attach my PCB.. there is a good 5 volt regulated supply there too that would feed the optional wired controller.. my board pulls about half of the current that the wired controller pulls... it however did take some ripple when the unit changes modes so I put a nice filter cap across the +5 going to my board to keep from enduring resets when the unit say kicks the reversing valve or such.

now if the mechanicals of these chinese units were better id be Ok.. the outdoor unit design on these Chigos leaves a bit to be desired.. but then I see similar in the LG's, Sanyo's, and other variants too..

it seems chigo for some reason felt it necessary for the coil temp sensors on the outdoor unit.. namely the compressor discharge and suction to actually penetrate the copper pipe and braze on a sleeve for the sensor to slide into...

well just yesterday my nifty little computer controller (and smart house) texted me the wonderful "P8" code - which in chigo terms is a Low charge indicator...

out with the gauges and I found 6 PSI in my unit!!.. just the night before it was pushing out 117 degree air into the house... heck I didnt even need the leak detector to find that one.. a little nitrogen and my ear was all I needed.. and if you have ever brazed inside an outdoor unit of a mini you know what I mean when I say tight quarters.. actually looking at all the pipework inside of these units over time its amazing any of them work at all...

im not sure I chose the correct Kit when I embarked on this project.. as well as I have had to repair several of these chigo units in the field for faulty pipework, leaky valves or bad "PFC" boards.. fortunately I can repair and recycle PFC boards as its just a Cap and a MOSFET that burns up on those..

there are a lot of AmcorAire units out there and since they are defunct their warranties are gone too.. ive been succesful in repairing those units but customers are NOT happy when a unit they bought last summer goes on the fritz and they have to pay for a repair
-Christopher

[mshynson]

cadillackid
stumbled on this post while searching for a new PFC boad for my Grunaire. you say theyre easy to repair? where can i have this done? can/will you repair it for me? any help would be appeciated.
marshall

[cadillackid]

is your Grunaire out of warranty?

if not that board is one they will send you if you bought it at AC-wholesalers....

typically on the PFC board it is one of the Large capacitors and the 3 pin MOSFET that goes bad on it....

the CAP is a standard 450 Mic 250 volt cap..

the gray rubber sleeve slips off of the MOSFETS and you should be able to get the number off of it.. if not I can look it up later when im at the house..

it is an easy to order part at digikey and is through-hole so its simple to solder in...

PFC board is real common failure on these units.. esp if it is a grunaire 121-HX..
-Christopher

[mshynson]

thanks for the reply. im looking at the board now. how can i tell which cap is bad? they look to be 530MFD 450VDC.
marshall

[CamAir]

I am impressed with your work cadillackid, I saw your thread and decide to join.

I see you had a lot of experience with AmcorAire and likes. I have three units, one running and the two others used as spare and I am running out of parts. I need to start repairing the condenser control modules.

Is there a fix once for all for the units? Especially for the 121 HX.

Where can I find PCB schematics for the AmcorAir OAS 121 HX? You see, my boards are badly damaged from a flashover.

Thanks

Camille

[candoan]

is your Grunaire out of warranty?

if not that board is one they will send you if you bought it at AC-wholesalers....

typically on the PFC board it is one of the Large capacitors and the 3 pin MOSFET that goes bad on it....

the CAP is a standard 450 Mic 250 volt cap..

the gray rubber sleeve slips off of the MOSFETS and you should be able to get the number off of it.. if not I can look it up later when im at the house..

it is an easy to order part at digikey and is through-hole so its simple to solder in...

PFC board is real common failure on these units.. esp if it is a grunaire 121-HX..
-Christopher

Hi Christ,
Finally, I think I found a right door to knock on.
I have 6 amcoraires installed in May last year. 4 of AWS 091HX and 2 of AWS 121HX. All 4 of 9000 BTU are still running, thank God, but 2 of 12000 BTU has stopped working. One has F1 code flashing and the other has P8 code flashing.
As you know Amcor has been out of business without notice to their customers and Pridiom won't want to help.
With your experience and knowledge on Amcoraire, please help me out of this problems. It's still summer in Boston, MA and both units are in my kitchen and living rooms where my family spend most of our time there.
You can PM me at candoan@gmail.com.

Thanks for your time and help,
Can Doan

[jbeckham]

retired at 42? i can see why. you're dang near smart.

that's some of the most intensive tinkering i think i've come across. definitely keep us posted on your projects.