Dometic/Cruisair controls

[Hurricane]

1k is a lot per cabin/compressor...
I'd be impressed if no one has started an open source such project for a microcontroller on the compressor mated to a mobile/small epaper touch screen to give instructions and feedback info to the user wirelessly.
worth a go as a package I think and will be fun keeping the braincells active
but if you go ahead, avoid using onewire protocol temp sensors! or carefully read their async mode properties and configure accordingly!

Yep - sounds like a possible idea.
My concern is the significant loads that are being switched.
Whilst Googling, I think I saw mention of a "soft start" extra which "kind of" adds to my concern about the high loads.
Here's a pic of the control board from my main system - I've got 5 like this:-

 

[jrudge]

I do have one of those I bought in error years ago. The issue is I have moved house twice ( next time is Thursday ) and I won’t be in new place until sept. If I ever find it I will stick it in the post.

Try

mailto:david.hancock@nauticool.co.uk

 

[vas]

Yep - sounds like a possible idea.
My concern is the significant loads that are being switched.
Whilst Googling, I think I saw mention of a "soft start" extra which "kind of" adds to my concern about the high loads.
Here's a pic of the control board from my main system - I've got 5 like this:-

View attachment 156044

Mike, a few more pics all around would help, but pretty sure the board itself is not dealing with high currents at all!
Not saying it's a walk in the park, but doesn't look too complex (at least the bit we can see here)

 

[jrudge]

I would agree. The units will have a low power control input I suspect. Frankly all they do is

- call for heat or cool which turns on or off the flow to the air handler. That is it.

- fan speed ( setting it to mid speed would also be entirely fine )

On my boat and I suspect anything else that is not brand new the compressors / pumps etc just run if the ac is on ( they cut out when the loop is cold enough ) and the sole control is to open of close the valve to the air handler.

There are modes like turn on fan when cooling / off when not but these just wake you up in the night as they go on and off

Finding out the call for cool signal will not take long I suspect with a volt meter. You then just need a thermostat of which as you know there are many for pence on eBay or a sonoff ns panel if you want it to look flash

 

[hinch]

Having just g one through all this with replacing wall panels, and new controller boards (there's about 30 different variants for the same model AC unit) I ended up ripping the old split chiller dometic out and fitting a new combined unit where the old fan unit was leaving the space where the compressor was as spare space now.

 

[Hurricane]

Mike, a few more pics all around would help, but pretty sure the board itself is not dealing with high currents at all!
Not saying it's a walk in the park, but doesn't look too complex (at least the bit we can see here)

Vas
There are relays and contactors in that box - here are a few more pics

Also bear in mind that the A/C consumes so much power, that it has its own 32a shore supply.

 

[Hurricane]

Having just g one through all this with replacing wall panels, and new controller boards (there's about 30 different variants for the same model AC unit) I ended up ripping the old split chiller dometic out and fitting a new combined unit where the old fan unit was leaving the space where the compressor was as spare space now.

Doesn't that make it noisy?
All my 5 systems are split DX systems with the compressors in the engine room - just the evaporator fans in the living areas.
I don't really want to end up stripping the DX system out throughout the boat - that would be loads of pipework to replace with raw water cooling for each system.

 

[hinch]

the compressors are silent in the newer combined units (my compressors were below the saloon floor with fan units under the cabin beds and saloon sofa) the new combo unit fan is no noisier than the old fan units were so overall noise is the same no better or worse just i have more space now.

 

[hinch]

also if you're swapping newer revision controller boards onto the compressors you have to change to the newer control panel too as they're not cross compatible if you use an old controller with a newer board you can pop the 2nd large black plastic cap and they cost about 45 quid each.... ask me how many I went through before someone at dometic actually told me that.

 

[jakew009]

Vas
There are relays and contactors in that box - here are a few more pics

Also bear in mind that the A/C consumes so much power, that it has its own 32a shore supply.

View attachment 156064

View attachment 156065

View attachment 156066

View attachment 156067

View attachment 156068

The reality is there is hardly anything on that board.

Most of it is the microcontroller that does the serial protocol to speak to the other PCB and all it’s supporting circuitry (voltage regulators, crystal, transformer etc).

There’s only a handful of wires actually leaving / going to the board and most of them seem to be doubled up anyway.

What’s at the top of the board off the picture?

If you map out where each wire goes I don’t think it would be very difficult to put together a much more ‘analogue’ control system with a few relays and a thermostat.

 

[vas]

+1 on what Jake says above. Mike, try to post a pic of the transistors on the top of the PCB of pic1. PCB has some cuts which imply there's high current high temp bits hidden above the ali piece (guess it's a heatsink of some sort). Still nothing special, just 20yo electronics in probably a 30+yo design.
pic2 has all the high current AC bits plus the square on the right must be a rectifier for the 230AC to DC. Only 4 thick cables to worry about the two purple a white and a black. The rest are plain signals (mA) that a pi will be happy to deal with. The high(ish) power transistors at the top barely visible at pic1 can be easily be replaced with suitable solid state relays if you don't want to deal with sorting out a custom PCB with heavy gauge plating and proper design.
TBH, I'd prototype one, check it and then do a run of 10pcbs for 30-40quid and have them as backup.
The main issue is finding a decent (suitable for the hole in the cabin) display and the sorting out the protocol to communicate with the rpi (or whatever) below deck

OTOH, Jeremy's approach to leave the below deck board as is, figure out the right signals and piggyback a rpi there to "control" the control board is easier as long as the controller board is doing well...

V.

 

[Hurricane]

I had the cover off and took some photos a couple of weeks ago when I was last on the boat.
There is one last photo that I haven't yet posted.
I think it will answer Jake's question.
There isn't really anything at the top of the board - just connectors.
This is the only pic I didn't post



The wires are 240v capable of quite large loads.

 

[vas]

oops!

so all these heavy lines (good for 20A) go straight in the pcb, not good, thought it was just hidden transistors there.
still doable but not simple as initially thought.

 

[Hurricane]

+1 on what Jake says above. Mike, try to post a pic of the transistors on the top of the PCB of pic1. PCB has some cuts which imply there's high current high temp bits hidden above the ali piece (guess it's a heatsink of some sort). Still nothing special, just 20yo electronics in probably a 30+yo design.
pic2 has all the high current AC bits plus the square on the right must be a rectifier for the 230AC to DC. Only 4 thick cables to worry about the two purple a white and a black. The rest are plain signals (mA) that a pi will be happy to deal with. The high(ish) power transistors at the top barely visible at pic1 can be easily be replaced with suitable solid state relays if you don't want to deal with sorting out a custom PCB with heavy gauge plating and proper design.
TBH, I'd prototype one, check it and then do a run of 10pcbs for 30-40quid and have them as backup.
The main issue is finding a decent (suitable for the hole in the cabin) display and the sorting out the protocol to communicate with the rpi (or whatever) below deck

OTOH, Jeremy's approach to leave the below deck board as is, figure out the right signals and piggyback a rpi there to "control" the control board is easier as long as the controller board is doing well...

V.

I like your ideas but maybe there is a middle approach.
Maybe someone makes a basic A/C control system and then we just control it with some sexy electronics.
There are lots of "home assistant" electronics about these days - sexy wall mounted panels running Android for example.

Actually, my background 45 years ago was in Heating Ventilating and A/C - in fact I'm formally trained in that field.
In those days, we would control A/C systems but most of the time, we were using dedicated chillers and our controls only switched low voltage/current interfaces.

 

[Hurricane]

Maybe a good place to start would be with a circuit diagram.
It could probably be quite a simple diagram.
Contactors to switch the heavy loads.

It would be really useful if we could find a circuit diagram for the Dometic/Cruisair system.
Note that there are several types of Dometic/Cruisair systems.
DX (Dirext Expansion) and ones that use chilled water etc.

 

[vas]

gone are the 80s when most devices would come with a couple of pages of circuit diagrams in their manual...

 

[John100156]

Please let me know because I'm hoping that will fix mine.
I won't be on the boat until next month to give it a try.

I have used this reset function before and it did clear the 'then' fault I had on one of my units with my SMXht controller.

I note that you mention RJ14 sockets (6P6C) are you sure that's what you have? Mine are RJ12 and there is a slight difference in the plug configuration IIRC. I have a multiple RJ45/RJ12/RJ11 cable tester which I intend to take out next trip.

I also have various hard copy Crusair mauals on the boat, as you know, I will be there in June (Having completed the kitchen tiling yesterday ;-)

There is often a start relay used on smaller hermetic compressors.

 

[jakew009]

oops!

so all these heavy lines (good for 20A) go straight in the pcb, not good, thought it was just hidden transistors there.
still doable but not simple as initially thought.

But do those wires actually go anywhere on the PCB other than to the big caps in the bottom of the box?
If you follow the traces there’s a huge copper pour under the terminal block that doesn’t really go anywhere other than to the spade connectors.

I think they have just used the PCB as a convenient terminal block to spade connector adapter.

I can’t see anything on that PCB that could switch 20A

 

[jakew009]

In fact the only mosfet I can see is the P channel mosfet that looks like it’s controlling the fan in the top right.

Is it a 2 layer or 4 layer PCB? Are there are components on the back?

 

[John100156]

Just a single layer board, compressor relay is off board, images of both sides of my PCB as follows, after repair of the RJ12 display socket: