Mini split wiring

This should be an easy one for you guys?

I want to buy a mini-split AC system, but not as a complete system. I want to shop around for separate used indoor evaporators and exterior condenser units. They seem to be much cheaper this way. I don't want to get into the refrigerant and different capacities, I understand all of that from my refrigeration training.

My question is about the wiring between the evaporator and condenser units.
I know that this comprises power and a communication wire.

What is the communications wire? I understand that it is the control between the indoor and outdoor units, but are they all standard?

For instance, is it a pair of thermostatic contacts that open and close with the demand of the indoor unit, or a switched 24vdc demand signal, a 110vac (or220vac) demand signal, or something more complicated. Is it a standard throughout the industry?

Thank you in anticipation...

as these unit work on pcbs and programmed chips i don't think you can mix and match unit just to save money

Wow, this is interesting. 75 views and no one knows!?

the signals on interconnecting wires are pulses on inverter ac units this is why you can not mix units

What about older units which don't use inverter technology?

if they are working on relays and contactors then you can fit your own type of control thermostat and voltage to suit the unit you buy

So, in summary, none of you have a clue?

If you supply the makes and models you’re thinking of getting you’ll get the answers you want !

they are not standard it will depend on the manufacture but from a cost point it will be cheaper to buy a compleat system rather than try to mix different unit

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Originally Posted by Wickfut

Wow, this is interesting. 75 views and no one knows!?

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Jeez fella, you do have an appropriate forum name.

Seeing as Martin already answered your question why would anyone else just repeat the answer?
You should think yourself lucky he went on to answer your next query.
Good luck in your install...

Andy.

I never received an answer to my question. Is there any point in moving on an asking a question on inverter compressors and it's relation to subcooling? I probably shouldn't hold my breath? Or you could all dazzle me with your brilliance and help me?

having answered your questions and you not being able to understand the answers i think you must be the rudest people ever to post

Enough for me, member shut down and thread closed, sorry folks.