I am looking to put Nest thermostats in the house, I have now found out my entire house (one in each room, 6 of them) has been wired with HVAC Chinese U12A UNIVERSAL A/C CONTROL SYSTEM urrgh – they have none of the connects Rh, C, W, W2 etc that Nest tells me to check for... this Chinese kit has just a board (HVAC controller?) and the display that plugs in to this board via a 10 pin unlabeled connector.

Will I need to replace the entire controller board (how much do they cost each), or do proper thermostats have all the controls built in and not need an external controller?

If so would it be a case of running wires down from the fan/compressor/valves to the new thermostat and hey presto or anything else i should look for?

The units wiring diagram is below:

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  • How many wiress are there actually running from the 10 pin connector? – wallyk Mar 31 '16 at 5:29

It looks as if you'll have to replace your entire HVAC controller board with something that supports a standard thermostat interface. From there, you can then install whatever thermostat you wish.

Another option would be to use a control adapter such as one of these -- they "fool" the control board by replacing its room-temp sensor with a signal from the adapter.

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