How to wire A/C Thermostat given different wiring conventions

Question

I've just moved to a new apartment in which I'd like to replace the current central A/C thermostat with a new one with WIFI control. I hope it's possible! I have basic diy electric skills but no knowledge in Air conditioners.

Current Thermostat

The current thermostat has only two switches (beside the temperature knob) :

1. Cool / Off / Heat
2. Low / Med / High fan speed

The wiring of my current thermostat is as follows :

L1-~ L2-0 COMP R.V LOW MED HIGH

If I understand it correctly, the LOW, MED, HIGH are for fan control,

the L1-~, L2-0 are for line and neutral

andR.V, COMP are for 24V from the unit and for the compressor.

There's another loose wire connected to nothing.

New Thermostat

In the product I wish to buy, there's a different wiring diagram, in which the I don't understand which wire goes where. 7 Live Wire 6 Valve OFF - for three-wire electric valve and fan coil 5 Valve ON - for two-wire electric valve and fan coil 4 Low 3 Medium 2 High 1 Neutral

Matching Between the Thermostats

I've figured out the Low Med High should be the same, however I'm not sure about the L and N wires and I definitely have no clue what is the Valve ON/OFF terminals are. So far this is my match between the two diagrams

Old New L1-~ -> Live Wire L2-0 -> Neutral COMP -> ????? R.V -> ????? LOW -> Low MED -> Med HIGH -> High

Here are the diagrams from the product's documentation:

Finally, the questions :

1. Are these thermostats compatible?
2. How to wire the new one to my A/C?
3. What are the Valve wires?

If there's a solution, a diagram would be much appreciated! If I'm just a noob with no clue and this is not possible, please be gentle :)

Answer 1

It does not seem that the thermostats are compatible, no. Your existing thermostat is designed to control a heat pump with a multispeed air handler:

• L1/L2 are likely 24VAC in
• COMP controls the heat pump compressor
• R.V. controls the heat pump reversing valve
• HIGH/MED/LOW control fan speeds
• the unused wire is just that -- it looks like someone wired your 'stat with network cable BTW, which is a bit of a no-no.

The new thermostat you have is designed to control multispeed air handlers in zoned hot water (hydronic) systems instead -- instead of controlling a compressor and a two position reversing valve, they are designed to control a variable-position hydronic zone valve, typically for heating only as they have no heat/cool changeover system or extra outputs for controlling cooling components.