EC button, when to use ?

Hi. I May sound ignorant but can anyone tell me that in the winter when the air conditioning is not required, should the EC button be pressed to on (illuminating that light) or should it be left off?
This is when the heaters are set to hot (winter conditions). unfortunately I do not have a handbook. 
 
Thank you

You want air conditioning ALL year! Air conditioning with the heater removes moisture from the air and stops fogging, on a wet winter day that is a life-safer. Air conditioning is just that, it conditions the air - not just cools it. In winter the air from outside, or inside when you press the recirculation button, is first cooled, which removes the moisture, THEN heated; you get nice dry warm air which removes fogging and makes you all comfy and cozy!

Lawrence

Concur. Let the A/C system work in auto controls all year. You will be better off on the human side and keeping the A/C - heat system always running/exercised correctly.