3 port valve- what does the setting arm do ?

[Chri5]

The Danfoss unit indoors has a metal slider switch. What does the switch do ?

Reason I ask is that the unit is stuffed in the corner of the airing cupboard and SWMBO thinks she caught a towel on it and moved the switch.

Y plan CH config if that helps.

 

[DeltaT]

This is how it works if it helps;

http://www.diyfaq.org.uk/plumbing/controls/midpositionvalve.htm