Now the summer is here and the thermostat is on cool setting. Can the thermostat be turned off during the time when we're out or no one is home? or does it work like when it set during heating season (meaning set the thermostat 24/7 almost the same or just 2 degree notch)?

Thanks

A lot depends where you are located. If you are located in a heating dominate climate you should be able to set back your stat. HOWEVER...allowing your home to warm too much is not recommended. The Geo simply has to run too long making up the set back costing more than it would to keep your home at temp.

Bergy

I would beg to differ / or at least say its not that simple .
The big concern with set backs is use of aux heat , this can not happen in cooling.
In situations where the house temp is raised to or close to the outdoor temp for period of time there are significant savings with setbacks
Use it how you like but with the exception of recovery limitations there is little sence in cooling your home for 8-12 when your not home
Lowering the Delta between IDT and ODT decreases heat gain which decreases the number of BTU's you have to move out
I would venture this holds truth holds up even in the face of 2 stage equipment

We have 2 zone thermostat. We live in NJ. Right now, the weather is not too hot yet mid 70's to 80's. So we set our thermostat cool setting at 77 which is still pleasant to us. The ground floor thermostat is actually off because it's cooler than the 2nd floor. Actually, the system is not running continuously as it is not too hot outside yet. But as Geo fan says, the big concern during heating season is when the aux. heat kicks in because of long heat recovery which doesn't happen during cooling season..makes sense..thanks!

For what it's worth, we hit near 90 degrees over the weekend. The house was at 84 after we spent the day outside, so I turned on the a/c and dialed the t-stat down to 76. (I was putting heat back into the ground for next winter. That's my story and I'm stickin' to it.)

It took my 8-ton about 50 minutes to get our 3,800sft of west-facing glass windows down to 77 (at which point I shut it off, since it had cooled off outside significantly). I expect that time will increase in the high summer, when the ground loop is no longer 35 degrees.