Discovered a closed ball valve before the zone valve for the half of the house that was not being heated. Opened ball valve confirmed that their was hot water on each side of the zone valve. Confirmed that the space was heating up. Space went from 68-70 and is still rising. Temperature guage on the return went up 15 degrees from 60-75 and continued to rise. No charge for today. Thank you for choosing CPI Plumbing and Heating Inc