An HVAC unit at Bethel High School is broken, but will be replaced this weekend.  The unit on the roof above the gym during the freezing temperatures earlier this month.  It affected other systems across campus.  Officials had to move some classes and install temporary heating systems in the interim.  A crane is needed to remove the unit and install the new one. Some delays on Whittlesey Drive are expected Saturday while the crane is being staged, and then on Sunday when the work is done.