Installed a CT87N thermastat problem with air conditioning. Can't seem to control temperature. Thermastat runs continually to the point where windows frosted up. Can't turn it off so had to turn of circuit breaker. Just installed yesterday, know it is installed correctly

If you know it is installed correctly must be something wrong somewhere else, maybe a short between red and yellow wire or a stuck/welded contactor in condenser unit

Thank you, returned thermastat to store. Replacement is fine so believe the original thermastat was defective.