Performed 1 system heating maintenance. No form of power protection at furnace. Recommend installing surge protector to keep electrical components from damage. Blower wheel has large amounts of dirt and grime and needs to be cleaned to restore air movement system efficiency and balance. Pvc has clean out tee outside of pan and will overflow on drywall if line clogs. Recommend installing e-z flow switch to shut down system if backup is noticed. Installed e-z flow inline switch. Chemically cleaned blower wheel. System operating properly at this time.