To　improve　the　defrosting　accuracy　of　air　source　heat　pumps　(ASHPs),　this　paper　proposes　a　novel　defrosting　control　method　by　applying　tube　encircled　photoelectric　sensors　(TEPSs).　A　field　test　was　conducted　for　two　heating　seasons　in　Beijing,　China,　to　verify　the　feasibility　and　practicality　of　the　novel　TEPS　method.　The　test　results　revealed　that　irrespective　of　the　environmental　conditions,　the　TEPS　method　can　initiate　defrosting　in　similar　situations:　most　of　the　heat　exchanger　surface　had　been　covered　by　frost;　the　compressor　suction　temperature　decreased　by　similar　to　9　degrees　C;　the　compressor　discharge　temperature　increased　by　similar　to　16　degrees　C;　and　the　heating　capacity　decreased　by　similar　to　30%.　Furthermore,　the　TEPS　method　was　verified　to　make　more　accurate　and　more　reasonable　defrosting　decisions　than　the　traditional　T-T　method　under　both　frosting　and　non-frosting　conditions.　The　results　indicate　that　the　TEPS　method　is　a　competitive　defrosting　control　method　that　can　be　used　for　ASHPs.　(C)　2015　Elsevier　Ltd　and　IIR.　All　rights　reserved.