It　has　been　known　that　for　space　heating　ASHPs,　different　operations　and　configurations　can　influence　their　frosting　suppression　performances.　However,　the　practical　applications　through　varying　the　operations　and　configurations　of　ASHPs　for　frosting　suppression　has　not　been　well　documented.　Therefore,　in　this　paper,　field　investigations　on　frosting　suppression　for　variable-capacity　ASHPs　through　optimizing　their　operations　and　configurations　are　reported.　The　investigations　were　based　on　two　multi-compressor　ASHPs　of　the　same　size,　one　being　conventional,　and　the　other　being　optimized,　with　respect　to　their　operations　and　configurations.　The　outdoor　airflow　rate　and　the　surface　area　of　outdoor　coils　of　the　optimized　ASHP　were　twice　as　much　as　those　of　the　conventional　ASHP.　By　comparing　the　field　measured　results　from　the　optimized　ASHP　with　those　from　the　conventional　ASHP,　it　could　be　found　that　for　the　optimized　ASHP,　its　frosting　rate　and　frosting-defrosting　loss　efficiency　could　be　reduced　by　37.2%　to　39.6%,　and　31%　to　34.2%,　and　its　operating　performances　improved　by　5%　to　22%,　respectively.　Therefore,　optimizing　the　operations　and　configurations　of　ASHPs　would　have　significant　potential　for　improving　their　frosting　suppression　performances,　and　consequently　their　actual　operating　performances　under　part-load　conditions.　(C)　2020　Elsevier　B.V.　All　rights　reserved.