In　this　paper,　an　experimental　performance　evaluation　of　a　direct　expansion　ground-coupled　heat　pump　(DX-GCHP)　system　in　heating　mode　is　presented.　The　DX-GCHP　uses　R134a　as　the　refrigerant,　and　consists　of　three　single　U-tube　copper　ground　heat　exchangers　(GHEs)　placed　in　three　30　m　vertical　boreholes.　During　the　on-off　operations　from　December　25,　2007,　to　February　6,　2008,　the　heat　pump　supplied　hot　water　to　Fan-coil　at　around　50.4　degrees　C,　and　its　heating　capacity　was　about　6.43　kW.　The　energy-based　heating　coefficient　of　performance　(COP)　values　of　the　heat　pump　and　the　whole　system　were　found　to　be　on　average　3.55　and　3.28　at　an　evaporating　temperature　of　3.14　degrees　C　and　a　condensing　temperature　of　53.4　degrees　C,　respectively.　The　second　law　efficiency　on　the　DX-GCHP　unit　basis　was　around　0.36.　The　exergetic　COP　values　of　the　heat　pump　and　the　whole　system　were　obtained　to　be　0.599　and　0.553　(the　reference　state　temperature　was　set　equal　to　the　average　outdoor　temperature　of　-1.66　degrees　C　during　the　tests),　respectively.　The　authors　also　discussed　some　practical　points　such　as　the　heat　extraction　rate　from　the　ground,　refrigerant　charge　and　two　possible　new　configurations　to　simultaneously　deal　with　maldistribution　and　instability　of　parallel　GHE　evaporators.　This　paper　may　reveal　insights　that　will　aid　more　efficient　design　and　improvement　for　potential　investigators,　designers　and　operators　of　such　DX-GCHP　systems.　Copyright　(C)　2009　John　Wiley　&　Sons,　Ltd.