{HEAD ~ The heat pump} in accordance 1 or 2, wherein said {TAIL ~ second reversing means} is a four way valve 
wherein
{ HEAD ~ The heat pump } in accordance 1 or 2 , wherein said { TAIL ~ second reversing means } is a four way valve
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH REL OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH