Originally Posted by JCole21961
I have installed Hitachi heatpumps in my home in Brazil which use R407. The contractor is having difficulty charging the R407 so that the pressurestat protection devices do not kick out the compressors. In heating mode, with normal charge the suction pressure drops below 25PSI when temperatures are below 5C. If he adds refrigerant so this does not happen, on warmer days above 15C, the pressure exceeds the top limit of 450PSI. What are the normal operating limits for R407 in both heating and cooling modes? Is R407 commonly used? I do not know whether it is A, B or C.