En-Met's ISO-3T is a 3 relay ISOPAC that can be used for 240 / 115V single
stage Heating and Cooling
systems, as well as single stage Heat Pump systems. An external transformer is
required. It can also be used in the
"wire save" mode, with the addition of 2 diodes, back-to-back, installed in the
the ISO-3T data sheet.