A charge control circuit includes a resistance module, a voltage comparing module, and a charge control module. The first and second stations are equipped with first and second drives for driving circulatable surfaces of the respective station along the transport track. It has a second heat transfer fluid freezing point, lower than the first heat transfer fluid freezing point, and sufficiently low to operate without freezing when the outdoor air temperature drops below a first predetermined relationship with the first heat transfer fluid freezing point. A second substrate having a second patterned circuit layer thereon is provided.