Environmentally controlled chamber system utilizing hydrocarbon refrigerants

A method of controlling an environmentally controlled chamber system comprising:

• providing an environmentally controlled chamber system comprising:
• insulated enclosure having an access door;
• a humidification/dehumidification chamber enclosure positioned outside of the insulated enclosure and arranged and disposed to provide humidification or dehumidification to the insulated enclosure;
• a refrigerant loop comprising:
• an enclosure evaporator, a dehumidification evaporator, at least one condenser, at least one variable speed compressor and piping for directing refrigerant from the at least one variable speed compressor to the enclosure evaporator, the dehumidification evaporator, and the at least one condenser;
• and
• an electrical heating element having a first electrical heating element positioned on the bottom and in contact with the enclosure evaporator, the first electrical heating element being arranged and disposed adjacent to the enclosure evaporator, the first electrical heating element having little or no exposure to an induced airflow and a second electrical heating element positioned such that the induced airflow goes over the enclosure evaporator prior to going over the second heating element;
• directing the refrigerant to a high-pressure differential between inlet and outlet and modulation of the refrigerant flow going to the dehumidification evaporator or the dehumidification evaporator with one or more valves;
• and
• heating at least a portion of the enclosure evaporator by energizing one or both of the first electrical heating element and the second electrical heating element to offset cooling of the enclosure evaporator during operation of the variable speed compressor.