Hot Deck, Cold Deck – Short #182

In this short episode, Bryan discusses the unique features of hot deck, cold deck systems. These systems have separate heating and cooling components (if not entire systems).

Older systems may have completely separate duct systems: one for heating and one for cooling. These ducts would go to each space, and you'd essentially have twice the ductwork you'd expect nowadays. Some systems also have a separate hot deck and cold deck in a single appliance (a bit like gas furnaces with case coils).

We also use the term “hot deck, cold deck” to refer to systems with secondary fluid in a single appliance that produces heating and cooling. Heat recovery or heat-pump chillers use secondary fluids to carry heat around (these fluids don't expand and change state like refrigerant). A traditional chiller is often used in combination with a boiler system, and both can be shut on or off; this configuration can be tricky in shoulder seasons, and a hot deck, cold deck system could be beneficial instead.  Buffer tanks also allow energy to be stored in a hot deck, cold deck configuration.

Hot deck, cold deck systems may also be beneficial in humid climates if the cooling component is before the heating component; the system could provide heating, cooling, and dehumidification. You could also use hot deck, cold deck systems for domestic hot water (via a heat exchanger) and cold plunges. It's even possible to use flammable refrigerants in heat recovery chillers that use this configuration.

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