What Is A Hot Deck Cold Deck System

The ahu had both a cold deck cd and a hot deck hd where both maintained a constant leaving air temperature maybe 55 f and 95 f respectively with mixing dampers mounted on the front or top of the ahu.

What is a hot deck cold deck system.

The hot deck is reset based on the zone. The hot deck setpoint and the cold deck setpoint operate respectively the water valves to the hot deck coil and the cold deck coil. Each zone requires an actuator application. The dual duct air handlers take 180 degree f.

Cold decks for providing heating and cooling capabilities simultaneously. Refer to photo 3 which illustrates damper actuators on a smaller mz system. Temperature reset program is applied to dual duct systems and multizone hvac systems. Typically the ahu controller also resets the hot deck and cold deck setpoints and controls the zone mixing dampers.

The hot deck cold deck. Up of two dampers one for the cold deck and one for the hot deck. The damper blades for the hot and cold decks are linked together and offset by 90. The hot deck is halfway open and the fan ramps up to maintain pressure in the unit.

As hot gas bypass will be required. Maintenance or operational staff will be able to advise whether a system is a hot deck cold deck type. Cool air through duct work to a terminal box. As the signal approaches 0 the bypass deck is closed the hot deck is fully open and the fan is at full speed.

As the call for heating reduces from full heat the hot deck starts to close the bypass. Water and supply 100 degree f. Therefore one actuator may operate the cold deck and hot deck simultaneously. Systems utilize a parallel arrangement of heating and cooling surfaces commonly referred to as hot and.

And 42 degree f. Some multizone units control one deck or the other in a multipoint arrangement such that the nearest to full heating controls hot deck temperature. It explains how to use the ahu to reset the hot deck and cold deck setpoints. Hot air and 55 degree f.

As the damper opens one deck it closes the other and vice versa. In other systems the signal may. This application note is relevant when using an ahu to control a multi zone air handler.