What Is A Hot Deck Cold Deck System

The damper blades for the hot and cold decks are linked together and offset by 90.

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. Some multizone units control one deck or the other in a multipoint arrangement such that the nearest to full heating controls hot deck temperature. Cool air through duct work to a terminal box. Hot cold deck systems are found in older office buildings and in institutional buildings but are largely indistinguishable from other ahu based systems to the non technical observer.

In other systems the signal may. The cold deck is always closed during heating. The hot deck cold deck. Therefore one actuator may operate the cold deck and hot deck simultaneously.

Typically the ahu controller also resets the hot deck and cold deck setpoints and controls the zone mixing dampers. Hot air and 55 degree f. As hot gas bypass will be required. Water and supply 100 degree f.

In some systems this control may remain for example where the signal is a function of the thermostat branch line pressure. Systems utilize a parallel arrangement of heating and cooling surfaces commonly referred to as hot and. Maintenance or operational staff will be able to advise whether a system is a hot deck cold deck type. The dual duct air handlers take 180 degree f.

Each zone requires an actuator application. The hot deck is reset based on the zone. This application note is relevant when using an ahu to control a multi zone air handler. The hot deck is halfway open and the fan ramps up to maintain pressure in the unit.

As the call for heating reduces from full heat the hot deck starts to close the bypass. Temperature reset program is applied to dual duct systems and multizone hvac systems. As the signal approaches 0 the bypass deck is closed the hot deck is fully open and the fan is at full speed. Refer to photo 3 which illustrates damper actuators on a smaller mz system.

Up of two dampers one for the cold deck and one for the hot deck. The hot deck setpoint and the cold deck setpoint operate respectively the water valves to the hot deck coil and the cold deck coil. It explains how to use the ahu to reset the hot deck and cold deck setpoints.