Supply Air Temperature Cooling

For example if the air supply system is designed for a constant air supply temperature of 55 f the valve controlling the supply of hot water to the heating coil will close as the supply air temperature approaches 55 and will open wider if the supply air temperature begins to drop below 55 f.

Supply air temperature cooling.

The cold air systems distribute air at a temperature much lower than 55 f. The coldest practical air temperature is about 38 f with most cold air designs using 42 48 f. When the odb is at or above 26 7c the setpoint is the off coil air temperature set point. Your cooling schedule that sets cooling setpoint temperature changes values between 0 and 24 on weekdays and the summer design day which is the design day used for cooling sizing.

The well known fact that 55 degrees is the preferred supply air temperature comes to us from the commercial world. 2 outdoor air temperature reset reset the cooling supply air temperature based on the following default rules. In cooling mode the cool supply air typically around 55 f 13 c saturated at design conditions exits an outlet at high velocity. So even though there s no single ideal temperature you do want a 16 22 f difference from the supply air and return air.

The supply air temperature can be always maintained at its design setpoint 55 f by modulating the outside airflow using the outside air and return air dampers. In between the setpoint is varied linearly. Professionals call this temperature difference the evaporator delta t. Mixing systems generally supply air such that the supply air mixes with the room air so that the mixed air is at the room design temperature and humidity.

The unit controller compares the supply air temperature to the supply air temp alarm for cooling and initiates the alarm based on the following criteria. The temperature your ac puts out is relative to the temperature you set on your thermostat. All the stages of cooling have been on for 10 or more minutes. First let s start with 55 degrees.

For a given air conditioning load as the supply air temperature is reduced the supply air volume is reduced proportionally. Since the lowest supply air temperature is already achieved without any mechanical cooling supply air temperature optimization is not necessary in this outside air condition. Why use cold air distribution.