Can use the same concept of central AHU for the FCU in regard to pre-cooling or reheating?

Question

As we know that for  FAHUs, outdoor air after passing the precool coil and main cooling coil its temperature reduces to 12 to 14 degC at 100% RH, after that the Reheat coil rises the air temperature to 24 C / 50%RH and then supply to rooms.

My question is why we are not using a reheat coil in FCUs even if  the cooling coil reduces the air temp to 12 degC and 100%humidity. Both cases are similar.

Answer 1

Fan coil units are small in physical size and there is no room for installing the additional coils, otherwise cannot fit in a regular room or celling plenum. The pre- cooling or pre-heating coils in central AHUs are for cooling outside air in hot season or heating outside air in cold season to around 80 degree Fahrenheit to have better temperature control in main coil. The RH (relative humidity) of outside air need to be reduced by the certain cooling coil or increase by the humidifier. With regular cooling or heating coil cannot control the humidity level.