When calculating the net capacity of an air handling unit, it is sometimes important to calculate the impact of fan motor heat gain. When working with an engineer who as asked for AHU cooling coil performance, first clarify if their leaving coil condition takes into account fan motor heat gain. If not, you’ll need to calculate it.
When selecting an air handling with two coils in series, we may need to include a minimum 18” access plenum between coils per ASHRAE 62.1-2019 paragraph 5.13.2 as follows:
Recently, I have seen an increase in AHU specifications calling for the AHU manufacturer to be responsible for sizing the base rails so that there is enough vertical clearance to install an adequate condensate trap. The purpose of this white paper is to teach you how to calculate the required vertical distance from the centerline of the drain pan connection to the floor.
The energy code requires engineers to meet a minimum airflow rate per unit of fan power. There are two rules based on if the system is constant volume or variable volume. Each of these rules has two options for compliance: meeting a maximum motor nameplate horsepower, or meeting a maximum brake horsepower. The requirements are summarized in the table below.
ECM (electronically commutated motor) applications are becoming more prevalent as the motor abilities increase in size and application. VFD (variable frequency drive) motors are applied most typically when varying the speed of an induction motor. The question often heard currently is “which technology is better”? This topic can expand to subjects of motor loss differences, switching frequencies, and power factor correction to name a few. This document will address the questions from a further distance as we examine a common Fanwall application and look at overall costs and efficiencies.