Before we can advocate for our customers on HVAC equipment & system design, we must know the basics of Mechanical Engineering. Key to the understanding of this discipline is Thermodynamics & Heat Transfer. This EWP is dedicated to Heat Transfer.
In EWP 11 (Heat Balance) Ken taught us about the heat balance in water cooled chiller system and why it is important not to just use 3gpm/ton when sizing a cooling tower. This white paper is meant to expand on the heat balance & energy equations for air and water as it relates to typical equipment schedules.
The purpose of HVAC equipment is to maintain indoor temperature, humidity and air quality. This is a complex task, and we often need tables and formulas to describe the processes involved. However, tables and numbers are a poor way to communicate with our customers and sell equipment. The psychrometric chart is a tool for graphing the temperature and humidity of air as it goes through HVAC processes, and this paper
is an introduction to using it as a communication and sales tool.
Most HVAC equipment generates sound. Even equipment with no moving parts can generate sound- think louvers with too much airflow through them whistling. Sound can be perceived as annoying or distracting. And in some cases, the sound our equipment will generate can even be harmful to our ears. Because of this there are sound compliance codes and Sound Engineers that design & analyze sound in systems. For these reasons and more it is important that we all know the basics of sound and how it is utilized so we effectively navigate this important aspect of equipment selection & compliance.
For anyone familiar with chiller sizing, 2.4 GPM/ton will give you a 10F delta-T across the evaporator. For cooling tower sizing, the rule of thumb is 3.0 GPM/ton for a 10F delta-T across the tower. You may also be aware that although a cooling ton is 12,000 BTUH, a heat rejection ton is 15,000 BTUH.
While we are not electrical engineers or electricians there is a baseline knowledge required of us to ensure our equipment interfaces properly with the buildings electrical system. This white paper is meant to make you aware of these electrical characteristics, explain why they matter, and to show you how to do the calculates to ensure a proper application to the building electrical system.
We sell a lot ABB variable frequency drives as well as variable speed compressors on chillers & rtu’s. It is not often that we have to deal with the subject of harmonics or IEEE519 compliance in the sale but when it does come up you need to know the basics. Not knowing these basics can prevent you from selling your drives or worse causing a problem with the electrical system and connected components.
We all know about space temperature but when it comes to relative humidity or humidification in general not many have a good grasp on the subject. This white paper is meant to give you a basic understanding of humidity & humidification. Typically, moisture in the air is removed through the cooling process or outside air, controlling the high end of humidity. We will focus on the low end of humidity (dry air) and the addition of moisture (humidification) to maintain a minimum relative humidity.
Indoor pools are becoming more popular yet not frequent enough for everyone to stay sharp in the design considerations and rules of thumb. This document provides the means for calculating dehumidification loads, guidelines for airflow and its distribution, as well as concerns with lack of control.
The purpose of this white paper is to explain the energy code requirements for water‐cooled centrifugal chillers. I often get requests to send IPLV ratings for a centrifugal chiller to prove energy code compliance. However, unless the chiller is designed to operate at AHRI standard conditions (2.4 GPM/ton of chilled water leaving at 44°F and 3.0 GPM/ton of condenser water entering at 85°F), this is an invalid request. Figure 1 below from the 2015 WA State Energy Code establishes the rules for determining minimum efficiency levels for centrifugal chillers designed to operate at non‐AHRI Standard 550/590 conditions. Oregon uses ASHRAE 90.1-2016 which contains the same requirement. However, the baseline chiller efficiencies are slightly different in Oregon (see page 5).