In the first of a pair of articles on motor fundamentals for HVACR, the author gets into everything from industry standards and service conditions to changing speeds, enclosures, and the often misunderstood service factor. You’ll want to save this one for your team’s reference library.
These days, designs are favoring higher total system capacities, larger generators at higher output voltages integrated into “campus-type” power distribution systems, and security. Review design approaches, lessons learned, and relevant codes.
In my experience, one of the trouble spots in project specifications is coordinating the control panels furnished with mechanical equipment with the standards that apply to the balance of electrical equipment on the project. Regardless of what you may include about NEMA enclosure types, short-circuit ratings, and other features, manufacturers tend to supply their standard control panel. The result is often an installation that cannot be verified to meet code or project requirements.
Microprocessor-based systems greatly increased the power and flexibility of BMS while lowering the cost of sophisticated control. A similar evolu-tion in electrical metering and protection devices has increased the amount of power system information available to building operators.
For motors in certain applications, the boilerplate approach to specification and design will get the system stopped because the motor won't start. Consider voltage, speed, and torque for these special instances, and follow along with the Case Of The Not-So-Centrifugal Pump Curve and the Case Of The Frequent Motor Failure to do some real-life motor- starting sleuthing. By Tim Coyle, P.E.
Retrieving every last bit of performance from the system while stopping short of the surge line is no small feat. Dig into sizing, tower selection, chilled water loads and stability, and condenser water management to leave no efficiency stone unturned. Read more in April issue