Building Systems Operations & Maintenance Flashcards

Which ASHRAE standard establishes minimum requirements for a water management program to reduce Legionella risk in building water systems such as cooling towers?

Answer: ASHRAE Standard 188

ASHRAE 188 covers Legionellosis risk management for building water systems, including cooling towers.

A water-cooled chiller shows a steadily rising condenser approach temperature while load is unchanged. What is the most likely cause?

Answer: Fouled or scaled condenser tubes

Scale or fouling on condenser tubes reduces heat transfer, widening the approach between refrigerant and leaving water temperatures.

MERV ratings used to select air filters are defined by which test standard?

Answer: ASHRAE Standard 52.2

ASHRAE 52.2 defines the Minimum Efficiency Reporting Value test method for air cleaning devices.

What is the primary function of an air-side economizer on an air handling unit?

Answer: Use cool outdoor air for free cooling when conditions allow

An economizer increases outdoor air intake when its temperature or enthalpy is low enough to reduce mechanical cooling.

Why is regular blowdown performed on a steam boiler?

Answer: To remove concentrated dissolved solids and sludge from the boiler water

Blowdown controls total dissolved solids and removes sludge that would otherwise cause scale, carryover, and corrosion.

A steam trap that has failed in the open position will most likely cause which problem?

Answer: Live steam passing into the condensate return, wasting energy

A trap failed open blows steam through to the return, wasting fuel and potentially pressurizing the condensate system.

Per the pump affinity laws, if a VFD reduces a centrifugal pump's speed to 50%, approximately what percentage of full-speed power will it draw?

Answer: 12.5%

Power varies with the cube of speed, so 0.5³ equals about 12.5% of full power.