Building Engineering Mechanical Engineering 3

Question 1

In a two-pipe hydronic heating/cooling system, what is the main operational limitation compared to a four-pipe system?

Accepted Answer

Cannot simultaneously heat some zones while cooling others

Answer

A two-pipe system uses the same piping for both heating and cooling, so it can only be in heating mode or cooling mode at any given time, not both simultaneously.

Question 2

What is the function of a pressure-reducing valve (PRV) in a domestic water system?

Accepted Answer

Reduces incoming street pressure to a safe working pressure for building fixtures

Answer

A PRV reduces the typically high municipal supply pressure (often 80–150 psi) to a safe building pressure, usually 50–80 psi, protecting fixtures and piping.

Question 3

Which refrigerant property is expressed by the term 'superheat' at a compressor suction port?

Accepted Answer

Temperature of vapor above its saturation temperature at that pressure

Answer

Superheat is the number of degrees by which a vapor's temperature exceeds its saturation (dew point) temperature at the same pressure.

Question 4

According to IMC/IBC, what is the minimum clearance required between the bottom of a gas-fired furnace and a combustible floor?

Accepted Answer

0 inches if listed for floor installation

Answer

Gas furnaces listed and labeled for installation on combustible floors may be installed with zero clearance when installed per manufacturer instructions.

Question 5

A chilled water system uses 'delta-T' as a key performance metric. What does a degraded (low) delta-T across a chiller evaporator indicate?

Accepted Answer

Fouled heat transfer surfaces reducing capacity

Answer

Low delta-T syndrome means the difference between return and supply chilled water temperatures is smaller than design, often caused by fouling, coil bypass, or low coil loads that reduce heat transfer.

Building Engineering Practice Test

Building Engineering Practice Test

Building Engineering Mechanical Engineering 3