ASHRAE Handbook — HVAC Applications, Water Treatment
What it means on the job
Visible scale on condenser tubes indicates water treatment failure. Scale acts as insulation on heat transfer surfaces — 1/16" of scale increases energy consumption by approximately 11%. The condenser must be chemically or mechanically cleaned, and the water treatment program must be corrected to prevent recurrence.
Tested in 1 CraftIQ puzzle
- whats-wrongCondenser Water Chemical Treatment
Related ASHRAE sections
ASHRAE Guideline 36 / Manufacturer Requirements
Chillers require a minimum runtime (typically 15-30 minutes) and minimum off-time (typically 15 minutes) to prevent compressor short-cycling. Frequent starts damage the compressor motor and reduce equipment life.
ASHRAE Handbook — Fundamentals, Chapter 7
A thermostat behind a door that is typically held open will be in stagnant air and will not sense the true space temperature. It must be in an area with representative airflow of the occupied zone.
ASHRAE Handbook — HVAC Applications
Rooftop units must have vibration isolation to prevent noise and vibration transmission to the building structure. Required by ASHRAE and most building codes.
ASHRAE Handbook — HVAC Systems
Hot water reheat coils must have isolation valves for maintenance and balancing. Without them, the entire zone piping loop must be drained for any coil work.
ASHRAE Handbook — HVAC Systems / ASME B31.9
Valve stems and packing glands must not be insulated over. Covering valve operators prevents maintenance access and traps moisture that accelerates stem corrosion and packing failure.
ASHRAE Handbook — HVAC Systems and Equipment, Centrifugal Pumps
The cavitation noise (sounds like gravel passing through the pump) confirms insufficient NPSH available. Continued operation will erode the impeller vanes, damage seals, and ultimately destroy the pump. The pump must be shut down and suction piping corrected before returning to service.
CraftIQ explanations are original educational commentary written in trade language and verified against the cited standards. Always confirm requirements against the code edition adopted by your jurisdiction — this is training material, not a substitute for the code book or your AHJ.