Vent connectors shall not be increased in size more than________ greater than the listed appliance categorized vent diameter, flue collar, or draft hood outlet.

When larger A/C loads require larger contactors that operate on line voltage because of their larger size, what additional component must be used to control these contactors?

In the HVAC and plumbing industry, steel pipe is usually joined by _______________ pipe threads.

Carbon monoxide in significant amounts is formed during fuel gas combustion:

The approximate heating value of natural gas is:

What type of flame is characteristic of incomplete combustion?

When soldering, the main function of flux is to 

What instrument is used primarily for measuring the air tightness of a duct system?

What is the purpose of excess air in fuel gas combustion?

The refrigerant at the outlet of the compressor does not correspond to a temperature/pressure chart because the refrigerant is