HVAC PIPING

What is the most common range for minimum velocities in a horizontal line carrying refrigerant vapor?

500 to 700 ft/min

What is considered a long line application for residential air condition?

80 ft residential ; 100 ft commercial

Excessive pressure drop in liquid line can create what?

Flash gas

What effect does oil have on a systems coils?

It acts as an insulator

Why are oil lifts needed in tall vertical refrigerant risers?

Keeps oil from flowing back through a pipe/ to help move oil

What problems are caused by undersized suction lines?

Loss of efficiency

Suction line must be sized for proper _________ return

Oil

All vapor carrying lines should have ____ _______ installed to maintain proper oil return

Oil trap

What can prevent refrigerant from being drained or moved back into the compressor?

Oil trap

When units are level the suction line should be...

Pitched 1/2 inch per every 10 feet

What two factors affect the hot gas line size?

Pressure drop and velocity

What problems are caused by oversized suction lines?

Slows down to the point oil drops out of refrigerant

Why may the liquid line need to be insulated?

So it maintains its temp and efficiency

Why might the hot gas line be insulated?

So it maintains its temp and efficiency

Why is refrigerant oil flow through the liquid line not a problem?

The oil mixes with refrigerant so it can flow

What are two common reasons the suction line is insulated?

To heat line, if not insulated

What are two major functions of refrigeration piping?

To move refrigerant, transfer heat, and move oil

Refrigeration/air conditioning line sets must be sized based on what three things?

Velocity, Pressure drop, and refrigerant charge

What is liquid slugging?

When liquid flows back to an operating compressor