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
