Vacuum pump

A vacuum pump removes air and moisture from a refrigeration circuit before charging. It is the step that determines whether the system will work: moisture left in the circuit freezes at the expansion valve, forms acid with the oil, and destroys the compressor over months rather than days.

Two families are offered. The single stage pumps - VK115, VK125, VK135, VK155, VK160, VK180, VK190 and SVK115 - reach an ultimate vacuum of 5 Pa and cover 1.5 to 10 CFM at 50 Hz (1.8 to 12 CFM at 60 Hz). The dual stage pumps - VK215, VK225, VK235, VK245, VK260, VK280 and VK2100 - reach 3 x 10-1 Pa, which is the level needed when a system has to be evacuated to a deep vacuum and held there, or when moisture has to be removed at low temperature.

Motor ratings run from 1/4 HP to 1 HP, oil capacity from 170 to 550 ml and weight from 5.0 to 18.0 kg. Inlet ports are 1/4 inch flare, or 1/4 inch and 3/8 inch flare on the larger models, so the pump can be connected to a manifold or directly to a large line.

The difference between the two families shows up in practice on large systems and on systems that have been open to atmosphere: a single stage pump will pull a deep vacuum eventually, but a dual stage pump gets there faster and holds it, which matters when the evacuation time is being watched.

Maintenance points: change the oil after every few evacuations, or whenever it looks milky - moisture in the oil is what limits the vacuum the pump can reach. Keep the inlet capped between jobs, and do not use the pump to pull liquid refrigerant; it will carry oil out of the pump and contaminate the charge.