The primary disadvantage of using electric rental units is the time it takes to set them up on site and get them producing compressed air. Wiring for the three phase power required for these units, between the customer's disconnect and the rental equipment, is usually the most time consuming part of hooking up an electric rental compressor. Therefore, when done under emergency conditions, electric units are frequently just too time consuming to be a realistic option. If electric drive is preferred, and quick deployment is required, you must prepare in advance for setting up the rental equipment. The compressed air quality that is needed is a critical element when it comes to compressor rentals.
Different machines vary widely in terms of the purity of the delivered air.
But because they are truly oil-free, they rent for higher rates than lubricated compressors. An industrial aftercooler can condense some oil vapor right along with the water vapor. However, since they are not inherently oil-free, there is a possibility of oil carryover, in the event of a primary separator element failure. Thus, an element of risk is accepted should this type of equipment be used on a true oil-free application. Standard electric rotary screw rental compressors typically have aftercoolers on board, and usually operate with oil carryover rates of 2-5 ppm downstream of the aftercooler.