UNDERHOOD 40 Compressor Engagement Delay

Technical Support Subject UNDERHOODTM 40 Compressor Engagement Delay Version Document Department Revision Details Author Reviewed by Implemented Tech. Eng. A EXT-UH-018 Tech Document Release BDJ MSP N/A 4 July 2023 Page 1 of 1 Knowledge Base: http://kb.vmacair.com/ Email: tech@vmacair.com Web: www.vmacair.com Technical Support: 1(888)241-2289 Sales:1(800)738-8622 Fax: 1(877)740-3201 SYSTEM OR PARTS AFFECTED • UNDERHOOD 40 Air Compressor Systems OVERVIEW The control system in UNDERHOOD 40 air compressor systems includes a programmed 12 second delay that begins counting down when the compressor clutch disengages after the system builds full air pressure (150 psi). The compressor clutch will not re-engage until the 12 second delay has passed. The purpose of this delay is to ensure that the system has had ample time for internal pressure to blow down prior to re-engagement of the compressor, preventing premature wear of the compressor’s clutch and potential shaft seal failure. In some applications this delay could be a nuisance. 2 ways to remedy this issue are: 1. Increase the size of the air receiver tank in the system to provide enough reserve air to keep working through the delay period. The use of an air receiver tank (minimum 6 USG) is required with UNDERHOOD 40 systems. 2. Install a valve downstream of the WHASP discharge port that can be opened to vent a small amount of air to the atmosphere to prevent the compressor clutch from disengaging between air tool usage. Some experimentation may be necessary to find the balance between adequate air bleed to keep the compressor running, and too much, such that system pressure suffers for air tool use..