Q&A | Emergency Pressure Control Systems

Question: What is an emergency pressure control system?

Answer: An emergency pressure control system (EPCS) is a pressure-limiting safety system that is required by many current Fire Codes (International Fire Code and NFPA 1). The EPCS has replaced the Emergency Control Box (sometimes called Dump Box, Red Box, Fire Department Box, etc.) as a code required safety system for over-pressurization events. The EPCS differs from the Emergency Control Box in many ways. The two (2) most significant differences are:

• An EPCS is activated automatically, whereas an ECB can only be activated manually.
• An ECB includes a provision for manually discharging the refrigeration system. An EPCS has no such provision.

Essentially, the EPCS is a relief device which activates in an over-pressure situation above the pressure limiting device set pressure, but below the relief valve set pressure to allow the portion of the system subject to over-pressure to be relieved of its pressure by moving refrigerant through a solenoid valve to a lower pressure portion of the system. ANSI/IIAR 2-2008 Addendum B Appendix K provides the most thorough description of proper EPCS installation and operation. The following is a summary of proper EPCS functionality:

• EPCS must be activated at not greater than 90% pressure relief valve setting of the section of system that it is protecting [ANSI/IIAR 2-2008 Appendix K.4.5.3]
• Upon activation, all compressors must be stopped by a means that is independent of all other safety controls [ANSI/IIAR 2-2008 Appendix K.4.5.6]
• Upon activation, the cross-over valve must be opened [ANSI/IIAR 2-2008 Appendix K.4.5.6]
• Upon activation, a signal must be provided to personnel responsible for refrigeration system maintenance [ANSI/IIAR 2-2008 Appendix K.4.5.7]
• EPCS must remain active until manually reset [ANSI/IIAR 2-2008 Appendix K.4.5.8]
• EPCS crossover isolation valves must be locked open [ANSI/IIAR 2-2008 Appendix K.4.4.2]

In addition, a written procedure for operation and testing of the EPCS must be developed [ANSI/IIAR 2-2008 Appendix K.4.7.1] so that the EPCS can be tested as part of the annual system safety tests [ANSI/IIAR 2-2008 Appendix K.4.6.1].