Q&A | Condenser Relief Valves

Question: Are pressure relief valves required to be installed on an evaporative condenser?

Answer: This is a very good question and one that gets asked frequently. Since an evaporative condenser is not a pressure vessel, it is not a black and white requirement as it is for the vessels throughout a refrigeration system. However, the condenser has the potential to contain large quantities of ammonia and if isolated incorrectly can lead to hydrostatic expansion and equipment rupture. The most current codes are now addressing this danger with greater clarity. Below you can read a section from ANSI/ASHRAE 15-2010 Safety Standard for Refrigeration Systems. It addresses the issue pretty succinctly:

In other words, if ammonia can be trapped in an evaporative condenser during normal operation, then relief valves must be installed. If ammonia can only be trapped during maintenance (temporary operations) then administrative controls (procedures) are sufficient to prevent over-pressurization. Usually the question I ask to get to the bottom of this is…”Does the facility isolate the condenser as part of normal operation because of fluctuating load patterns?” If the answer is “Yes“, then relief valves should be installed on each evaporative condenser circuit.

IIAR also addresses the issue in a similar fashion ANSI/IIAR 2-2008 Equipment, Design, and Installation of Closed-Circuit Ammonia Mechanical Refrigerating Systems. You can read their requirements below:

From the text above, relief valves are only required when automatic isolation and trapping of liquid is possible to occur. OSHA has recently acknowledged that the language in IIAR addresses their safety concerns which is a good sign for our industry moving forward.