Installation manual

IM 1029-2 Magnitude™ Frictionless Centrifugal Chillers – Model WMC 21
Relief Valves
As a safety precaution and to meet code requirements, each
chiller is equipped with pressure relief valves located on the
condenser and evaporator for the purpose of relieving excessive
refrigerant pressure (caused by equipment malfunction, fire,
etc.) to the atmosphere. Most codes require that relief valves be
vented to the outside of a building and this is a desirable
practice for all installations. Relief piping connections to the
relief valves must have flexible connectors.
Note: Remove plastic shipping plugs (if installed) from
the inside of the valves prior to making pipe connections.
Whenever vent piping is installed, the lines must be run in
accordance with local code requirements; where local
codes do not apply, the latest issue of ANSI/ASHRAE
Standard 15 code recommendations must be followed.
• Condensers have two 200 psi, 1.0-inch female NPT relief
valves as a set with a three-way valve separating the two
valves. One valve remains active at all times and the second
valve acts as a standby.
• Evaporators have a single 200 psi valve. Each valve has a 1.0-inch female NPT connection.
• Each suction line on dual compressor units has a single 200 psig relief valve rated at 6.9 lb/min air with a
3/8-inch flare connection.
• Vessel valve capacity is 75 lb/min air.
Figure 17, Condenser 3-Way Relief Valve
Refrigerant Vent Piping
Vessel relief valve connection size is 1-inch FPT and are in the quantity shown in Table 2 and Table 3 on
page 9. Twin relief valves mounted on a transfer valve are used on the condenser so that one relief valve can
be shut off and removed for testing, leaving the other in operation. Only one of the two is in operation at any
time.
Vent piping is sized for only one valve of the set (but connected to both) since only one can be in operation at
a time. In no case would a combination of evaporator and condenser sizes require more refrigerant than the
pumpdown capacity of the condenser. Condenser pumpdown capacities are based on the current
ANSI/ASHRAE Standard 15 that recommends 90% full at 90°F (32°C).