Relief Valves - McQuay WMC Installation, Operation And Maintenance Manual

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.
• Condensers have two 200 psi, 1.0-inch female NPT relief
valves as a set with a three-way valve separating the two
valves. (See Figure 8.)
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.
• When purchased with a suction isolation valve, each
suction line has a single 200 psi relief valve rated at 6.9
lb/min air with a 3/8-inch flare connection.
• Vessel valve capacity is 75 lb/min air.
CAUTION
Units are shipped with refrigerant valves closed to isolate the
refrigerant in the unit condenser. Valves must remain closed
until startup by the factory service technician.
Most codes require that relief valves be vented to the outside
of a building. Relief piping connections to the relief valves must
have flexible connectors.
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 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.
Condenser Relief Valves
As stated previously and as shown in
have two 200 psi, 1.0-inch female NPT relief valves separated
by a three-way valve.
Figure 8: Condenser Three-Way Relief Valve
Three-Way Valve
Relief Valves
In order to ensure proper installation, it is important to know
how the three-way relief valve functions. When the stem of the
three-way valve is pushed into the valve completely, the valve
is in "Front Seated Position" and all refrigerant will flow through
the back outlet port, as shown in
IOM 1210-1 • MAGNITUDE
One valve remains active at all
Figure 8, condensers
Figure 9. When the stem of
MODEL WMC CHILLERS
®
the three-way valve is pulled back completely, the valve is in
"Back Seated Position" and all refrigerant will flow through the
front outlet port as shown in
Figure 9: Three-Way Valve, Front Seated Position
Figure 10: Three-Way Valve, Back Seated Position
When the valve stem is not pushed forward or pulled back
completely, the valve is in "Mid Position," as shown in
11.
Do not operate the system with the three-way valve stem in
the Mid Position.
Figure 11: Three-Way Valve, Mid Position
10
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Figure 10.
CAUTION
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