Refrigerant Piping—Pressure
Relief Valves
(ETL Marked Units Only)
All units have individual refrigerant circuits and each circuit is
provided with a spring loaded relief valve . The valve is set to
open when refrigerant pressure reaches 600 psig . The relief
valve accommodates a 3/8" flare connection for applications
where it is necessary to connect vent piping and run it outside
the building .
CAUTION
When refrigerant is vented to the outside of the building,
install the vent piping as recommended in
ASHRAE Standard
15-1994
. Failure to vent properly can result in personal injury .
Water Connections
Due to the variety of piping practices, follow the
recommendations of local authorities . They can supply the
installer with the proper building and safety codes required for
proper installation .
For best performance, install the piping with a minimum
number of bends and elevation changes . Size piping to
minimize system pressure drop .
Piping should contain the following:
1 . Vibration eliminators to reduce vibration and noise
transmission to the building .
2 . Shutoff valves to isolate the unit from the piping system
during unit servicing .
3 . Manual or automatic air vent valves at the high points of
the system .
4 . Some means of maintaining adequate system water
pressure (e .g ., expansion tank or regulating valve) .
5 . Temperature and pressure indicators located at the unit
to aid in servicing .
6 . A strainer or some means of removing foreign matter,
which can damage the pump and shorten unit life, from
the water before it enters the pump . Such damage is
not covered by warranty . Place it far enough upstream
to prevent cavitation at the pump inlet (consult pump
manufacturer for recommendations) . Using a strainer
prolongs pump life and helps maintain system
performance .
Condenser Piping
1 .
Units can be specified with water and condensate
connections on either the left or right side of the unit .
2 . All condensers are factory piped for a common condenser
water supply and a common condenser water return
connection .
3 .
Make field piping connections to factory-provided piping,
locating them as indicated on the unit submittal drawings .
Run the piping connections to the outside of the unit
cabinet . Standard connections are ODS copper with
victaulic connections .
4 . Make supply and return water connections at the proper
locations as indicated by the dimensional drawings .
5 . Units with factory-mounted water side economizer should
not require head pressure control . The economizer
typically elevates the water temperature by 5°F to
10°F before entering the condenser, allowing suitable
condenser water temperatures whenever the tower supply
temperature is 50°F (10°C) or higher . Mechanical cooling
is locked out below 55°F (12 .8°C) EWT .
6 . If entering condenser water temperatures will go below
55°F (12 .8°C), provide head pressure control . Fan cycling
and/or modulating discharge dampers on the cooling
tower are often used, or a 3-way bypass around the
tower is used to maintain condenser water temperature .
If multiple units are in the loop, it is generally more cost
effective to use cooling tower control to maintain the
temperature at >55°F (12 .8°C) .
The factory installed water regulating valve is placed in
the water line entering the condenser; and shuts down
to prevent water from siphoning out of the condensers .
For systems where a constant pumping head is required,
install the water regulating valve in a bypass line around
the condensers . It then must open on falling discharge
pressure .
These typical systems, depending on the specific
application, must maintain a constant condensing
pressure regardless of temperature conditions and must
provide adequate head pressure for proper thermostatic
expansion valve operation . A minimum head pressure of
294 psi (21 .3 bar .) (95°F [35°C] condensing temperature)
is recommended .
7 . Condenser tube velocities must not exceed 10' per
second (3 m/s) (approximately 7 .5 gpm/ton [0 .47 lps/ton]) .
Figure 11: Condenser Regulating Valve
IM 1032-2 • Self-Contained Air Conditioning System 10 www .DaikinApplied .com
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