Water Connections; General; Condenser Piping - McQuay SWP 018 Installation And Maintenance Manual

Water Connections

General

Due to the variety of piping practices, it is advisable to fol-
low the recommendations of local authorities. They can sup-
ply the installer with the proper building and safety codes
required for a safe and proper installation.
The piping should be installed with a minimum number of
bends and elevation changes for best performance. Piping
should contain:
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
from the water before it enters the pump. It should be
placed far enough upstream to prevent cavitation at the
pump inlet (consult pump manufacturer for recommen-
dations). The use of a strainer will prolong pump life
and help maintain system performance.
7. Size piping to minimize system pressure drop.

Condenser Piping

1. Units may be specified with water and condensate con-
nections on either the left or right side of the unit.
2. All units have an individual condenser per refrigerant
circuit. All condensers are factory piped for a common
condenser water supply and a common condenser water
return connection.
3. Field piping connections are made to factory provided
piping located as indicated on the unit submittal draw-
ings. The piping connections are run to the outside of
the unit cabinet. Connections are located behind a fac-
tory mounted shipping cover. All connections are cop-
per sweat connections as indicated on unit dimensional
drawings.
4. Supply and return water connections must be made at
the proper locations as indicated by the dimensional
drawings. Supply (water in) connection is always the
lower connection.
5. Units with factory mounted water side economizer
should not require head pressure control. The econo-
6
mizer will typically elevate the water temperature by 5
to 10°F before entering the condenser, allowing suitable
condenser water temperatures whenever the tower sup-
ply temperature is 50°F or higher. Mechanical cooling is
locked out below 55°F EWT.
6. Head pressure control must be provided if entering con-
denser water temperatures will go below 55°F. Fan
cycling and/or modulating discharge dampers on the
cooling tower are often used, or a 3-way bypass around
the tower to maintain condenser water temperature.
Cooling tower control to maintain the temperature at
>55°F is generally more cost effective if multiple units
are in the loop. If valves are installed on the individual
SWP units, a single water regulating valve controlled by
circuit #1 head pressure should be used. The Lead/Lag
option needs to equal "NO". When Lead/Lag equals
"NO" circuit #1 is always first on and last off. The
refrigerant pressure line from the valve should be con-
nected to a gauge port on any liquid line service valve
located in the compressor #1 refrigerant circuit. Com-
pressor #1 is located at the far left of the cabinet.
If the water regulating valve is placed in service with the
unit condensers, it should be installed in the water line leav-
ing the condenser and should shut down to prevent water
from siphoning out of the condensers. For systems where a
constant pumping head is required, the water regulating
valve may be installed in a bypass line around the condens-
ers. It must then open on falling discharge pressure.
These typical systems, depending on the specific appli-
cation, must maintain a constant condensing pressure regard-
less of temperature conditions and must assure adequate
head pressure for proper thermal expansion valve operation.
A minimum head pressure of 180 psi (95°F condensing tem-
perature) is recommended.
7. Condenser tube velocities must not exceed 10 feet per
second.
Figure2. Condenser Regulating Valve (refrigerant
pressure controlled
)
IM708