Johnson Controls York VERSECON YSWD 012, Installation Operation & Maintenance

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JOHNSON CONTROLS
FORM 145.05-NOM1 (708)
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If valves are installed on the individual units,
a single water regulating valve controlled by
the lowest discharge pressure of the operating
compressor(s) will control head pressure.
•
If the water regulating valve is placed in
service with the condenser, it should be in-
stalled in the water line leaving 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 con-
densers. It must be 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 thermal
expansion valve operation.
•
A minimum head pressure of 180 psi (95° F
condensing temperature) is recommended.
Condenser tube water velocities must
not exceed 10 feet per second to pre-
vent erosion of the pipe.
Cooling Towers
Cooling tower control affects the unit cycle rates.
Condenser water temperature swings from 10-15° F
may cause excessive compressor, water valve and unit
cycling. Be sure to set the tower controls to minimize
compressor unit cycling.
Waterside Piping Arrangements
Install a condenser water pump between the cooling
tower (either open or closed) and the self-contained
unit. Lay out the remainder of the system’s condenser
piping in reverse returns. This helps balance the system
by equalizing the length of supply and return pipes.
Multistory buildings may use a direct return system
with balancing valves at each floor.
Install the supply riser and its return in close proximity.
Furnish both with permanent thermometers to check
the waterside balance during start-up and routine
maintenance checks. Also, include strainers at each
pump inlet and unit. Install drain valves at the riser’s
base to allow drainage points for system flushing during
start-up and routine maintenance. For condenser draining
and header removal, include a shutoff/balancing valve
on the entering and leaving waterside pipes, drain tees,
and unions of each unit. Also, install a shutoff valve on
the unit entering water pipe for condenser draining.
Water Temperature Requirements
On units without a waterside economizer, do not allow
the condensing water temperature to drop below 55.0°
F. Water temperatures below this value will cause the
compressors to shut down and the mechanical cooling
function will lock out.
On units with water side economizer the condensing
water temperature can drop to 50.0° F without effecting
the operation of the compressors.
Condensate Drain Connections
The condensate drain connection is 1-1/8” O.D.S.
copper and is located on the same side of the unit as the
condenser water connections. The drain is internally
trapped (no external trap is required). The condensate
line should be pitched away from the unit with a
minimum slope of 1/8” per foot.
Drain pans and the drain traps should be kept clean by
periodic cleaning. A cleanout is provided as standard
in the trap to aid in cleaning.
STATIC PRESSURE TRANSDUCER INSTALLATION
(VAV UNITS ONLY)
All units provided with a VFD include a factory
mounted static pressure sensor (SPS1). The unit can
also have an optional second static pressure sensor,
(SPS2). The second static pressure transducer would
be used if the main supply duct split into two main
branches. The control can be programmed to maintain
the lowest input, highest input or the average of the two.
The sensor is factory wired and requires field installation
of ¼” ID sensor tubing to the selected duct location. A
field supplied static pressure probe and tubing must be
installed in the field prior to unit start up.