Johnson Controls L-Series, Engineering Manual

Page: 72 / 82

FORM 145.05-EG2 (618)
72 JOHNSON CONTROLS
Guide Specifications (Cont’d)
Condensate Management
The coil section shall include an integral drain pan constructed of 16-gauge, type 304
stainless steel with a minimum depth of 2 inches. The drain pan shall be sloped in all
directions towards a single condensate drain connection to provide positive drainage, and
shall comply fully with ASHRAE 62.1.
The unit shall include a factory installed drain line including drain trap with a cleanout, to
ensure adequate access to the trap. The condensate line shall be made out of schedule 40
PVC pipes. Copper drain lines shall be insulated with a minimum of ½ inch closed cell
pipe insulation to avoid sweating. No external drain trap shall be required.
WATERSIDE ECONOMIZER
Waterside economizer cooling coil shall be constructed of seamless 0.50-inch outside
diameter copper tubing with a wall thickness of 0.016-inches. The copper tubes shall
be mechanically expanded to the aluminum fins. Coils shall be a minimum of 4 rows,
with a minimum of 11 fins per inch. The circuiting of the coil shall be such to allow
the lowest water pressure drop. Waterside economizer water coils shall have a vent and
drain. The coil shall be provided to be chemically [optionally mechanically] cleanable.
The coil shall be leak tested with high-pressure air in a warm water bath. The complete
economizer package, including the coil, valves, and piping shall be rated for 300 psig
waterside working pressure.
To control the condenser water flow through the coil, a factory installed modulating con-
trol valve package shall be provided. A valve package includes the valve(s), actuator(s),
wiring, and piping internal to the unit. The condenser water piping connections shall
be located inside, close to the exterior of the unit, located for easy connection to the
building risers. One set of connections (one for inlet and one for outlet) is needed for
each unit.
Economizer operation shall be controlled to maximize free cooling operation as the enter-
ing condenser water is colder than the entering air (mixed air = outdoor air + return air)
temperature to the unit. If the condenser water is suitable for cooling, the economizer
valve shall modulate to maintain temperature set point. If the cold condenser water cannot
satisfy the cooling load, mechanical cooling shall assist the pre-cooling to achieve temper-
ature set point. To maximize energy savings, the economizer shall pre-cool until disabled
when the condenser water becomes too warm compared to the entering air temperature.
When the economizer is disabled, the economizer valve shall shut and the condenser
valve shall open to allow 100% water flow through the condenser.
When the unit is not in operation, the economizer is disabled and the economizer valve
is always closed. The condenser valve can be set to either close or 100% open. If the
condenser valve is closed, the system water flow shall be reduced, thus saving pumping
energy. If the condenser valve is set to close in the unit is not in operation, the valves shall
be controlled to work independent of the economizer valve. If the condenser valve is set
to be 100% when the unit is not in operation, the valves shall work in reverse acting.
[A non-averaging type freezestat shall be factory installed. When the freezestat senses the
entering air temperature is below the set point, the unit shall be put into the unoccupied
mode and the economizer valve shall be driven to 100% open and the condenser valve
shall be driven closed.]