Evaporator Coil Face Damper; Return Air Bypass Damper - York eco2 050 Installation Operation & Maintenance

Installation
Smoke Purge Input
A contact-closure input is provided for a smoke purge
sequence. When a contact-closure occurs at this input,
one of Þ ve purge sequences will be initiated, depending
on unit programming. This input will cause a speciÞ c
operation of supply fan, exhaust fans, return dampers,
outside air dampers, and exhaust dampers. The Þ ve pos-
sible smoke purge modes (Shutdown, Pres sur iza tion,
Exhaust, Purge, and Purge with Duct Pressure Control)
are described in the controls section of this manual.
This state is maintained until the input is de ac ti vat ed
(contacts open).
Contacts Closed = Smoke Purge Operation
Contacts Open = Normal Operation.
Note that 24 volts (R), terminal 16, must be used as the
24 volt AC source for switching the contact to the unit
controller Shutdown input. Use of any power source
external to the con trol ler will result in dam age to the
unit controller.
No external power source may be used
when fi eld wiring any of the above dry
contact in puts. The 24 volt AC source
on ter mi nal 16 (R) of the Ter mi nal
Block CTB1 must be used as the pow er
source when fi eld wiring these in puts,
as shown in Fig. 7. Fail ure to do so
will re sult in im prop er unit op er a tion
and dam age to the unit con trol ler.
VAV Heat Relay Output
This is a Þ eld wired OUTPUT that is used to com mand
the VAV boxes to full open during smoke purge opera-
tion. This 24VAC sig nal should have a maximum current
draw not to exceed 20VA. If the VA requirement of the
VAV boxes ap proach es 20VA, isolation relays should
be Þ eld sup plied and in stalled to avoid over load ing the
unit pow er sup ply.
Note that this signal is used to drive the VAV boxes
open in purge operations. Failure to drive the VAV
boxes open during this mode of operation can cause
unit shutdown and/or damage to the duct work due to
overpressurization.
26
The VAV Heat Relay Output cannot
exceed a current draw of 20VA. If the
power re quire ments of the VAV boxes
exceed this amount, isolation relays
must be fi eld supplied and in stalled
to pre vent over load ing the unit con-
trol ler pow er sup ply.

EVAPORATOR COIL FACE DAMPER

An evaporator coil face damper is only used on units
built with the Flexsys option. The damper is designed
to shut off airß ow to the top section of the evaporator
coil when only one compressor system is operating.
This forces all the airß ow through the lower coil result-
ing in higher low side pressures. The damper motor is
normally open and is driven closed. In a power failure
the damper will open.

RETURN AIR BYPASS DAMPER

Units built with the Flexsys option will have an open-
ing in the base of the unit between the evaporator coil
and the supply air blower. A Flexsys unit requires a
means to bypass return air and mix it with the air off
the evaporator coil. York does have a special curb with
the return duct bypass and bypass damper built into the
curb. The purpose of the damper is to temper the sup-
ply air to the under ß oor system by mixing return air
with the air off the evaporator coil. After the system is
initialized, the mixed air damper modulates based ratio
of the difference between the mixed air temperature
minus the supply air temperature compared to the return
air temperature minus the supply air temperature. As
the return air temperature decreases, the damper opens
allowing more air to bypass the evaporator coil resulting
in a higher mixed air temperature supply to the under
ß oor system.
The mixed air damper must be wired and installed into
the system in the Þ eld. The wires to connect the actuator
are located in the supply fan section, in the proximity
of the actuator in the supply fan section ß oor, opposite
the supply fan motor side. The plug assembly/wires are
attached with an elastic band and must be wired to the
actuator, and the "plugs" mated together. Connect the
wires to the motor as follows:
• Wire labeled "2(COM)" to terminal 1 in the actuator
• Wire labeled "200" to terminal 2 in the actuator
• Wire labeled "5(AO)" to terminal 5 in the actuator
FORM 100.50-NOM1 (604)
YORK INTERNATIONAL