York R-407C Manuale Utente

FORM 100.50-EG1

YORK INTERNATIONAL

less than the Return Air enthalpy and the Outside Air
temperature is less than the reference temperature set-
ting. This method of economizing is the most accurate
and provides the highest degree of energy efficiency
for a packaged rooftop economizer.

When the unit goes into the Occupied mode of opera-
tion, the unit controller shall open the Outside Air
Damper to a fixed minimum position. The damper shall
remain at this position as long as the unit is in the occu-
pied mode. The minimum position may be overridden
more open by the unit controller when Outside Air con-
ditions are suitable for economizing.

With Variable Air Volume units, there are two Minimum
OA Damper Positions, one when the unit is at full speed
and the second when the unit is at approximately half
speed. These two points allow the control to linearly
reset the position of the OA damper in response to fan
speed.

When the unit goes into the Occupied mode of opera-
tion, the unit controller shall monitor the speed of the
supply fan and open the Outside Air damper to a calcu-
lated minimum position based on the fan speed. This
minimum position shall vary as the speed of the fan
changes. The damper shall remain at this calculated
position as long as the unit is in the occupied mode.
The minimum position may be overridden more open
by the unit controller when Outside Air conditions are
suitable for economizing.

When the unit is equipped with an air measurement
station, the unit controller shall control the Outside Air
damper to a measured flow rate through the Air Mea-
surement Station.

When the unit goes into the Occupied mode of opera-
tion, the unit controller shall control the Outside Air
damper to maintain the Minimum AirFlow Setpoint
through the Air Measurement Station. The unit control-
ler shall control the Outside Air damper to this flow rate
as long as the unit is in the Occupied mode. The Out-
side Air damper may be overridden more open by the
unit controller when Outside Air conditions are suitable
for economizing.

If an optional CO2 sensor is connected to the unit, the
unit controller can reset the minimum OA damper
position(s) or minimum flow rate based on demand.

The unit controller shall monitor the CO2 level within the
building. If the CO2 level rises above the CO2 setpoint,
the controller will temporarily increase the Minimum OA
Damper Position or Minimum OA flow rate to increase
ventilation. If the CO2 level drops below the CO2 set-
point, the controller will decrease the Minimum OA
Damper Position or Minimum OA flow rate to decrease
ventilation.

Demand Ventilation shall remain active as long as the
unit is in the Occupied mode of operation.

The optional barometric exhaust system consists of a
lightweight barometric relief damper installed on the end
of the unit in the Return Air section. As more outside air
is introduced into the controlled zone due to Econo-
mizer and Ventilation control sequences, the pressure
inside the building rises. This increase in building pres-
sure forces the barometric relief damper open to allow
exhaust air to escape.  Because this type of exhaust
system is not powered, it is limited to small amounts of
exhaust.

This optional fixed volume powered exhaust system
consists of a fixed speed fan that is controlled ON and
OFF based on the position of the Outside Air Damper.
During operation, when the Outside Air Damper opens
to a selected turn-on point, the Exhaust Fan is cycled
ON. The fan remains on as long as the Outside Air
damper is above a selected turn-off point. If the Out-
side Air Damper closes to the selected turn-off point,
the Exhaust Fan is cycled OFF. The turn-on and turn-
off points are user selectable from the OptiLogic™ User
Interface panel.

This optional fixed volume powered exhaust system
consists of a fixed speed fan that is controlled ON and
OFF based on the pressure inside the building. During