Sequence Of Operation - Bard D36A2P/BLD.10304 Installation And Service Instructions Manual

SEQUENCE OF OPERATION

D-SERIES WALL-MOUNT UNIT
SEQUENCE OF OPERATION
Overview
This product is designed to function like a typical
Telecom air conditioning system with an outdoor air-
cooling damper. However, the DC-FCU system does
have some special features, like a PLC control which
allows for advanced alarming and a "DC Free Cooling"
feature that allows for forced emergency ventilated
cooling anytime "shore power" VAC power from the
utility company is lost. The internal controls within
this unit automatically recognize a loss of shore power,
energizing the indoor blower motor and powering the
actuator to open the damper to bring in outdoor air.
The power utilized during this time is the stored battery
power from the equipment shelter.
Indoor Blower
The indoor blower is a 48VDC motor, completely
separate from the VAC circuit(s). For the blower to
activate, two (2) separate actions must take place:
1. 24VDC from terminal N07 (Blower Motor Start
Relay)
2. 0-10VDC signal from terminal Y1 (Speed Voltage)
While the 24VDC from N07 will always stay the
same, the 0-10VDC signal from terminal Y1 will vary
depending upon the mode. See Table 2.2.
DC Free Cooling Damper
This controller is enabled for dewpoint control,
specifically examining the combination of temperature
and relative humidity to determine the proper control
of cooling. This calculated dewpoint property then
determines the proper mode of cooling—Outdoor Air,
Mechanical Cooling, or both. To signal the 24VDC
damper actuator to open, a 2-10VDC signal must
come from the Y2 terminal. Additionally, while other
modes get only a single speed from the indoor blower,
free cooling mode will get two (2): one for outdoor air
Model Blower Only
D36A/D36L
Same as
D42A/D42L
Free Cooling
D48A/D48L
Mode
D60A/D60L
Manual 2100-620A
Page 42 of 107
TABLE 2.2
Blower Speed Voltage Chart
Free Cooling Mode
Free Cooling Mode
Below 40°F
(CFM/VDC
(CFM/VDC
Speed Voltage)
Speed Voltage)
1800/7.0
temperature above 40°F (faster), and another for those
below 40°F (slower). See Table 2.2.
Cooling Call
When a call for cooling generates from the controller,
the system will first determine which mode of cooling
to employ based on the outdoor temperature, the
outdoor humidity, and the indoor temperature.
• If the outdoor temperature and humidity ratio are
conducive to free cooling, the control board will
send:
1. 2-10VDC Signal from Y2 (Damper Signal)
- Modulates damper to achieve 55°F at
supply air temperature sensor
2. 24VDC from terminal N07 (Blower Motor Start
Relay)
3. 0-10VDC signal from terminal Y1 (Speed
Voltage)
• If the outdoor conditions are conducive to free
cooling, but a 2nd stage cooling call is generated,
the board will additionally add 24VAC signal
from the N02 terminal to the CCM, activating the
compressor. The damper will limit outdoor air to
keep supply air temperature at 55°F.
• If conditions outside are not conducive to free
cooling, the control board will send:
1. 24VAC signal from N02 to CCM (Compressor)
2. 24VDC from terminal N07 (Blower Motor Start
Relay)
3. 0-10VDC signal from Y1 (Speed Voltage)
Heating Call
When a call for heating generates from the controller,
the control board will send:
1. 24VAC signal from terminal N04 to heat strip
contactor.
Cooling
(CFM/VDC
Speed Voltage)
800/2.8 1100/3.8
950/3.1 1250/4.7
1100/3.8 1600/6.3
1100/3.8 1600/6.3
Electric Heat
1800/7.0