Sequence Of Operation; Figure 1.3A D25A, D25L, D35A, D35L Table 2.2 Blower Speed Voltage Chart - Bard D25A2PA 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 Free Cooling Unit
system does have some special features, like a control
board 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 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. The system will utilize free cooling when the
following conditions are true:
Model Blower Only
D25A/D25L
D28A/D28L
D35A/D35L
Same as
D36A/D36L Free Cooling
Mode
D42A/D42L
D48A/D48L
D60A/D60L
Manual 2100-643C
Page 24 of 59
TABLE 2.2
Blower Speed Voltage Chart
Free Cooling Mode
Free Cooling Mode
Below 40°F
(CFM/VDC
(CFM/VDC
Speed Voltage)
Speed Voltage)
1500/6.0
1. The outdoor temperature is below 70°F
2. The dewpoint of the outdoor air is below 60°F
3. The outdoor humidity is below 80% RH
4. The indoor humidity is below 60% RH
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:
one for outdoor air 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.
Cooling
(CFM/VDC
Speed Voltage)
900/2.0 900/2.0
800/2.8 1100/3.8
1100/3.0 1100/4.0
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
1100/4.0
1800/7.0
1100/4.0
1800/7.0
1800/7.0
1800/7.0
1800/7.0