Economizer Operation; Mechanical Cooling Operation - Daikin RoofPak RPS Series Installation And Maintenance Manual

Economizer Operation

Refer to Figure 90 on page
suitable for free cooling, the switch in enthalpy sensor OAE is
in position "3" (line 248, Figure 90 on page
analog input AIX5. When AIX5 energizes, the economizer
is enabled. (Note: If selected from the keypad, the enthalpy
decision can be made based on outdoor temperature. In that
condition, if the outdoor air temperature is less than or equal
to the changeover set point, the economizer is enabled.)
If cooling is required, the economizer dampers (ACT3) are
modulated to maintain the discharge air temperature setpoint.
Analog input AIX5 drives the outdoor air dampers toward the
open and closed (line 256) position. If the outdoor air dampers
are wide open and more cooling is required, the dampers hold
their positions and mechanical cooling is activated (see below).
When the outdoor air is not suitable for free cooling, the switch
in enthalpy sensor OAE is in position "1," de-energizing analog
input AIX5. (Alternatively, the outdoor air temperature is above
the changeover setpoint plus the economizer changeover
differential). When the economizer is disabled, the dampers
are held at their minimum position.

Mechanical Cooling Operation

4-Compressor/4-Stage Unit
Refer to Figure 90 on page 76
as you read this sequence of operation. In this configuration
there are four equally sized compressors and two cooling
circuits. In the following description, compressor #1 is lead.
However, if Auto Lead/Lag Staging is selected on the keypad,
the lead compressor is the one in the lead circuit with the least
number of run hours.
When the unit disconnect is closed, 115 V (ac) power is
supplied directly from control transformer T1 to the compressor
crankcase heaters, HTR-1, 2, 3, and 4 (lines 836 - 848, 853)
and motor protectors MP1, 2, 3, and 4 (lines 836 - 848, 854).
This same 115 V (ac) source also goes through:
• System switch, S1 (line 203,
• The optional phase voltage monitors, PVM1 and 2 (lines
203, 802, not shown)
• The optional ground fault relays, GFR1 and 2 (lines 203,
802, not shown)
IM 926-3 • ROOFPAK APPLIED SYSTEMS
76. When the outdoor air is
76) energizing
and Figure 91 on page 78
Figure 88 on page 72)
Compressors are staged by 115 V (ac) power supplied to the
following:
• Frost protect FP1 to CCB1-BI8 (line 812, not shown)—
Optional when no hot gas bypass is ordered on the unit
• Frost protect FP2 to CCB2-BI8 (line 823, not shown)—
Optional when no hot gas bypass is ordered on the unit
• HP relay R1 to CCB1-BI7 (lines 812)
• HP relay R2 to CCB2-BI7 (lines 823)
• Compressor contactor status M1 to CCB1-BI9 (line 812)
• Compressor contactor status M2 to CCB2-BI9 (line 823)
• Compressor contactor status M3 to CCB1-BI10 (line 814)
• Compressor contactor status M4 to CCB2-BI10 (line 825)
Cross Circuit Loading
See line 812, Figure 91 on page
if HP1 is satisfied, then DO1 closes. If MMP1 and MP1 are
satisfied, then M1 compressor contactor is energized to bring
on compressor 1 on refrigerant circuit 1 (line 708 - 710,
86 on page 70. The M1 auxiliary brings on:
• required condenser fans (line 854)
• liquid line and optional hot gas solenoids (lines 855 and
856)
Compressor 2 (refrigerant circuit 2) is the 2nd stage of cooling
and is brought on in the same manner (line 823, Figure 95 on
page 82 and lines 708 - 710,
Circuit 2 condenser fans and solenoids are controlled in the
same manner on lines 861 - 865).
The 3rd stage of cooling is controlled by DO2 (line 814) and
brings on compressor 3 if MMP3 and MP3 are satisfied.
The 4th stage of cooling is controlled by DO4 (lines 826) and
brings on compressor 3 if MMP3 and MP3 are satisfied.
Lead Circuit Loading
The loading and unloading process is similar except that both
compressors in the lead cooling circuit 1 energize before
energizing any compressors in lag circuit 2.
Heating
Gas Furnace, Super Modulating Burner (20:1
Turndown)
Refer to Figure 89 on page 74
58
Sequences of Operation
78. During a call for cooling,
Figure
Figure 86 on page 70).
for a sequence of operation.
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