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IM 893-10 • ROOFPAK SINGLEZONE UNITS 50 www.DaikinApplied.com
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Economizer Operation
. When the outdoor air is suitable for free
cooling, the switch in enthalpy sensor OAE is in position “3”
(line 248,
) energizing 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.
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.
Fixed Speed Compressor Operation
4-Compressor/4-Stage Unit
061 Condensing Unit Control (With Fixed Speed Scroll
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.
NOTE:
Lead lag is not available with the variable speed
inverter compressor.
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, Figure 68 on page 64)
• 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)
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)
Cross Circuit Loading
. During a call for cooling, 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,
.
The M1 auxiliary brings on:
• Required condenser fans (line 854)
• Liquid line drop solenoids (lines 855 and 856)
The drop solenoids are electrically energized by compressor
contactor auxiliary contacts. They open when the first
compressor turns ON and they close when the last compressor
turns OFF.
Compressor 2 (refrigerant circuit 2) is the 2nd stage of cooling
and is brought on in the same manner (line 823,
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)