47
Economizer Mechanical Cooling Delay — This type of me-
chanical cooling delay is relevant to the all machine control
types.
If the economizer is able to provide free cooling at the start
of a cooling session, the mechanical cooling algorithm checks
the economizer’s current position (
Run Status
ECON
ECN.P
) and compares it to the economizer’s maxi-
mum position (
Configuration
ECON
EC.MX
) – 5%.
Once the economizer has opened beyond this point a
2.5-minute timer starts. If the economizer stays beyond this
point for 2.5 minutes continuously, the mechanical cooling
algorithm is allowed to start computing demand and stage
compressors.
Economizer Control Point (
Run Status
VIEW
EC.C.P
)
— There are 4 different ways to determine the economizer
control point when the economizer is able to provide free
cooling:
If no mechanical cooling is active and HVAC mode = LOW
COOL
EC.C.P
=
Setpoints
SA.LO
+
Inputs
RSET
SA.S.R
If no mechanical cooling is active and HVAC mode = HIGH
COOL
EC.C.P
=
Setpoints
SA.HI
+
Inputs
RSET
SA.S.R
When the first stage of mechanical cooling has started
EC.C.P
= 53 F plus any economizer suction pressure reset
applied
When the second stage of mechanical cooling has started
EC.C.P
= 48 F plus any economizer suction pressure reset
applied
Heating Control —
The A Series
Comfort
Link control
system offers control for 3 different types of heating systems to
satisfy general space heating requirements: 2-stage gas heat, 2-
stage electric heat and multiple-stage (staged) gas heat.
Variable air volume (VAV) type applications (
C.TYP
= 1, 2,
3, or 5) require that the space terminal positions be commanded
to open to Minimum Heating positions when gas or electric
heat systems are active, to provide for the unit heating
system’s Minimum Heating Airflow rate.
For VAV applications, the heat interlock relay (HIR) func-
tion provides the switching of a control signal intended for use
by the VAV terminals. This signal must be used to command
the terminals to open to their Heating Open positions. The HIR
is energized whenever the Heating mode is active, an IAQ
pre-occupied force is active, or if fire smoke modes, pressuriza-
tion, or smoke purge modes are active.
WITHOUT MOTORMASTER OPTION
60 Ton MCHX
Contactor
OFM(s)
Software
Board
Conrolled
Controlled
A
CONDFANA
MBB Rly 6
OFC4
OFM4
A
CMPA1/A2
MBB Rly 3/4
OFC3
OFM3
B
CONDFANB
MBB Rly 5
OFC2
OFM2
B
CMPB1/B2
MBB Rly 1/2
OFC1
OFM1
# of Fans ON
Fans ON
# of Fans ON
Fans ON
Stage 1
OFC3
1
OFM3
Stage 1
OFC1
1
OFM1
Stage 2
OFC3,4
2
OFM3,4
Stage 2
OFC1,2
2
OFM1,2
WITH MOTORMASTER OPTION
60 Ton MCHX
Contactor
OFM(s)
Software
Board
Conrolled
Controlled
A
CONDFANA
MBB Rly 6
OFC4
OFM4
A
MM_A_RUN
SCB Relay 1
n/a
OFM3
B
CONDFANB
MBB Rly 5
OFC2
OFM2
B
MM_B_RUN
SCB Relay 2
n/a
OFM1
# of Fans ON
Fans ON
# of Fans ON
Fans ON
Stage 1
MM3
1
OFM3
Stage 1
MM1
1
OFM1
Stage 2
MM3, OFC4
2
OFM3,4
Stage 2
MM1, OFC2
2
OFM1,2
Stage 2 starts with MM_A_VFD / MM_B_VFD at 50%, then modulates to control HP setpoint
Stage down starts with MM_A_VFD at 50%, then modulates to control HP setpoint
If the SCTB sensor has failed, then the control defaults to control based on the OAT sensor and turns on CONDFANB when the
ambient is above 65 dF and off when the ambient temperature is below 50 dF. If the SCTB and OAT sensors have all failed then the
control turns on CONDFANB when any compressor is on.
Stage up occurs if SCTA > HPSP or OAT > 75
Stage up occurs if SCTB > HPSP or OAT > 75
Stage down occurs if SCTA < HPSP - 40 for two minutes and
OAT < 73
Stage down occurs if SCTB < HPSP - 40 for two minutes and OAT <
73
If the SCTA sensor has failed, then the control defaults to control based on the OAT sensor and turns on CONDFANA when the
ambient is above 65 dF and off when the ambient temperature is below 50 dF. If the SCTA and OAT sensors have all failed then the
control turns on CONDFANA when any compressor is on.
Comp B1 or B2 ON, speed Via MM_B_VFD
Circuit A
Circuit B
Circuit
Controlling Output
Logic
Comp A1 or A2 ON, speed Via MM_A_VFD
If the SCTB sensor has failed, then the control defaults to control based on the OAT sensor and turns on CONDFANB when the
ambient is above 65 dF and off when the ambient temperature is below 50 dF. If the SCTB and OAT sensors have all failed then the
control turns on CONDFANB when any compressor is on.
Comp B1 or B2 ON (Compressor AUX contactor)
Circuit A
Circuit B
When CMPA1 or CMPA2 staged ON, OFC3 on due to AUX
contactor
Stage down occurs if SCTA < HPSP - 40 for two minutes and
OAT < 73
When CMPB1 or CMPB2 staged ON, OFC1 on due to AUX contactor
Stage down occurs if SCTB < HPSP - 40 for two minutes and OAT <
73
Stage up occurs if SCTA > HPSP or OAT > 75
Stage up occurs if SCTB > HPSP or OAT > 75
If the SCTA sensor has failed, then the control defaults to control based on the OAT sensor and turns on CONDFANA when the
ambient is above 65 dF and off when the ambient temperature is below 50 dF. If the SCTA and OAT sensors have all failed then the
control turns on CONDFANA when any compressor is on.
Circuit
Controlling Output
Logic
Comp A1 or A2 ON (Compressor AUX contactor)
MM
3
MM
1
2
4
Fig. 9 — Outdoor Fan Staging Sequence (cont)
Содержание Carrier Weathermaker 48A2
Страница 105: ...105 Fig 20 Typical Main Control Box Wiring Schematic 48 50A2 A3 A4 A5 Units...
Страница 106: ...106 Fig 21 Typical Auxiliary Control Box Wiring Schematic...
Страница 107: ...107 Fig 22 Typical 2 Stage Gas Heat Wiring Schematic Size 060 Units Shown a48 8357...
Страница 108: ...108 TO NEXT PAGE Fig 23 Typical Staged Gas Heat Wiring Schematic Size 060 Units Shown A48 7296...
Страница 109: ...109 Fig 23 Typical Staged Gas Heat Wiring Schematic Size 060 Units Shown cont A48 8358...
Страница 110: ...110 Fig 24 Typical Electric Heat Control Schematic 50 Series Size 060 Units Shown a50 8228...
Страница 111: ...111 Fig 25 Typical Power Schematic 48 50A2 A3 A4 A5 060 Unit Shown...
Страница 112: ...112 Fig 26 Typical Low Ambient Controls Option Wiring...
Страница 113: ...113 Fig 27 Typical Small Chassis Component Location Size 020 035 Units...
Страница 114: ...114 Fig 28 Typical Large Chassis Component Locations Size 040 060 Units...
Страница 118: ...118 Fig 30 Economizer Control Board ECB1 and VAV Control Board ECB2 A48 7706...
Страница 142: ...142 A48 3733 Fig 56 Main Burner Removal...
Страница 176: ...176 APPENDIX C VFD INFORMATION cont Fig F Internal Enclosure Fan Replacement A48 7716...
