Space Temperature Control Mode Response For C.typ=4; C.typ = 5 (Spt Multi - Carrier 38APS025 Manual

Sequence of Operation — The MBB monitors the thermostat
inputs to make a determination of capacity stage. When Y1
closes, no more than 50% of the unit's capacity will be ener-
gized. When Y2 closes, the remaining capacity will be ener-
gized. Thermostat inputs can be monitored at the unit's inter-
face device: Y1 Thermostat Input (Inputs GEN.I Y.1) and
Y2 Thermostat Input (Inputs GEN.I Y.2).
For mechanical cooling, the unit's Control Method, (Con-
figuration OPT2 CTRL), and inputs must allow the ma-
chine to run. See Control Methods on page 60 for additional
information.
On power up or changing from Off to Enabled, the machine
will remain off until Minutes Off Time (Configura-
tion OPT2 DELY) timer has expired. See Minutes Off
Time on page 128 for additional information. Liquid line sole-
noid valve operation is described in Liquid Line Solenoid
Valves on page 40. Time Guard is honored for all compres-
sors. For specific information on Time Guard, see MDTG -
Time Guard Active on page 135.
In this Control Type, Space Temp Control Mode, Run Sta-
tus VIEW SPT.M=0 (Off Cool) as long as Run Sta-
tus VIEW STAT=1 (Off Local), 2 (Off CCN), 3 (Off
Time), or 4 (Off Emrgcy). When the Control Mode STAT=5
(On Local), 6 (On CCN), or 7 (On Time), SPT.M=1 (Lo Cool)
if Y1 is closed, Inputs GEN.I Y.1=ON, SPT.M=2 (High
Cool) if Y2 is closed, Inputs GEN.I Y.2=ON, or SPT.M=0
(Off Cool) if Y1 and Y2 are both open, Y.1=OFF and
Y.2=OFF. With this Control Type, if the Indoor Fan Status
Switch opens (Inputs GEN.I ID.F.A=OFF), STAT will
change to 8 (IDFS Not On), the unit will remain with SPT.M=0
(Off Cool) if Y1 and Y2 are both open, Y.1=OFF and
Y.2=OFF. If Y1 or Y2 close, Y.1=ON or Y.2=ON, the unit
Control Mode will change from STAT=8 (IDFS Not On), to 4
(Off Emrgcy) as an alarm is generated. Table 30 shows the

space temperature control mode response for C.TYP=4.

Table 30 — Space Temperature Control Mode
Response for C.TYP=4
Y1
CONTROL
STATUS STATUS
MODE STAT
Y.1
1 (Off Local) Off or On Off or On
2 (Off CCN) Off or On Off or On
3 (Off Time) Off or On Off or On
4 (Off Emrgcy) Off or On Off or On
Off
5 (On Local) On
Off or On
Off
6 (On CCN) On
Off or On
Off
7 (On Time) On
Off or On
8
Off or On Off or On
(IDFS Not On)
9
(SPT Satisfied)
38APD Units — On a call for cooling, Y1 closure, Indoor Fan
Status Cir A (Inputs GEN.I ID.F.A) is checked. The
switch must be closed before the capacity routine will start.
The lead circuit is determined. See Lead/Lag Determination
on page 112. The lead compressor will be determined and start-
ed. See Circuit Compressor Staging on page 112. The solenoid
corresponding to the lead compressor circuit is opened 30 sec-
onds after the Y1 closure. The lead compressor is started 20
seconds later. Compressors will be staged at 70-second
SPACE
INDOOR
TEMPER-
Y2 FAN
ATURE
STATUS
CONTROL
Y.2 CIR A
MODE
ID.F.A
SPT.M
Off or On 0 (Off Cool)
Off or On 0 (Off Cool)
Off or On 0 (Off Cool)
Off or On 0 (Off Cool)
Off Off or On 0 (Off Cool)
Off On 1 (Lo Cool)
On On 2 (Hi Cool)
Off Off or On 0 (Off Cool)
Off On 1 (Lo Cool)
On On 2 (Hi Cool)
Off On 0 (Off Cool)
Off Off or On 1 (Lo Cool)
On On 2 (Hi Cool)
Off 0 (Cool Off)
Not Applicable
intervals until the unit's capacity is as close as possible to 50%
without exceeding it. If additional capacity requires the lag cir-
cuit to start, the lag circuit's lead compressor will be deter-
mined. The lag circuit solenoid valve will be energized. When
the Y2 contact is closed, the remaining capacity will be started,
staging compressors at 60-second intervals. During operation,
the controls will stage the condenser fans to maintain head
pressure. See Head Pressure Control on page 117.
As part of normal operation, if a single compressor in a mul-
tiple compressor circuit (38APD040-130) operates for the cu-
mulative time of 60 minutes without an increase in circuit ca-
pacity, an oil recovery routine is initiated. When this routine is
initiated, a second compressor in the circuit is started. Once
started, the normal capacity control routine takes priority and
will turn off the compressor if needed.
As the capacity requirement begins to decrease and the Y2
contact opens, the machine controls will reduce the unit's ca-
pacity by removing compressors. The first compressor will
turn off between 30 and 60 seconds following the loss of the
Y2 signal. The remaining compressors will turn off in 90-sec-
ond intervals until the unit is as close as possible to 50% capac-
ity without exceeding it. Finally, as the Y1 contact opens, the
remaining capacity is removed immediately.
38APS Units — On a call for cooling, Y1 closure, Indoor Fan
Status Cir A (Inputs GEN.I ID.F.A) is checked.
switch must be closed before the capacity routine will start.
The solenoid is opened 30 seconds after the Y1 closure. The
lead compressor will be determined and is started 20 seconds
later. See Circuit Compressor Staging on page 112. Compres-
sors will be staged at 70-second intervals until the unit's capac-
ity is as close as possible to 50% without exceeding it. When
the Y2 contact is closed, the remaining capacity will be started,
staging compressors at 70-second intervals. During operation,
the controls will stage the condenser fans to maintain head
pressure. See Head Pressure Control on page 117.
As part of normal operation, if a single compressor operates
for the cumulative time of 60 minutes without an increase in
circuit capacity, an oil recovery routine is initiated. When this
routine is initiated, a second compressor in the circuit is started.
Once started, the normal capacity control routine takes priority
and will turn off the compressor if needed.
As the capacity requirement begins to decrease and the Y2
contact opens, the machine controls will reduce the unit's ca-
pacity by removing compressors. The first compressor will
turn off between 30 and 60 seconds following the loss of the
Y2 signal. The remaining compressors will turn off in 90-sec-
ond intervals until the unit is as close as possible to 50% capac-
ity without exceeding it. Finally, as the Y1 contact opens, the
remaining capacity is removed immediately.
C.TYP = 5 (SPT MULTI) — This configuration will allow
the MBB to monitor the space temperature sensor and compare
it to the Space Temperature Set Point (Setpoints COOL
SPS.P) to make a capacity determination. The unit is allowed
to use multiple stages of cooling control and perform VAV-
style operation in an attempt to meet the current Control Point
(Run Status VIEW CTPT).
The Control Point is the Active Set Point (Run Status
VIEW SETP), either Cooling Setpoint 1 (Setpoints
COOL CSP.1) or Cooling Set Point 2 (Setpoints
COOL CSP.2) depending on the difference between the
Space Temperature (Run Status VIEW SPT) and SPS.P,
adjusted for any temperature reset that is applied. See Tempera-
ture Reset on page 129 for information on Temperature Reset.
Additionally, with an appropriate space temperature sensor,
a space temperature offset can be applied to the space tempera-
ture as sensed in the conditioned space. This offset adjusts the
actual space temperature reading being sent to the 38AP con-
trols, thereby changing the system's response.
71
The