69
On power up or changing from Off to Enabled, the machine
will remain off until Minutes Off Time (
Configuration
o
OPT2
o
DELY
) timer has expired. See Minutes Off Time on
page 128 for additional information. Liquid line solenoid valve
operation is as described in Liquid Line Solenoid Valves on
page 40. Time Guard is honored for all compressors. For spe-
cific information on Time Guard, see MDTG - Time Guard
Active on page 135.
In this Control Type, Space Temp Control Mode,
Run Sta-
tus
o
VIEW
o
SPT.M
=0
(Off Cool) as long as Control Mode
Run Status
o
VIEW
o
STAT
=1
(Off Local),
2
(Off CCN),
3
(Off Time),
4
(Off Emrgcy), or
9
(SPT Satisfied). 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
o
GEN.I
o
Y.1
=ON
or
SPT.M
=2
(High Cool) if Y2 is closed,
Inputs
o
GEN.I
o
Y.2
=ON
. If Y1 and Y2 are both open,
Y.1=
OFF
and
Y.2=
OFF
,
STAT=
9
(SPT Satisfied) and
SPT.M=
0
(Off Cool) will be displayed. In this Control Type, if
the Indoor Fan Status Switch opens (
Inputs
o
GEN.I
o
ID.F.A=
OFF
), Control Mode (
STAT
) will change to
8
(IDFS
Not On) as long as there is no call for cooling,
Y.1=
OFF
and
Y.2=
OFF
. If there is a call for cooling,
Y.1=
ON
or
Y.2=
ON
the
unit will alarm and
STAT
switch to
4
(Off Emrgcy). Table 28
shows the space temperature control mode response for
C.TYP=
3
.
Table 28 — Space Temperature Control Mode
Response for C.TYP=3
38APD
— On a call for cooling, the Indoor Fan Status Cir A,
(
Inputs
o
GEN.I
o
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 started. See Circuit
Compressor Staging on page 112. If the lead compressor is a
digital compressor and is enabled, the compressor will start ful-
ly loaded for 90 seconds prior to starting to cycle between load-
ed and unloaded. Compressors will be staged until the unit’s
capacity meets the Control Point (
CTPT
) as described in Sup-
ply Air Temperature Control on page 110. If additional capaci-
ty requires the lag circuit to start, the lag circuit’s lead compres-
sor will be determined and started. During operation, the con-
trols 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, the ma-
chine controls will reduce the unit’s capacity to maintain the
Control Point. If the unit is equipped with Minimum Load
Control, it will not be active until the unit is on its last stage of
capacity.
38APS Units
— On a call for cooling, the Indoor Fan Status
Cir A (
Inputs
o
GEN.I
o
ID.F.A
) is checked. The switch must
be closed before the capacity routine will start. The lead com-
pressor will be determined and started. See Circuit Compressor
Staging on page 112. If the lead compressor is a digital com-
pressor and is enabled, the compressor will start fully loaded
for 90 seconds prior to starting to cycle between loaded and un-
loaded. Compressors will be staged until the unit’s capacity
meets the Control Point (
CTPT
) as described in Supply Air
Temperature Control on page 110. During operation, the con-
trols 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, the ma-
chine controls will reduce the unit’s capacity to maintain the
Control Point. If the unit is equipped with Minimum Load
Control, it will not be active until the unit is on its last stage of
capacity.
C.TYP =
4
(TSTAT 2 STG) — This configuration allows
the MBB to monitor the thermostat inputs to make capacity
stage decisions. If Y1 input is closed, no more than 50% of the
circuit capacity will be energized. If Y2 is closed, 100% of the
circuit capacity will be energized for that circuit and air han-
dler. Y1 closure is not required for 100% capacity.
Recommended Applications — This control type is recom-
mended for constant volume, non-digital compressor applica-
tions with units with less than 3 stages of compression. It is not
recommended for units with more than two stages of capacity.
This control scheme cannot be used with:
• Units with digital compressors. Digital operation is not
supported with this control scheme.
• Minimum Load Control is not supported with this con-
trol scheme.
Hardware Requirements
• 2-stage thermostat
Required Configurations — Table 29 lists the configurations
required for proper operation.
Wiring — See Fig. 82.
Table 29 — C.TYP=4 (Tstat 2 Stg) Required
Configuration
CONTROL
MODE
STAT
Y1
STATUS
Y.1
Y2
STATUS
Y.2
INDOOR
FAN
STATUS
CIR A
ID.F.A
SPACE
TEMPER-
ATURE
CONTROL
MODE
SPT.M
1
(Off Local)
Off
or
On
Off
or
On
Off
or
On
0
(Off Cool)
2
(Off CCN)
Off
or
On
Off
or
On
Off
or
On
0
(Off Cool)
3
(Off Time)
Off
or
On
Off
or
On
Off
or
On
0
(Off Cool)
4
(Off Emrgcy)
Off
or
On
Off
or
On
Off
or
On
0
(Off Cool)
5
(On Local)
On
Off
On
1
(Lo Cool)
Off
or
On
On
On
2
(Hi Cool)
6
(On CCN)
On
Off
On
1
(Lo Cool)
Off
or
On
On
On
2
(Hi Cool)
7
(On Time)
On
Off
On
1
(Lo Cool)
Off
or
On
On
On
2
(Hi Cool)
8
(IDFS Not On)
Off
or
On
Off
or
On
Off
0
(Cool Off)
9
(SPT Satisfied)
Off
Off
On
0
(Cool Off)
CONFIGURATION MODE
SUBMODE ITEM DISPLAY
ITEM
DESCRIPTION
COMMENT
OPT2
C.TYP
X
Machine Con-
trol Type
Default: 4
Range: 1 to 9
Set item to 4
(Tstat 2 Stg)