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105
C.TYP =
8
(DUAL TSTAT) — This configuration allows for
the connection and control of a single 38APD unit to two sepa-
rate air handlers. The configuration allows the MBB to monitor
the thermostat inputs from each of two separate thermostats to
make a determination of mode and capacity for each circuit of
the 38APD unit. With this control scheme, Thermostat T1, Y1
and Y2 contacts operate circuit A. Thermostat T2, Y3 and Y4
contacts operate circuit B.
Recommended Applications — This control method is rec-
ommended for 38APD dual-circuit units with two separate air
handlers connected, one to each circuit. Ideally, the 38APD
unit should have no more than 2 compressors in the circuit.
Units with more compressors in the circuit may not provide ad-
equate control due to the large capacity steps.
This control scheme
cannot
be used with:
• Units with digital compressors. Digital operation is not
supported with this control scheme.
• Minimum Load Control, which is not supported with this
control scheme
• Single or 2-Step Demand Limit, which are not supported
with this control scheme
• 38APS units
Hardware Requirements
• energy management module
• 2 two-stage thermostats, one for each air handler
• 4 SPST relays for thermostat input. If Minimum Load
Control will be used, install DPDT Relays in place of the
SPST Relays.
With this configuration, Single or 2-Step Demand Limit is
not available as the inputs for this option are used by the second
thermostat. If Demand Limit is required, 4 to 20 mA or De-
mand Limit through CCN communications is available.
Required Configurations — Table 35 lists the configurations
required for proper operation.
Table 35 — C.TYP=8 (Dual Tstat) Required
Configuration
Wiring — See Fig. 140.
Sequence of Operation — The MBB monitors the thermostat
inputs to make a determination of circuit capacity stage. If Y1
or Y3 input is closed, no more than 50% of the circuit capacity
will be energized. If Y2 or Y4 is closed, 100% of the circuit ca-
pacity will be energized for that circuit, if available. Y1 or Y3
closure is not required for 100% capacity. Thermostat inputs
for circuit A can be monitored at the unit’s scrolling marquee,
Inputs
o
GEN.I
o
Y.1
(Y1 Thermostat Input) and
Inputs
o
GEN.I
o
Y.2
(Y2 Thermostat Input). Thermostat inputs for cir-
cuit B can be monitored at the unit’s scrolling marquee,
In-
puts
o
GEN.I
o
Y.3
(Y3 Thermostat Input) and
Inputs
o
GEN.I
o
Y.4
(Y4 Thermostat Input).
For mechanical cooling, the unit’s Control Method
(
Configuration
o
OPT2
o
CTRL
) and inputs must allow the
machine to run. See Control Methods on page 60 for addition-
al information.
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
specific information on Time Guard, see MDTG - Time Guard
Active on page 135.
In this Control Type, Space Temp Control Mode,
Run
Status
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), 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
Inputs
o
GEN.I
o
Y.1=
ON
or Y3
Inputs
o
GEN.I
o
Y.3=
ON
is closed.
SPT.M=
2
(High Cool)
if Y2
Inputs
o
GEN.I
o
Y.2=
ON
, or Y4
Inputs
o
GEN.I
o
Y.4=
ON
is closed.
SPT.M=
0
(Off Cool) if Y1, Y2, Y3 and Y4
are all open,
Y.1=
OFF
,
Y.2=
OFF
,
Y.3=
OFF
and
Y.4=
OFF
.
With this Control Type, if the Indoor Fan Status Switch for cir-
cuit A or B opens,
Inputs
o
GEN.I
o
ID.F.A=
OFF
or
In-
puts
o
GEN.I
o
ID.F.B=
OFF
,
STAT
will change to
8
(IDFS
Not On), the unit will remain with
SPT.M=
0
(Off Cool) if Y1,
Y2, Y3 and Y4 are all open,
Y.1=
OFF
,
Y.2=
OFF
,
Y.3=
OFF
and
Y.4=
OFF
. If Y1, Y2, Y3 or Y4 close,
Y.1=
ON
,
Y.2=
ON
,
Y.3=
ON
or
Y.4=
ON
, Control Mode will change from
STAT=
8
(IDFS Not On), to
4
(Off Emrgcy) as an alarm is generated. Ta-
ble 36 shows the space temperature control mode response for
C.TYP=
8
.
38APD Units
— On a circuit B call for cooling, Y1 closure,
Indoor Fan Status Cir A (
Inputs
o
GEN.I
o
ID.F.A
) is
checked. On a circuit B call for cooling, Y3 closure, Indoor
Fan Status Cir B (
Inputs
o
GEN.I
o
ID.F.B
) is checked. The
circuit fan status switch must be closed before the capacity rou-
tine will start for the circuit. The lead compressor of the circuit
will be determined and started. See Circuit Compressor Stag-
ing on page 112. The solenoid corresponding to the circuit is
opened 30 seconds after the Y1 or Y3 closure. The lead com-
pressor is started 20 seconds later. Compressors will be staged
at 70-second intervals until the unit’s capacity is as close as
possible to 50% without exceeding it. When the Y2 or Y4 con-
tact is closed, the remaining capacity will be started, staging
compressors at 60-second intervals. 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 and the Y2
or Y4 contact opens, the machine controls will reduce the
unit’s capacity by removing compressors. The first compressor
will turn off between 30 and 60 seconds following the loss of
the Y2 or Y4 signal. The remaining compressors will turn off
in 90-second intervals until the unit is as close to 50% capacity
without exceeding it. Finally, as the Y1 or Y3 contact opens,
the remaining capacity is removed immediately.
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 8
(Dual Stat)