Table of Contents
Advertisement
ITEM
DMD.L
DEMAND LIMIT CONFIG.
DM.L.S
Demand Limit Select
D.L.20
Demand Limit at 20 ma
SH.NM
Loadshed Group Number
SH.DL
Loadshed Demand Delta
SH.TM
Maximum Loadshed Time
D.L.S1
Demand Limit Sw.1 Setpt.
D.L.S2
Demand Limit Sw.2 Setpt.
Where Greenspeed control is involved, it may also be referred to
as low ambient control. The Greenspeed/low ambient option or
the factory-installed Motormaster control option will be directly
implemented in the ComfortLink software. It is not compatible
with the field-installed Motormaster V control as found in
CESR131343-07-xx and earlier software versions that used an
accessory with part numbers CRLOWAMB033A00 through
CRLOWAMB038A00. These field-installed accessory Motor-
master V speed controls are completely self-contained control
units and are not controlled by the unit's ComfortLink controller.
Head Pressure Control Operation
Condenser head pressure control for the 48/50P Series rooftops is
controlled discretely by the unit, except when the unit is equipped
and configured for Greenspeed/low ambient or factory-installed
Motormaster option control where head pressures would be con-
trolled via factory-installed VFDs. For a unit with factory-installed
Motormaster option, the control would be able to cycle up to three
stages of outdoor fans to maintain acceptable head pressure.
For 48/50P units, fan stages react to discharge pressure transduc-
ers (DPT) (Pressures
REF.P
connected to the compressor discharge piping in circuit A and B.
The control converts the pressures to the corresponding saturated
condensing temperatures (Temperatures
SCT.B). The specific staging sequence for a unit depends on the 3
factors: the unit size (tonnage), which refrigeration circuits are
currently operating, and whether or not Motormaster is enabled.
See Fig. 6 for fan staging sequencing.
The condenser fan output controls outdoor fan contactors and out-
door fans for each unit tonnage as shown in Fig. 6. Each stage of
fans is also shown. The ComfortLink controller adds or subtracts
stages of fans based on SCT.H and SCT.L. When the SCT rises
above SCT.H, a fan stage will be added. The ComfortLink con-
troller will continue to add a fan stage every 10 seconds thereafter
if the SCT remains above SCT.H. If SCT rises above 130°F, the
controller will turn on the maximum fan stages for the unit. When
the SCT drops below the SCT.L, a fan stage will be subtracted.
The ComfortLink controller will continue to drop a fan stage every
2 minutes thereafter if the SCT remains below SCT.L.
When a condenser fan output is common to both refrigeration cir-
cuits (in other words, when the fan(s) will affect both circuit A and
circuit B), the following logic is used: in order to add a fan stage,
the SCT of either circuit must be above SCT.H for 30 seconds and
in order to subtract a stage, the SCT of both circuits must be below
SCT.L for 30 seconds.
Whenever outdoor ambient temperature (OAT) is above 70°F, the
maximum stage will always be on when the compressors are on.
On the initial start-up of a circuit, the condenser fans will start
3 seconds prior to the unit ready for engaging the compressor
starting, in order to ensure proper head pressure of the compressor
immediately at start-up. After the compressor starts, the normal
head pressure routine will begin 30 seconds after the condenser
fan pre-start. What stage fans starts depends on the outdoor ambi-
ent temperature. The three situations are:
OAT < 50°F
50°F < OAT < 70°F
OAT > 70°F
See Fig. 6 for what stage of fans starts for each scenario.
Table 41 — Demand Limit Configuration
EXPANSION
DP.A and DP.B) which are
REF.T
SCT.A and
RANGE
UNITS
0 to 3
0 to 100
%
0 to 99
0 to 60
%
0 to 120
min
0 to 100
%
0 to 100
%
If the unit is equipped with the optional Greenspeed / low ambient
control, the Outdoor VFD installed configuration (Configuration
COOL
OV.EN) must be set to YES, to fully utilize head pres-
sure control function for optimal operations.
The SCT.A and SCT.B sensors, which are connected to the con-
denser coils in circuit A and B, will be used to measure the saturat-
ed condensing temperature and may be used to control head pres-
sure. The saturated condensing temperatures can be viewed in the
Temperatures
REF.T submenu. The equivalent refrigerant
pressure values, DP.A and DP.B, can be viewed under the Pres-
sures
REF.P submenu.
Head Pressure Configurations
There are two configurations provided for head pressure control
that can be found at the local display based on the option being in-
stalled in the factory:
1.
Configuration
Setpoint) and SCT.L (Head Pressure Low Setpoint)
2.
Configuration
and Configuration
Point) for units with Greenspeed/low ambient option only.
Head Pressure Outputs
There are up to four condenser fan relays used to control head
pressure for standard non-outdoor VFD option units:
Outputs
FANS
CDF.1: Condenser Fan Output 1
Outputs
FANS
CDF.2: Condenser Fan Output 2
Outputs
FANS
CDF.3: Condenser Fan Output 3
Outputs
FANS
CDF.4: Condenser Fan Output 4
For units with Greenspeed/low ambient option, the head pressure
would be controlled by the Outdoor Fan VFD A and B (Out-
puts
FANS
OV.A / OV.B).
ECONOMIZER INTEGRATION WITH MECHANICAL
COOLING
When the economizer is able to provide free cooling (Run Sta-
tus
ECON
ACTV = YES), mechanical cooling may be de-
layed or even held off indefinitely.
NOTE: Once mechanical cooling has started, this delay logic is no
longer relevant.
Multi-Stage Cooling Economizer Mechanical Cooling Delay
This type of mechanical cooling delay is relevant to the following
machine control types:
C.TYP = 1 VAV-RAT
C.TYP = 2 VAV-SPT
C.TYP = 3 TSTAT-MULTI
C.TYP = 4 SPT-MULTI
If the economizer is able to provide free cooling at the start of a
cooling session, the mechanical cooling algorithm (SumZ), checks
the economizer's current position (Run Status
ECN.P) and compares it to the economizer's maximum position
(Configuration
ECON
has opened beyond this point, a 150 second 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 and unloaders.
59
CCN POINT
DMD_CTRL
0
DMT20MA
100
SHED_NUM
0
SHED_DEL
0
SHED_TIM
60
DLSWSP1
80
DLSWSP2
50
COOL
SCT.H (Head Pressure High
COOL
OV.EN (Outdoor VFD Enabled)
COOL
LASP (Low Ambient Set-
EC.MX) – 5%. Once the economizer
DEFAULT
ECON
Advertisement
Table of Contents
Troubleshooting
