Operating instructions

42
To configure this option with the Touch Pilot™ display:
To configure this option with the Navigator™ display:
In the example in Fig. 27, at 4 mA no reset takes place and
at 20 mA, 5° F (2.8° C) chilled water set point reset is required.
Demand Limit — Demand limit is a feature that allows
the unit capacity to be limited during periods of peak energy
usage. This allows the owner to keep energy costs down. There
are three types of demand limiting that can be configured. The
first type is through 2-step switch control, which will reduce
the maximum capacity to 2 user configurable percentages. The
second type is by 4 to 20 mA signal input which will reduce the
maximum capacity linearly between 100% at a 4 mA input
signal (no reduction) down to the user-configurable level at a
20 mA input signal. The third type uses the CCN Loadshed
module and has the ability to limit the current operating capaci-
ty to maximum and further reduce the capacity if required. De-
mand limit control can be based on a calculated capacity level
or by compressor current level.
NOTE: If using the compressor current level for demand limit,
take into account the other power draws such as the condenser-
fan motors when determining the limit value desired.
SWITCH CONTROLLED DEMAND LIMIT — The con-
trol system is capable of demand limit based on a field-sup-
plied switch for 1-step demand limit or 2 switches for 2-step
demand limit. One-step Demand Limit is standard. The 2-step
switch control of demand limiting requires the Energy Man-
agement Module (EMM). Demand Limit steps are controlled
by two relay switch inputs field wired to TB5-5 and TB5-14
for Switch 1 and TB6-14 and TB6-15 for Switch 2.
For demand limit by switch control, closing the first de-
mand limit contact will put the unit on the first demand limit
level, either by capacity or compressor current. The unit will
not exceed the percentage of capacity or compressor current
entered as Demand Limit Switch 1 set point. Closing contacts
on the second demand limit switch prevents the unit from ex-
ceeding the demand limit entered as Demand Limit Switch 2
set point. The demand limit percent capacity or compressor
current that is set to the lowest demand takes priority if both de-
mand limit inputs are closed. If the demand limit percentage
does not match unit operation, the unit will limit capacity or
current to the closest step without exceeding the value.
To use Demand Limit, select the type of demand limiting to
use by configuring the Demand Limit Select variable (De-
mand Limit Type Select, DMDC) to Switch. Configure the
Demand Limit set points based on the type selected.
0
1
2
3
4
5
6
7
60 65 70 75 80
Space Temperature (deg F)
Degrees Reset (deg F)
Cooling Reset
Deg. Value,
DGRC
Space T Full Reset Value,
CRS2
Space T No Reset Value,
CRS1
Fig. 26 — Space Temperature Reset
a30-4481
DISPLAY NAME PATH
LINE
NO.
VALUE
Cooling Reset
Select
Main Menu
ConfigUSER
19
Default =0
(No Reset)
3 (4-20mA
Control)
Current No
Reset Value
Main Menu
SetpointSETPOINT
9
4.0 mA
Default = 0.0
Current Full
Reset Value
Main Menu
SetpointSETPOINT
10
30.0 mA
Default = 0.0
Cooling Reset
Deg. Value
Main Menu
SetpointSETPOINT
13
Default =
0.0 F (0.0 C)
ITEM ITEM EXPANSION PATH VALUE
CRST
Cooling Reset
Ty pe
Configuration
RSET
Default =
No Reset
4-20mA Input
CRV1
Current No
Reset Temp
Setpoints
COOL
4.0 mA
Default = 0.0
CRV2
Current Full
Reset Temp
Setpoints
COOL
20.0 mA
Default = 0.0
DGRC
Degrees Cool
Reset
Setpoints
COOL
5.0 F (2.8 C)
Default = 0.0