Specifications

CLOSE CONTROL ( ) — When configured for Close
Control, the control is allowed to use any loading/capacity
control devices required to maintain better leaving fluid tem-
perature regulation. All stages of unloading are available. See
Appendix B for an example.
LEAD/LAG DETERMINATION ( ) — This is a con-
figurable choice and is factory set to be automatic. The value
can be changed to Circuit A or Circuit B leading, as desired.
Set at automatic, the control will sum the current number of
logged circuit starts and one-quarter (Version 3.0 and later)
of the current operating hours for each circuit. The circuit
with the lowest sum is started first. Changes to which circuit
is the lead circuit and which is the lag are made when shut-
ting off compressors.
On 30HX206-271 and 30GX205-265 units set for staged
loading, the control fully loads the lead circuit before start-
ing the lag circuit and unloads the lag circuit first. When these
units are set for equal loading, the control maintains nearly
equal capacities in each circuit when the chiller is loading
and unloading.
CAPACITY SEQUENCE DETERMINATION ( ) —
This is configurable as equal circuit loading or staged circuit
loading with the default set at staged. The control deter-
mines the order in which the steps of capacity for each cir-
cuit are changed. This control choice does NOT have any
impact on machines with only 2 compressors.
MINIMUM LOAD VALVE ( ) — When this option
is installed and configured, the first stage of capacity is ini-
tiated by energizing the Minimum Load valve relay. The con-
trol energizes loaders as needed thereafter. Similarly, the
Minimum Load valve relay will be energized for the last stage
of capacity to be used before the circuit is shut down.
CAPACITY CONTROL OVERRIDES — The following over-
rides will modify the normal operation of the routine.
Deadband Multiplier — The user configurable Deadband Mul-
tiplier ( ) has a default value of 1.0. The range is from
1.0 to 4.0. When set to other than 1.0, this factor is applied
to the capacity Load/Unload Factor. The larger this value is
set, the longer the control will delay between adding or re-
moving stages of capacity. Figure 4 shows how compressor
starts can be reduced over time if the leaving water tempera-
ture is allowed to drift a larger amount above and below the
set point. This value should be set in the range of 3.0 to 4.0
for systems with small loop volumes.
First Stage Override — If the current capacity stage is zero,
the control will modify the routine with a 1.2 factor on add-
ing the first stage to reduce cycling. This factor is also ap-
plied when the control is attempting to remove the last stage
of capacity.
L1
L2
L3
T1
T1
T3
3
2
1
1
2
3
4
6
5
COMPRESSOR JUNCTION BOX
JUMPER BARS
COMPRESSOR CONTACTOR
1
2
3
21
22
23
TERMINAL BLOCK
Fig. 2 — Across-the-Line (XL) Compressor Wiring
1
2
3
4
5
6
1
2
3
T1
T1
T1
T2
T2
T2
T3
T3
T3
S
2M
1M
L3
L3
L3
L2
L2
L2
L1
L1
L1
1
2
3
22
21
23
TERMINAL BLOCK
COMPRESSOR STARTER ASSEMBLY
COMPRESSOR JUNCTION BOX
21
22
23
4
6
5
Fig.3—Wye-Delta Compressor Wiring
7