9
The chiller is now configured for minimum load valve
control.
Test Minimum Load Relay Outputs — After the unit is re-
configured, test the operation of the relay and solenoid valve
using the Quick Test software function. Test Circuit A as fol-
lows (the LOCAL/OFF/REMOTE (LOR) switch must be in
the OFF position):
1. Press
on the HSIO-2 keypad.
2. Press the down arrow
until the display reads:
MIN. LOAD VALVE A
RELAY IS OFF
3. Press
.
4. The display may read as follows. (If not, skip to Step 7.)
PASSWORD PROTECTED FUNCTION
ENTER PASSWORD
5. Press
.
6. The HSIO-2 again displays the following:
MIN. LOAD VALVE A
RELAY IS OFF
7. Press
to energize the relay. The display reads:
MIN. LOAD VALVE A
RELAY IS ON
An audible click will be heard. Verify that the solenoid valve
for Circuit A is energized.
8. Press
to turn off the minimum load valve relay for
Circuit A.
To check the operation of the solenoid valve on Circuit B,
follow the same procedure as the preceding, but enter
in Step 1, instead of
. The display screens will be for
Circuit B instead of A.
Adjust Setting of Minimum Load Ball Valve — The mini-
mum load ball valve must be adjusted to suit the application.
Calibrate one circuit at a time as follows:
1. Adjust the ball valve so that it is approximately half open.
2. Operate the chiller in Manual Control mode, with one circuit
operating, and all compressor loaders deenergized. See Man-
ual Control Mode section on page 32 for further information.
3. Record the cooler
∆
T (the difference between cooler enter-
ing fluid temperature and cooler leaving fluid temperature)
at this fully unloaded condition.
4. Use the Manual Control feature to enable the minimum load
valve for the circuit that is operating.
5. Observe and record the cooler
∆
T with the minimum load
valve energized.
6. Adjust the minimum load ball valve until the cooler temper-
ature difference reading from Step 5 is equal to half of the
temperature difference reading from Step 3.
7. Open the ball valve to decrease the temperature difference or
close the ball valve to increase the temperature difference
(
∆
T). When the valve is adjusted correctly, the difference
between cooler entering and leaving fluid temperatures
when the minimum load control is energized must be at least
half of the temperature difference when the minimum load
control is deenergized. For example, if the difference
between the cooler entering and leaving water temperature is
3
°
F with the valve deenergized, then the difference between
cooler entering and leaving water temperature must be at
least 1.5
°
F with the valve energized.
Once the outputs have been tested and the ball valve ad-
justed, the installation is complete. Disable manual control and
return chiller to desired operational status.
CAPACITY CONTROL OVERRIDES — The following
overrides will modify the normal operation of the routine.
Deadband Multiplier — The user configurable Deadband
Multiplier (
) 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 ap-
plied 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 temperature
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 sys-
tems 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 adding
the first stage to reduce cycling. This factor is also applied
when the control is attempting to remove the last stage of
capacity.
Slow Change Override — The control prevents the capacity
stages from being changed when the leaving fluid temperature
is close to the set point (within an adjustable deadband) and
moving towards the set point.
Ramp Loading (
) — Limits the rate of change of leav-
ing fluid temperature. If the unit is in a Cooling mode and con-
figured for Ramp Loading, the control makes 2 comparisons
before deciding to change stages of capacity. The control calcu-
lates a temperature difference between the control point and
leaving fluid temperature. If the difference is greater than 4
°
F
(2.2
°
C) and the rate of change (
°
F or
°
C per minute) is more
than the configured Cooling Ramp Loading value (
),
the control does not allow any changes to the current stage of
capacity.
Low Entering Fluid Temperature Unloading — When the
entering fluid temperature is below the control point, the con-
trol will attempt to remove 25% of the current stages being
used. If exactly 25% cannot be removed, the control removes
an amount greater than 25%, but no more than necessary. The
lowest stage will not be removed.
Low Discharge Superheat — If a circuit’s discharge superheat
is less than 15
°
F (8.3
°
C), the control does not increase the cur-
rent capacity stage. If the discharge superheat is less than 5
°
F
(2.8
°
C) and decreasing, the circuit is unloaded every 30 sec-
onds until the superheat is greater than 5
°
F (2.8
°
C). The final
capacity stage is not unloaded unless an alarm condition exists.
This override is ignored for the first 3 minutes after a compres-
sor is started.
Low Saturated Suction Temperature — To avoid freezing the
cooler, the control will compare the circuit Saturated Suction
temperature with a predetermined freeze point. If the cooler
fluid selected is water, the freeze point is 28 F (–2.2 C). If the
cooler fluid selected is brine, the freeze point is 8
°
F (4.4
°
C)
below the cooling set point (lower of 2 cooling set points for
dual configuration). If the saturated suction temperature is
below the freeze point, the unit capacity is not allowed to
increase.
For brine applications, the freeze point (Brine Freeze Point)
can be entered by pressing
and scrolling 12 items
down. The control will use the Brine Freeze Point value less
6
°
F (3.3
°
C) as the freeze point to compare with the Saturated
Suction temperature. The default for the Brine Freeze Point is
34 F (1.1 C) which means the control will use 28 F (–2.2 C) as
the freeze point. The brine freeze point is adjustable from –15 F
to 34 F (–26.1 to 1.1 C).
ENTER
ENTER
ENTER
ENTER