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T T a a n n k k a a n n d d P P u u m m p p M M o o d d u u l l e e
Fill the Storage Tank
The tank and pump module may contain a pressurized
storage tank. The tank is pressurized during operation
and maintains pressure when the chiller is turned off.
The tank also has a vacuum vent to prevent the tank
imploding.
1. Turn off the pump using the two switches on the
electrical and control panel.
2. Bleed any air pressure in the tank by pressing the
vacuum vent valve on the top of the tank. The
storage tank has a float-type tank level switch; if the
level falls below a factory-set point, an alarm will
activate.
3. Open the tank fill port valve and fill the tank.
N N O O T T I I C C E E
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w w a a t t e e r r s s u u p p p p l l y y . .
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l l e e a a d d t t o o s s y y s s t t e e m m f f a a i i l l u u r r e e d d u u e e t t o o f f r r e e e e z z i i n n g g . .
4. Ensure that both the front fill port and service valve
remain closed during operation.
5. The pressure relief valve is set to 100 psi to prevent
over-pressurizing the tank.
Variable Flow Tank and
Pump Module Sequence
of Operations
1. The chiller is designed to operate with high voltage
power supplied to the unit at all times. This will
provide power to the compressor crankcase
heaters, and minimize liquid refrigerant from
migrating to the compressor sumps.
2. As long as there is power on the chiller, the primary
microprocessor selects the primary module and
rotates this lead once every 168 hours week. The
lead module's electronic isolation valve will initially
be provided with full power input driving the valve
fully open.
3. The chiller is enabled when the on/off switch on the
built-in (or remote) interface panel is energized, and
the remote start/stop relay is enabled (either
through a contact closure or through the building
management system.)
4. The variable frequency drives for the chiller pumps
monitors the opening and closing of the electronic
B–2
valves which are controlled based on leaving water
temperature. The variable frequency drives allow
the pumps to deliver the required flow through
each operating evaporator. The pump speed varies
proportionally to the number of modules that are
operating (electronic valves open) in the chiller.
5. Since the electronic isolation valve of the primary
module is already energized, the pump must
produce the minimum flow required by the primary
module. A system bypass with valve must be
provided by the customer and installed externally
from the chiller at the most remote fan coil or
device to ensure that the pump can provide the
minimum flow required through the primary
module if the return flow to chillers could be
completely restricted with all fan coils or devices
isolated. (A high quality pressure-independent
valve is recommended for this bypass so as to
provide accurate bypass control regardless of
system pressure differential between supply and
return headers.)
6. When this minimum flow is established and the
system demand (based on leaving fluid
temperature) indicates that there is a requirement
for cooling, the lead compressor of the lead module
will energize provided all safeties of that
refrigeration circuit are satisfied.
7. When there is a system load, the BMS will
modulate the system bypass decreasing the bypass
flow, as the flow rate through the fan coils increase.
This control is provided by the customer external of
the chiller, and is presumed to be based on the
pressure differential across the most remote fan
coil or user.
8. As the system demand continues to increase, the
second compressor within that module will
energize provided all safeties on that circuit are
satisfied.
9. As the system demand continues to increase, the
leaving fluid temperature from the chiller will
slowly increase until the differential set point is
reached. When the differential is reached, a second
module will be brought on-line. Instead of opening
the valve fully in this chiller module, which will
cause a substantial drop in flow in the previously
operating module and create a low leaving water
temperature condition, both valves will modulate in
both modules to maintain a constant leaving fluid
temperature.
10. As the flow and demand continue to increase, and
the temperature once again reaches the set point
plus differential setting, the second compressor on
the second module will energize.
11. With a decrease in system demand (and flow) such
that the leaving water temperature reaches the set
point minus the differential, a compressor will de-
energize, and the modulating valves will once again
balance the flow between the operating modules.
ARTC-SVX001B-EN
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