Close System vs. Open System
The mini chiller has been designed with an application for a close water piping system.
However, it is still possible to use the unit with an open system by means of an additional
buffer tank.
In such a system, the chiller will discharge the chilled water into the tank while a secondary
external pump will then pump the water to the fan coil units.
It is recommended that the tank to have a baffle plate in between to isolate the two return
water from the chiller and fan coil load. This will prevent the hotter return water temperature
from the load mixing with the cold chilled water from the chiller.
Such a method is suitable for:
- multiple chillers operation
- multiple secondary pumps supplying chilled water to several zones
The water volume in the tank can also be sized to act as a storage to provide cold water to the fan
coil units. By doing so, the chiller may be cycled-off for longer periods of time, hence saving energy
costs.
However, since this is an open system, there is a higher chance of air entering the water.
Care must also be taken to ensure there are no leakages along the pump suction line else
air will enter the system. The air will be drawn into the buffer tank and accumulate there. This
may affect the water flow rate and trip the chiller unit. Always ensure the automatic air vent
on the buffer tank is operating properly to release any trapped air.
Supply to load
Return from load
Tank
Chiller Secondary pump
Check if this air
vent is OK or not!!
Buffer tank
*** See Page 25 for more information
Section 2 Page 14
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