JOHNSON CONTROLS
FORM 160.84-EG1 (617)
30
Series/Parallel Arrangement – Chillers may be applied in pairs with chilled water circuits
connected in series and condenser water circuits connected in parallel. All of the chilled
water flows through both evaporators with each unit handling approximately one-half of
the total load. When the load decreases to a customer selected load value, one of the
units will be shut down by a sequence control. Since all water is flowing through the oper-
ating unit, that unit will cool the water to the desired temperature.
EVAP.1
EVAP.2
T
S1
S2
COND. 1
COND. 2
S – Temperature Sensor for Chiller Capacity Control
T – Thermostat for Chiller Capacity Control
FIGURE 2 - SERIES EVAPORATORS PARALLEL CONDENSERS
Series Counter Flow Arrangement - Chillers may be applied in pairs with chilled water
circuits connected in series and with the condenser water in series counter flow. All of the
chilled water flows through both evaporators. All of the condenser water flows through
both condensers. The water ranges are split, which allows a lower temperature difference
or "head" on each chiller, than multiple units in parallel. For equal chillers, the machine
at the higher temperature level will typically provide slightly more than half the capacity.
The compressor on each chiller is often matched, such that the high temperature machine
can operate at the low temperature conditions when one unit is cycled off at partload (as
compared to series-parallel chillers which are typically not identical).
LD18372
S – Temperature Sensor for Chiller Capacity Control
T – Thermostat for Chiller Capacity Control
FIGURE 3 - SERIES EVAPORATORS SERIES-COUNTER FLOW CONDENSERS
Series counter flow application can provide a significant building energy savings for large
capacity plants which have chilled and condenser water temperature ranges greater than
typical AHRI requirements.
Application Data (Cont'd)
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