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HydroBank MS Installation and Operation Manual MAMM-WSHP-IOM-1MSA (October 2014)
Optional Water Side Economizer Piping and Control
Optional Water Side Economizer Piping and Control
The waterside economizer option (WSE) allows pre-
cooling of the entering air to take advantage of cool
loop fluid and to reduce compressor operation during
cool weather. Water lines and condensate drain lines are
attached to the unit as shown in Figure 16. All water lines
and valves should be insulated to prevent condensation.
The condensate drain for the WSE coil must be trapped
(the unit drain is internally trapped).
Each waterside economizer includes a water-to-air coil, a
3-way water diverting valve, an aquastat (water tempera-
ture switch), a relay and interconnecting wiring to the unit
controls box. The aquastat is factory set at 65°F. It is field
adjustable from 45° to 75°F. See Figure 16 for the loca-
tion of the access panel to adjust the switch.
Control Sequence with One-Stage Thermostat
On a call for cooling, the 3-way diverting valve opens
for economizer cooling if the entering water temperature
is below the set point of the aquastat. If it is above the
aquastat set point, the compressor is automatically ener-
gized for mechanical cooling.
Control Sequence with Two-Stage Thermostat
On a call from the thermostat for stage-one cooling, the
3-way diverting valve opens for economizer cooling if
the entering water temperature is below the set point of
the aquastat. If it is above the aquastat set point, the
compressor is energized for mechanical cooling.
On a call for stage-two cooling, the compressor starts
for simultaneous compressor and economizer cooling. If
the entering water temperature rises above the aquastat
set point, the 3-way valve closes to stop economizer
cooling and the compressor remains energized for
mechanical cooling.
Figure 15: Water Side Economizer Wiring Diagram
Figure 16: Water Side Economizer Piping
Unit and WSE
condensate drains
Water in from WSE
Water out to loop
Horizontal Unit
Vertical Unit
Water out to unit
Access panel for water
temp switch (aquastat)
Water in from loop
Unit condensate drain
Water out to loop
Water in from WSE
WSE condensate drain
(with trap)
