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FHP560 Controller
Applications Manual
Bosch Thermotechnology Corp.
Data subject to change
Page____ of ____
6 Explanation Of DDC Options
AUXILIARY ELECTRIC HEAT:
Used to provide a single stage of electric heat by way of a factory-installed electric heater option, or
fi
eld-installed electric heater accessory. It may
be used as a supplementary source of heating for units with mechanical heating/cooling capabilities where additional heating capacity is needed
to maintain space setpoint; or as the sole source of heat for straight cool units (mechanical cooling only). The con
fi
gured controller output is
energized to enable the heater based on unit con
fi
guration and parameter setup.
BOILERLESS CONTROL:
An option that allows a water source heat pump to be operated in heating safely when installed in a system that has no means of heating the water
loop. A factory installed Entering Water Temperature (EWT) sensor (thermistor) is connected to the FHP560 controller and used with this option.
During a thermostat call for heating, if the EWT sensor detects a drop in water temperature below a pre-set limit (adjustable in the software), the
FHP560 will disengage the compressor output(s) and provide a 24VAC signal to divert unit operation from compressor heating to an alternate heat
source (generally
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eld-installed electric heat). The option is also used to proactively prevent coils from freezing.
FAN PROVING:
This option uses an optional factory-installed current sensor to prove fan operation prior to unit operation. The status output of the current sensor
is used to establish fan operation for the unit when a proven fan call is established. If con
fi
gured the FHP560 disables unit compressor operation
when the current in the monitored conductor drops below the rated threshold, indicating the fan is non-operational. The current sensor output
may be wired directly to the FHP560, or to an Input Expansion Module (IEM) connected to the FHP560 when multiple options requiring switched
inputs are involved. Please consult the applications department when including this option as an engineering add-on.
FLOW PROVING (DPS):
This option employs the use of an optional Differential Pressure Switch (DPS) to prove water
fl
ow across a unit’s water-to-refrigerant heat
exchanger. If con
fi
gured the software enables unit compressor operation when a pressure drop of 1.5 psi or more is detected across the water
to refrigerant heat exchanger, indicating adequate water
fl
ow. This option prevents nuisance cut outs on high head pressure or freeze protection
when there are interruptions in water
fl
ow.
LOOP WATER VALVE CONTROL:
This option uses an optional factory-installed condenser water valve to control water
fl
ow through the condenser coil. The normally closed valve
includes an auxiliary end switch that may be wired to the controller to determine the status of the valve. When the FHP560 is con
fi
gured for this
option, compressor operation is disabled until valve-open status from the Valve End Switch is veri
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ed.
HOT GAS REHEAT (ON/OFF):
Hot gas reheat helps actively control humidity by reheating cooled and dehumidi
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ed air back to a neutral temperature using waste heat from the
compressor. Doing this allows the unit to continue to operate and remove moisture from the space after the sensible cooling set point has been
satis
fi
ed. Hot gas reheat is well suited for conditioning outside ventilation air and for maintaining ideal humidity levels in schools, commercial
buildings and even homes. A binary output on the FHP560 controller is used to provide the signal for activating the reheat valve when the
necessary conditions are met. Relative humidity readings may be acquired from a wall-mounted ZS combo sensor, a third-party hardwired 0-5V
humidity sensor, or from RH values pushed to the FHP560 over a network.
INPUT EXPANSION MODULE (IEM):
The IEM is used when multiple options that require a binary input are desired for a single application with DDC. The IEM is connected in input
#5 (IN-5) of the FHP560 controller and is software con
fi
gured to enable a trio of preset combinations that include: Fan Status, Valve Status,
Damper Status, Pump Status, Filter Status, Secondary Drain Pan Status, Differential Pressure Switch Status, and Smoke/Fire Detector Status. The
appropriate switches (binary inputs) must be
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eld installed where applicable.
LOOP PUMP CONTROL:
The Loop Pump option uses the FHP560 and a factory installed current sensor to control and monitor a
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eld or factory installed loop pump for
the WSHP units. The pump is indexed to turn on by the controller whenever there’s a call for heating or cooling. The status output of the current
sensor may be used to establish pump operation for the unit when a proven pump call is established. The FHP560 is con
fi
gured to disable unit
compressor operation when the current in the pump’s monitored conductor drops below the rated threshold, indicating pump is not operational.
The current sensor output may be wired directly to the FHP560, or to an Input Expansion Module (IEM) connected to the FHP560 when multiple
options requiring switched inputs are involved. Please consult the applications department when including this option as an engineering add-on.
OUTSIDE AIR DAMPER:
Allows the capability for pre-
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ltered outside air to enter the unit while in operation via a remote motorized damper, based on unit occupancy, fan
operation, or CO
₂
levels in the monitored space. A binary output on the FHP560 controller is used to provide the signal for activating the damper
solenoid when the necessary conditions are met. CO
₂
readings may be acquired from a wall-mounted ZS combo sensor, a third-party hardwired
0-5V CO
₂
sensor, or from CO
₂
values pushed to the FHP560 over a network. A damper end switch connected to the FHP560 may be used to verify
damper status and disable compressor operation when the damper fails.
WATER SIDE ECONOMIZER:
An option package consisting of a water-to-air heat exchanger (economizer coil), a thermistor (EWT sensor), and a 3-way diverting valve. When
there is a call for cooling, the EWT sensor connected to the FHP560 will monitor the entering water temperature to the unit and determine if the
compressor should be used for cooling or if the water temperature is low enough to cool the entering air with the economizer coil. If the entering
water temperature is below a selected user-adjustable setpoint, the diverting valve will be indexed by the FHP560 to divert the entering water
through the economizer coil to cool the air stream. The water is then passed through the water to refrigerant coil in case additional cooling is
required. This DDC option can only be used for cooling operations.
AIR ECONOMIZER:
This option utilizes a
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eld-installed fresh air damper, and requires an outdoor air temperature and humidity combo sensor. When there’s a call
for cooling, the OAT/RH sensor connected to the FHP560 will monitor the outside air temperature and humidity levels and determine if the
compressor should be used for cooling or if the outdoor air is ideal to condition the space with just the fan. If the air temperature and humidity is
within a user-con
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gurable range, the damper solenoid will be energized to open by the FHP560, the compressors will be indexed off, and the fan is
used to cool the space. This option is only available in the cooling mode.
