Sequence Of Operation; Unit Options - Bosch BP070 Installation And Maintenance Manual

10 CP/BP Series
Considerations
1. Always check incoming line voltage power supply
and secondary control voltage for adequacy.
Transformer primaries are dual tapped for 208
and 230 volts. Connect the appropriate tap to
ensure a minimum of 18 volts secondary control
voltage. 24 volts is ideal for best operation.
2. Long length thermostat and control wiring
leads may create voltage drop. Increase wire
gauge or up-size transformers may be required
to insure minimum secondary voltage supply.
3. Bosch recommends the following guidelines for
wiring between a thermostat and the unit: 18
GA up to 60 foot, 16 GA up to 100 ft and 14 GA
up to 140 ft.
4. Do not apply additional controlled devices to
the control circuit power supply without
consulting the factory. Doing so may void
equipment warranties.
5. Check with all code authorities on requirements
involving condensate disposal/over flow
protection criteria.

SequenCe of oPeraTIon

Cooling Mode
Energizing the "O" terminal energizes the unit
reversing valve in the cooling mode. The fan motor
starts when the "G" terminal is energized.
When the thermostat calls for cooling (Y), the loop
pump or solenoid valve if present is energized and
compressor will start.
Once the thermostat is satisfied, the compressor shuts
down accordingly and the fan ramps down to either fan
only mode or off over a span of 30 seconds.
Note that a fault condition initiating a lockout will
de-energize the compressor.
Heating Mode
Heating operate in the same manner as cooling, but
with the reversing valve de-energized. The
compressor will run until the desired set
temperature on the thermostat is achieved.
Once the thermostat is satisfied, the compressor
shuts down and the fan ramps down either fan only
6 720 220 045
mode or off over a span of 30 seconds. Auxiliary
electric heating coils are not available on the CP/BP
product line.

unIT oPTIonS

HoT GaS reHeaT (HGr)
Hot gas reheat allows the user to not only control
space temperature, but also humidity levels within
the conditioned space. An excess of moisture in the
space can allow mold growth leading to damage in
the structure or interior surfaces as well as
reducing the air quality and creating an unhealthy
environment.
The typical control of a unit is by a thermostat that
senses the temperature in the space. By utilizing a
humidistat in addition to the thermostat we are
able to monitor the humidity levels in the space as
well. The HGR option allows cooling and
dehumidification to satisfy both the thermostat and
humidistat.
Once the thermostat reaches set point temperature
and the humidity is above set point the unit will
operate in the hot gas reheat mode first by cooling
and dehumidifying then reheating the air using hot
refrigerant gas before delivering it to the space
usually 2°F to 5°F below room temperature. The
unit is operating as a dehumidifier. By reheating the
air along a constant sensible heat line the relative
humidity of the supply air is reduced.
The moisture removal capacity of a specific heat
pump is determined by the unit latent capacity rating.
A heat pump's latent capacity can be determined by
reviewing the heat pump specification data sheets.
Depending upon the entering water and air
conditions a total and sensible capacity can be
interpolated from the data sheets. Subtracting
sensible capacity from total capacity yields latent
capacity. Dividing the latent capacity by 1069 (BTU/
LB of water vapor at 80° DB and 67° WB) yields the
amount of moisture removal in pounds per hour.
Sequence of operation - on/off Control
The sequence of operation in the cooling and
heating mode is the same as a regular heat pump.
In the reheat mode on a call from the humidistat the
reheat relay coil is energized through the "H" circuit.
The blower relay, reversing valve and compressor
Subject to change without prior notice
Sequence of operation
Revised 01-11