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Sequence Of Operation Two-Stage Units; Well Water Systems; Installation Of Pressure Regulating Valves; Cooling Tower / Boiler Application - Bosch CE025 Installation And Maintenance Manual

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Well Water systems

seQuenCe of oPeraTIon—
TWo sTaGe unITs
(Figure #13 Wiring Diagrams)
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. Note that the fan motor
will take 30 seconds to ramp up to operating speed and
will run at fan only rated air flow as long as there is no
call for compressor or heater operation.
When the thermostat calls for first stage cooling (Y1)
the loop pump or solenoid valve is energized and the
first stage of compressor capacity starts. The fan
ramps up to first stage cooling air flow in 30 seconds.
When the thermostat calls for second stage cooling
(Y2) the second stage (or full compressor capacity)
is initiated. The fan ramps up to full cooling air flow.
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 irrespective
of which stage is engaged.
HeaTInG Mode
The first two stages of heating (Y1 & Y2) operate in the
same manner as cooling, but with the reversing valve
de-energized. On a call for auxiliary heat (W1), the fan
ramps up to auxiliary heat air flow immediately and the
electric heater package is energized along with the
compressor. As the thermostat is satisfied, the heaters
will shut off as soon as W1 is de-energized, and the
compressors will remain on until the thermostat stages
are satisfied. Note that if the unit compressor lock out
for any reason at this time, the electric heaters will
continue to function normally.
Once the thermostat is satisfied, the compressor
shuts down and the fan ramps down either fan only
mode or off over a span of 30 seconds. If emergency
heat (W2/EM) is called for, the fan will ramp up to
emergency heat air flow immediately and the heater
package will energize in emergency heat mode, all
heater elements coming on. On shut down the fan
will ramp down over a period of 30 seconds.
Revised 05-12
Subject to change without prior notice
Well WaTer sYsTeMs
(Figure #10)
In well water applications water pressure must
always be maintained in the heat exchanger. This can
be accomplished with either control valve or a
bladder type expansion tank. When using a single
water well to supply both domestic water and the
heat pump care must be taken to insure that the well
can provide sufficient flow for both. In well water
applications a slow closing solenoid valve must be
used to prevent water hammer.
Solenoid valves should be connected across Y1 and
C1 on the interface board for all. Make sure that the
VA draw of the valve does not exceed the contact
rating of the thermostat.
InsTallaTIon of Pressure
reGulaTInG ValVes
Pressure regulating valves are used to increase or
decrease water flow through the heat pump in
response to refrigerant pressure. In some cases more
water may be required in heating than in cooling, or
vice versa. With the CE heat pumps these valves are
not required. However, if installed, a pair of valves are
required for proper operation, one valve for cooling
(direct acting) and another valve for heating (indirect
acting). A refrigerant tap is provided in the refrigerant
line located between the reversing valve and the
water-to-refrigerant heat exchanger for proper
monitoring of the refrigerant pressures.
The discharge water from the heat pump is not
contaminated in any manner and can be disposed of
in various ways depending on local building codes
(i.e. discharge well, dry well, storm sewer, drain
field, stream or pond, etc.) Most local codes forbid
the use of a sanitary sewer for disposal. Consult your
local building and zoning department to insure
compliance in your area.
CoolInG ToWer/boIler sYsTeMs
(Figure #11)
The cooling tower and boiler water loop temperature
is usually maintained between 50˚ F to 100 ˚ F to
assure adequate cooling and heating performance.
In the cooling mode, heat is rejected from the unit
into the water loop. A cooling tower provides
6 720 220 048
CE Series

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