Bosch TW Series Specifications download pdf (Page 9)

6 720 220 047

Revised 03-11 Subject to change without prior notice

TW Series / Water to Water

compressor in a two stage unit). When the set point

is satised the compressor is turned off.

In a two stage unit after the rst stage activation if

the water temperature drops an additional two

degrees below the set point, the second stage

(terminal Y2) will be activated (if control is

congured for both compressors). Both stages will

be on until the set point is satised.

When the unit runs after power is applied or the

mode is changed from cooling to heating, if the

uid temperature is below set point and doesn’t

change for 3 minutes, the second stage of heating

will be activated. This only applies for a two stage

machine.

There will be 5 minutes delay on break after the unit

cycles off on temperature, a power interruption or

because of a fault condition.

At any point in time the control will ignore a low

pressure switch condition for 120 seconds before

turning off the compressor.

COOLING MODE

When the unit is operated in the cooling mode and

the leaving water temperature is above the

temperature set point plus the differential setting,

terminals Y1 will close (rst stage compressor of a

two stage unit) and the unit will operate in the

cooling mode. When the set point is satised the

compressor is turned off. The reversing valve is

always activated when the unit is in the cooling

mode.

On two stage units, after rst stage activation if

water temperature increases two degrees above

the set point, the second stage (terminal Y2) will be

activated (if control is congured for both

compressors). Both stages will remain on until the

set point is satised.

When the unit runs after power is applied or the

mode is changed from heating to cooling, if the

uid temperature is above cooling point and

doesn’t change for 3 minutes, the second stage of

cooling will be activated. This only applies for a two

stage machine.

There will be 5 minutes delay on break after the unit

cycles off on temperature, a power interruption or

because of a fault condition.

AUTO CHANGEOVER MODE

The controller’s auto changeover mode control

feature will switch from the heating mode to

cooling mode and vice versa based on the setting of

the change over sensor. There will be a dead-band

where the control will not call for either heat or

cool. The dead-band setting is adjustable in the

conguration mode. When the auto changeover

mode is selected the changeover set point will be

displayed for 5 seconds however this set point is

only adjustable when the controller is in the

conguration mode. Once the controller has

switched to either the heating or cooling mode,

pressing the Up or Down buttons will display the

set point for that particular mode.

When the reading from the changeover sensor is

above the changeover set point plus the dead-band

setting, the unit will operate in the cooling mode

and will maintain the cooling set point temperature.

While in the cooling mode the user can adjust the

cooling set point. Likewise when the changeover

sensor is below the changeover set point minus the

dead-band setting, the unit will switch to the

heating mode and will maintain the heating set

point temperature. While in the heating mode the

user can adjust the heating set point.

Once the reading from the sensor enters the

dead-band zone it will terminate the call for cooling

or heating even if the set points are not satised.

Mode switching will be HEAT – COOL – OFF in a

closed loop. If the changeover sensor is shorted

when the control is in Auto changeover mode then

the control will switch to the OFF mode. If no

sensor is connected the controller will indicate a

sensor error code.

UNIT PROTECTION

The unit controller will protect the unit against a

high or low pressure condition and brownout. To

avoid nuisance lockouts an intelligent reset

function is built into the controller to allow the unit

to restart one time in the event of a fault condition.

If a fault condition is initiated on any circuit the

corresponding compressor will be turned off and

the 5 minute delay on break time period timer is

initiated. After the delay expires the unit will

attempt to restart. If the fault condition still exists

Cooling Mode

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Bosch TW Series Specifications Page 9

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