19
The reset is calculated as follows if the
value of the “Voltage for zero reset”
exceeds the value of the “Voltage for
maximum reset”:
• The reset is zero if the external 0-10 V
d.c. reset signal exceeds the reference
value “Voltage for zero reset”.
• The reset equals the maximum reset value
if the external 0-10 V d.c. reset signal is
lower than the reference value “Voltage
for maximum reset”.
• If the 0-10 V d.c. reset signal is between
the reference values “Voltage for zero
reset” and “Voltage for maximum reset”,
the reset value is calculated by linear
interpolation between the “Maximum
reset” value and 0.
The reset is calculated as follows if the
value of the “Voltage for zero reset” is
lower than the value of the “Voltage for
maximum reset”:
• The reset is zero if the external 0-10 V
d.c. reset signal is lower than the
reference value “Voltage for zero reset”.
• The reset equals the “Maximum reset
value” if the external 0-10 V d.c. reset
signal exceeds the reference value
“Voltage for maximum reset”.
• If the 0-10 V d.c. reset signal is between
the reference values “Voltage for zero
reset” and “Voltage for maximum reset”,
the reset value is calculated by linear
interpolation between 0 and the
“Maximum reset” value.
Sample voltage reset configuration:
In this example, the cooling setpoint starts to
be reset with effect from 6.6 V d.c. (full load)
up to a maximum reset of 3°C at 5.0 V d.c.
This example assumes that the:
• Voltage reset has already been configured
in the configuration menu (see section
4.2.10, configuration).
The configuration shall be as follows:
• Zero reset if the external signal (“Voltage
for zero reset” - Item 8) is greater than 6.6
volts;
• Maximum reset 3°C (Maximum reset
value - Item 12) if the external signal
(“Voltage for maximum reset” - Item 9) is
lower than 5.0 volts.
Items 8-9-12 Voltage reset - Cooling mode values
Items 13-14-17 Voltage reset - Heating mode values
This function is only active when reset
based on an external 0-10 V d.c. signal
has been selected (see section 4.2.10).
Voltage reset is based on an external
0-10 V d.c.
signal applied to specific inputs
on the customer terminal block (see section
3.4.10). The source of this signal is usually
a 0-10 V d.c. external ambient or air
temperature probe which gives a measure
of the load trends for the building. If this is
the case, the reset parameters are generally
configured to deliver the following:
• In cooling mode, an reset with a
negative slope. The controller
automatically resets the chilled water
setpoint upwards in response to a drop
in the outside or ambient temperature.
• In heating mode, an reset with a posi-
tive slope. The controller automatically
resets the chilled water setpoint
downwards in response to a rise in the
outside or ambient temperature.
However, the reset parameters remain
accessible to any type of configuration
and make it possible to obtain any
combination of slope and reset origin in
response to the 0-10 V d.c. input signal.
Voltage reset is a linear function which
requires three parameters to be
configured:
• A 0-10 V d.c. reference value at which
the reset is zero: this is the “voltage for
zero reset” (item 8 for cooling mode -
item 13 for heating mode).
• A 0-10 V d.c. reference value at which
the reset is at maximum: this is the
“voltage for maximum reset” (item 9
for cooling mode - item 14 for heating
mode).
• The maximum reset value: this is the
“maximum reset value” (item 12 for
cooling mode - item 17 for heating
mode).
Range: Voltage for zero reset:
0 to 10 volts
Voltage for maximum reset:
0 to 10 volts
Maximum reset value:
-16.6 to 16.6°C
To Next Page
Loading...
