28
Setting: ENABLE or DISABLE
Procedure: Enable or disable the INHIBIT CONTROL for the control point being programmed.
Notes:
• The
EXTERNAL INPUT must also be programmed as INHIBIT before this parameter can be set.
See section 3.6.3 on page 29 for further details.
• If the autocycle feature is enabled, it will continue to function even when the
INHIBIT mode is
active.
• Fail-safe mode is inactive if the
INHIBIT mode is active.
• Both of the
LOW TS ALARMS are inactive if the INHIBIT mode is active.
3.5.27 OVERRIDE SOURCE (V3.11 AND UP)
Purpose: An override signal can be sent to the
HTC from one of two sources. This override signal
can be used to override the controller’s temperature control and force the output switch off or
on. This is especially useful when the user wishes to turn a controller or a group of controllers
off over the summer months, during maintenance, or when a line is flowing and does not require
heating.
Setting:
REMOTE or EXT. INPUT
Procedure: If the override signal will be generated remotely and received by the HTC via the
optional communications interface, select
REMOTE as the OVERRIDE SOURCE. If the override sig-
nal will be received by the HTC via the external input terminals on the 920 terminal board, select
EXTERNAL INPUT as the OVERRIDE SOURCE.
Notes:
•If the
EXTERNAL INPUT is not configured as either INHIBIT or FORCE ON then OVERRIDE SOURCE
will always automatically be set to
REMOTE. See section 3.6.3 on page 29 for further details.
• If the autocycle feature is enabled, it will continue to function even when an
INHIBIT override
signal is being received as long as load shedding is not active.
• Fail-safe mode is inactive if an
INHIBIT override signal is being received.
• Load shedding and fail-safe mode are inactive if a
FORCE ON override signal is being received.
• Only the
LOW TS ALARMS for temperature sensors used by the TS CONTROL MODE are inactive
if an INHIBIT override signal is being received.
3.5.28 LOAD SHEDDING ENABLING
Purpose: The load shedding function allows the controller output to be forced
OFF by way of a
remote contact input on the 780 Group Communications Controller or using the communica-
tions port and an upstream device. It may be used to turn
OFF the output of one or more control-
lers in order to reduce energy consumption to avoid peak demand surcharges, remove power
from unused circuits, or remove power from circuits that may be subjected to steam cleaning.
Setting:
ENABLE or DISABLE
Procedure: Enable or disable the load shedding control mode as desired.
Notes:
• To completely configure the
HTC for load shedding operation, the following additional param-
eters must be set up if using the Model 780/GCC-9000:
– Fail-safe mode
– Load shedding
GCC contact association
• These additional parameters may only be accessed using the Group Communications Con-
troller. See the appropriate section of the
GCC manual for further details.
• Fail-safe mode is not supported when using proportional ambient
SSR mode or proportional
ambient contactor mode.
• Fail-safe mode is not supported if the
TS CONTROL MODE = EXT. INPUT, FAIL OFF/ON.
• For fail-safe mode to function, at least one
LOW TS ALARM of the controlling temperature sen-
sor(s) must be enabled and the corresponding
LOW TS ALARM temperature setting must be
less than the
CONTROL SETPOINT temperature.
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