Tyco DigiTrace 920 Series - Appendix D HTC Load Shedding Sequence

74
Appendix D HTC Load Shedding Sequence
1. If an HTC is associated with more than one contact input, all inputs must be activated before
the
HTC will go into a Load Shedding mode.
2. If communications between an HTC and an upstream device such as a GCC or supervisory
software are interrupted, or if the power has been reset to the
HTC, the HTC will hold its out-
put
OFF, waiting for a Load Shedding command
3. Only if the Low Temperature Alarm is ENABLED.
4. For 920 Series controllers, a “<Load Shedding>” message will displayed after the load
current reading.
Load
shedding
command
received?
HTC
load shed
enabled?
All other
contact inputs
active?
[1]
Is
communications
active?
[2]
Has HTC
power been
reset?
Fail safe mode
enabled?
HTC temp. at
low temp.
alarm SP?
[3]
Y
Y
Y
Y
N
N
N
N
N
N
N
Y
Y
Y
Control at low
temp. alarm setpoint
HTC holds its output
OFF for 30 seconds
Normal control
mode
All matching HTCs set their
outputs to OFF
HTC display indicates load
shedding mode [4]