Watlow Series D8 - Manual (Page 27)

Series D8 User’s Guide Chapter 1: System Overview
Doc. 0600-3120-2000 Watlow Anafaze 9
vice such as an mechanical contactor. The limit controller
monitors for a hazardous condition such as an under-temper-
ature or over-temperature fault. If a hazardous condition is de-
tected, the limit controller sends a signal to open the contactor.
The safety shutdown device (limit controller and contactor)
must be independent from the process control equipment.
WARNING! The controller may fail in a 0 percent or 100
percent output power state. To prevent
death, personal injury, equipment damage or
property damage, install external safety shut-
down devices that operate independently
from the process control equipment.
With proper approval and installation, thermal fuses may be
used in some processes.
Power-Fail Protection
In the occurrence of a sudden loss of power, the D8 controller
can be programmed to reset the control outputs to off (this is
the default). The controller can also be configured to restart to
data stored in memory.
A memory-based restart might create an unsafe process con-
dition for some installations. Use a memory-based restart only
if you are certain your system will safely restart. See Power
Up Loop Mode on page 128.
When using the controller with a computer or other master de-
vice, you can program the software to automatically reload
desired operating constants or process values on powerup.
These convenience features do not eliminate the need for in-
dependent safety devices.
Contact Watlow Anafaze immediately if you have any ques-
tions about system safety or system operation.