HP 11744195 - Manual (Page 8)

Chart Environmental Chambers Description of Safety Features
Description of Safety Features
On each unit, there are a number of features, which help to ensure safe operation. These
features are:
❏
Temperature High/Low Limit Control:
A user-programmable limit control is provided as an independent measure of safety
against thermal runaway (hot or cold), which could occur from, but not limited to, the
following:
Programming error
Primary controller failure
Thermocouple breakage
Heater SSR failure
Circulation blower failure
The limit control is wired into the control devices to provide a totally independent safety
system. A separate thermocouple is provided for the limit control and located inside the
air plenum. If this device has reached an alarm condition, the system must be reset by
pressing the “Chamber Reset” button on the control console.
WARNING!
: The alarm set point of this device should never be set higher
than +200 ° C or lower than –80°C as these are the
maximum design temperature of the system.
It is important to note that this safety controller does not protect from a possible failure of
the cooling solenoid valve. It is possible for this valve to fail and allow liquid nitrogen to
continue flowing into the chamber, resulting in extremely cold temperatures. As a result,
Chart recommends changing the solenoid valve on a regular basis as a preventative
maintenance measure against such occurrences.
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