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This is a less energy efficient approach to heat trace control,
but is consistent with what is routinely provided with ambient
sensing mechanical thermostats controlling a contactor
between a distribution panel’s main circuit breaker and the
branch breaker panel board.
4.3: Proportional Control and Power Clamp
If “on/off with soft start” is selected with any Power Clamp
percentage other than 100% the circuit will operate as
follows:
•
Below the Low Temperature alarm (LTA) setpoint, the
heater will be “full on” 100% of the time.
•
When the temperature reaches/exceeds the LTA, the
soft start feature will energize the heater “full on” for
the Power Clamp (time) percentage selected (n% of 1
second) and over 90 seconds will ramp up to “full on”
for 100% of the time.
*
Regardless of what Power Clamp (time) percentage
is selected, it will take a maximum of 90 seconds for
the heater to be “full on” for 100% of the time.
*
The heater will be turned off once the Maximum
Temperature (Maintain Temperature plus Control
Band, or MT+CB) is reached, even if that temperature
is reached in less than 90 seconds.
*
Once the heater is at MT+CB (Maximum
Temperature), it will continue to cycle based on
the soft start settings. In other words, once MT+CB
is reached the heater is de-energized until the
temperature drops to the Maintain Temperature
(MT), then the heater will be energized “full
on” starting at the selected Power Clamp (time)
percentage (n%) and will go through the 90 second
ramp up to “full on” for 100% of the time, or until
the MT+CB is again reached.
Section 5: Genesis Testing and Start-Up
All heat trace circuits should be properly terminated and
megger tested prior to energizing the TraceNet Genesis
control panels. In addition, all pipes should be insulated
with weather barrier to achieve the required temperatures
to be maintained.
Troubleshooting Tips
When starting up a newly installed heat trace and control
system, it is common to encounter numerous circuit
alarms and possibly circuit “trip” events. Data entry errors,
unanticipated temperature conditions and/or dead band
settings that are too narrow, and other possible installation
errors can be expected.
A table of Troubleshooting Tips is provided in Appendix C
to assist during start-up.
Section 6: Operation and Maintenance of
the Genesis Control and Monitoring System
6.1: Maintenance
Preventive maintenance consists of inspection,
testing, checking connections, and general cleaning of
equipment at scheduled intervals. The maintenance
recommendations that follow are intended to support
and in some cases “add to” those procedures detailed in
the facility’s Planned Maintenance System (PMS). In case
of conflicts, contact the project engineer for resolution.
When carrying out the scheduled maintenance program,
the following safety precautions should be observed.
Safety Precautions the heat tracing can be powered by the
project specified nominal voltages ranging from 100 to 600
Vac. It is important that only authorized trained personnel
conduct these maintenance and service activities. Before
conducting any maintenance or service procedure, exercise
required lockout and tag out procedures at the appropriate
circuit breakers. Additionally, do additional testing within
the control panel to ensure that the specific heat tracing
and control circuit of interest is fully de-energized and the
equipment is grounded. If it becomes necessary to service
or test live equipment, the following instructions must be
followed:
•
Use one hand when servicing the equipment. Accidental
death or severe injury may occur especially if a current
path is created through the body from one hand to the
other.
•
First, de-energize the equipment. To de-energize any
capacitors connected into the circuits, temporarily
ground the terminals where work is to be done.
•
Connect the multi-meter/instrument to the terminals of
interest using a range higher than the expected. Make
sure that you are not grounded whenever a need arises
to adjust equipment or test circuit operation. Verify that
all test equipment used is properly maintained and safe
for the intended use.
•
Without touching the multi-meter/instrument energize
the equipment and read the values indicated on the
multi-meter/instrument.
•
Remove the test leads after de-energizing the circuit of
interest.
6.2: Maintenance Schedule Recommendation
The service schedule is somewhat dependent on the
“in service” hours. As a general rule, however, it is
recommended that the heat tracing control and monitoring
panel be serviced on a twelve month basis to start. The
schedule may be adjusted depending on the operating
history of the panel and as the historical maintenance
records dictate.
