CM-2201/CM-2202
General Operation
©2018 Nelson Heat Tracing Systems
www.nelsonheaters.com
GA2497 Rev.6
7
5.2
Keypad
The keypad is “capacitive” touch sensitive and keys are
activated by simply touching the area of the desired key with a
finger, even when wearing gloves. Note that a stylus or other
item used to touch the keypad will usually not activate the keys.
5.4
LED Functions
LED indicators will show the status of the respective functions.
The power LED will be illuminated when the controller is
connected to a source voltage. The heater LED will be
illuminated when voltage is applied to any heater. The system
LED will illuminate if there is an internal hardware issue with the
controller. The comm LED will illuminate when the controller is
sending data through external communication. The alarm LED
will flash when there is a current active alarm condition or any
circuit; the alarm LED will illuminate solid when an alarm was
previously present but is not currently active.
5.5
Monitoring
By touching the “Actual” button follow the arrow and
the controller will scroll through all the active parameters.
5.6
Alarm Management
All alarm(s) will be saved in the alarm log. If no alarms are
active (alarm LED solid red) the Alarm LED can be turned off by
touching “Reset” once for every alarm that previously occurred.
If any alarm is active (alarm LED flashing red) the user cannot
reset the alarm. The two alarm relays are SSR type. To set the
contacts of the relays go to Settings – Heater Setup – Alarm
contact. By choosing up/down arrow, the contacts can be
selected to function as Normally Open or Normally Closed.
Press “Enter” to save the selection. (See 7.2.12 for further
information on the Alarm contacts setting).
Power-Limiting Feature
The Power-Limiting feature operates similarly to the Soft-
Start in that it restricts the amount of time the cable is
energized during any given period thereby reducing the
average current draw of the cable during that period.
For example, if a cable normally draws 8 Amps, but current
limit is set to 6 Amps, then the cable would be energized
only 75% of the time.
5.7
Ground Faults
Ground faults typically are the result of damaged or
improperly installed cables which allow current-carrying
conductors/ surfaces/parts to be in contact with grounded
objects.
For example, if a heating cable has been secured to a pipe
with a clamp, and if the clamp has been overtightened,
then the ground braid and/or the pipe may come in
contact with current carrying parts within the cable. This
would result in current leakage to ground through the
ground braid of the cable and/or the pipe itself. This type of
fault can eventually become serious, resulting in
overheating/fire/shock hazards. Current leakage to ground
can be monitored by electronic circuitry and the SPC/DPC can
be programmed to either alarm or trip when leakage
current exceeds the specified maximum
allowable amount.
5.9 Soft-Start Feature
The Soft-Start feature enables self-regulating cables to
be energized at low temperatures without causing excessive
load on the electrical system and extending cable life by
reducing cable internal heating due to inrush currents. The
resistance of self-regulating cables decreases as the
cables get colder, which results in higher current and can
result in breaker trips if temperatures are very cold and
the installed length of cable is long. The Soft-Start feature
operates by initially only energizing the cable for a very short
period of time – while the current draw may be high during
this period, the period is usually short enough to reduce
average load on the electrical system.
This short energization period is repeated and eventually
increased; after a few minutes, the cable is usually warm
enough such that the resistance has increased and the
current decreased to the point where it can be continuously
energized.
