Troubleshooting
CM-2201/CM-2202
©2018 Nelson Heat Tracing Systems
www.nelsonheaters.com
GA2497 Rev.6
16
9.1
Operator Checks
Upon receipt of the controller, or to check the controller for
an indication of normal operation, follow the operational
procedures shown below. These procedures are designed to
familiarize the operator with the controller and to provide an
understanding of its operation.
To determine if a fault is associated with the heat tracing,
wiring or the controller, it will be necessary to troubleshoot
the wiring and tracer circuit. If the
Fault remains, remove power from the controller and exchange
it with another controller. This may require some
reprogramming of the new CM2201/CM-2202. Refer to the
following sections for the appropriate topic.
9.2
Ground Fault
Ground fault warning /alarms can be caused by incorrect
installation as well as current leakage resulting from wet
system components or damaged cables.
The CM2201/CM2202 Controller detects ground faults by
summing the outgoing and return trace currents
through an internal current transformer. Under normal
operating conditions (no ground fault condition) this
current will be zero. When there is a flow of current from
one of the trace supply wires to ground, a ground
fault condition occurs.
If a ground fault alarm is present on start-up of a new
installation it is likely due to a wiring error or damaged
cable.
To verify this condition:
a)
Check that the heating circuit neutrals return to
the controller and are not connected directly to
the distribution panel. This can be a common
problem if the installation is a retrofit situation.
b)
On paralleled circuits, be certain that ALL neutrals
return. The late addition of a circuit may not be obvious.
Note: The controller monitors the integrity of the ground
fault(GF) detection. If a fault is detected, the controller
will generate a GFI warning/alarm depend of the settings.
9.3
RTDs
RTD failures after installation can generally be attributed to
incorrect wiring or improper installation of the sensor.
Troubleshooting of these failures is a very simple procedure if
the proper steps are undertaken in the correct order.
Some specific RTD problems and the correct methods for
troubleshooting are outlined as follows.
1.
RTD Failure Alarm(s)
If the CM2201/CM-2202 controller indicates a failure of an RTD:
a)
Ensure that the RTD is a 3-wire 100 (Platinum Type).
TURN THE POWER TO THE CONTROLLER OFF BEFORE
PROCEEDING!
b)
Disconnect the RTD wiring from the input terminals.
c)
Measure the RTD’s resistance between the source (RED) and
sense (RED) leads at the controller (it should not exceed 40
Ω). Excessive lead resistance will cause a RTD FAILURE
ALARM and must be corrected. Look for loose terminals,
excessive lead length, or insufficient wire gauge and correct
as necessary.
d)
Measures the RTD’s resistance between the source (RED) or
sense (RED) lead and the common (WHT) lead of the RTD at
the controller (should be between 60 and 330 Ω depending
on the temperature and the lead resistance. Verify
that the RTD is wired correctly—the heat tracing controllers
will always be terminated in the order: source (RED),
common (WHT), sense (RED).
When wiring to the CM2201/CM2202, the terminals are marked as
follows:
Terminal No.
Description
GND Bus
Shield
RA
RTD A Source (RED)
WA
RTD A Common (WHT)
RA
RTD A Sense(RED)
GND Bus
Shield
RB
RTD B Source (RED)
WB
RTD B Common(WHT)
RB
RTDB Sense(RED)
The RTD manufacturer will typically color code the leads with
the source and sense being the same color, and the common a
different color. Ensure that the RTD extension wire shield is
terminated at one end only, normally using the terminal block
provided at the terminal board.
