Troubleshooting - Heat Controller HP Series Installation, Operation & Maintenance Manual

Heat Controller, Inc.
General
If operational difficulties are encountered, perform
the preliminary checks below before referring to the
troubleshooting charts.
• Verify that the unit is receiving electrical supply power.
• Make sure the fuses in the fused disconnect switches
are intact.
After completing the preliminary checks described
above, inspect for other obvious problems such as
leaking connections, broken or disconnected wires, etc.
If everything appears to be in order, but the unit still fails
to operate properly, refer to the "CXM Troubleshooting
Process Flowchart" or "Functional Troubleshooting Chart."
CXM Board
CXM board troubleshooting in general is best summarized
as simply verifying inputs and outputs. After inputs and
outputs have been verified, board operation is confirmed
and the problem must be elsewhere. Below are some
general guidelines for troubleshooting the CXM control.
Field Inputs
All inputs are 24VAC from the thermostat and can be
verified using a volt meter between C and Y, G, O, W.
24VAC will be present at the terminal (for example,
between "Y" and "C") if the thermostat is sending an input
to the CXM board.
Sensor Inputs
All sensor inputs are 'paired wires' connecting each
component to the board. Therefore, continuity on
pressure switches, for example can be checked at the
board connector.
The thermistor resistance should be measured with
the connector removed so that only the impedance of
the thermistor is measured. If desired, this reading can
be compared to the thermistor resistance chart shown
in the CXM manual. An ice bath can be used to check
calibration of the thermistor.
Outputs
The compressor relay is 24VAC and can be verified using
a voltmeter. The fan signal is passed through the board
to the external fan relay (units with PSC motors only).
The alarm relay can either be 24VAC as shipped or dry
contacts for use with DDC controls by clipping the JW1
jumper. Electric heat outputs are 24VDC "ground sinking"
and require a volt meter set for DC to verify operation.
The terminal marked "24VDC" is the 24VDC supply to the
electric heat board; terminal "EH1" is stage 1 electric heat;
terminal "EH2" is stage 2 electric heat. When electric heat
is energized (thermostat is sending a "W" input to the CXM
controller), there will be 24VDC between terminal "24VDC"
and "EH1" (stage 1 electric heat) and/or "EH2" (stage 2
electric heat). A reading of 0VDC between "24VDC" and
"EH1" or "EH2" will indicate that the CXM board is NOT
sending an output signal to the electric heat board.
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HP SerieS

TROUBLESHOOTING

Test Mode
Test mode can be entered for 20 minutes by shorting
the test pins. The CXM board will automatically exit test
mode after 20 minutes.
CXM Troubleshooting Process Flowchart / Functional
Troubleshooting Chart
The "CXM Troubleshooting Process Flowchart" is a quick
overview of how to start diagnosing a suspected problem,
using the fault recognition features of the CXM board. The
"Functional Troubleshooting Chart" on the following page is
a more comprehensive method for identifying a number of
malfunctions that may occur, and is not limited to just the
CXM controls. Within the chart are five columns:
• The "Fault" column describes the symptoms.
• Columns 2 and 3 identify in which mode the fault is likey
to occur, heating or cooling.
• The "Possible Cause column" identifies the most likely
sources of the problem.
• The "Solution" column describes what should be done to
correct the problem.
WARNING! HAZARDOUS VOLTAGE!
DISCONNECT ALL ELECTRIC POWER
INCLUDING REMOTE DISCONNECTS
BEFORE SERVICING.
Failure to disconnect power before servicing
can cause severe personal injury or death.
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Installation, Operation & Maintenance
� WARNING! �