Daikin ComfortNet DX7TC Service Instructions Manual page 87

SERVICING
Electric Heat Sequencer Outputs
HIGH VOLTAGE
Disconnect ALL power before servicing or installing
this unit. Multiple power sources may be present.
Failure to do so may cause property damage, personal
injury or death.
1. Turn on power to air handler or modular blower.
Line Voltage now present.
2. Disconnect the 4-circuit harness connecting the control to
the electric heater kit.
3. Provide a thermostat demand for low stage auxiliary heat
(W1). Measure the voltage between circuits 1 and 3 at the
on-board electric heat connector. Voltage should measure
24VAC. Replace control if no voltage is present.
NOTE: Allow for any built-in time delays before making
voltage measurements. Any electric heater faults that are
present may prevent the heater output from energizing.
Verify that no heater faults are present before making
voltage measurements.
4. Provide a thermostat demand for high stage auxiliary heat
(W1 + W2). Measure the voltage between circuits 1 and
3 at the on-board electric heat connector. Measure the
voltage between circuits 2 and 3 at the on-board electric
heat connector. Voltage should measure 24VAC. Replace
control if no voltage is present.
Communications (Applies only to Systems with Compatible
ComfortNet™ Outdoor Unit and CTK0*Thermostat)
The integrated air handler control has some on-board tools that
may be used to troubleshoot the network. These tools are: red
communications LED, green receive (Rx) LED, and learn button.
These are described below
A. Red communications LED – Indicates the status of the
network. Refer to the Network Troubleshooting Chart for
the LED status and the corresponding potential problem.
B. Green receive LED – Indicates network traffic. Refer to the
Network Troubleshooting Chart for the LED status and the
corresponding potential problem.
C. Learn button – Used to reset the network. Depress the
button for approximately 2 seconds to reset the network.
Voltages between the two data lines and between each data
line and common may be used to determine if the network is
operating properly.
WARNING
WARNING
Do the following to measure the voltages on the
communications data lines.
Line Voltage now present.
DATA LINE VOLTAGE TROUBLESHOOTING AND
BIAS SWITCHES
Proper data voltage is essential to robust and reliable
communication on the ComfortNet™ system. Any wiring issues
must be corrected for good communication.
• Poor wiring connections at the terminal blocks
• Low voltage wires that are shorted, grounded or broken.
• Communicating wires that are not connected to the proper
terminals at the connector.
• 24 volt common outside and inside are not at the same
ground potential
• Bias dip switch setting conflicts between indoor board and
outdoor board.
• It is STRONGLY recommended that you do not connect
multiple wires into a single terminal on the wiring
connector.
• Wire nuts are recommended to connect multiple wires to
connector ensuring one wire is used for each terminal.
• Failure to do so may result in intermittent operation.
• Typical 18 AWG thermostat wire may be used to wire the
system components. One hundred feet is the maximum
length of wire between indoor and outdoor units or between
indoor unit and thermostat.
• When outdoor transformer is used and there at least three
thermostat wires running to the outdoor unit use one of the
extra wires to connect the two 24 volt commons together.
This will ensure both 24 volt commons are at the same
ground potential.
• When outdoor transformer is used and there are only two
thermostat wires running to the outdoor unit ground the 24
volt common "C" of the outdoor transformer to a chassis
ground (earth0 ground. This is not as good as the third wire
but it is better than leaving the outdoor 24 volt common
floating).
SEQUENCE OF OPERATION
DVPTC/MBVC with DX**TC Condenser and CTK0*
Communicating Thermostat
The DVPTC or MBVC air handle/modular blower matched
with an DX**TC condensing unit and CTK0* communicating
thermostat constitute a network. The three components, or
subsystems, making up the system communicate with one
another with information passed between all three components.
WARNING
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