Duke HDC3 Manuale di servizio - Pagina 12

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Service Manual for Dry Channel HDC3/HDC6 Units

24 Volt Step-Down Transformer

The 24 Volt Step-Down Transformer (Transformer)
is located in the Relay Box.
WARNING
USE EXTREME CARE WHEN
PERFORMING THIS TEST.
MEASUREMENTS ARE PERFORMED
ON CIRCUITS WITH VOLTAGE
APPLIED.
1. Set the Main Power On/Off Switch to the off
position.
2. Remove Relay Box cover.
CAUTION: Ensure that primary of
Transformer is correctly
connected for input voltage
source.
3. Set voltmeter to AC and select a range to
measure the 208/240 VAC input voltage
level.
4. Attach voltmeter across Transformer primary
terminals.
5. Set the Main Power On/Off Switch to on.
Measure voltage across the Transformer
primary. Voltage should be the same as the
input voltage source. If no voltage is present,
check wiring to Transformer.
12
124 Ohms
248 Ohms
Figure 14. Foil Wrap Heater Configuration
6. If correct voltage is present at primary, measure
the secondary voltage.
7. If the secondary voltage is near 24 VAC,
Transformer is operating properly. If voltage is
low or 0 VAC, disconnect wire from Transformer
secondary and recheck secondary voltage.
If voltage is still near 0 VAC, replace
Transformer.
8. If voltage is now near 24 VAC, a short exists
somewhere else in the circuit. Further trouble
isolation testing is required.

Heater Element and Hi-Limit Thermostat

Check the Heater Element and Hi-Limit Thermostat
by measuring the resistance of the Heater Element.
To access the Heater Element, follow the procedure
described in the CHANNEL ASSEMBLY paragraph
in the COMPONENT REPLACEMENT section.
1. Remove the suspect Channel Assembly from
the Dry Channel Tub.
2. Disconnect the wires to the Channel Assembly
to be tested.
3. Connect an ohmmeter across the heater leads
and verify that the resistance is approximately
124Ω between one end of the Heater Element
and the Hi-Limit Thermostat. The resistance
across both heat elements should be
approximately 248Ω
4. Replace Dry Channel Assembly if the Foil
Wraps tests open.
124 Ohms