Hubbell JHX, Installation, Operation And Maintenance Manual

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6. Repeat the above step with the lower terminal block (inlet thermistor).
7. If either of these readings is not consistent with the chart (within ±10,000
Ω
), replace
that thermistor.
8. If all ohms readings are acceptable, proceed to Check the Flow Meter.
Check the Flow Meter:
1. Set the unit to diagnostic mode by pressing and releasing the UP and DOWN buttons
simultaneously.
2. Turn on the hot water to ensure a good flow rate through the unit.
3. If the flow rate on the display reads ‘F00.0’ then continue with the next step.
Otherwise, proceed to Check the Temperature Controller.
4. Verify that the wiring from the flow switch is connected to the control board in the
order
WHITE
/
GREEN
/
BROWN
from left to right.
5. With no flow on the unit, using the multi-meter probes with the setting at Volts –
Direct Current, place one probe on the terminal block where the
WHITE
wire is
connected (F1) and the other probe where the
BROWN
wire is connected (F3). A
voltage reading in the appropriate range (5V) should be indicated.
6. If the voltage reading is not in the appropriate range (5V), replace the temperature
controller.
7. Turn on the hot water to ensure a good flow rate through the unit and using the multi-
meter probes with the setting at Volts – Direct Current, place one probe on the
terminal block where the
WHITE
wire is connected (F1) and the other probe where
the
GREEN
wire is connected (F2). A voltage reading in the appropriate range (2.5V)
should be indicated.
8. If the voltage reading is not in the appropriate range (2.5V), replace the flow meter.
9. If all voltage readings are acceptable, proceed to Check the Temperature Controller.
Check the Temperature Controller:
1. At the top of the temperature controller there are 4 sets of terminal blocks. Verify the
wiring is correct as indicated in the wiring diagram specific to the model.
2. Check the voltage between the terminal block where the
RED
wire is connected (this
will be the leftmost terminal) and the metal heater chamber cover. A voltage reading
in the appropriate range (120V) should be indicated.
3. If no voltage is present, verify that the
RED
wire in the terminal block is properly
tightened and verify that the opposite end of the
RED
wire is properly connected to
the power distribution block, magnetic contactor, or transformer, as applicable.
4. Check the voltage between the terminal block where the
BLACK
wire is connected at
the second terminal from the left and the metal heating chamber cover. A voltage
reading in the appropriate range (120V) should be indicated. Repeat this step for each
of the
BLACK
wires.
5. If no voltage is present, verify that the
BLACK
wire in the terminal block is properly
tightened and verify that the opposite end of the
BLACK
wire is properly connected
to the power distribution block, magnetic contactor, or transformer, as applicable.
6. If voltage is present where both the
RED
and
BLACK
wires connect to the terminals
and there is no display, replace the temperature controller.
7. Check the voltage between each additional
BLACK
wire from left to right and the
metal heating chamber cover. A voltage reading in the appropriate range (one half of
the incoming power voltage, i.e. if the incoming power is 480V, then the reading
should be 240V) should be indicated.
8. If no voltage is present, verify that the
BLACK
wires in the terminal block are
properly tightened and verify that the opposite ends of the
BLACK
wires are properly
jumpered to the previous
BLACK
wire connection terminal or properly connected the
magnetic contactor, as applicable.
9. Turn on the hot water to ensure a good flow rate through the unit and set the
temperature at the highest setting so the unit calls for full power.