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Identification Of Cables When Color Code Is Unknown (SINGLE-PHASE
3-WIRE UNITS) |
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If the colors on the individual drop cables cannot be found
with an ohmmeter, measure:
- Cable 1 to Cable 2
- Cable 2 to Cable 3
- Cable 3 to Cable 1
Find the highest resistance reading.
The lead not used in the highest reading is the yellow lead.
Use the yellow lead and each of the other two leads to get two
readings:
- Highest is the red lead.
- Lowest is the black lead.
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EXAMPLE:
The ohmmeter readings were:
- Cable 1 to Cable 2--6 ohms
- Cable 2 to Cable 3--2 ohms
- Cable 3 to Cable 1--4 ohms
The lead not used in the highest reading (6 ohms) was
- Cable 3?Yellow
From the yellow lead, the highest reading (4 ohms) was
- To Cable 1?Red
From the yellow lead, the lowest reading (2 ohms) was
- To Cable 2?Black
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Single-Phase Control Boxes |
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| Checking and Repairing Procedures
(Power On) |
| WARNING:
Power must be on for these tests. Do not touch any live
parts. |
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A. VOLTAGE MEASUREMENTS:
- Step 1. Motor Off
- Measure voltage at L1 and L2 of pressure switch or
line contactor.
- Voltage Reading: Should be ± 10% of motor rating.
- Step 2. Motor Running
- Measure voltage at load side of pressure switch or
line contactor with pump running.
- Voltage Reading: Should remain the same except for
slight dip on starting. Excessive voltage drop can be
caused by loose connections, bad contacts, ground faults,
or inadequate power supply.
- Relay chatter is caused by low voltage or ground faults.
B. CURRENT (AMP) MEASUREMENTS:
-
- Measure current on all motor leads.
- Amp Reading: Current in red lead should momentarily
be high, then drop within one second to values on Page
13. This verifies relay or solid state relay
operation. Current in black and yellow leads should
not exceed values on Page
13.
- Relay or switch failures will cause red lead current
to remain high and overload tripping.
- Open run capacitor(s) will cause amps to be higher
than normal in the black and yellow motor leads and
lower than normal in the red motor lead.
- A bound pump will cause locked rotor amps and overloading
tripping.
- Low amps may be caused by pump running at shutoff,
worn pump, or stripped splines.
- Failed start capacitor or open switch/relay are indicated
if the red lead current is not momentarily high at starting.
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CAUTION:
The tests in this manual for components such as capacitors,
relays, and QD switches should be regarded as indicative
and not as conclusive. For example, a capacitor may test
good (not open, not shorted) but may have lost some of
its capacitance and may no longer be able to perform its
function.
To verify proper operation of QD switches or relays, refer
to operational test procedure described above in Section
B-2. |
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