GREE GMV5E DC INVERTER VRF UNITS SERVICE MANUAL
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the unit.
4) Check air switches and fuse links for their models and using methods.
a. Commercial air conditioning units must be installed with independent air switches, fuse links,
and similar protectors. Reasonable models and using methods should be selected for air
switches and fuse links.
Remarks:
a1. Air switches work for overload and short-circuit protection. Air switches provide a less breaking
current than fuse links and air switches react more slowly than fuse links. The advantage of air switches
is that they can be manually reset after a protection action.
a2. Fuse links only work for short-circuit protection. They provide a large breaking current and act
slowly. However, fuses must be replaced after a protection action.
b. Select air switch models according to the power cable diameter and air switch specifications.
In general, the rated current of air switches should be larger than or equal to the load current
calculated based on the line, and less than or equal to the persistent current rating allowed by
the conductor.
5) Check components in the electric box.
In the case of unit power-off, visually check whether any component in the electric box drops during
transportation. Then, check whether any component or cable is loose or drops by hand. For a
large-scale unit, power cable terminals of the patch panel and cable terminals connected with
connectors must be tightened with a sleeve spanner or screwdriver, and tightened once more after two
months of normal operation. Auxiliary contacts of AC connectors cannot be removed because they have
been debugged upon factory departure.
3.3.2.5 Check the input power.
a. Power consistency check: Measure the power supply to be connected with the air conditioning
unit for its voltage, frequency, three-phase voltage unbalance factor, and frequency offset.
Specifications of the power supply should be consistent with power specifications displayed on
the unit nameplate. The fluctuation range of voltage should be within ±10%.
b. Phase sequence check:
b1. After powering on the unit, measure the grounded voltage value of N-bit on the power patch
panel and the voltage value between every two of L1, L2, and L3 bits. In general, the voltage between
N-bit and L1/L2/L3-bit should approach 220 V and the voltage between every two of L1, L2, and L3 bits
should approach 380 V. If the measurement result does not match the above-mentioned normal value,
check whether the external power cable is inversely connected between the N wire and one of L wires.
b2. Observe the code displayed on the digital LED of the main board AP1. If the fault code “U3” is
displayed, it indicates that the phase sequence of the external power cable connected with the air
conditioning unit is incorrect. Power off the unit and exchange any two phases among L1, L2, and L3 bits
on one end of the external power cable. Power on the unit and observe the code again. The fault code
“U3” should disappear.
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