Vertiv | Liebert® DM | User Manual 90
System Operation and Maintenance
Chapter 7: System Operation and Maintenance
This chapter explains the system maintenance of the Liebert® DM units, including electrical inspection, indoor unit
maintenance, outdoor unit maintenance and maintenance inspection checklist.
• Switch o the circuit breaker and cut-o the unit power supply before maintenance unless the power is
necessary for commissioning the unit.
• Prior to operation and maintenance, the lethal voltage may be present in the unit which can be fatal. All
notes, warnings, and cautions marked on the unit as well as the ones mentioned in the manual must be
considered, otherwise, it may lead to injury and fatality.
7.1. Electrical Inspection
Visually inspect the control board, power detection board, outdoor fan speed controller board, display panel, temperature
and humidity sensor, infrared humidification leak detection board on a semi-annual basis for any loose electrical connection
and circuit corrosion.
The micro-processing controller has six circuit boards, which jointly complete the system fault diagnosis process.
Inspect the boards one by one according to the procedures below:
1. Conduct overall electrical insulation test: Find out the unqualified contacts and handle them carefully.
2. Statically check and test the contactors before powering on and ensure that contactors can act freely without any
obstructions.
3. Clean the electrical and control components with a brush or compressed dry air.
4. Check the end of contactors for arcs or signs of burning. Replace the contactors if necessary.
5. Fasten all the electrical connection terminals.
6. Check if the temperature of all MCBs and contactor terminals become higher.
• All circuit boards are not hot-pluggable. Big instant current will be produced when the board is plugged or
unplugged with powering on and it may lead to unrepairable damage to the circuit.
• All control boards can only be maintained after the micro-processing controller is powered o.
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