Method Statement Title: Installation of Earthing System
1.0 Scope
1.1 This method statement details the method of installation of Earthing System as per specification section 16060.
2.0 Material
2.1 Material used for the system is as per BS : 7671 and BS : 7430.
3.0 Applicable Locations
- Basement, Ground level, roof, Mechanical, Electrical rooms at all levels. All mechanical services exposed will be bonded to the earthing system, all extraneous metal below 2.5 Mtrs shall be bonded. Ceiling grids and other such metals & systems shall be measured to assess whether bonding maybe required.
4.0 Method
4.1 Storage
- All materials received at site shall be inspected by QA Engineer and ensured that the materials are as per approved material submittal.
- Any discrepancies, damages etc. shall be notified and reported for further action.
- Material found not suitable for the project to be removed from site immediately.
- Earthing material shall be stored in a covered/dry place at all the time to avoid corrosion.
- Installation of LV Earthing System
- As per approved shop drawings identify location of earth pits.
- Co-ordinate with Main Contractor for installation of earth pits with approved fixing details.
- The copper earth rod will be driven manually in earth. After achieving a minimum depth of approximately 3 meters, the earth resistance will be measured. If the earth resistance value is not satisfactory, the process of adding further earth electrodes shall be continued till expected resistance value of less than 1 ohm is achieved.
- Adjacent earth electrodes shall be spread to atleast 1 length of one of the driven electrodes (6 mtrs) to achieve result of less than 1 ohm. Work Inspection Request (WIR) to be issued.
- The earth pit shall be installed after completion of installation of earth rods and a clear gap of 50 mm shall be maintained between top of earth electrode and earth pit cover. The top of earth pit shall be in level with the finished floor level in the area. Earth rods (electrode) connection to be protected with Denso tape.
- The PVC sheathed single core earthing cables of specified sized as per shop drawings shall be laid between the earth pit and the earth bar inside the building and terminated with proper type lugs/clamps.
- The interconnection of earth pit shall be as per approved shop drawing.
- All earthing connections shall be made after cleaning the surfaces thoroughly and tightness checks for each connection shall be performed.
- Continuity of earth connections shall be checked for every link in the network by ETA QA Engineer. Issue WIR. All joints to rods to have shrink-wrap protection applied.
- The down-stream earthing connections from earth bars shall be made to the panel boards, frames and other equipment as per approved shop drawings.
- Along with all power cables on earth cable of size as per approved shop drawings shall be laid and it shall be terminated to the earth bar of the panel/equipment, which it feeds to, in addition with local earthing from earth bar.
- On completion of total earthing system and testing, WIR will be submitted for approval to Design Consultant.
- The extent of bonding requirements to be identified and agreed between R&P and MACE in line with project specifications, DEWA standards, statutory requirements & clause 3.0 above.
- Installation of Equipotential Bonding
- The metallic frame of all electrical equipments shall be connected to the nearest earth bar with a specified size of earth cable.
- The earthing continuity of cable trays and trunking shall be maintained with earth links on each joints of cable trays and trunking shall be connected to earth bar with specified size of earth cable.
- Flexible earth cable spiral shall be used for the earthing connections when there is possibility of expansion/contraction and also where vibrating equipment is installed.
- The metallic water lines shall be bonded by an earthing cable of size not less than 6mm2
- All bonding connections shall be checked for correct tightness and cleanliness.
- WIR will be issued for signature to NMX/Consultant.
6.0 Safety
6.1 All safety precautions shall be followed as per established project safety plan and procedure.
7.0 Records
7.1 Inspection request duly signed-off by NMX and Consultant.