Background
On the 6th of November 2018 at around 9.00am a Programmed Facility Management (PFM) approved electrical contractor from New Zealand (NZ) was working with a PFM approved plumber to install a new hot water cylinder at a tenanted residential property. The property was built in 1954. On arrival at the property the electrical contractor isolated the power to the hot water cylinder, completed the disconnection and left the property. The plumber then proceeded to remove the hot water cylinder which involved cutting through a copper pipe. At approx. 3.30pm the contractor returned to the property and confirmed that the isolation was still in place and proceeded to rewire the hot water cylinder.
Whilst pulling down the new cable the contractor received an electric shock. The contractor tested the cables and found that the cable from phase to earth and phase to neutral was dead. The copper pipe was tested which revealed that the pipe had 180 volts from the pipe to the earth. Further investigation found the neutral wire at the point of entry to the property to be floating and had corroded, there was no earth peg and the copper pipe was used as earth.
How are the people involved?
The contractor sustained hand burns and was monitored at the emergency department via ECG and blood tests and was certified unfit for work for two days. The contractor has since made a full recovery.
What immediate actions were taken?
- Mains power to the property was turned off.
- The main neutral was repaired, a new earth and earth peg was installed.
- A certificate of compliance was provided and all work was checked by an electrical inspector.
- Toolbox sessions have been held with electricians and plumbers on the following: Checking for earth pegs on all properties pre 1970. Use of bridging conductors when cutting metal pipes, correct PPE to be worn and what to do after an electrical shock.
*** Note: In order to prove equipment functionality, electricians must check multimeters against a known source before and after checking isolations.**
What further actions are required?
- An analysis of all properties pre 1970 is being conducted to determine potential extent of this issue.
- A meeting is to be held with the client to discuss the findings and possible further controls.
WHAT SYSTEMS FAILED AND HOW DID THESE FAILURES CONTRIBUTE TO THE INCIDENT?
- The contractor made contact with the copper pipe resulting in phase passing through the contractors body to find earth.
- The electrical installation at the property was old and the main earth was through the copper pipe, a practice that was prohibited in 1970 in NZ and 1976 in Australia.
- The neutral at the point of entry to the property was “floating” and had corroded so it was no longer connected.
- There was no earth peg at the property.
- There had been no work orders received for the property that would have triggered an electrical inspection so it is unknown as to how long the property had been in this condition.
For more information regarding this incident please contact:
HSE Representative: Leanne Wardle, HSEQ Manager, Facility Management New Zealand
Contact Number: +64 9 571 3553
Date of Issue: 13/12/2018
