This case study reviews a situation involving recurring disruptions to the incoming power of a home, the investigation and the best practice to permanently repair it.
Our client has a 25 year old home with an underground electrical system. Over the past several years she has had several disruptions to her power. Each time she called service electricians out to assess her incoming electrical service wiring. Repairs were made to the system but the problem kept recurring. The most recent recurrence resulted in several parts of the house without working receptacles, or lighting, The remaining area of the house with power was experiencing dimming, surging, and flickering lighting.
Our client informed us that this was at least third time she had to have someone out to repair the system, and chose the Shock Doctors this time because of our three-part approach of diagnosis, treatment and cure with a 100% guarantee.
Our client explained that when the house was constructed the general contractor misread the drawings and had the house plan reversed, so the meter base and incoming wires servicing the house were on the opposite side of the property from where the original engineering specified. In order to make it “work” without spending any extra money the wires were not buried to a Code prescribed depth. At the time our client was told that it would be “no big deal because the paving and stonework in the front yard would protect the wires.”
A thorough inspection of the entire electrical system showed that the electrical panel was a 200 amp breaker panel in good repair. The grounding of the home was adequate for its needs and properly connected. There were no signs that the problem was related to the interior equipment.
The incoming electrical service showed major trauma . It was obvious that there was damage to the incoming service as the meter base was pulled away from the wall, the conduit protecting the wires was askew, and a large portion of the incoming service conductor was exposed and unprotected. We would have to repair the electrical meter.
With the cooperation of Hydro One, the utility service provider, the power was disconnected from the home, and the meter base was opened to inspect the inside of the damaged area, and it was found that the main feed wires entering the top were taut and under obvious strain.
Diagnosis and prognosis:
The meter base had been pulled from the house as a result of the ground shifting and pulling the service feed cable down with no flexibility available for the wire to move with the ground. This is a life threatening an ESA code defect. Worsening of this problem will result in the main power shorting out. If the ground shifted enough to pull the wires loose, they would short and the resulting fault would be like a bomb going off complete with shrapnel. Anyone in proximity of the meter base could be mortally injured.
Although the original general contractor constructing the house thought that the paving and stonework would compensate for the service cable not buried deep enough he did not properly think through the consequences. The paving was not completed for a few years after the final construction of the building and vehicle traffic over the cable drove frost down into the ground, forcing the cable deeper. This caused the first fault to the system. At that time the cable was lengthened at the base of the home and reconnected, but no provision was made for expansion and contraction with the weather changes. The second fault to the system was caused when the excavation and grading for the paving was finally commenced and the excavator cut the line (neglected to get proper cable locates because he relied on the original, and incorrect, engineering drawings for the building). An underground splice was used as a repair, again with no provision made for expansion and contraction.
The severe cold of 2015 contracted the cables again causing the third round of damage.
The repair for this damage has multiple parts:
First, the mounting location for the meter base on the side of the house must be repaired so the new meter base can be safely and securely attached to the building.
To repair the electrical meter box, a new, non-damaged, meter base is installed.
Then, preventative measures must be taken so the damage does not reoccur and the cure is permanent. This is achieved by adding an expansion box below the meter base to allow for future movement of the cable. This is also the point of connection for the old service wires and the new wires added to give additional movement when the ground shifts.
A large loop is left in the box that will allow the ground to move 10″ (highly unlikely) before there are any cable issues.
Additionally, an expansion joint is installed in the pipe that runs from the expansion box to the ground allowing an additional 8″ of expansion/contraction in the system.
Finally duct seal is used at the junction point of the service conduit and the underground duct (Big “O”) to prevent water from entering and creating havoc with the freeze/thaw cycle of the seasons.
With these preventative measures and taken, the prognosis is no re-occurrence of this disorder.
There is no doubt that failing to comply with Electrical Safety Authority Code requirements caused these incidents.
- The original builder should have not misread the drawings and built the house as per the engineered specifications.
- Failing this the original builder should have purchased the correct length of underground duct and cable to bury it to a safe depth, and left an expansion loop at the intersection of the underground duct and the service entrance conduit.
- The assumption that pavement and stone makes up for incorrect depth of trenches was and is totally incorrect due to the heat/freeze cycle of our climate.
- The first repair should have included the expansion box and expansion joint.
- The second repair should have included an expansion loop at the splice.