Mike Dolt Enterprises
Mike Dolt Enterprises
User: malachi constant, Location: Minneapolis
Asked on: Wednesday, June 1, 2011 at 10:23 am EDT
Answered on: Tuesday, May 14, 2024 at 6:04 am EDT
Question: I'm the engineer on this one. Renovation of existing building, the inspector is making us bring the elevator up to code (NEC '08). In the course of performing some of the flagged upgrades the electrician noticed there is not presently a ground conductor from the existing panel to the existing elevator disconnect switch. I directed him to pull a new ground. His foreman tried but was unable to without pulling out the wiring.The options are:(A) Pull out the old wiring and pull in new 130' feeder w/ ground. OR(B) Use the existing IMC as ground, which he has visually inspected for solid connections and confirmed is bonded at the distribution panel.I looked at elevator article 620 sections VII (OCP) and IX (grounding) and confirmed they don't require anything unusual - deferring to article 430 part V, and article 250 parts V and VII, respectively.All that to say I readily admit grounding is not my area of expertise, but this doesn't look like too tricky of a question. Just want to make sure I don't (A) waste owner's money on something not required by code, or (B) direct the contractor do do something that does not meet code.Any help? Thanks!
Option A: Pulling New Feeder with Ground Advantages
Complies with all applicable codes (NEC '08, Articles 430, 250) Provides a dedicated ground conductor, which is the preferred method
Disadvantages
Requires extensive labor and materials May involve pulling out existing wiring, which can be disruptive
Option B: Using Existing IMC as Ground Advantages
Faster and less expensive than Option A Utilizes existing infrastructure
Disadvantages
May not meet NEC requirements for grounding Relies on visual inspection of IMC for proper bonding, which may not be conclusive IMC could be damaged during future work, compromising the ground connection
Code Requirements NEC '08, Article 430.122 requires that the elevator hoistway grounding system be connected to the grounding electrode system at the main service disconnecting means.* NEC '08, Article 250.118 requires that metal raceways be used as equipment grounding conductors only if they are "effectively grounded."Recommendation
Based on the NEC requirements and the potential drawbacks of Option B, the recommended course of action is to pull out the old wiring and pull in a new 130' feeder with a ground.This approach ensures compliance with all applicable codes, provides a dedicated ground conductor, and minimizes the risk of future grounding issues. While it may be more expensive and time-consuming, it is the safest and most reliable solution in the long run. Flag for review