Clarification on best way to get looped
I have a bit of a problem with one of the items presented in the article “Applying simple solutions to common maintenance problems” (PE, January 1998, p 39, File 5540).
I believe that the idea “Looping now prepares for later” is a potentially dangerous practice, both in the resistance caused by the lugs attached in a concentrated area, and the practice of connecting equipment while the lines are live. I wonder what OSHA would have to say about this? — Robert P. Wurst, Hydraulic Supervisor, Port Erie Plastics, Harborcreek, PA
Contributor’s reply: It is obvious that the explanation and illustration I submitted could have been clearer. The suggestion involved a manner of terminating and/or splicing main feeder conductors that will simplify adding additional loads at a later time.
Many electrical feeders supply multiple loads along the path, or to a specific location. Junction boxes and/or trough style wireways may be used as access points to the feeder. Within these enclosures, smaller conductors will be connected to tap into the main feeder wiring, in accordance with NEC 240-21 (commonly known as the 10 and 25-ft rule). Changes and additions will periodically be needed.
The addition of a new significant load should always involve a review of the involved distributed system, particularly its ampacity capability and demands currently on it. When a new feeder is installed, it is normal practice to increase its capacity by as much as 50% or more to allow for possible additions. The extra cost is nominal as an upgrade, compared to the same capacity installed separately. It is a case-by-case judgment call based on the customer’s long-term plans.
When a new feeder is installed, it can be done in a manner to allow easy, economical access to tap on a new load. The closed loops I mentioned in the article are merely extra tails (pigtails) for future use. The loop ends terminate within the main compression connection. By adding a few extra tails off of a main connection during installation, additions can be made much easier at a later date with minimal time and materials.
When an addition is made, the main connections are not disturbed and a loop from it meeting the new load’s wire requirement will be cut to provide two individual tapping points. Connect the new load’s wiring to one of these tails and insulate the other for later use. This will avoid the much higher cost of breaking the main lug connections.
I cannot agree with the resistance issue stated. These tails, prior to their use, are energized, but are not a part of any current path. Also, if a tail is eventually used, a single, properly made compression connection should not add any significant resistance to any portion of the circuit.
Concerning the safety question, as an electrician I worked in new construction and service before entering manufacturing maintenance. In no case would work be performed on a “live and under load” electrical distribution system if there was even a slight amount of risk involved. Handling live wiring is not usually an option within a typical maintenance operation. In all cases, a mentality of relaxed caution and constant self awareness is required while working with an energized circuit.
Each job’s actual conditions should be reviewed and discussed, all possible precautions should be taken, and all members involved should be satisfied that it is safe to perform the job, or don’t do it. — J. Michael Stone, Electrical/Mechanical Technician, Jefferson Smurfit Corp., Greensboro, NC