Mike Dolt Enterprises
Mike Dolt Enterprises
User: mjmike, Location: California
Asked on: Wednesday, March 30, 2011 at 8:03 pm EDT
Answered on: Tuesday, May 14, 2024 at 3:31 am EDT
Question: I am working on arc flash and short circuit calculations for a client. The facility is rather large with about 5 stories, 6 distribution boards, and about 50 branch panels. There is also an emergency system. The service main board is 480/277v 3-phase and about 3200a. The step-down voltage is 208/120 3-phase. Ther is no existing one-line.I can easily create the one-line and get the breaker data, but the trouble I am having is determining the condutor length. The facility is older so most conduits are in the masonry structure and can't be visually traced or measured. I am looking for advise on how do figure out the conductor length. I can de-energize the facility so is there some type of electronics equipment, like a tracer, that will determine length? Thanks for any opinions.
Determining Conductor Length Without Existing One-Line1. Use Building Plans and Drawings
Obtain architectural plans or drawings that may show the conduit routes and approximate lengths. Utilize building management software or as-built documentation.
2. Partial Measurements and Extrapolation
Measure accessible portions of the conduit routes, such as those exposed in ceilings or walls. Use a tape measure or laser distance meter to determine total length by extrapolating from accessible sections.
3. Tracer Equipment
Consider using a
conduit tracer to trace the route of concealed conduits. This device emits a signal that can be detected along the conduit's length, providing an approximate measurement.4. Electrical Inspection and Testing
Conduct a
V/A (volt/amp) drop test to measure the voltage and current drop across a conductor. Using Ohm's law (R = V/I), calculate the conductor resistance (R) and multiply by the conductor length (L) to estimate L.5. Manufacturer's Data
If available, consult the manufacturer's specifications for the branch panels or distribution boards to obtain approximate conductor lengths.
6. Data Logging and Simulation
Install temporary current or voltage loggers at strategic locations to monitor electrical flow and identify possible conduit routes. Use simulation software to create a model of the electrical system and estimate conductor lengths based on the measured data.
Note: De-energizing the facility is essential for safety when using tracer equipment or performing electrical tests. It is recommended to obtain multiple measurements and estimates to ensure accuracy. Consider consulting with an experienced electrical engineer or contractor for professional assistance. Flag for review