I have a client that wishes to put a fence around a new 480V switch-gear that they are installing inside the plant. They want to do this to limit access to the equipment. I know that I need to meet the requirements of 110.26. My question is do I bond the fence to the building grounding system...
Hi,
I have a customer who has asked that a 13.8kV feed be fed overhead about a mile to a 13.8kv/4.16kV transformer. NESC says that a ground connection should be made to the neutral at the source. The issue is the switchgear that will be feeding this line is only 3W 3PH. Where do I get my...
Hi,
I have an installation where two sets of parallel 400 MCM conductors were installed in a cable tray. They were installed as individual conductors in a single layer. The voltage of the system is 480 three phase and the circuit is feeding from a switchgear to an MCC MLO main.
An engineer at...
I have a site where a concrete foundation will be being poured for a new building. I had planned to connect to the re-bar with a bonding jumper in order to use the concrete as a grounding electrode. I have since found out that the foundation will be poured on a vapor barrier. My understanding...
NEC code 250.66 discusses the minimum sizing for the grounding electrode conductors. It shows that the largest size required as 3/0 when the area of the incoming service conductors exceed 1100 kcmil. 250.66(A) shows the minimum size for connecting ground rods, pipe & plates as 6 AWG...
Hi all,
I am in the process of trying to put together a very competitive bid. I am used to using Hoffman enclosures for all of my control equipment. I have always been pleased with Hoffman's quality.
My question to y'all is who else make a less expensive enclosure that are the same level of...
I am reworking a panel that currently is using one din rail to handle the 120VAC controls and 240VAC motor power. The 120 and 240 terminals are one the same strip and separated by 3 empty terminals. Is this a code violation? I normally uses separate strips for separate voltages.
Thanks for...
I have a question concerning the secondary side wiring. There are 4 taps X1, X2, X3 & X4. I know to get 240 I tie X2 & X3 together and get 240 between X1 & X4. Is there a problem grounding X4 and having 240 with a neutral? This would be similar to a 120 type arrangement and would seem to...
I have a question about conductor sizing. I have been reviewing an MCC drawing that shows 2 X 3/C 500 MCM Armored cables running from the switchgear to the MCC incoming section. The lugs are 75C, the voltage 480VAC, the cable run via open cable tray. The switchgear breaker is 800A. My...
There has been some discussion at my office concerning e-stop push buttons and shrouds. One of the mills we do work for has a number of stations that have the e-stop button shrouded by a sleeve around the red mushroom head button. This sleeve is there to stop somebody from falling on the...
I have to run 12 - 750MCM service conductors underground into my switchgear. What configuration of the conductors will give me the best performance?
The run will be about 60'. I would like to avoid derating the conductors as much as possible. Code states that parallel conductors installed in...
I have a 2500 KVA transformer (23k/480 from utility) supplying 480V to a switchboard located inside the plant. I am adding a significant load to the plant and would like to increase the KVA of that transformer to 3750 KVA the largest 480 transformer supplied by my electric company. By doing...
I am curious if an MCC must be located in a special room or if any location on a wall is acceptable. I have seen them in various location in various facilities. I can't seem to find anything in the NEC that dictates the equipment be in a special room, but thought I would ask here to see if...
I have a question about running some control wiring. I will have an 120 VAC cable tray and a 24 VDC cable tray running between my controller and field devices. I have one field device that will require 24 VAC. Should I run this cabling in the low voltage DC tray or the 120 VAC tray? I am not...
We have an application that is requiring a 3H.P. motor to run at its FLA of 3.95A constantly for extended periods of time (2-3 days). The motor has a service factor of 1.15. Would I buy anything by going to a larger motor from a reliability standpoint.
Thanks for you input in advance!
Doug
I have a question concerning code. I have a 40 HP motor being run by an allen-bradley VFD that will be set to protect the motor. I have the incoming line going through an 80A trip circuit breaker (which is the size A-B recommneds for the drive) and then to a line reactor. The line reactor is...
I have some concerns about adding load onto a 1500 KVA transformer and wanted to find out what the accepted method of determing the allowable load to the transformer. It appears from the drawings I have of this and several other 1500 KVA transformers that the total H.P. + KVA attached to them...
I am relocating a 125 HP DC motor from one plant to another and have a question concerning derating the wiring. The old wiring ran in tray and will be placed in coduit at the new location. If I follow what NEC says that 4-6 current carrying conductors in a raceway must have thier ampacities...
Can anyone tell me if there is a chart anywhere that can that provides AC voltage drops? I have a 300' pull to a 125 HP motor and want to make sure that the voltage drop will not be a problem. Thanks in advance!
