I just ran by an issue where I have a 3phase, 100A disconnect feeding (2) 3phase, 50A disconnects that serve electric space heaters. The load side of the disconnect has (3) #2AWG feeding into a wire gutter where Polaris splices were used to splice down to (2) 50A feeders at #8AWG each going to...
The new California Energy Code has adopted the fine print notes of the NEC for voltage drop. I am well aware of the undesirable affects of excessive voltage drop on circuits, especially motor loads (decrease in starting torque and overheating of the winding) but me and a coworker were wondering...
NEC allows for a maximum 250% the FLA of a motor for an inverse-time CB. Is there somewhere in the NEC that allows you to use a 20A CB as the minimum CB size for protecting motors?
As an example, I have a 1-1/2HP 460V, 3PH motor with an FLC of 3A. 3A x 2.5 = 7.5A, so does the circuit...
All,
I have been a little unsure about this, so I was hoping the community could help clear it up for me. For a 3 phase, Wye distribution, I have read that a three phase bolted fault is a balanced fault and a single line to ground fault is an unbalanced fault.
If a three phase bolted fault...
Hey All,
Did a search and couldn't find a previous post... Does anyone know if it is acceptable to add a knock out to the side of an existing panel in which there is no more room on the top of the panel for a new conduit? Would doing this void the UL listing of the panel?
Thanks for any...
We have a project where we will be installing a new Eaton Magnum DS Low Voltage Switchgear with an arc flash reduction maintenance switch.
1. Does the maintenance switch set the main breakers to their lowest settings to reduce arc flash hazard while working on the gear?
2. If so, should the...
I am using SKM to perform a power system analysis (short circuit,coordination, and arc flash). When performing he arc flash calculations through the software per IEEE 1584, the table summary gives me the bus bolted fault current, bus arcing fault current, protective device bolted fault current...
I tried to find a previous post that answered this question but had no luck. Please feel free to steer me in the correct direction if there is a previous post that covers this question:
I am failing to see the reason for having a Motor Starter with a Motor Circuit Protector (MCP) when there is...
I am working on a project where we are installing a sputtering system. The manufacturer is calling for us to drive (2) new ground rods (not bonded to the building ground electrode system) to ground the vacuum chamber. This ground will be in addition to a safety ground coming from the...
Today I was looking at the as-built drawings for a physics lab that is adjacent to a lab I will be renovating. I noticed on the electrical plans that the engineer provided isolated/insulated grounds to all the receptacles and also called for the branch circuits to be twisted with a twist rate...
I was under the assumption that for calculating voltage drop on a 3 phase, 4 wire (Wye) feeder from a distribution panel to a panel you only take into account the 1-way distance from the distribution panel to the panel because the assumption is the loads are balanced resulting in no current on...
I have a project where there is no ground bar in the existing electrical room and the grounding electrode from the UFER ground and water pipe was run directly to the ground bar in the main switchboard. We are redoing the electrical infrastructure and the main switchboard is being demolished and...
I have a project with two laboratory buildings, side-by-side, with connecting hallways between the two buildings. One building was built a year later than the other in the 80s and over their life span the electrical system has been added onto so that now some of the equipment in one building is...
All,
I have an existing electrical transformer room with (2) 12kV-277/480V transformers, and I am trying to determine if the room is compliant with NEC 2008. The room is rectangular with a single double door in the middle of the north wall of the room. The transformers sit on either side of...
All,
I am a junior engineer and I just received an email with a statement that I believe to be incorrect. Can you let me know what your thoughts are? Here is the statement:
'Transformer transfers energy thru magnetic induction coils and its associated turn ratio. There is no direct contact...
I am a assisting a senior engineer on a project where we are renovating the emergency system of a commercial building. Due to the distances involved, the plan is to install a 1250KW/480V genset, step up to 12KV and then step back down to 480V in the electrical transformer room at the northwest...
I am assisting a senior engineer on an installation of a PV system for one of our commercial projects. I have been given the task for calculating the voltage drop and I have a few concerns. The following is the basic outline of the design:
- 4 separate PV arrays on different parts of the...
I am looking into short circuit analysis software for low voltage to medium voltage distribution systems. Does anyone have any recommendations?
Thanks.
DJR
