I was tasked to add a 240/120v single phase transformer and panel on a marine vessel. I have access to 440V 3 phase. I have no marine experience. Is there a special type of transformer I will need? A vendor mentioned to me that nothing should be grounded on a marine vessel. Can someone guide...
I have an emergency exit and emergency back up lights that all have battery back up power. My boss is telling me that the circuit that feeds the back up lights and exit sign must be on its own circuit in its own conduit. I’m telling him that the battery is the “emergency circuit” and other...
I'm designing the electricl lighing and exit signs for a stairway in an office building. I have spec'ed out exit lights and stair lights with battery backup in each fixture. My question is because I have battery backup in each device, do these fixtures have to be feed on their own circuit? or...
I’m trying to figure general Lighting Load on an office building that is 11,400ft2. Using table 220.12 I will multiply 11400ft2*3.5VA/ft2 =39,900VA.
The part I’m confused about is how to calculate the amperage to size the 208Y/120V panel. Would it be calculated as 39,900VA/208*1.73?
I think...
If I understand the code correctly I can put 5KV and 15KV MV Cable in the same cable tray without haveing any barriers or up sizing the 5KV's insulation. Is this correct?
I have a substation in a Class 1 Div 2 area. Can I bring Tray Cable through the subs bulkhead via a Myers Hub and a CGB fitting? Will this be sufficient for the classification?
I don't do MV cable much and I'm a little confused on an grounding issue. I have 13.2kv coming form a overhead line going underground to Switchgear. I'm pulling single conductors MV Cable in the conduit. Should I ground the shields just at the Overhead pole or at both the pole and the...
I have a situation where I need to run 9 medium voltage cables in an underground duct bank. Looking at the NEC, if I run these in concrete duct bank I need to keep a 7.5” spacing center to center.
I have a client that wants to bore a 24” casing under a road and pull 9-5” pvc conduits in the...
I’m about to order a transformer and was wonder if I need fusing in the transformer to protect the secondary buss?
I have 13.2KV going through a fused (175E fuse) disconnect to a 13.2kv to 480v, 2500kva, Delta-wye, Transformer then feeding a MCC through a 3200a breaker. I do not have any...
I'm doing a project in an old plant where there is a 13.2kv to 480v, 1500kva, delta - delta transformer. The 'B' phase on the secondary is grounded. What advantage or disadvantates of this phase being grouned? Why not just have a floating ground?
Is sizing a Medium voltage feeder like sizing low voltage?
When sizing a 13.2kv feeder off a 175A fuse, should I multiply the 175A fuse by 125% and figure for the feeder size or should I just compare against the 175A fuse size?
Eg..
1.25 * 175A fuse = 219A and compare aginst 310.77 detail 3 =...
At what horsepower should I change from 480v to 4160v? I may have a 250hp or larger motor that I will need to feed. What is a general a rule of thumb for maximum horse power on a 480v circuit.
Is there any rule in the NFPA that will not allow for an Electrical substation with positive pressure ventilation in a Class 1 Div 2 area, within 40 feet from a gas heater?
