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Hi Guys, I'm finding difficult to inteperate T 250.66 I have two parallel conduits, each having 2#500 kCMIL and 1#1/0 GND conductor. How do I size the grounding electrode? T 250.66 says to consider equivalent area of ungrounded parallel conductors. One 500kCMIL has the area of 0.7073 in. Thanks

Hi Guys, I have an unbalanced delta load. Phase AB 7.7Amp Phase BC 7.7 Amp Phase CA 7 Amp. The power is also supplied form a delta source. I have also calculated the vector IAB = 7.08+3i, IBC = 7.08+3i and ICA = 6.44+2.73i Also IA = - (0.644+ 0.27i) IB = 0+0i IC =...

Hi Guys, I'm doing a lighting design for interior lighting. To find the total # of luminaries I need to know the "coefficient of utilization" (C.U.) I have effective reflectance of ceiling and walls as 50 and 10 respectively. And the room cavity ratio (RCR) is 0.54 When I look up the table...

I'm not gettting it. The length is fixed based on supply voltage and and the Circuit Breaker size. I don't have any problem with that. I'm using self regulating cables but it really doesn't matter much what kind of cable you are using to determine the circuit breaker size. The method for...

Itsmoked, Let me put it this way. The normal operating current(at ambient temperature) is 18.5Amps. But if the heater is to START at -20 degree centrigrade, the heater would require more current then the normal current. I would like to know that 'starting current'. Any factors or formule for...

It does not say about sizing a breaker. All I know is the CB should be sized based on ambient temperature (which is -20) in my case. This is based on the fact that the heater will draw more current as the temperature drops.

Hi Guys, Can anyone provide me the formula for calculating the 'start up' current for heat tracing? If I have normal heater operating amps 18.5 A, How would I determine the 'start up' current? Thanks.

Bare Parts.

Thanks mcgyvr, What do you mean by "opposite polarity"? There are three bus bars (from a 3 ph system) with clearance 3/8" between adj phases.

Table 408.56 gives information on minimum spacing between bare metal parts. I have 600V systems and clearance between two bus bars is just 3/8 inch! (should have been 1 inch according to the code) What could be the possible suggestion to overcome this? Thanks for reading.

Davidbeach, What do you refer a 'ground' conductor? Terminology is NEC is confusing. Here's how I interperate, ungrounded = hot grounded = neutral grounding = ground

Thanks DanDel, Clear about my 1st doubt. In my second question, First paragraph-I assumed that there is a ground fault ( a hot conductor touching a metal surface). It is just a background anyway. Second paragraph-I am assuming that the conductor is not insulated and somebody intentionally...

Bonding is the connection of all electrically conductive materials (which are likely to be energized) to each other and to the neutral conductor in order to create a low impedance fault current path, back to the source. My question is. 1. Since the neutral conductor also has current in it, will...

I have been working with photovoltaic sytems so the power that I was talking about was not from any dc motor or such. I got the answer. Thanks burnt2X, davidbeach and everybody for sharing.

Guys, How do you determine the size of an inverter. For example, if I have 220kW dc power, then can I use 225kW inverter?? Thanks for your reply.

Hi Guys, Does the TCC Clipping current of a fuse necessarily be equal to the short circuit current? Thanks.

I'm from SE Asia, but work here in US.

Here is my approach. Current at Secondary side Isec = 500 watts/120V = 4.17A (I've skipped the power factor) Iprimary= (120/480)*4.17 =1.04A Voltage drop on conductor at 480V =I*Z*L = 1.04*0.000777*100 (length is 100ft) = 0.081V For Transformer (3kVA...

This is not a home work problem. I was thinking of transferring the voltage drop on primary side of the transformer and the voltage drop on the 480V conductor to secondary side by the transformation ratio (120/480) And then to calculate the voltage drop on the 120V conductor, and add up total...

Experts, I'm new to my job. How would you find the total voltage drop from a main swich yard(at 480V) to a load at 120V? The details are follows. Conductor at 480V is 100ft(impecence= 0.000777), then a transformer(480/120V, 3 kVA, 3.5% impedence)and load(500 Watt) at a distance of 50...