Thanx in Advance:thumbsup: ]]>

What is the minimum size copper conductor needed for a 208 V three-phase machine located 140 feet from the power source? ( Machine draws 27 amperes, 3% voltage drop, use 12.9 K) ]]>

1.What % of secondary current is protected by primary ocpd?(I forget trx setup or %s)

2. Whats minimum times current is a fuse allowed to protect >600v service? Smallest choice was 1.

3. What is voltage to ground for b phase on 240v ungrounded(?) delta? I chose 208, but what's reference ground, primary ground?

ty ]]>

I am trying to learn design and i was browsing Mikeholt website for books and i came across the DVD set for the whole code..Just want to know if its worth it to buy those coz they are little expensive than regular textbooks..

Any opinions or advice is really appreciated.. ]]>

While Ive gotten some value from their materials, the material is rife with typos, formatting errors and is based on 2005/2008 NEC. Boo. I also have extreme strengths in some areas and weakness' in others due to the unorthodox method I entered and worked in the field. Note that the CSLB has accepted my application irregardless. I'm weak in safety regs, big jobsite protocols and employment labor laws, etc.

However, I'm very strong technically, so I'm mystifed by this question:

Question 10: |
In a school, twenty 75-watt incandescent lights were replaced with twenty 20-watt fluorescent bulbs. If they pay $0.10/KWH, how much will they save in a year? |
|||

$100 |
||||

$275 |
||||

$375 |
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$475 |

The New array is .4kw so costs .4x $.10 per hr or $.04 so yearly costs are $.04 x24x365=$350 a year

~ Approx 1/4 power, 1/4 the cost, so the savings should be greater then any of those values unless I'm making a mistake. Any help would be appreciated. Thx, Humble Hank. ]]>

Any clues would be helpful.

Thx,

"Humble Hank" ]]>

thx ]]>

- I hope this ok to ask--I'm new here

thx,

js ]]>

Annex d example d3(a): Subtotal actual load 95.5kVa. Directly adjacent, actual amperage is calculated using actual load of 99kVa. Where did the 99kVa come from? One reply to op in other thread gave power factor as the reason. I haven't seen pf used in any load adjustments in nec.

thanks in advance ]]>

There were a couple questions that I was hoping you could help me out with. I reviewed the material I have from Mike Holt and did some digging around online for similar questions and couldn't find anything. Any help would be appreciated.

Question 1:

-A 3-hp pump is installed 220 feet from the 220-volt main service. What is the voltage drop when using 12 AWG solid wire?

I have been reviewing the voltage drop calculation material and can't seem to find anything similar to this question. They don't give you the current which makes it confusing to me. I'm not sure which type of equation I should be using.

Question 2:

-A feeder supplies a continuous lighting load of 45 amperes and a single motor load of 30 amperes. What is the ampere rating of the feeder?

My answer: 86 amps

Correct Answer: 94 amps

I used code section 215.2(A)(1)(A) and am not quite sure what I missed.

215.2 Minimum Rating and Size.

(A) Feeders Not More Than 600 Volts.

(1) General. Feeder conductors shall have an ampacity not

less than required to supply the load as calculated in Parts

III, IV, and V of Article 220. Conductors shall be sized to

carry not less than the larger of 215.2(A)(l)(a) or (b).

(a) Where a feeder supplies continuous loads or any

combination of continuous and noncontinuous loads, the

minimum feeder conductor size shall have an allowable

ampacity not less than the noncontinuous load plus

125 percent of the continuous load.

Question 3:

-Approximately how many kilowatts are used by a three-phase, 480-volt ac motor that draws a current of 52 amperes and has a power factor rating of 88%?

I'm not sure what equation to use for this one either.

Thanks again,

Mike ]]>