please clarify an example given for a one-family dwelling, specifically, the calculation for neutral for feeder and service...

to recap: the example gives the net calculated load thus:

18000 va, divided by 240 = 78 amps...bumped up to 100 amps as per 230.79 C

the calculated load for neutral figures the range and dryer at 70% thus:

14550 va divided by 240v = 61 a.

beyond the fact that the feeders needed to be rated for 100 amps, has it occurred to you pros that a one-family dwelling service used a neutral ampacity other than that sized for the two ungrounded conductors?

said another way, in determining the service for a small residential dwelling, has it occurred that the neutral calculation indicated that the neutral ampacity conductor differed from that determined for the two ungrounded conductors?

attempting to fathom the practical need for the Annex D1 (a) neutral calculation--is it fairly rare that neutral and hot would differ in ampacity for a small dwelling?

thank you ]]>

Thanks! ]]>

Determine the minimum size conductor permitted to be paralleled for a new electric service. ]]>

Quote:

(c) 10 AWG

(b) 12 AWG

(d) 8 AWG

Let's walk through the solution:

in 2011 NEC, 310.16, we find THHN in the third column @90C temp rating...60C temp rating lists 'types TW, UF'...it shows a 15amp copper conductor @ 14AWG

furthermore, a THHN @60C temp does not appear in this NEC edition...and, the 14**AWG is rated at 25amps (again, @90C temp)...

please help clarify, re: the correct reading of table 310.16 for Mike's example...

thank you ]]>

Any suggestions will be appreciated. ]]>

the conductor ampacity calculation has a wound-rotor motor, 30hp, 460v, 3 phase, nameplate 38a (primary) and 65a (secondary)...

in determining the proper feeder conductor, the wound-rotor primary value appears to derive from 430.250 is 40 amps (i.e., 30hp @ 460v), but the

both the 40a and 65 amp figures are then factored @ 125% : 50a and 81a respectively.

1) is all of the above a correct interpretation of D8?

2) are the resulting derived figures then simply added to determine the conductor size without further factoring (310.16)?

thank you ]]>

va / (volts x 1.732)

19,000 /(208 x 1.732) = 52.74 amps rounded to 53 amps

branch circuit OCP has to be sized @ 125% of the 53 amps

53 x 1.25 = 66.25 = 66 amps. So a 70 amp OCP

To select the conductor I believe I have to increase 125% also.

66 amps in the 75 degree column requires #4 @ 85 amps

Since there are more than 3 current carrying conductors in the race way I have to correct the #4 THHN.

The instruction at this point say use the 90 degree column for the ampacity and then correct it at 80%

Any comments? Yeah I know you can't fix stupid, but... ]]>

A service rated 2000 amp 480v 3 phase shall have the service raceway bonded with a copper equipment grounding conductor not less than _________.

Could someone help me work through this calculation PLEASE!?

I am looking for an electrical designer course that can be taken online. A few months ago browsing through the internet I found a course offered at a New York Institute or University, but I forgot to bookmarked it. Please if you know a good online school, can you provide the link.

Thank you. ]]>

Started to read about contractors and motor starters ,

It shows a pic of a contractor with auxiliary contacts on it and says auxiliary contacts

May be added to a contractor to form an electrical holding circuit .

In the line diagram it shows stop and start puch buttons

Controlling a starter , the aux contacts are in series with the start button

I don't understand what aux contacts do could someone explain some senerios were u would use

Aux contacts and are their only normally open or do they also make nc auxiliary contacts aswell

and say if you have a norm open push button when you manually puch it does it go back to norm open

when your finger comes off button ]]>