Electrical Calculations

Preparing for an Electrical Exam

Preparing for an Electrical Exam

Apr 07, 2022

Not every electrical license exam is the same, so here are some important steps that you can take to improve your chance of passing this difficult exam.

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Ground Resistance Testing

Ground Resistance Testing

Mar 03, 2022

How do we know if our single ground rod has the proper earth resistance? We don’t know unless we have a ground resistance tester and know how to use it. So let’s look at how we perform this test.

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Derating Current-Carrying Conductors for Conditions of Use

Derating Current-Carrying Conductors for Conditions of Use

Aug 05, 2020

If you ask a seasoned electrician how many No. 12 AWG conductors will fit into a 3/4" EMT conduit system, you may get a response such as “one more!” While this is amusing (and typically true), there are precautions that must be taken according to the NEC whenever conductors are bundled together in a raceway, cable, or even in a ditch in the earth.

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Conduit and Cables Exposed to Sunlight on Rooftops

Conduit and Cables Exposed to Sunlight on Rooftops

Sep 25, 2019

Anyone who has been on top of a roof on a hot summer day knows what it’s like to stand in the middle of an oven. Extreme temperatures from the sun can bake everything in sight, from shingles to appliances, and even electrical conductors and conduit. Conductor insulation is meant to provide long lasting protection from expected heat due to the flow of electricity and normal environmental factors. However, excessive heat from solar radiation can damage conductors and cause premature failures.

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Sizing RV-Park Electrical Services Using NEC Table

Sizing RV-Park Electrical Services Using NEC Table

Oct 05, 2018

The Electrical Service supplying an entire RV park must be sized to accommodate the electrical demands of multiple modern recreational vehicles drawing power simultaneously from the individual park sites.

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Feeder Conductor Ampacity

Feeder Conductor Ampacity

Jan 24, 2017

The conditions of use must be considered when determining the minimum size of a feeder conductor. A continuous load, such as the lighting load in a store building, generates heat in the feeder conductor that must be compensated for. Ambient temperatures above 86oF or more than...

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Feeders Part 2: Overcurrent Protection

Feeders Part 2: Overcurrent Protection

Dec 06, 2016

The general rule in 215.3 is that a feeder overcurrent device shall have a rating not less than the noncontinuous load plus 125% of any continuous loads supplied by the feeder. Unless permitted for specific applications, such as motor circuits, the rating of the feeder overcurrent device is selected as...

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210.23(A)(1)&(2) Permissible Loads, Multiple-Outlet Branch Circuits.

210.23(A)(1)&(2) Permissible Loads, Multiple-Outlet Branch Circuits.

Sep 26, 2016

A multiple-outlet branch circuit is a branch circuit that supplies two or more outlets. With the exception of the required small appliance, laundry, and bathroom receptacle circuits in dwelling units, those outlets may be a combination of lighting outlets for luminaires, receptacle outlets for cord and plug connected utilization equipment...

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Single Family Dwelling Calculation, Optional Method.

Single Family Dwelling Calculation, Optional Method.

Jul 18, 2016

If you are preparing to take an electrical licensing exam, you will need to know how to calculate the feeder or service load for a single family dwelling. Refer to section 220.82(A)&(B) in the 2014 National Electrical Code (NEC). Here is a sample problem. Use the optional calculation to find...

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Applying NEC 310.15(B)(7)

Applying NEC 310.15(B)(7)

Nov 26, 2014

The fact that the table was removed is neither here nor there. More importantly is how to apply the 83% and when the Code section allows us to use it. Applying 310.15(B)(7) to one-family dwellings or the individual dwelling units of two-family and multi-family dwellings, has always been dependent on a few important factors:

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Selecting the Short Circuit Current Rating of Equipment

Selecting the Short Circuit Current Rating of Equipment

Jul 15, 2014

In the Summer Newsletter article, we discussed marking our service equipment with the maximum Available Fault Current (AFC) as well as the date the fault current calculation was performed to comply with NEC 110.24(A). We selected circuit breakers with an AIC rating equal to or greater than the AFC. So...

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