Author: Jake

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ANNEX D EXAMPLE “7” RESIDENTIAL SERVICE TABLE

Below you will find a picture of Annex D example 7 from the 2017 NEC pages 799/800.  It was put back in the Code to do away with the confusion that was created when they took the table out of the Code book and made it into a calculation.  To many inspectors, plan reviewers, engineers, and architects have been wrongfully applying this section of the Code for a while now.  I get numerous calls and emails about having to use 3/0s for a 200a service when in the past we used 2/0s.  I only use the 200a service as an example.  The Code panelists never meant to make it so difficult to figure out what they wanted, but unfortunately they did.  When they made it a calculation they did not change the sizes of the wires in the table they just made it into a calculation, that for some reason we’ve had a tuff time understanding.  As long as the load calculation does not exceed 200a the 2/0s are the conductors needed to feed a 200a service. This method works for all services of a100a on up to and including a 400a service   So in the 2017 NEC they placed the residential table back in the Code back in Annex D.  Probably the most misunderstood part of this Code section is that the conductors being used will have a load calculation that is above the ampacity of the conductor involved. Maybe the Code panel should include this section with the other conductor applications listed in 240.4(G).

If you have any comments or questions about this change please email me at jleccemail@hotmail.com

Can’t see the whole slide just click on it.

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Till next time be safe work safe.

Jake

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404.22 Electronic Lighting Control Switches.

This section gives us a date to stop making connections to an equipment grounding conductor on January 1, 2020, at switch locations that have electronic dimmers or controllers installed.  After that date we need to be using a neutral conductor to make these devices work,  no longer allowing the equipment ground to be used for this purpose.  Although a neutral is not necessary at all switch points section 404.2 C instructs us when and where a neutral is needed. And with all good Code changes there are exceptions,  this does not apply to replacements or retrofits, and has a limit of 5 (five) devices per branch circuit and 25 (twenty five) per feeder connected on the load side in the system or main bonding jumper. A neutral busbar in compliance with 200.2 B has no limits as to the number of electronic devices connected to it.

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Can’t see the whole picture just click on it.

Have a question email me at jleccemail@hotmail.com

Till next time be safe work safe.

Jake

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250.52(B) Not permitted for use as Grounding Electrodes

New to this section the reinforcing steel that forms a swimming pool shell.  A swimming pools’ steel cage is not to be used as part of our grounding electrode system.  I have heard stories where the inspector required that the contractor run the pool bond back to the ground rod?  This practice a “violation” and could endanger the occupants of the pool with stray currents or ground-fault current introduced on this grounding electrode system.

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Can’t see the whole picture then just “Click” on it.

Till next time be safe work safe.

Jake

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2017 Code Changes

This week we will start a series of Code Changes found in the 2017 NEC.  Every couple of weeks we will explore one of the changes.  If you have questions please email me at jleccemail@hotmail.com.  REMEMBER THESE ARE NOT IN USE BECAUSE THE FLORIDA BUILDING COMMISION HAS NOT ADOPTED THE 2017 NEC YET!!!!!

The first one we will look at is in Article 110.14(D) Installation (of devices outlets, switches etc., etc..).  This new section requires us to torque all connections that require torqueing which would now include switches and receptacle outlets, or any equipment that has a numerical value on the device or in the instructions provided by the manufacturer.  A couple of manufacturers have come out with devices that come with a snap in tails which would not require torqueing.  See the slides below, if you can not see the entire slide just click on it to make it bigger.  

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But for those who don’t have the snap in tails , you will need a torqueing screw driver.

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Till next time be safe work safe.

Jake

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310.15(B)(7) 120/240-Volt, Single-Phase Dwelling Services and Feeders.

I keep getting calls from contractors that tell me that this town or that county no longer allows them to use 2/0 Cu. for a 200a dwelling service or feeder.  This section changed in the 2014 Code but the only thing that changed is they took out the Table and made it into a calculation using 83%.  This 83% rule has seemed to throw off a lot of people in our trade (plan reviewers, inspectors, and contractors).  Just so you know the old table from 2011 Code will still work nothing has changed.  It is not just the 2/0s its all the conductor we use to use in the old Table (see the Table below) they all still work for serving the loads that are shown to serve in the old Table.  They work for both feeders and services.

EXAMPLE:

A 2/0 conductor in the 75 degree column in 310.15(B)(16) is good for 175 amperes

A 200 ampere service rating multiplied by 83% equals a 166 amperes.

So as you can see a 2/0 will be large enough to serve 166 ampere service rating.

                                                                                                                                                                                                                                                                                                                  

As long as your load calculation does not exceed 200 amperes the “CODE” allows you to exceed the rating of the 2/0 conductors ampacity, by applying the 83% rule in 310.15(B)(7)(1)(2).

                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      

See #1 and #2 below to see what the conductors ampacity is based on “SERVICE RATING” and FEEDER RATING”

310.15(B)(7)

(1) For a service rated 100 through 400 A, the service conductors supplying the entire load associated with a one-family dwelling, or the service conductors supplying the entire load associated with an individual dwelling unit in a two-family or multifamily dwelling, shall be permitted to have an ampacity not less than 83 percent of the service rating.

(2) For a feeder rated 100 through 400 A, the feeder conductors supplying the entire load associated with a one-family dwelling, or the feeder conductors supplying the entire load associated with an individual dwelling, unit in a two-family or multifamily dwelling, shall be permitted to have an ampacity not less than 83 percent of the feeder rating.

3/0 is not needed for a dwelling service rated 200 amperes unless it is not feeding the entire load to that dwelling.

Below you will find a dwelling service table from the 2014 Florida Building Code 5th Edition that was taken out in the 6th Edition of the FBC, but it still works and it includes  both copper and aluminum conductors plus the size of the required grounding electrode conductor.  Use it in good faith that it will give you the right size service and/or feeder to your dwelling unit. .

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Till next time be safe work safe

Jake

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Picture of the week 1/13/2019

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This week picture comes from Howard Borna, he found this in Jupiter.  Thanks Howard always good to hear from you.

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It came with a side order of working clearance violations.

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This is a good example of why we need permits even to replace pool equipment.

Till next time be safe work safe and do it right!

Jake

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MC Cable and ANTI-SHORTS

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Got a call this week from a contractor who was told by his inspector that he needed ANTI-SHORTS on all his MC cables.  If you are using MC cable per 330.40 of the Code you are not required to have ANTI-SHORTS installed, they are only required when you use AC cable. Looking at sections 330.40 and 320.40 these section are easy to read and understand when anti-shorts are required.  See my graphic below to help understand when they are required and when they are not.  In the field today we mostly use MC cable I personally have not seen AC cable used in a long time we just got use to calling MC, “AC cable or BX”.  This contractor had to spend a day and a half inserting something that was not required.  When you buy the reels on MC most come with anti-shorts because some places have required them because they wanted them, not because the Code required them. See the link below to NEMA’s bulletin for the use of ANTI-SHORTS.

MC cable has a plastic strip inside of it NO PAPER OR CARDBOARD

AC cable has paper and or cardboard fillers surrounding the conductors.

https://www.nema.org/Technical/Documents/Use%20of%20Anti-Short%20Bushings%20for%20Terminating%20Type%20MC%20Cable.pdf

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As always if you are having trouble seeing the graphic just click on it.

Till the next time be safe work safe.

Jake

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