Author: Jake

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Sizing a service 230.90(A) Exception 3 and FBC Residential E3603.3.1 Exception.

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This weeks post comes from a couple of questions asked these past couple weeks about sizing a service.  I was asked why you have to add the breakers up to get the size of the main!  I told them to look at section 230.90(A) Ex.. #3in the NEC and in the Florida Building Code Residential E3603.3.1 exception.  This is not a new so I don’t understand how someone could come to the conclusion that the main “MUST” be based on adding up all the breakers in the panel or all the mains at a service.  The exception to this section allows us to size the main based on a calculation, and not by adding the breakers together, because if that was the correct way to size the main I would need 600 amps for the main in my home and my 2/0 wire would be way to small.  In the slides below there is a 400 ampere service with four 200 ampere mains, which to the layman would look like an 800 ampere service but in reality it is only a 400 ampere service, because the calculated load was only 340 amperes and we used 500 Kcmil Cu. wire which has an ampacity of 380 amperes at 75c which is good for a 400 amp service see 240.4(B).

 

230.90c

230.90b  

Hope this helps.

 

Jake

Continue ReadingSizing a service 230.90(A) Exception 3 and FBC Residential E3603.3.1 Exception.

110.21 (B) Field-applied Hazard Markings.

This weeks change is for field-marking our equipment out in the field.  Information that could change can be hand written based on the exception to (B)(2).  So the AIC rating or Arc Flash information that could change on a label can be hand written.  See the label below.

 

 

110.21(B) label 2014

 

Till next time work safe be safe

 

Jake

Continue Reading110.21 (B) Field-applied Hazard Markings.

250.52 (A(3) Concrete-Encased Electrode

This weeks column is not about a Code change it is about a common problem we all face on a regular basis.  Footer steel, when is it required to be made part of the Grounding Electrode System?  We will have to check with the building plans examiner or the building inspector and see if there is going to be steel in the footer and if it will need to be made into a Grounding Electrode?

What will require it to be made into a concrete-encased electrode.  There are three requirements to make a good concrete–encased electrode.  The first is that the rod be at least 20’ in length, and it does not have to be one 20’ piece, it can be several shorter pieces connected together to make a 20’ piece.  The second is that it has to be at least a 1/2” in diameter. and the third and probably the most important is that it cannot be isolated from the Earth by a vapor barrier.

We are creating another electrode for our Grounding System.  In section 250.50 they talk about the Electrode being present.  What do we do when it is already poured. I get calls all the time about what to do when they miss the steel in the footer.  At that point I feel that the steel is not available and although you may want to chip into a footer to find a piece of steel rebar how do you know if it is 20’ long, and is not above a vapor barrier?  I have spent time trying to come up with a solution, because chipping into a slab is probably not the best answer. You could cause cracks in the concrete by hitting and vibrating the steel rebar when chipping into the footer.  So when someone calls me in the future and they ask what to do, my solution will be to get them to dig a trench and lay a 20’ piece of 1/2” rebar and make a connection to it and then encase it in at least 2” on concrete.  Maybe next time they will remember to connect the steel and call for an inspection. 

We just need to train the General Contractors and the Electrical Contractors that if this steel if available it is required to be part of our Grounding Electrode System.  If the building plans don’t call for steel in the footer we cannot make them put it in.  It is only required when there is steel and the footer has no vapor barrier and is called out for on the  plans.

 

GESa GESb

Till next time be safe and work safe

 

Jake

Continue Reading250.52 (A(3) Concrete-Encased Electrode

210.8 GFCI protection 7/31/2016

On 7/10 I did a piece showing the new GFCI requirements from the 2014 Code.  On 7/20 I watched a Webinar with NFPA and found that in the 2017 NEC it places an exemption on a Code requirement that was new in the 2014 Code.  It stated  in the 2014 NEC that around kitchen sinks it would be a requirement to have GFCI protection within 6’ of the sinks edge on all 125 volt 15 and 20 ampere receptacles.  Then in the Webinar they exempted the garbage disposal outlet from needing this protection.  I’m still waiting to see the published edition of the 2017 NEC, but I am sure that they would not have made a statement about the garbage disposal if they hadn’t exempted it in the new edition of the Code.  Dishwasher are still going to be required to be GFCI protected in the 2014 and the 2017 NEC. 

Till next time

Check your circuits before working on them.

Jake

Continue Reading210.8 GFCI protection 7/31/2016