Sizing Conductors for Continuous Loading

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Re: Sizing Conductors for Continuous Loading

Bob and bphgravity, that's the kind of quality feedback I've been waiting for; well thought out arguments from what appears to be well educated individuals. For the rest of you who dislike my attitude, don't read my postings and your feelings won't get hurt.
 
Re: Sizing Conductors for Continuous Loading

Originally posted by rlee:
For the rest of you who dislike my attitude, don't read my postings and your feelings won't get hurt.
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Thats fine, the question still remains why you have such bad manners. :p

[ November 20, 2005, 06:37 AM: Message edited by: iwire ]
 
Re: Sizing Conductors for Continuous Loading

For the rest of you who dislike my attitude, don't read my postings and your feelings won't get hurt.
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At first I was going to write a post similar to some of yours but I've decided not to sink to your level. The last thing we're worried about is you hurting our feelings. But thanks for the free advice. Hopefully everyone that posts here will take it. I know that I will.
 
Re: Sizing Conductors for Continuous Loading

I was going to reply also, but I couldn't recall if that word way hyphenated or not :roll:
 
Re: Sizing Conductors for Continuous Loading

As mentioned in one of the posts, using an 8AWG terminated to a 50 ampere rated circuit breaker... that is permitted, just remember the 50 amp breaker under continuous load is permitted to carry 80% of it's rating. Of course unless it is rated for continuous loading - of which a 50 ampere rated CB will not be rated continuous, as posted by Bryan.

BTW- Bryan, that was very good history... the site should think of starting a history thread, I think it would help in the understanding of the NEC - even if we still do not agree with some of it ;)
 
Re: Sizing Conductors for Continuous Loading

rlee,

For the rest of you who dislike my attitude, don't read my postings and your feelings won't get hurt.
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I don't know why you want to persist with this type of response but it doesn't add anything to this forum. There are people here who have knowledge of the NEC and its rules that I will never achieve. They are here to help with problems regarding the interpretation of this manual. You can continue with this type of attitude and find that none of your questions will be answered or you can apologize and become a part of this forum. Its up to you.
 
Re: Sizing Conductors for Continuous Loading

The initial question I posted at the beginning of this thread was first e-mailed directly to Mike Holt himself. Keep in mind I'm a paying customer who just forked over $620.00 for the calculations DVD set. After waiting five days for a response and getting none, I decided to call Mike Holt Enterprises Inc. The lady on the other end of the phone tells me that Mike is a busy guy and sometimes forwards questions to this board. I ask if I should post my question on this board and she assurse me that someone representing Mike Holt or Mike Holt himself will answer my question on the board. I'm thinking, great a place to get a creditable answer to my question. Now, this whole process is new to me and I discover some of the responses I'm getting not only fail in answering my question but are flat out wrong.

When I'm dealing with paying clients who have honest questions, I make every effort to ensure they get an honest and qualified answer, if not from me then from someone I know who has the correct information. It appears that Mike Holt Enterprises is more than willing to sell me a product but they are not interested in answering legitamate questions. So ya, I'm a little miffed at this whole process. Who in this thread is qualified to represent Mike Holt with regard to the question I reference directly from his text book? That's the qualifier I failed to state at the beginning of my initial question. That's the mistake I made and for that I apologize.

If Mike Holt Enterprises is not interested in dealing with customer questions then I'll purchase my training material from a different source.
 
Re: Sizing Conductors for Continuous Loading

You've been misled.
I believe that everyone (with the exception of maybe one or two) that responds to posts on this forum are unpaid by, and not representing the Holts.
We are good natured folks who discuss and banter back and forth about code and other electrical related topics.
 
Re: Sizing Conductors for Continuous Loading

I'll bet he's a hoot in restaurants, too.

So, after all is said and done, has the question been answered to your satisfaction, rlee?

Edit: by the way, they're still recovering from a hurricane at Holt's HQ in Florida.

[ November 20, 2005, 11:52 PM: Message edited by: georgestolz ]
 
Re: Sizing Conductors for Continuous Loading

Well, believe it or not, just shortly after I posted my complaint on this board about Mike Holt, I did indeed recieve a response to my e-mailed question from a Mike Holt representative and it was like someone flipped on the light switch. The answer made perfect sense and now I have a clear understanding of the continuous rating concept as it applies to T310.16. If anyone is interested, I'll post the response. Sometimes ya gotta rattle the tree to get the apples to fall.
 
Re: Sizing Conductors for Continuous Loading

Originally posted by rlee:. . . and I discover some of the responses I'm getting not only fail in answering my question but are flat out wrong.
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You did not get any "flat out wrong" answers. The first responses did not give you what you were looking for, but they were not wrong.

It is the responsibility of the person asking the question to clearly state the question, so that the reader understands what information you are trying to obtain. It may come as a surprise to everyone, but clearly stating a question is a difficult task, and very few people are capable of doing it well. Therefore, we should all have a bit more patience, and we should ask for clarification if we are not certain what the Original Poster is trying to learn.

Originally posted by rlee: Who in this thread is qualified to represent Mike Holt with regard to the question I reference directly from his text book?
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Nobody.

If the person you spoke to at MHE gave you the impression that any member of this Forum represents Mike or represents MHE, then that was an unfortunate error. I will send them a suggestion that they take care not to give that impression in the future.

There are over 25,000 members of this Forum. I believe that two, and only two, are on the payroll of Mike Holt Enterprises. One is the Webmaster. The other supports the training side of Mike's business on a part time basis.

For the record, the Moderators are not compensated for our efforts in supporting this Forum.

The membership of this Forum comprises all aspects of the electrical industry. We are all voluntary participants. We are here to help each other, and we do so freely.
 
Re: Sizing Conductors for Continuous Loading

Originally posted by charlie b:There are over 25,000 members of this Forum. I believe that two, and only two, are on the payroll of Mike Holt Enterprises. One is the Webmaster. The other supports the training side of Mike's business on a part time basis.
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Make that five. I forgot that Mike Holt is a member of the Forum. Looking at the first page of the membership directory, I recognize two other employees of MHE.
 
Re: Sizing Conductors for Continuous Loading

We are awarded the greatest compensation one can ever receive - a free education. I for one find that to be more valuable than any wage I could ever earn. I remember a while back the idea was being tossed around to charge for the privilege of entering this Forum. Based on how much I know Mike Holt is paying to maintain this site and the immense amount of knowledge and education I have received, I consider the value of this Forum to be greater than that of a 4-year college tuition. :cool:
 
Re: Sizing Conductors for Continuous Loading

Here's the response I just received from Mike Holt Enterprises regarding my question with the ampacity ratings of T310.16. I'll repeat my question below with the response afterward for clarity.

QUESTION:

I just purchased the calculations DVD set and I've come across an issue I'm failing to understand. That issue relates to sizing conductors for continuous loads. On page 246 of the Electrical NEC Exam Preparation text book under the heading "Overcurrent Protection of Conductors" there is a question asking me to size a conductor for a 104A continuous load. The 104A load is then multiplied by 125% to arrive at 130A for a 1 THHN conductor on 75 degree terminals.

This all makes perfect sense accept for the fact that table 310.16 states in its title the following: Allowable ampacities of Insulated Conductors...

According to article 100, the definition of ampacity is stated as follows: The current, in amperes, that a conductor can carry continuously under the conditions of use without exceeding its temperature rating.

So, my question is this; Why am I increasing the ampacity of a conductor for continuous loading if table 310.16 already takes continuous loading into account?

RESPONSE:

I have never seen what I consider to be a good answer to this very good question. I have thought about this at some length, and here is my opinion:



The breaker or fuse must be increased to 125% to avoid tripping the circuit. If you have a 20 amp continuous load on the 20 amp breaker or fuse, you run the risk of it opening the circuit due to overload (this is why you have the 100% rated exception in 210.20(A)). Because we have increased the size of the overcurrent device, we must now increase the size of the conductor, because it is no longer protected anywhere near its ampacity.



If we have a continuous load of 50 amperes, we would have to use a 70 amp breaker (50*1.25=62.5, next standard is 70). If we didn?t increase the conductor by 125%, we would have a 50 amp conductor being protected by a 70 amp device. You can see where this is a problem. By increasing the conductor 125%, we now have a conductor good for 62.5 amps (6 AWG), which is more than enough to handle the load. We also have the rule of 240.4(B) that allows us to protect a 6 AWG conductor with a 70 amp device.



Ryan Jackson

Code Consultant, Mike Holt Enterprises
 
Re: Sizing Conductors for Continuous Loading

Just a question for you, did Ryan offer a suggestion as far a remedy for your bad manners? :D

Couldn't help myself. ;)

Roger
 
Re: Sizing Conductors for Continuous Loading

If you were to go back to some of the responses and take alook at them without the "attitude", you will see that this was mentioned to you before in this thread.

But Ryan did a nice job of it. He is home grown on this site ;) :cool:
 
Re: Sizing Conductors for Continuous Loading

It's a bird, no it's a plane, no it's SuperCode Man! Here again to save the day. You are my hero Ryan! :D

That is a good response.
 
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