Derating a circuit

[Herman H]

I am finding it difficult to find out how to de-rate a circuit. I am trying to figure if I can put two 8ga. 220V, 2-wire THHN, circuits in a 1" conduit, with each circuit on a 40 amp breaker. I think I figure 80% of 55amp wire, which would be 44. Am I figuring this right? Also, Should I purchase an NEC or someones interpretation of it?

 

[jusme123]

......

 

[qcroanoke]

I am finding it difficult to find out how to de-rate a circuit. I am trying to figure if I can put two 8ga. 220V, 2-wire THHN, circuits in a 1" conduit, with each circuit on a 40 amp breaker. I think I figure 80% of 55amp wire, which would be 44. Am I figuring this right? Also, Should I purchase an NEC or someones interpretation of it?

4 #8's in a 1 inch conduit is no problem.
You have to de-rate with 4 conductors in a raceway and 80% sounds right........
So #8 on a 40 amp breaker is good.
Yes, you should purchase a code book and seek out classes in your area on the code.
And hang out here. You will learn a lot!
Welcome to the forum!!!!

 

[augie47]

Since the Code is new to you I would suggest you go to Mike's Home page https://www.mikeholt.com/index.php and look at the books he has for sale and pick the one best suited to you and your budget, The "Understanding the NEC" series is good.
If you have questions give them a call.

 

[Julius Right]

In my opinion too, 40A is o.k. However, for record only:
you may use 90oC column if you are positive the equipment connected with is marked for 90oC. See NEC 2014 art.110.14 Electrical Connections.(1) Equipment Provisions.
So for 75oC rated insulation 8 # copper conductor maximum 50 A is permissible.

 

[kwired]

I am finding it difficult to find out how to de-rate a circuit. I am trying to figure if I can put two 8ga. 220V, 2-wire THHN, circuits in a 1" conduit, with each circuit on a 40 amp breaker. I think I figure 80% of 55amp wire, which would be 44. Am I figuring this right? Also, Should I purchase an NEC or someones interpretation of it?

They would fit in 3/4 inch raceway.

What is the application? Something like a motor/motor operated appliance that requires a 40 amp breaker may not necessarily need 40 amp conductors. Non inductive or capacitive loads that require a 40 amp breaker should also require a 40 amp conductor though.

 

[junkhound]

Should I purchase an NEC

You should look at your local and state AHJ (Authority Having Jurisdiction) most recent laws regarding the code. You can access that online for almost any AHJ.

The supreme court ruled a few years ago that if something is enacted into law it is 'open source', don't recall the exact court ruling.

Anyway, what that means is that nearly all states and jurisdictions that have enacted the entire code, (or portions of, or revised with added paragraphs) that the code is not subject to most copyright distribution laws; hence, you can get the entire code AS ENACTED BY YOUR STATE or city, etc, usually on-line.
e.g . WA state has the NEC as revised by WA online in pdf form, as it is part of state law, you should be able to find similar for your location. WAC 296-46B, online at http://apps.leg.wa.gov/WAC/default.aspx?cite=296-46B, similar should be available at your location.

If you are just starting out, we know $$ are tight. Many local libraries now have printers that allow you 50 or 70 pages per week free printing. You can soon have your own copy of your LOCAL version of NEC for just your time invested.

 

[kwired]

You should look at your local and state AHJ (Authority Having Jurisdiction) most recent laws regarding the code. You can access that online for almost any AHJ.

The supreme court ruled a few years ago that if something is enacted into law it is 'open source', don't recall the exact court ruling.

Anyway, what that means is that nearly all states and jurisdictions that have enacted the entire code, (or portions of, or revised with added paragraphs) that the code is not subject to most copyright distribution laws; hence, you can get the entire code AS ENACTED BY YOUR STATE or city, etc, usually on-line.
e.g . WA state has the NEC as revised by WA online in pdf form, as it is part of state law, you should be able to find similar for your location. WAC 296-46B, online at http://apps.leg.wa.gov/WAC/default.aspx?cite=296-46B, similar should be available at your location.

If you are just starting out, we know $$ are tight. Many local libraries now have printers that allow you 50 or 70 pages per week free printing. You can soon have your own copy of your LOCAL version of NEC for just your time invested.

NFPA still wants to sell the NEC. If your AHJ has adopted NEC without any amendments why should they publish anything other then the laws that reference which edition of NEC applies? That said there is still free on line access to the document, but it may not be the most convenient way of using the document.

 

[junkhound]

NFPA still wants to sell the NEC. If your AHJ has adopted NEC without any amendments why should they publish anything other then the laws that reference which edition of NEC applies? That said there is still free on line access to the document, but it may not be the most convenient way of using the document.

NFPA just plain got greedy in 1987. They still operate in the black.


For Herman's benefit, he may be interested in some history in the following link:

https://www.mikeholt.com/mojonewsarchive/NEC-HTML/HTML/NECinPublicDomain~20030916.htm

 

[kwired]

NFPA just plain got greedy in 1987. They still operate in the black.


For Herman's benefit, he may be interested in some history in the following link:

https://www.mikeholt.com/mojonewsarchive/NEC-HTML/HTML/NECinPublicDomain~20030916.htm

Just was reading in another thread that the California Code sells for about $180, at least at the site that was linked to in that thread, there they essentially are writing their own law and apparently selling the copies as well.

 

[iwire]

The supreme court ruled a few years ago that if something is enacted into law it is 'open source', don't recall the exact court ruling.

Not 'the' Supreme Court just one Supreme court for one area.

NFPA just plain got greedy in 1987. They still operate in the black.

Hmm, have you ever checked out the pricing for other standards and say school text books?

My code book is costing me about $80.00 for three years. That is less than I pay for cable TV / Internet each month.

Over the three year period my book is good for it will cost me about $2.22 a month, less than I pay for coffee everyday and to me a code book is a required tool of this trade.

Anyway just my own personal view, code books are not that expensive and the salary I get from this trade is not that low.

 

[GoldDigger]

Not 'the' Supreme Court just one Supreme court for one area.

AFAIK the US has only one Supreme Court.
Each state will have its own state Supreme Court, but they are not likely to get involved with Federal copyright issues in the first place.

On the Federal level you have local courts, courts of appeals, and district courts before you get the Supreme Court Of The United States.

 

[iwire]

AFAIK the US has only one Supreme Court.
Each state will have its own state Supreme Court, but they are not likely to get involved with Federal copyright issues in the first place.

On the Federal level you have local courts, courts of appeals, and district courts before you get the Supreme Court Of The United States.

Well not a lawyer here and I don't pretend to be one on the Internet but as I recall Don G. posted info about the case and it only applied to a certain district or some such thing.

 

[GoldDigger]

it only applied to a certain district or some such thing.

:thumbsup:

I don't pretend to be a lawyer on the internet either, but I sometimes talk like one.