QOD for 2/9/04

Originally Posted By: dbush
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Okay, I promised an electrical topic, here we go. The topic will be electric all week as several people have requested. If anyone has a request for a topic next week just e-mail or pm me.



Dave Bush


MAB Member


"LIFE'S TOUGH, WEAR A HELMET"

Originally Posted By: Blaine Wiley
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never mind, had a brain fart icon_confused.gif


Originally Posted By: kpapp
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Dang Mr Bush you had to make me think after my coffee, That almost gave me a brain cramp eusa_doh.gif



_______________________________________


If you dont have time to do it right the first time, When will you have the time to go back and fix it?

Originally Posted By: jpope
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Quote:
Given that you have a #6 copper wire. 100 main breaker, panel rated for 150 amps, what is the service amps?


This would be "overfusing" would it not?


--
Jeff Pope
JPI Home Inspection Service
"At JPI, we'll help you look better"
(661) 212-0738

Originally Posted By: jfarsetta
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I suspect I know the correct answer, though I did not choose it. The panel being rated at 150 amps is the red herring. So long as the voltage and amperage does not exceed the panel rating, you’re okay.


The relation of the #6 copper to the 100A main breaker is the key. I'm assuming the #6 is the size of the service entry cable. Is that correct Dave?


--
Joe Farsetta

Illigitimi Non Carborundum
"Dont let the bastards grind you down..."

Originally Posted By: dvalley
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A #6 copper SE wire will have a tendancy to melt in this situation (if an overload occurs), causing a fire. The 100 amp breaker is waiting for 100 amps of surge before it will trip. Not gonna happen with a #6 copper wire. This #6 wire will only give that 100 amp breaker a max of 60 amps of electricity.


A definite Fire hazard.






David Valley


MAB Member


Massachusetts Certified Home Inspections
http://www.masscertified.com

"Some cause happiness wherever they go; others, whenever they go."

Originally Posted By: dvalley
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Dave,


I just stumbled over this QOD forum today. Great job. I look forward to this forum on a daily basis.
![](upload://dWMJihcl2Xt9tW15cZLivKWRmDK.gif)


--
David Valley
MAB Member

Massachusetts Certified Home Inspections
http://www.masscertified.com

"Some cause happiness wherever they go; others, whenever they go."

Originally Posted By: kleonard
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Very stange scenario here.


It seems that someone updated their panel & breakers without updating the service. ![eusa_wall.gif](upload://hILV5Z8gRVLwzVpRIDJEm01uB52.gif)

Obviously not done by a Qualified Sparky.


Originally Posted By: Bob Badger
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kleonard wrote:

It seems that someone updated their panel & breakers without updating the service.

Obviously not done by a Qualified Sparky.


Ditto on that sentiment.

A chain is only as strong as the weakest link.


--
Bob (AKA iwire)
ECN Discussion Forums
Mike Holt Code Forum

Originally Posted By: Blaine Wiley
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I’m still having a brain cramp today, but isn’t #6 copper only rated for 55 amps?


Originally Posted By: Bob Badger
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Blaine, no brain cramp you are correct. icon_cool.gif


310.16

8 AWG @ 60 C = 55 amps

8 AWG @ 75 C = 65 amps

Most modern equipment (panel, breaker, meter terminals) will be marked as 75 C allowing the use of the 75 C amp rating.

If all the terminals involved are not marked as 75 C then you would have to use the 60 C rating, assuming 75 C or 90 C insulation. 110.14

My guess is the old cloth covered stuff along with TW is 60 C insulation.

But 240.4(B) could allow the use of the next size standard breaker for this application.

It would be tough to check for the terminal ratings during a home inspection, but considering 240.4(B) the use of 6 AWG on a 60 amp breaker would not seem strange to me.

Bob


--
Bob (AKA iwire)
ECN Discussion Forums
Mike Holt Code Forum

Originally Posted By: Mike Parks
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“Given that you have a #6 copper wire”


100 amp service.

"a" #6 = one wire, could be the EGC

100 amp "main" = 100 amp service

No info on service conductors given.

Given the 4 options 100 amp would be the correct anwser.

Mike P.


Originally Posted By: gbeaumont
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Quote:
No info on service conductors given.


I think that you can take it that the #6 was refering to the SEC's, or at least that was the way that I read it.

Regards

Gerry


--
Gerry Beaumont
NACHI Education Committee
e-mail : education@nachi.org
NACHI phone 484-429-5466

Inspection Depot Education
gbeaumont@inspectiondepot.com

"Education is a journey, not a destination"

Originally Posted By: roconnor
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be taken to mean the SE conductors since the question is about “service amps” … icon_idea.gif


Trick question boys and girls, but there is a correct answer ...


--
Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee

I am absolutely amazed sometimes by how much thought goes into doing things wrong

Originally Posted By: jfarsetta
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I said 100 amps. So which is it? 60 or 100



Joe Farsetta


Illigitimi Non Carborundum
"Dont let the bastards grind you down..."

Originally Posted By: jpope
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Recommend further evaluation and correction by a State licensed electrical contractor ![icon_biggrin.gif](upload://iKNGSw3qcRIEmXySa8gItY6Gczg.gif)


--
Jeff Pope
JPI Home Inspection Service
"At JPI, we'll help you look better"
(661) 212-0738

Originally Posted By: gbeaumont
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Hi Jeff,


within the terms of the question, it should be noted that it is in fact a 60 amp supply due to the rating of the conductor, therefore the fact that it has a 100 amp main disconnect is somewhat an extra.

this question is very typical of those questions used on NHIE and other licensing exams, quite often the question or answers seem somewhat ambiguous, but there is actually only one answer that can be totaly correct given the options available in this question 60 amp is the only correct answer.

But I must admit, the discussion is as useful as the questions ![icon_confused.gif](upload://qv5zppiN69qCk2Y6JzaFYhrff8S.gif)

Regards

Gerry


--
Gerry Beaumont
NACHI Education Committee
e-mail : education@nachi.org
NACHI phone 484-429-5466

Inspection Depot Education
gbeaumont@inspectiondepot.com

"Education is a journey, not a destination"

Originally Posted By: jpope
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Gerry,


I agree, it's a 60 amp service (even though I answered incorrectly at 100 amps originally)


--
Jeff Pope
JPI Home Inspection Service
"At JPI, we'll help you look better"
(661) 212-0738

Originally Posted By: dvalley
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I apologize for giving away the answer too early.


I was not aware that these should be answered only after everyone had the opportunity to guess at the question.


Won't happen again.![](upload://7GiJHa9oLOP2YGWNNJqyitFikFi.gif)


--
David Valley
MAB Member

Massachusetts Certified Home Inspections
http://www.masscertified.com

"Some cause happiness wherever they go; others, whenever they go."

Originally Posted By: roconnor
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Hmmmmm … well lets see now.


If it's one set of #6 Cu service feeders (3-#6) then the conductors would limit the service capacity to 60A.

If its two sets of #6 Cu (6-#6) service feeders (parallel conductors), then the MD would limit the service capacity to 100A.

It could be taken that it's a standard 3-wire service, since there is no mention of parallel conductors and current model codes would usually limit parallel conductors to #1/0 and larger. Then again current codes would not allow anything less than a 100A service with #4 Cu for a typical residence ... ![icon_wink.gif](upload://ssT9V5t45yjlgXqiFRXL04eXtqw.gif)

[Okay, thats a stretch ... but Dave gave away the "correct" answer ... ]


--
Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee

I am absolutely amazed sometimes by how much thought goes into doing things wrong