Remodel with main panel in bathroom

[charlie b]

I look that #6 Thhn up (copper) can handle 75 amps.

No, it can only handle 65 amps. You can't use the 90C column to look up ampacity, because it is very unlikely that all the terminations are rated for 90C. Reference 110.14(C).

 

[Dennis Alwon]

3/0 thhn copper is the smallest you use for a 200 amp feed.

You better check Table 310.15(B)(6). I believe this is a residence

 

[growler]

I'll update the thread later. Thanks guys.:smile:

Is it later yet?

 

[weressl]

No, it can only handle 65 amps. You can't use the 90C column to look up ampacity, because it is very unlikely that all the terminations are rated for 90C. Reference 110.14(C).

Plus you have to derate it because it originates on the outside so you have to use the temp correction factors below the table.

The panel size matters little though as the fusing on the POCO side that protects this wire, so it has to be sized accordingly. You can put in a 200A panelboard if that's what you have lying around or thinking of the future, but if the POCO only allows you 100A service and fuses you accordingly that is what you have to size your feeders for as the minimum.

We often install say a 2000A gear, but only running 1-500MCM service for starters as the load is not there yet. Then years later install the parallel 500's in the future and dial up the relay protection as loads are added. Sometimes the load growth does not materialize, but sometimes it is a real savings when you can just run additional feeders without needing to replace the gear.

 

[weressl]

You like to pull out all the stops eh? Go get 'em, Jim.

Is that how you recommend somebody to build a favorable reputation? DOn't need to be nasty, work with the guy. Assume that it WAS a mistake made out of ignorance, not malice.

Be kind.....

 

[sguinn]

Okay so we meet with a "guy" at the site yesterday and gain access to the inside. I took one of the building inspectors with me to look at the carpentry work. No permits pulled for the job and within a few minutes of looking around I can tell it's all new elec. work. New NM cable at panel, sw, receps, sw legs, etc. Even got lucky enough that all the light fixtures weren't installed, date on the NM sheathing was October 2007. Mind you this house was built in the 40's so I was looking for "tar wire". Asked the "guy" who did the work and all he could do was plead the 5th. Said he was just a friend of the owner and was trying to help her out, but during the course of talking to him we found out that he was a former GC on disabilty so I guessed he was pretty much lying through his teeth, just trying to slide it under the radar by finishing the project, getting the service inspected on a power permit and Bob's your uncle... Kharma came back to bite him on this one though, because now the POCO is involved and I wrote up my report with pictures and turned it all over to the Board of Commissioners, the insurance company will want in on it too I bet. So now we wait. tick,tick,tick...

 

[brother]

No, it can only handle 65 amps. You can't use the 90C column to look up ampacity, because it is very unlikely that all the terminations are rated for 90C. Reference 110.14(C).

Without actually KNOWING what it is , that phrase 'very unlikely' is very subjective. I understand your point, but is it not possible that the 'terminations' of that panel is rated for that temperture?? where would you go to find out the temperture rating?? the manufacture??

 

[iwire]

Without actually KNOWING what it is , that phrase 'very unlikely' is very subjective. I understand your point, but is it not possible that the 'terminations' of that panel is rated for that temperature?? where would you go to find out the temperture rating?? the manufacture??

The temperature ratings are on the equipment, you just have to read all those white stickers on the equipment. :smile:


Basically there are no breakers below 600 volts that will allow you to use the 90 C column. There are breakers that require 90 C conductors but still require the 75 C column.

 

[220/221]

you just have to read all those white stickers on the equipment.

I can't read that stuff with THREE pairs of glasses

 

[iwire]

Yeah, some of it really is ridiculously small.

 

[brother]

The temperature ratings are on the equipment, you just have to read all those white stickers on the equipment. :smile:


Basically there are no breakers below 600 volts that will allow you to use the 90 C column. There are breakers that require 90 C conductors but still require the 75 C column.

Ok, lets see if i understand your comment. How can the manufacturer require a 90 C conductor and at the same time require 75 C column of the code book.??? the column is the rating of the conductor

I thought since the breaker has a rating for a #14-#8 copper / aluminum 75 C stamped on the side of the breaker, where is the 90 C conductor come into play?? I actually have a spare Square D breaker i bought from home cheapo a few weeks ago and im reading the side of it with this info on it. By the way I can BARELY see the info on this white sticker, I know this 'issue' is probably overlooked and not even paid attention to by alot electricians nor do they derate. ( I know ive seen it alot in the field).

Just trying to get a better understanding.

 

[brother]

No, it can only handle 65 amps. You can't use the 90C column to look up ampacity, because it is very unlikely that all the terminations are rated for 90C. Reference 110.14(C).

By the way I went back and read that article again. The last part says you can use a higher rating for ampacity conductor for adjustments.

Temperture Limitations: .....Conductors with temperture ratings HIGHER than specified for terminations shall be PERMITTED to be used for ampacity adjustment, corretion, or both.

 

[brother]

good example

good example

This site gives a good example.

http://www.iaei.org/subscriber/magazine/00_b/pauley.htm

 

[iwire]

Ok, lets see if i understand your comment. How can the manufacturer require a 90 C conductor and at the same time require 75 C column of the code book.??? the column is the rating of the conductor.

The UL and the manufacturer can require anything that meets or exceeds the NEC.

Here is what I know.

A typical breaker has an instantaneous trip for short circuits and a thermal element that will trip the breaker for overload.

If conductors where operated at 90 C the heat of the conductor would transfer into the breaker causing the thermal trip to trip early.

On a large breaker, say a 3000 amp Square D they called for 90 C conductors, required them to be calculated at 75 C.

The purpose there is the conductors are used as a heat sink to pull the heat out of the breaker.

Besides the fact that copper and aluminum are great electrical conductors they are also great thermal conductors.

 

[weressl]

On a large breaker, say a 3000 amp Square D they called for 90 C conductors, required them to be calculated at 75 C.

This does not make sense. Weather the conductor is rated to 75C or 90C it will reach the same temperature when subjected to the same current.

 

[hillbilly]

This does not make sense. Weather the conductor is rated to 75C or 90C it will reach the same temperature when subjected to the same current.

That's true if the wire size remains the same, but I think that you missed I-Wire's point.

When the conductor temperature rating changes from 90C to 75C for a given amperage, the wire size increases.

If the wire is specified with 90C insulation, and the ampacity is selected from the 75C column, the wire will be larger than if selected from the 90C column.
Therefore it will operate at a lower temperature at a given load.

It's just a way (IMO) for the manufacturer to require 90C insulation on the conductors and operate them at 75C....just a little more insurance.:smile:

just my opinion
steve

 

[weressl]

That's true if the wire size remains the same, but I think that you missed I-Wire's point.

When the conductor temperature rating changes from 90C to 75C for a given amperage, the wire size increases.

If the wire is specified with 90C insulation, and the ampacity is selected from the 75C column, the wire will be larger than if selected from the 90C column.
Therefore it will operate at a lower temperature at a given load.

It's just a way (IMO) for the manufacturer to require 90C insulation on the conductors and operate them at 75C....just a little more insurance.:smile:

just my opinion
steve

duh.......of course