Ok, if I have 100 AMP panel, in 60 degree ambient temperature, how would I size the wire??

Do I just do 100A x 1.25 for continuous = 125A then Table 5A says at 60 degrees using the middle column wire is .67
so then 125A / .67 = 186.5
So then I go back to table 2 using the middle column wire, I would choose 3 aught? (210AMP rated)

OR:
since 100AMP panel can use #3 rated for 105AMP. I just goto 105AMP / .67 for the 60 degree ambient temp and get: 156.7 = 2 aught (185AMP rated wire from middle column of Table 2 )

OR
is 100amp panels with #3 wire feeders only allowed for residential dwellings, and since it doesn't specify as a residential application/installation for this panel do I stick to the first method?

Thank you.

60 degree ambient is pretty warm. Do you mean 60 degree rating on the breaker?

ambient...
it's a pen/paper test question.

I don't know that breakers are okay in a 60 degree ambient. Is it a trick? I'll give it some thought, anyway. Is it a 2012 code question?

26-402 says no panels in high ambient rooms. When do I get my marks?

Gentlemen:

Two (2) posts to this thread were deleted today. PMs were sent to the two gentlemen involved.

based on 2009 CEC book.
hmm... table 5b (going off memory.. somewhere there... )
ambient adjustment factors to derate wires are listed there accordingly.
It's not for the panel, but for the wire. I guess where the wire run is happening, it can reach that temp.

^^ nevermind that last response. I noticed my original question was regarding panels, not wire runs!!!

Thanks twh!

I got an interesting one for you. It is tricky.
I gotta look it up from my notes.
Here it is....

if I have 2500 WATTS heater and 240 VOLTS. I'd like to size the conductors.
do I go about it as such:
2500 / 120 = 20.833
So, here's the part that is tricky ( to me )
Do I need to pad that wire by x 1.25 for continuous load?
If so, I get 26AMP, and it's an easy #10 AWG answer from Table 2. However, if not, I'm left with 20.8A. That means, in T2 for conductor size, I would have to pick #10 since it is over 20. BUT..... SEC 8-106(1) states that if the next smaller size conductor has not more than 5% less than this minimum, the smaller size is permitted. Since 5% of 20 would be 1, and this falling at 20.8, does that mean I can use #12 ??

Or, am I totally misunderstanding 8-106(1) rule?

2009: http://www.codemath.com/cgi-bin/Run.pl?script=CecAwgRw
2012: http://www.codemath.com/cgi-bin/Run.pl?script=CecAwgRw2012

2500 watts and 240 volts = 10.4 amps

#14 and 15 amp circuit is fine even if you add the 1.25 factor which I am not sure about needing.

hmm.. would this be more appropriate?
heater 2500 / 240 = 10.4 AMPS. x 1.25 for continuous load = 13.
since 15AMP breaker is max 12AMP at 80% load.
Isn't #12 the more correct choice since it can handle up to 16 amp?

btw: I should probably thank you guys for going thru a couple of these with me, and tolerating the side tracking at times.

Sid:



A 'Thanks' would always be appreciated, IMHO.

I'm taking a backseat on CEC.

No, #12 is wrong.Stop there. That's your minimum circuit ampacity.

You did the 80% load thing twice. Once when you did 1.25 x load and then again when you did 80% of breaker.

Method 1 for a commercial
100 / .67 = 149.25 for resi service = 1/0

Method 1? Are you saying that all commercial 100 amp panels, in Victoria, (excluding derating for temperature) are fed with #1 awg?

When you determine the panel size, it might be based on 125% of the load, but the wire size isn't again increased. That would be applying the 125% rule twice. Once for the minimum circuit ampacity and a second time to the conductor.

Thank you. I get it now.
Here is a more interesting one....
I've got 4 x #10tw75 in a 41mm conduit. How many more #16tw75 can I fit into the conduit?
I go to table 9 and I get my max wire size (area in mm) for 41mm conduit in the 40% fill zone.
Then, I goto table 10 to get the area of #16 to calculate my fill, and I see there is no #16. It stops at #14. How can I get the area size of #16 TW75 wire so I may complete the question.?
Or is it a trick question? ie: some rule about having lower than #14 size wire in conduit, and needing some kind of separation?

No #3 is still good for a 100 amp panel but feed a 100 amp panel through a 60 degree ambient and derating factors can bump it up a lot.
I think it would be a hugely bad idea to put a panel in a 60 degree ambient as most of the breakers would trip at values musch lower than the number on the breaker.
What would the ampacity be for a 60 degree breaker in a 90 degree ambient? 0 amps

You're right. 60 degree is unreasonable. Even for just a question.
Let me phrase it better....
lets say 200A panel, but lets assume the panel is not in the ambient room, just the supply wires run through somewhere, where it will be 40 degrees ambient. Whats the min size coppers we can use to supply this?
Now, here's my confusion, and it's probably silly. But i need to learn the right way.
So, I would goto Table #2. I see that 210 A is the min rated wire to supply at least 200 A. Which is 3/0. I am not 100%. But I feel I should use this, as it doesn't state that this is a residential property. In which case if it did, I would use 2/0 rated for 185 A which is allowed in homes/individual dwellings.
Now, I feel I need to take that 210 A rated wire and do 1.25 x for continuous load for my panel. Then, I need to factor in the ambience for the wire at 40 degrees. Which is / by .9 using Table 5A.
At this point, I would get: 291.2 A. This leads me to 300Kcmil wire rated at 295 Amps. The issue I have is, that is not one of my multiple choice answer choices. So something is wrong in my way of thinking.
If I use a panel "assumed" (which I don't want to do since it's not stated) for a dwelling, I can choose 185 A. Then, I can just / .9 for ambience and I get 205.6 A which falls into one of my choices.
There are a couple other ways of looking at this. But I'm sure you get the idea, and I don't want to make a winded post.
My answer choices are:
1/0, 2/0, 3/0, and 4/0 wire sizing.

bump... ^^^ anybody?

I am reconsidering my answers. If the panel is in a 60 degree ambient the panel location is a fail. There is no derating method for panels, only the wire.

The second problem has a glitch too as baseboard heaters are allowed to load the wire to it's ampacity 62-114(7)so #12 can supply a 20 amp heater and connect to a 30 amp breaker if a 25 amp breaker is not made. #14 can supply 240 X 15 amps or 3600 watts and can be connected to a 20 amp breaker under 62-114(8)

If you are installing a 200 Amp panel, it is because the calculated panel size is 200 Amps. That will include the 125%, if applicable. The correction factor for a 40 degree ambient is .90.
Which ampacity, when multiplied by .90 is at least 200 Amps?

It isn't 2/0 because, even with the provision for residential services, it has an ampacity of only 200.

4/0 has an ampacity of 235 amps. 235 x .9 = 211.5. The answer is 4/0.

You must multiply the amperage by the correction factor. Do not divide.

It primarily depends on the voltage, distance and load. The longer the cable, the higher the resistance/impedance. There are also factors such as the ambient temperature, type of insulation, number of conductors, and whether it is buried in the ground or suspended in the air.

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