200a per leg

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Ive moved from CA to KY.At least some inspectors and utility company's say that a 200a service can not have more than 200atotal.Iwas told 125a per leg =250a which will burn up 200a panel.I was told by hvac buddy he has had to go 400a service to accomadate adding heat pump.Some how? Theyadd face value of breakers .Has anyone heard of this ?How do they come up with this?What happened to connected load or sq. foot load?
 
fastforward said:
Theyadd face value of breakers .Has anyone heard of this ?How do they come up with this?What happened to connected load or sq. foot load?
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I've heard of it, and it's truly an amateur level assumption to add breaker value to figure a service size.

Only a service calculation can determine the load.
 
Speedy, 200a at 240v is twice as much power as 200a at 120v. A 200a service can supply 200a at 240v. The two line conductors' currents do not add together. 200a is 200a.
 
fastforward said:
Iwas told 125a per leg =250a which will burn up 200a panel.
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You were told wrong, as Larry has already mentioned. I recommend to anyone and everyone that the phrase "amps per leg," and all phrases that resemble it, be permanently banned from our vocabulary. The phrase is worse than meaningless, in that it doesn't actually mean nothing. No, the problem is that it contains an apparent meaning that is false.
 
It is crazy to me that the authority having juristiction and utility rep both think that way.Has anyone had success in explaining ,so they understand ?Any recommended literature or phrases?
 
Maybe try showing them Ohm's Law. Only someone who does not understand this simple truth would belive that 125 amps @ 120 volt x 2 would equal 250 amps @ 240 volt in a panel.
 
charlie b said:

I recommend to anyone and everyone that the phrase "amps per leg," and all phrases that resemble it, be permanently banned from our vocabulary. The phrase is worse than meaningless, in that it doesn't actually mean nothing.
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Charlie,

I understand the concept that a 200 amp service will provide 200A @240V.
Thus if the load is balanced you could have 200 amps on each leg @120V.

I do not understand why you are so against the term amps per leg?

Are you saying that the two buses in such a load center are each rated for 400A? Such that you could use only one of the bus legs loaded with breakers and ultilize the full capacity as 400A @ 120V? That has never been my impression and I know it would not be a common useage or good practice for load center. Isn't their a place for a per leg rating as well?
 
Broken down into a simple schematic, a 2-pole circuit would look like this:

200apl.jpg


Transformer, Main breaker, branch breaker & load.

Each 'leg' has 200 amps on it, but it's the same amps. Remember, in a series circuit, I is always the same. 1/120th of a second later, the same 200 amps are flowing, but in the opposite direction. Nowhere in this circuit will you get an ammeter to read 400 amps.

For those who advocate adding the two numbers together (for 400), suppose all the loads are 120v loads? I don't think you're going to get 800 amps on the neutral (400+400).
 
ELA said:
I do not understand why you are so against the term amps per leg?
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It is because the word "per" carries the meaning of "divided by," or "each." That gives the reader the tendency to think, "well, 'each' leg has 200 amps, so the total must be 400 amps." That is not the way of the world, and I blame the word "per" for giving the wrong impression. The fact of the matter is, if you have 200 amps on Phase A of a single phase, 120/240 volt system, and if you have 200 amps on Phase B of the same system, then each electron that leaves the source via Phase A will return to the source via Phase B, so the 200 on one is the same as the 200 on the other. You don't get 200 + 200 = 400. Instead, you get 200 = 200. The word "per," in the phrase "amps per phase," does not correctly describe the actual situation.
 
Now, one could use the term, "120V per leg" because these voltages combine to yield 240V line to line.
 
As far as terminology,I did look at the labeling on the panel .When talking about ampereage rating its refered to as (185a for each circuit conductor)Thanks for your responses.Not all sparky's are equal.
 
charlie b said:

It is because the word "per" carries the meaning of "divided by," or "each." That gives the reader the tendency to think, "well, 'each' leg has 200 amps, so the total must be 400 amps." That is not the way of the world, and I blame the word "per" for giving the wrong impression. The fact of the matter is, if you have 200 amps on Phase A of a single phase, 120/240 volt system, and if you have 200 amps on Phase B of the same system, then each electron that leaves the source via Phase A will return to the source via Phase B, so the 200 on one is the same as the 200 on the other. You don't get 200 + 200 = 400. Instead, you get 200 = 200. The word "per," in the phrase "amps per phase," does not correctly describe the actual situation.
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My point is that someone might understand that the load center can supply 240V @ 200A or 48KVA. And further that this can be thought of as 200A* 120V + 200A*120V = 48KVA.
As has been pointed out they may then misunderstand that since it can supply 48KVA that it might also be able to supply 400A*120V =48KVA.

So I feel that there should be nothing wrong with stating that the load center can supply 48KVA with a maximum of 200A per leg.

I do not feel that the per leg reference itself is the causing misunderstanding. It works fine as a part of a complete specification.
 
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