Load capacity of 200-amp panel (2024 Update)

[Steve N.]

Agree.

If you also put a 120V load across Line 2 and the neutral, then

OK, you're right. If they're perfectly balanced. So lets make the Line

1-to-neutral load a 200A load (0.6 ohms), and the Line 2-to-neutral load 199A (0.603 ohms). Now we have an unbalanced current of 1 amp thru the neutral.So we have 200A thru one side of the breaker, and 199A thru the other side. So what's the total amperage now?? Is it 200A or 399A, or? It's all in how you look at it. In the end ,it's a matter of total energy or kW. 200A x 120V=24000W & 199A x 120V= 23880W for a total of 47880W or 47.88kW

With a perfectly balanced load - yes, one circuit. With a slightly unbalanced load - then, two circuits.

[trader4]

Yes, I agree, assuming there is one. In our hypothetical case I was ignoring any breakers.

We have been discussing continous loads at the service max, not transients. That 200 amp service can support a total load of 4800 amps at 10 volts, or 2400 amps at 20 volts. As I said before, you can slice it and dice it anyway you want, but you still have 200 amps max of current flowing in the service.

[trader4]

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No, it not. Once again, the physical current in the service cable is

200 amps. You have 200 amps flowing IN on one hot, 199 flowing OUT on the other hot and 1 amp flowing OUT on the neutral. The current flowing in that circuit is 200 amps. You don't count current twice.

How much current is flowing in a simple 120W light bulb plugged into a

120Volt outlet? 1 amp. Now simply add another single wire in parallel with one of those supplying the light bulb. The current will be split now, with some part of it going via one wire, some via the other. For sake of argument, let;s assume it just splits evenly. So, now you have 1 amp coming in on one wire, 1/2 amp leaving via one wire, 1/2 amp leaving via the second wire. How much current is flowing in this "service" circuit to the light bulb? There is no confusion, it's 1 amp.

It's a simple matter of applying Kirchoffs law.

Balanced or unbalanced matters not a wit. There is still a current of 200 amps coming and going either way. The only difference balance makes is which PATH that 200 amp current takes.

[Steve N.]

Yes, I agree, assuming there is one. In our hypothetical case I was ignoring any breakers.

200A thru each main-breakered leg - yes. But I'm not sure where the 4800A @ 10V is coming from. Do you think the transformer secondary windings will sustain at 4800A? Are you now taliing about continuous or transient??

[trader4]

Small correction to my previous post, where I left out a couple of zeros in the text.... Here'e the corrected version.

Here's a circuit diagram of a fully loaded, balanced 200 amp service:

-------------- 240 volt source----------- I I a I I b I I I------------------2.4 ohmRes-----------I I I I-----1.2 ohmR-----1.2 ohmR--------I

How much current is flowing in the "service", which is through the voltage source? 200 amps. It supporting one 240Volt 100 amp load and two 120volt 100 amp loads. By every circuit concept I've ever heard of there is but 200 amps flowing in the service cable here. Yet, some would have you believe it 300 amps.

If we want to include the neutral then it looks like this:

• -- + -- I------------120V----I-------120V--------- I I I I I I I I I I-----1.2ohms------I--------1.2ohms---I I I I-------------------2.4 ohms---------------I

The service now consists of 3 wires. In this case, because it's balanced no current is flowing in the neutral. You can unbalance it, do anything you like and still with a 200 amp service there is only

200 amps flowing in, 200 amps flowing out. And it;s not a "parallel " circuit either as Doug has claimed.

[Steve N.]

No, it not. Once again, the physical current in the service cable is

200 amps. You have 200 amps flowing IN on one hot, 199 flowing OUT on the other hot and 1 amp flowing OUT on the neutral. The current flowing in that circuit is 200 amps. You don't count current twice.

How much current is flowing in a simple 120W light bulb plugged into a

120Volt outlet? 1 amp. Now simply add another single wire in parallel with one of those supplying the light bulb. The current will be split now, with some part of it going via one wire, some via the other. For sake of argument, let;s assume it just splits evenly. So, now you have 1 amp coming in on one wire, 1/2 amp leaving via one wire, 1/2 amp leaving via the second wire. How much current is flowing in this "service" circuit to the light bulb? There is no confusion, it's 1 amp.

It's a simple matter of applying Kirchoffs law.

Umm...so you're saying that if you have a 200A load on Line1to neutral that you're going to have 200A going thru both sides of the 200A breaker regardless of the load on the Line 2 to neutral side??

What if you have a 200A load on the Line 1 to neutral side, and nothing loading the Line 2 to neutral side? Are you still going to have 200A going thru each "leg" of the main breaker?

[Steve N.]

With balanced loads that's true. But what about the following with with a 0.6 ohm load across L1 and the neutral, and NO load across L2 and the neutral (an open).

L1 side L2 side I000000000000000000000000000000000I The 00000s represent trans. windings I------120V----------I-------120V---------I I I I MB1= 200A main breaker Line 1 side I I I MB2= 200A main breaker Line 2 side MB1 I MB2 I I I I I I I-----0.6ohms--------I------ ------I

There will be 200Amps down thru MB1 and thru the load and back up thru the secondary winding using one half of the transformer secondary winding.to form a circular loop.. There will be NO current thru MB2 because there is no current path.

[usenet-659f31de7f953aeb]

Two 200A 120V loads in series makes a 200A 240V load.

The only way you can get 400A out of a 200A service is with a step-down transformer.

[usenet-659f31de7f953aeb]

Two 200A 120V loads in series makes a 200A 240V load.

The >That was precisely my point. That to support a 400 amp 120V load,

Two 200A 120V loads in series makes a 200A 240V load.

The only way you can get 400A out of a 200A service is with a step-down transformer.

[trader4]

I think we are in agreement, except for perhaps one point.

From your previous post, you clearly agree that you can in fact have two 120volt, 200 amp loads connected in series across the 240volt service. That is a perfectly balanced load. You now have 200 amps flowing in series through each load. In my world that is in fact "supporting" 400 amps of 120volt load. Lets say I had forty 10 amp,

120volt heaters. I could could clearly put twenty of them between one leg and neutral and twenty between the other leg and neutral and it would work. You now have a fully loaded balanced service. There is zero current flowing in the neutral and 200 amps flowing in the service. It works because the loads on one side are connected in series to the loads on the other side.

My whole point all along has been that the actual current in a 200 amps service is limited to 200 amps which clearly you agee with. And it has nothing to do with "parallel circuits", or power, voltage or anything else. It looks like the only difference we have is your definition of "supporting loads" may be stricter than mine.

And I think all of us are still waiting for a simple answer from Doug as to how many amps are actually flowing in a fully loaded 200 amp service cable circuit. I've asked that several times now and still have no answer, despite having fully answered all his questions.

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[trader4]

..

Yes. You have a 3 wire service cable coming into the house. Use Kirchoff's law and add up the current coming into the house at any point in time under any conditions through that cable any you have a max of 200 amps. Add up all the current leaving the house at the same point in time and you have a max of 200 amps. In my world, that's a 200 amp service. You don't measure 300, or 400 by counting electrons twice.

And also, to support a max of 400 amps of 120volt load in the house which is the hot topic, you have to have the special case where the loads are perfectly balanced so that 200 amps is on each side. And then you in fact have a SINGLE circuit with 200 amps flowing in on one hot leg, throught the loads in series, and back out the other hot leg. Nothing flows in the neutral. Again, in my world, that's 200 amps flowing in the service, not 400.

[trader4]

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m...

No, never said that.

You're going to have 200A flowing from Line 1 to neutral. Again, that is 200 amps flowing in the service cable. As I said, if it's fully loaded, you will have a max of 200 amps flowing in the service cable. That's 200 amps coming in, 200 amps going out. The only difference is whether some of the current flows on the neutral or not. If the neutral has some current, then one of the hot lines must have less than 200 amps or you'd violate Kirchoff's law.

[trader4]

.

Take twenty four .05 ohm resistors. Wire them is series. In series they equal 1.2 ohms, Connect them across the 240V, 200 amp service hot lines. You now have 10 volts across each resistor and 200 amps flowing through the circuit. So, you're supporting twenty four 200 amp, 10volt loads. Each resistor sees 10volts and 200 amps. Taken together that's 4800A at 10V. How much current is flowing in the service? Still 200 amps. Showing once again that this feature works because to get loads of more than 200 amps out of a 200 amp service, the loads have to appear in series.

[usenet-659f31de7f953aeb]

Your semantics create confusion. In NO CASE can you flow more than 200 amps through any single load. To say that you have many 120V loads drawing a total of 400A is WRONG and obscures the fact that two balanced 120V loads is absolutely identical to a 240V load.

[Steve N.]

No, never said that.

But you still didn't answer the question about the current flow path. If you have a 120V 200A load between Line 1 & neutral,and no load between Line 2 & neutral, how much current flows thru the Line 1 side of the main breaker, how much current flows thru the Line 2 side of the main breaker, and how much thru the neutral?

[bud--]

To get the max of 200A of 240V load you have to have the special case where the loads add up to 200A. The discussion is about the special cases of a fully loaded service.

What did the OP want to know? IMHO, the OP was asking how many amps of 120V load you can hang on a

200A 240V service. The correct answer is 400.

[JIMMIE]

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com...

There will be 0 amps in the neutral. The loads form two legs of a balanced bridge, the windings in the transformer form the other two legs, When they are balancedas you described therer will be ZERO current in the neutral. Dont believe me check it for yourself. Make a test circuit out of two 100 watt light bulbs connected in series, put them across a 240VAC connection with no neutral connection then connect the neutral between them. Measure the current in the neutral. It will be ZERO. measure the current in each hot leg. The neutral is only there to carry the difference between the two legs when there is an imbalance. If the current in one leg was 100 amps and the the other had 50 amps the neutral current would be 100 -50 + 50 amps.. When the load is balanced and you measure the current in each leg you are just measuring the same current twice.

Jimmie

[Steve N.]

Re-read the question. I'm asking about a SINGLE 120V 200A load between Line

1 & neutral, not 2 loads in series across 240V.

[trader4]

The correct answer is actually 400 amps of 120volt load IF THE LOAD IS PERFECTLY BALANCED. IF it's anything less than perfectly balanced, you can not support 400amps of load. If it's totally unbalanced, you only get 200 amps.. Partially ballanced, you get between 200 and

400. The only way you can get 400 is if it is perfectly balanced so that the 120volt loads are in SERIES and appear as a 200 amp 240volt load.

Agree?

[JIMMIE]

No, if the load is balanced there is no 120 volt loads just 240s. 240 X 20 also equal 48KW.

If what you were saying is true you could hang your ammeter on the neutral line and measure 400 amps.

It doesnt just appear to be a 240 volt 200 amp load IT IS. The two loads are in series, same electrons going through both of them. Its not fair to count electrons twice.

Jimmie