Thread: Determining the amperage mat a main disconnect fuse block

1. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Robert Meier
I posted a simple question requiring a one word answer, TRUE or FALSE, and again neither of the dynamic duo would answer it. I'm done with the dog chasing his tail routine. You guys are free to beat up on Jim for a while.
Oh, I'm so sorry! Yes/True, No/False.... The answer was True to a loaded question given by a simpleton. Now answer mine!

2. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Robert Meier
You know Jim I just asked a few simple questions in this thread and for the most part have yet to get a direct response. For example, here are two direct questions, look at the response:

I can make this one even easier, only a one word answer required:

TRUE or FALSE?

60 amp, 1Ø, 3 wire, 120/240 volt service with no loads:

This service have the capacity to supply one 240 volt, 60 amp heater or two 120 volt, 60 amp

heaters.

Here's the correct math AGAIN

3. Re: Determining the amperage mat a main disconnect fuse block

That math was posted 200 posts ago and you said it was wrong, now you say it was right. Robert and I both said that two 60 amp 120 circuits had the same capacity of one 240 volt. Amazing.

Someone asks a question analogous to how much water can two pipes supply to a house and some want to know how the water gets to the treatment plant.

4. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Jim Port
That math was posted 200 posts ago and you said it was wrong, now you say it was right. Robert and I both said that two 60 amp 120 circuits had the same capacity of one 240 volt. Amazing. I didn't say the correct math was wrong! And thanks for agreeing with me, that is 5 times now.
Someone asks a question analogous to how much water can two pipes supply to a house and some want to know how the water gets to the treatment plant.
Your analogy is screwy--to correct it you would need one water pipe going in (+) and one returning (-). Get it now

5. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Jim Port
That math was posted 200 posts ago and you said it was wrong, now you say it was right. Robert and I both said that two 60 amp 120 circuits had the same capacity of one 240 volt. Amazing.

Someone asks a question analogous to how much water can two pipes supply to a house and some want to know how the water gets to the treatment plant.
You gotta have coaster breaks to back peddle like that dude!

6. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Roland Miller
Your analogy is screwy--to correct it you would need one water pipe going in (+) and one returning (-). Get it now

The question was about supply. It was not about the neutral, never was.

7. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Jim Port
Fixed this for you. At 120 volts you still only have 60 amps available per leg.
Originally Posted by Jim Port
The load on the neutral doesn't matter in this example. Leg A carries 60 amps, leg B carries 60 amps equaling 120 amps of power. The 120 power is not returning on the other leg. It is on the neutral.
Originally Posted by Jim Port
The question was about supply. It was not about the neutral, never was.
Really Jim.

I see your basic knowledge of plumbing is as weak as your knowledge of electricity. For electricity to do work it must return to its source immediately. Water can do work, e.g. turn a water wheel, and dump into the sea, not to return to the headwaters of the river for thousands of years.

8. Re: Determining the amperage mat a main disconnect fuse block

Still confused by a 120 circuit I see.

9. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Chris McIntyre
I have followed this thread very closely and have found very educational....and confusing .

My question is for Jim & Robert to help me, and probably others, understand the argument. Are you saying that a 120 amp balanced load would not trip the 60 amp OCPD?

I apologize in advance if this is a stupid question.
I believe you have it. A total of a 120 amp load at 120 volts is achievable if you are drawing 60 amps per leg. Leg (A) has a 60 amp load and leg (B) has a 60 amp load. Vern continues to ask where we can actually measure 120 amps. The answer is you can't. There isn't anyplace in the panel you can place an amp meter to measure 120 amps. Even though 120 amps can't be measured, It can be calculated by adding the total ampacity of each leg together. 60 amps + 60 amps. If 60 amps total was all there was available as Vern keeps insisting, you would not have enough current to run a toaster, electric stove, coffee pot, microwave oven, nesco roaster, TV, lights, and furnace all at the same time like we do come thanks giving.

Last edited by Mike Borchardt; 08-13-2013 at 10:29 PM.

10. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Mike Borchardt
I believe you have it. A total of a 120 amp load at 120 volts is achievable if you are drawing 60 amps per leg. Leg (A) has a 60 amp load and leg (B) has a 60 amp load. Vern continues to ask where we can actually measure 120 amps. The answer is you can't. There isn't anyplace in the panel you can place an amp meter to measure 120 amps. Even though 120 amps can't be measured, It can be calculated by adding the total ampacity of each leg together. 60 amps + 60 amps. If 60 amps total was all there was available as Vern keeps insisting, you would not have enough current to run a toaster, electric stove, coffee pot, microwave oven, nesco roaster, TV, lights, and furnace all at the same time like we do come thanks giving.

Its the same 60 amps. If 120 was available you would be able to measure it because electricity is a science. See my other posts for the correct math and theory... Or read Vern's post here..he's the only other one that understands the math and theory so far..

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Originally Posted by Jim Port
Still confused by a 120 circuit I see.

Of course, the other issue here is the one of "self appointed experts" and who should you believe.

Jim, Robert, Jerry Peck, and HG all answer questions and promote them selves as "experts". The difference comes when someone disagrees with them. They then spin the question, redirect the issue, try to send you off to check with "someone that knows", accuse you of costing some innocent group money, say you can't even answer simple questions and are spreading misinformation. And call you a TROLL. And often they resort to insults and directly questioning whether you know anything about the subject. ..and add to that--They have checked with their buddy's and they agree with them.

This sure sounds a lot like BULLYING to me!

Thanks for the good example of BULLYING!

Last edited by Roland Miller; 08-14-2013 at 05:27 AM.

11. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Chris McIntyre
I have followed this thread very closely and have found very educational....and confusing .

My question is for Jim & Robert to help me, and probably others, understand the argument. Are you saying that a 120 amp balanced load would not trip the 60 amp OCPD?

I apologize in advance if this is a stupid question.
YES, a 120 amp balanced load would trip a 60 amp OCPD. Anything that exceeds the 60 amps should trip it. And if 120 amps actually existed anywhere in this circuit you could calculate it and measure it in a lab. The dark theory Jim and Robert presented does not exist in this world...

Last edited by Roland Miller; 08-14-2013 at 06:42 AM.

12. Re: Determining the amperage mat a main disconnect fuse block

Your math shows the same thing that others posted 200 posts ago, but you say yours is correct and theirs is wrong?

Lets try this; Step 1: Install three fully loaded 20 amp breakers all on Leg A. How much load is on the incoming leg? How much load is on Leg B? Do the circuits function properly?

Step 2: install three more fully loaded 20 amp breakers all on Leg B. How much load was just added to the panel? How much load is on Leg A? Has this changed since the addition of the three new circuits? How much load is now on Leg B? What is the TOTAL load that both Leg A and B are supplying? Do all six circuits function properly without opening the fuse or breaker? Turn off all the breakers on Leg A. Has the load on Leg B changed?

As far as the bullying comment, I don't remember anyone besides you and Vern using words like simpleton or advising a career change.

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Originally Posted by Roland Miller
YES, a 120 amp balanced load would trip a 60 amp OCPD. Anything that exceeds the 60 amps should trip it. And if 120 amps actually existed anywhere in this circuit you could calculate it and measure it in a lab. The dark theory Jim and Robert presented does not exist in this world...
Actually it would not. There would be 60 amps on each leg which is not over the trip limit of the breaker or fuse. In fact, your math even show the 7200 watts on each leg. Care to reconsider your answer?

13. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Jim Port
Your math shows the same thing that others posted 200 posts ago, but you say yours is correct and theirs is wrong?

Lets try this; Step 1: Install three fully loaded 20 amp breakers all on Leg A. How much load is on the incoming leg? How much load is on Leg B? Do the circuits function properly?

Step 2: install three more fully loaded 20 amp breakers all on Leg B. How much load was just added to the panel? How much load is on Leg A? Has this changed since the addition of the three new circuits? How much load is now on Leg B? What is the TOTAL load that both Leg A and B are supplying? Do all six circuits function properly without opening the fuse or breaker? Turn off all the breakers on Leg A. Has the load on Leg B changed?

As far as the bullying comment, I don't remember anyone besides you and Vern using words like simpleton or advising a career change.

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Actually it would not. There would be 60 amps on each leg which is not over the trip limit of the breaker or fuse. In fact, your math even show the 7200 watts on each leg. Care to reconsider your answer?
Here's the correct math for your example----------AGAIN

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Jim--your are still missing the fact that A phase and B phase are 180 degrees out of phase which makes one + and one - in respect on one another at any give time. And you can't take the total wattage at the 240 volts and divide it by 120 and have anything meaningful. The correct problem equivalent of 240 is the (2 X 120).. not a single 120. This leads to a mathematical error and an incorrect assumption..

The 2- 60 amp loads on A and B phases are added using vector addition and since they are 180 degrees out of phase it is as easy as sliding your finger up and down a number line ( much like in 5th grade).

Last edited by Roland Miller; 08-14-2013 at 07:51 AM.

14. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Jim Port

As far as the bullying comment, I don't remember anyone besides you and Vern using words like simpleton or advising a career change.

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Do you just make things up as you go along? Show me where I have said this..

15. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Vern Heiler
Oh, I'm so sorry! Yes/True, No/False.... The answer was True to a loaded question given by a simpleton. Now answer mine!
Here is one example.

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Originally Posted by Roland Miller
Here's the correct math for your example----------AGAIN

- - - Updated - - -

Jim--your are still missing the fact that A phase and B phase are 180 degrees out of phase which makes one + and one - in respect on one another at any give time. And you can't take the total wattage at the 240 volts and divide it by 120 and have anything meaningful. The correct problem equivalent of 240 is the (2 X 120).. not a single 120. This leads to a mathematical error and an incorrect assumption..

The 2- 60 amp loads on A and B phases are added using vector addition and since they are 180 degrees out of phase it is as easy as sliding your finger up and down a number line ( much like in 5th grade).
And you continue to miss that someone could add a 60 amp load to one leg or both legs and the panel will still function. This is the same premise from over 200 posts ago. This can be measured.

16. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Jim Port
Here is one example.
There you go--using a half-truth to make yourself look good. Again you are using oranges to prove and apple theory.

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Originally Posted by Jim Port
Here is one example.

- - - Updated - - -

And you continue to miss that someone could add a 60 amp load to one leg or both legs and the panel will still function. This is the same premise from over 200 posts ago. This can be measured.
Thanks for agreeing with me again.. Lets see that's 6 times now.... I have not missed that point---again you spin it and half-truth it to seem like you are right. And you are not!

17. Re: Determining the amperage mat a main disconnect fuse block

And you continue to miss that someone could add a 60 amp load to one leg or both legs and the panel will still function. This is the same premise from over 200 posts ago. This can be measured.

Thanks for agreeing with me again.. Lets see that's 6 times now.... I have not missed that point---again you spin it and half-truth it to seem like you are right. And you are not!

So 60 amps on two legs does not equal 120 amps of capacity? You can run two 60 amp 120 volt loads from one panel but the panel will not support 120 amps of load? Interesting.

I will bow out and leave you and Vern to your confusion. As Robert said many posts ago, it didn't matter how many times and different ways that this would work there is no light at the end of the tunnel.

Sorry that you never took the challenge to post this topic on an electrical forum.

18. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Jim Port

Sorry that you never took the challenge to post this topic on an electrical forum.

After 45 years of teaching and doing the math and science of electricity ( a degree in Communication Electronics and Science and a life long practicing master electrician) I would have to say I have probably taught some of them about the NEC or the science of electricity. Really Jim--it is simple enough that someone with a 5th grade education could grasp. I have said "I could teach anyone to be an electrician" but I am wrong because there are at least 3 of you wouldn't make it....

19. Re: Determining the amperage mat a main disconnect fuse block

Hello, all, I am new here. I would like to respond to the discussion about electrical cabinet capacity. I have been in the multifamily industry for nearly 40 years, and have a lot of experience with electrical circuits. This topic is a difficult one to grasp at times. The ampacity of the cabinet in question (or any cabinet, for that matter) is the rated ampacity for the main disconnect. In this case the disconnect is rated at 60 amps. This means that this cabinet has an ampacity of 60 amps. The "legs" (more correctly, "poles") are not additive. If one would employ a clamp-style ammeter, clamp around both poles (service drop conductors), one would see a reading on the ammeter of zero amps if both poles were utilizing 60 amps of current simultaneously. If one pole is using more current (for example, a 120 volt lighting circuit is being utilized in addition to a 240 volt HVAC system), the ammeter would display the current difference ONLY. I wrestled with this concept until I performed the action I described by clamping my digital ammeter around the main conductors in a service panel just to see the outcome. VOILA! My Four Rules for Living: #1- Don't panic (thanks Mr. Adams); #2 - Pay attention; #3 - Learn something every day; #4 - When all else fails, read the directions.

20. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Joe Palmer
Hello, all, I am new here. I would like to respond to the discussion about electrical cabinet capacity. I have been in the multifamily industry for nearly 40 years, and have a lot of experience with electrical circuits. This topic is a difficult one to grasp at times. The ampacity of the cabinet in question (or any cabinet, for that matter) is the rated ampacity for the main disconnect. In this case the disconnect is rated at 60 amps. This means that this cabinet has an ampacity of 60 amps. The "legs" (more correctly, "poles") are not additive. If one would employ a clamp-style ammeter, clamp around both poles (service drop conductors), one would see a reading on the ammeter of zero amps if both poles were utilizing 60 amps of current simultaneously. If one pole is using more current (for example, a 120 volt lighting circuit is being utilized in addition to a 240 volt HVAC system), the ammeter would display the current difference ONLY. I wrestled with this concept until I performed the action I described by clamping my digital ammeter around the main conductors in a service panel just to see the outcome. VOILA! My Four Rules for Living: #1- Don't panic (thanks Mr. Adams); #2 - Pay attention; #3 - Learn something every day; #4 - When all else fails, read the directions.

Hi Joe, Welcome to this forum. You will find lots of useful information here. I look forward to seeing you post more often. I might add that all threads are not like this one. Another qualified electrical guy like yourself is needed. You just have to be willing to sort out the BS and Bullying from the real information.

21. Re: Determining the amperage mat a main disconnect fuse block

If you insert one double pole 60 amp breaker and put a 60 amp load on it, you've maxed out the available amount of current on both legs and any more breakers whether it be single or double pole will blow a fuse. The amperage available, determined by the amperage of the fuses, is based on 240 volts, not 120 volts. If you exceed 60 amps at 120 volts on either leg, you will blow a fuse, If you exceed 60 amps at 240 volts, you will blow fuses. this is why its a 60 amp panel.[/QUOTE]

I wanted to quote this and clear it up - The difference between a double (or three breaker) and fuse cartridges is that the breaker [more than one pole] is tied to the other so if one leg exceeds the rating all poles trip - this is done to keep the load somewhat balanced between the hot legs.

You can draw 60 amps (using this example) off of each leg - so to make this more of a mess let's talk about industrial loads "Three Phase Power" In this situation you have three hot legs and each leg is 120 degree out of phase with each other, Sometimes you have a neutral and sometimes you do not. However Now you have three fuses rated at 60 amps (remember amps are amps no matter what the voltage is they are still amps) the rating of the service would be 60 amps because that is the most you can draw through a hot leg.

The return get's a little confusing in 120 v circuits when we start looking at the load of the neutral because the neutral is often tied to the ground and in a home the neutral coming off the street is earth grounded at the transformer with a grounding rod , just like in a house (often tied to a water pipe) so if you could isolate the neutral and the ground and actually measure it where you are drawing your power - you would actually have two current reading (I know what the code says about grounds not being load carrying conductors) and these two readings (done at the same time with two meters) would add up to 120 amps - if you were to draw 60 amps from each leg.

On a side note I have found this thread to be most amusing and really , stop pulling my leg.

22. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Dwight Doane
I wanted to quote this and clear it up - The difference between a double (or three breaker) and fuse cartridges is that the breaker [more than one pole] is tied to the other so if one leg exceeds the rating all poles trip - this is done to keep the load somewhat balanced between the hot legs. I will just leave this at "NO".

The return get's a little confusing in 120 v circuits when we start looking at the load of the neutral because the neutral is often tied to the ground and in a home the neutral coming off the street is earth grounded at the transformer with a grounding rod , just like in a house (often tied to a water pipe) so if you could isolate the neutral and the ground and actually measure it where you are drawing your power - you would actually have two current reading (I know what the code says about grounds not being load carrying conductors) and these two readings (done at the same time with two meters) would add up to 120 amps - if you were to draw 60 amps from each leg I will leave this with "only your wildest dreams with bad math, back to the drawing board."

On a side note I have found this thread to be most amusing and really , stop pulling my leg.
Pulling your leg about what? I have found it amazing what people believe and what actually can happen with electricity.

Thanks for posting--I will let Vern pick up from here.

23. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Joe Palmer
Hello, all, I am new here. I would like to respond to the discussion about electrical cabinet capacity. I have been in the multifamily industry for nearly 40 years, and have a lot of experience with electrical circuits. This topic is a difficult one to grasp at times. The ampacity of the cabinet in question (or any cabinet, for that matter) is the rated ampacity for the main disconnect. In this case the disconnect is rated at 60 amps. This means that this cabinet has an ampacity of 60 amps. The "legs" (more correctly, "poles") are not additive. If one would employ a clamp-style ammeter, clamp around both poles (service drop conductors), one would see a reading on the ammeter of zero amps if both poles were utilizing 60 amps of current simultaneously. If one pole is using more current (for example, a 120 volt lighting circuit is being utilized in addition to a 240 volt HVAC system), the ammeter would display the current difference ONLY. I wrestled with this concept until I performed the action I described by clamping my digital ammeter around the main conductors in a service panel just to see the outcome. VOILA! My Four Rules for Living: #1- Don't panic (thanks Mr. Adams); #2 - Pay attention; #3 - Learn something every day; #4 - When all else fails, read the directions.

You do not clamp around both conductors at the same time.

24. Re: Determining the amperage mat a main disconnect fuse block

Hey Dwight, Use this diagram to show us what you are thinking..

GRD&BOND.JPG

25. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Jim Port
You do not clamp around both conductors at the same time.

Really? I think Joe is on the right track. Why?? what would happen? I would say he would get some good information (scientific and all)...

26. Re: Determining the amperage mat a main disconnect fuse block

Why don't you share some more of your knowledge? I would have thought with all that experience you would know how to use a clamp on ampmeter.

I know the reading will be useless, even on a single pole circuit.

27. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Jim Port
Why don't you share some more of your knowledge? I would have thought with all that experience you would know how to use a clamp on ampmeter.

I know the reading will be useless, even on a single pole circuit.

Jim, Robert, Jerry Peck, and HG all answer questions and promote them selves as "experts". The difference comes when someone disagrees with them. They then spin the question, redirect the issue, try to send you off to check with "someone that knows", accuse you of costing some innocent group money, say you can't even answer simple questions and are spreading misinformation. And call you a TROLL. And often they resort to insults and directly questioning whether you know anything about the subject. ..and add to that--They have checked with their buddy's and they agree with them.

This sure sounds a lot like BULLYING to me!

You really do need to give it up.

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Originally Posted by Jim Port
Why don't you share some more of your knowledge? I would have thought with all that experience you would know how to use a clamp on ampmeter.

I know the reading will be useless, even on a single pole circuit.

Putting a clamp-on ammeter around the hot and neutral of a single pole? circuit will tell you if there are neutral to neutral faults in the circuit. If it reads anything except 0 amps the neutral current is going somewhere else. This creates, rather than cancels electric fields..

28. Re: Determining the amperage mat a main disconnect fuse block

I will add that a small portion of the population is physically sensitive to stray electric fields. They make them physically ill. They solve it by having all the neutral to neutral faults corrected and installing a special isolation transformer (scared yet?) to supply their residences. Not to mention stray electric fields have a direct interference to sensitive electronic equipment..

29. Re: Determining the amperage mat a main disconnect fuse block

That method would not tell you the load on the panel which was the subject under discussion. We were not looking for neutral to neutral faults.

30. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Jim Port
That method would not tell you the load on the panel which was the subject under discussion. We were not looking for neutral to neutral faults.
I was just addressing the questions you raised, or did you forget?

31. Re: Determining the amperage mat a main disconnect fuse block

Of course, Mr.Port, I am well-versed in the use of clamp ammeters, having owned both analogue and digital flavors (one of the first on the market, the A.W. Sperry Digisnap 1000, ca. 1982). I used them mostly to test the three-pole 300 amp contactors on the electric water heaters at the multifamily communities where I supervised the HVAC/plumbing crews. My present digital ammeter is bluetooth-enabled so that the meter can drop data into my laptop regarding voltage/current/temperature over time. I also use it to test start and run capacitors in HVAC systems. My intent was to illustrate that a simultaneous 60 amp load ON BOTH POLES OF THE SERVICE DROP does not constitute a 120 amp panel. The question has been answered many times here. The cabinet is a 60 amp panel. By the bye, the reading on a single-pole circuit would be 60 amps if there is a 60 amp load; your logic is erroneous, as one would be using the meter correcly, having clamped only one conductor, as is required for ampacity measurement.

32. Re: Determining the amperage mat a main disconnect fuse block

I read it as you were testing the load by clamping both conductors, not one. Sorry for the confusion.

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I read it as you were testing the load by clamping both conductors, not one. Sorry for the confusion.

33. Re: Determining the amperage mat a main disconnect fuse block

Well here we are at over 250 posts and Judge Judy is about to reign down her wrath. Before I am sent off to the hall I would like to apologize for loosing my cool to all of my friends on IN, including and most importantly to Jim and Robert.

I truly was just trying to help people understand what was happening inside the 3-wire circuit. It does not really matter if you understand it fully to be able to size breakers and wiring, using ohms law formulas. Knowing the maximum current that can be on each leg, you will come up with the correct answers, and the maximum current will be the breaker size.

Where the most problems came from in this thread was from the terms used. Jim and Robert used the term "amp load" throughout the discussion. Amp load is typically reserved for electric motor and battery loads. In this discussion the term "amp load" was used synonymously with "watts or power". The original question was directed at "current" which is only one part of the formula to find power.

The 3-wire circuit, as in all circuits, is a continuous loop. A good analogy of the loop would be that of the lazy river that is found in many amusement parks. All of the water leaves the pump and sends inner tubers down the river, some of the tubers may take a short-cut back to the pump station, because there is a traffic jamb on the return leg (less load or more resistance), but they are using just some of the same current that is taking the rest of the tubers the long way around. When the traffic (load) is the same on both legs of the river, no tubes take the short-cut (neutral) but return to the pump via the main return leg. We can get the current to do more work "power" by adding more tubers (loads) but it requires more current. The total current is still in a loop so whether we split it at the short-cut or not is irrelevant. The total current leaving the pump must equal the current returning to the pump.

I hope this has helped someone, and will now go take my beating for prolonging this thread.

34. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Vern Heiler
Before I am sent off to the hall I would like to apologize for loosing my cool to all of my friends on IN, including and most importantly to Jim and Robert.
I think you can quite holding your breath on this one.

35. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Rick Cantrell
I'm not about to choose a side, but you guys are to be commended.
Nearly 100 post on this and no name calling, slanders, or put downs.

You know Rick, I too noticed the same thing , no name call, no back stabbing , no cheap shots below the belt

There is something just Un American about the whole thing - it disgusts me

Actually , I am really proud to see people acting in a professional way trying to help someone understand a difficult concept.

36. Re: Determining the amperage mat a main disconnect fuse block

I may not have seen the answer I was looking for in the volume of posts written here, but the size of an electric service is determined by the lowest rating of the following three things: rating of the service conductors, manufacturer's rating of the equipment, and the rating of the over current device(s).

The size of the over current device is determined by the maximum size of load per hot leg. All other things equal, a 60 AMP fuse would limit a service size to a "60 AMP service". Two hot legs with 60 AMP fuses do not make a 120 AMP service any more than 3 of them make a 180 AMP service. Service size refers to the maximum size of an individual connected load. On a 60 AMP single phase service you can hook up a 240 volt 60 AMP load or two 120 volt 60 AMP loads. You can't hook up a single 120 volt 120 AMP load - ergo you have a 60 AMP service.

The maximum capacity of the service will be determined by the total wattage allowed by the voltage and overload size.

37. Re: Determining the amperage mat a main disconnect fuse block

As I know the correct answer for the previous thread, let me ask a question. How can a MWBC using # 12 wire for all of the conductors be allowed to be supplied by 20 amp breakers if the potential current on the grounded conductor is 40 amps? Is such an installation cited as non- compliant?

Last edited by Brad Richter; 09-04-2013 at 07:24 PM.

38. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Brad Richter
As I know the correct answer for the previous thread, let me ask a question. How can a MWBC using # 12 wire for all of the conductors be allowed to be supplied by 20 amp breakers if the potential current on the ungrounded conductor is 40 amps? Is such an installation cited as non- compliant?
Please read 254 posts

39. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Vern Heiler
Please read 254 posts
I did read the posts. Can you answer the question or not? You're hurting your head.

40. Re: Determining the amperage mat a main disconnect fuse block

A properly wired MWBC will have the two hots on opposite legs of the panel. The neutral will carry the difference, not the sum of the hots.

41. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Jim Port
A properly wired MWBC will have the two hots on opposite legs of the panel. The neutral will carry the difference, not the sum of the hots.
Thanks , Jim, I know the answer. Just posted the question to get answers from the inspectors that seem confused.

42. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Jim Port
A properly wired MWBC will have the two hots on opposite legs of the panel. The neutral will carry the difference, not the sum of the hots.

And so according to Jim you would need a 40 amp panel to support this 20 amp load. If you were to read the other posts.

Oh and thanks for agreeing with Vern and I for the 7th time.

43. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Roland Miller
And so according to Jim you would need a 40 amp panel to support this 20 amp load. If you were to read the other posts.

Oh and thanks for agreeing with Vern and I for the 7th time.
That in no way is what Jim has been posting.

44. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Vern Heiler
Please read 254 posts
I can certainly understand you probably had some difficulty following all these posts. Or you didn't take Vern's advice. Jim will try to tell you this configuration has 40 amps of capacity. It doesn't.

At least in regards to the original question.

45. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Roland Miller
I can certainly understand you probably had some difficulty following all these posts. Or you didn't take Vern's advice. Jim will try to tell you this configuration has 40 amps of capacity. It doesn't.

At least in regards to the original question.
Sorry, Jim is correct. 20 amps on each leg @ 120 volts.

46. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Jim Port
Ignore the transformer and focus on 2 60 amp single pole circuits. Each can flow 60 amps. You say you can understand the math, but cannot accept that 60 x 2 = 120?
Why does he say this over and over again in regards to the orginal post??

 U.S. Illiteracy Statistics Data Percent of U.S. adults who can’t read 14 % Number of U.S. adults who can’t read 32 Million Percent of U.S. adults who read below a 5th grade level 21 % Percent of prison inmates who can’t read 63 % Percent of high school graduates who can’t read 19 %

47. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Roland Miller
Why does he say this over and over again in regards to the orginal post??

 U.S. Illiteracy Statistics Data Percent of U.S. adults who can’t read 14 % Number of U.S. adults who can’t read 32 Million Percent of U.S. adults who read below a 5th grade level 21 % Percent of prison inmates who can’t read 63 % Percent of high school graduates who can’t read 19 %
Makes else to me and to most other electricians as well.

48. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Brad Richter
Makes else to me and to most other electricians as well.

I see I have made my point--

49. Re: Determining the amperage mat a main disconnect fuse block

Nice Try.

John Kogel
Member

Join DateFeb 2009LocationSouthern Vancouver IslandPosts3,603
Re: Square D panel

It appears to be a split bus panel with the 50 amp breaker protecting the lower half. But this reply will bump your thread ahead of that other one which has bored most of us for 3 weeks, so hopefully you will get your answer today.

50. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Brad Richter
That in no way is what Jim has been posting.
Thanks Brad.

Roland, I keep saying the same thing because it is the truth. Check Bill M's recent post. He can understand the issue also and agrees with Robert, myself, Brad and other's. You can't change the truth. Sorry you still don't understand.

51. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Jim Port
Thanks Brad.

Roland, I keep saying the same thing because it is the truth. Check Bill M's recent post. He can understand the issue also and agrees with Robert, myself, Brad and other's. You can't change the truth. Sorry you still don't understand.
You keeping saying the same thing trying to make it true, when it isn't. You can't dispute the math and science not matter how many times you say it. Vern as well as myself can prove our position, you can only state yours. You have a growing following though---3 or 4 now..

52. Re: Determining the amperage mat a main disconnect fuse block

Others have also explained numerous times the error of your understanding of the issue. It is such a shame that someone of your professed experience cannot grasp this simple concept.

53. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Robert Meier
I think that we should send a link to these generator manufacturers so that they can all fire their engineers for getting the generator output wrong:

Honda EB10000 Portable Industrial 10000 Watt Generator

 Order Model Voltage Hz Rated amps3 LPV fuel Rated amps3 NG fuel Circuit Breaker Cold weather equipped Certification 20GSBC-6727B 120/240 60 154/77 140/70

Cummins Onan

DuroMax RV Grade 4400 Watt 7.0 Hp Gas Generator w/ Electric Start & Wheel Kit
They would just call us idiots for thinking a generator was a 3 wire circuit!

54. Re: Determining the amperage at a main disconnect fuse block

Originally Posted by Scott Bray
I inspected an apartment in a building with 200 apartment units, The main disconnect for the sub panel of the apartment is located at the electrical meter in the basement of the building. There are two 60 amp cartridge type fuses in a fuse block as the disconnect. I stated that it was a 60 amp service and the building supervisor stated no it is a 120 amp service because you combine the two legs of the service. I am confusing my self, I always thought you rated the disconnect by the weakest link, which would be the 60 amp fuse. Which is correct, is it a 60 amp service or 120 amp service ? Thanks in advance.
Just so it is clear. The answer is a 60 amp service. The two legs are not added to give the capacity of the service. And when installed according to the NEC there will not be more then 60 amps present at any point in the circuit.

I see Jim has started with his bullying tactics. That's a real shame that you cannot rise above your mistake and your ego.

- - - Updated - - -

Originally Posted by Jim Port
Others have also explained numerous times the error of your understanding of the issue. It is such a shame that someone of your professed experience cannot grasp this simple concept.

Jim, Robert, Jerry Peck, and HG all answer questions and promote them selves as "experts". The difference comes when someone disagrees with them. They then spin the question, redirect the issue, try to send you off to check with "someone that knows", accuse you of costing some innocent group money, say you can't even answer simple questions and are spreading misinformation. And call you a TROLL. And often they resort to insults and directly questioning whether you know anything about the subject. ..and add to that--They have checked with their buddy's and they agree with them.

This sure sounds a lot like BULLYING to me!

Jim, you have agreed with me 7 times now but insist your statement is true. What's up with that?

55. Re: Determining the amperage mat a main disconnect fuse block

Roland, obviously I do not agree with you since I have said from somewhere on page 1 that the panel has a capacity of 120 amps at 120 or 60 amps at 240. I simply corrected your statement about the capacity per leg. You keep saying the limit is 60 amps regardless of voltage. It seems from the post from Robert concerning generator capacities that the engineers for those companies too agree with me. There never was an issue with the correct size of the service.

I again will invite your to post the same question as asked by the OP on an electrical forum and post a link to it. Since you have refused multiple times I will assume you do not want to submit yourself to ridicule and further embarassment.

Speaking the truth and refusing to waver is not a matter of ego. Simply because you do not like the answer does not make it wrong.

And once again you accuse me of being the bully when the true issue is your inability to understand a simple issue. I never posted literacy figures trying to infer anyone's lack of knowledge.

56. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Jim Port
Roland, obviously I do not agree with you since I have said from somewhere on page 1 that the panel has a capacity of 120 amps at 120 or 60 amps at 240. I simply corrected your statement about the capacity per leg. You keep saying the limit is 60 amps regardless of voltage. It seems from the post from Robert concerning generator capacities that the engineers for those companies too agree with me. There never was an issue with the correct size of the service.

I again will invite your to post the same question as asked by the OP on an electrical forum and post a link to it. Since you have refused multiple times I will assume you do not want to submit yourself to ridicule and further embarassment.

Speaking the truth and refusing to waver is not a matter of ego. Simply because you do not like the answer does not make it wrong.

And once again you accuse me of being the bully when the true issue is your inability to understand a simple issue. I never posted literacy figures trying to infer anyone's lack of knowledge.
I see you don't understand how a 240/120 volt generator is wired. I can certainly understand why you are confused about the connection of a single phase transformer. Again apples and oranges--will it never end? Or do you like fruit salad?

I still don't understand why you keep agreeing with me in between your insults?

The 60 amps you speak of is not +60 and +60 . You get your answer only with a math error. If one truly understands the math and the concept it develops what is known as adaptive reasoning. That is where you take what you know is correct problem solving and apply it to more complex problems and still come up with the correct answer.

Just a funny note though: I just watched a video of a teacher explaining to a PTA group why 3 X 4 = 11 is a correct answer under the new common core math model the President is driving. No wonder our economy and everything else is slipping into the dark pit...It was funny. I see you have already taken that course.

Last edited by Roland Miller; 09-07-2013 at 06:23 AM.

57. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Roland Miller
I still don't understand why you keep agreeing with me in between your insults?
You say I am wrong but you say I keep agreeing with you?

Just a funny note though: I just watched a video of a teacher explaining to a PTA group why 3 X 4 = 11 is a correct answer under the new common core math model the President is driving. No wonder our economy and everything else is slipping into the dark pit...It was funny. I see you have already taken that course.
Ironic that you say this since you clearly cannot get the correct answer from this:

The 60 amps you speak of is not +60 and +60 . You get your answer only with a math error. If one truly understands the math and the concept it develops what is known as adaptive reasoning. That is where you take what you know is correct problem solving and apply it to more complex problems and still come up with the correct answer.
You have stated numerous times that 60 + 60 = 60. I doubt that even a first grader would agree.

Perhaps you can explain the generator ratings posted by Robert above and tell us why the voltage ratings change the ampacities? Surely not all the engineers are wrong.

58. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Roland Miller
. You have a growing following though---3 or 4 now..
Thanks for noticing. Meanwhile your team still only has two players, and I am not so sure Vern is still on your team.

Funny how even those late to the game agree with me isn't it? You haven't managed to confuse them either.

59. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Jim Port
Thanks for noticing. Meanwhile your team still only has two players, and I am not so sure Vern is still on your team.

Funny how even those late to the game agree with me isn't it? You haven't managed to confuse them either.
You would be surprised at the PM's in my message box!

Originally Posted by Robert Meier
I think that we should send a link to these generator manufacturers so that they can all fire their engineers for getting the generator output wrong:
Or better still, we could tell G.E. and all the rest of the panel manufactures that they have been under selling there product as they only have a code for one current ratting per panel.

I have edited my analogy from post 251 to try and make it as clear as I can.

The 3-wire circuit, as in all circuits, is a continuous loop. A good analogy of the loop would be that of the lazy river that is found in many amusement parks. All of the water leaves the pump and sends inner tubers down the river, some of the tubers may take a short-cut back to the pump station, because there is a traffic jamb on the return leg (less load or more resistance), but they are using just some of the same current that is taking the rest of the tubers the long way around. When the traffic (load) is the same on both legs of the river, no tubes take the short-cut (neutral) but return to the pump via the main return leg. The same current that took the tubers down one leg will take them up the other. The total current is still in a loop so whether we split it at the short-cut or not is irrelevant. The total current leaving the pump must equal the current returning to the pump. We can measure the current on the down leg (A) and again on the up leg (B). As a matter of fact we could measure current at several more locations but it is all the same, or portion of the same, current that left the pump. The number of measurements taken are not additive.

As I said before in 251, we can use the current in each of the legs to calculate power using 120 volts and come up with the correct answer. But if you do not understand the "lazy river" then you do not understand the circuit.

I hope we can all agree and put this one to bed.

60. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Jim Port
You say I am wrong but you say I keep agreeing with you?

Ironic that you say this since you clearly cannot get the correct answer from this:

You have stated numerous times that 60 + 60 = 60. I doubt that even a first grader would agree.

Perhaps you can explain the generator ratings posted by Robert above and tell us why the voltage ratings change the ampacities? Surely not all the engineers are wrong.
I have posted this information before. Did you forget or just not read it? I am sorry you don't understand the generator wiring and make ignorant statements such as you did. Every major published textbook on AC/DC theory, electrical engineer, physicist and math professional as well as 100's of years of science are on my side and would agree with the math as I have stated it. I don't need any more on my team...

61. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Jim Port
Thanks for noticing. Meanwhile your team still only has two players, and I am not so sure Vern is still on your team.Funny how even those late to the game agree with me isn't it? You haven't managed to confuse them either.
You cannot add the rms AC Amperage limitation capacity of the two fused conductors and claim that the amperage capacity has doubled!

Each of these two "hot" conductors are SINGULARLY FUSED each in-line or series at the origination of the 3-wire (with or without ground) occupancy "mains" power feeder.

The rate (speed, accelaration, change of direction) of electron transfer as RMS'd does not increase. The ONLY thing that can increase (or decrease) is the RMS Voltage at max (amperage) capacity. The legs are not going to magically increase (for very long before the fuse opens - and for that matter the companion fuse) the number of electrons passed in a single second (60 cycles) or a tenth of a second (six cycles) to RMS 120 amps as long as functioning fuses and correctly rated (temp, voltage, type, etc.) are in place singularly in series with nothing but simple resistance loads and no induct. generator or other load-side.

There is NO WAY a simple properly wired/configured 120/240 Volts RMS AC split (center-tapped) single phase 3-wire FEEDER with fused on both hots with 60 amp fuses can be in any way confused to have a 120 Amp RMS capacity. (without some transformtation, inversion, generation, induction, introduction of of, etc. load side of same!)

120/240 = 1/2 = 180/360. 120 Vrms AC - ( - 120 Vrms AC) = 120 Vrms AC + 120 Vrms AC = 2(120 Vrms AC)V(A) = VA = V x A(V rms AC) x (A rms AC) = VA{120/240 V rms AC (that's a fraction - which is the product of 240V rms AC center tapped) V rms AC} x (60 A rms AC) = the Volt-Amps rms AC available (not really, there are a host of more complicated mathmetical functions to consider).

For both legs (2): (at the voltage side of the compound equasion) multiplies same (front end) by 2 (in the form of 2/1 actually). That function occurs to the modification of the Voltage factor BEFORE multiplying the voltage factor by the Amperage factor to determine approximate VA rms.

You can remember the "order" of the equasion by remembering (1) it is the voltage factor which has changed in your application and (2) the Intensity (amperage) for each conductor remains LIMITED by the FUSE present (in-line, in-series) in each conductor AHEAD of the Load. Finally, there is a reason we refer to the product as Volt-Amps, not Amp-Volts.

Remember, each conductor is FUSED at 60 amps, Line-side of the FEEDER. There is no CB.

Little of this five-page discussion has been on-topic of the OP.

The capacity is current-limited to 60 amps rms regardless of the voltage (as long as the fuse is capable of functioning properly in the presence of what ever voltage the conductors/feeder circuit is exposed to). Generally that would be approx 50 - 600 Vrms AC for the type of fuse commonly employed for a strictly residential occupancy, strictly single-phase; however we do not know the age, vintage, nor the SERVICE arrangement for the OP's TWO-HUNDRED-UNIT Apartment Building and Unknown building requirements as well as unknown other (mixed) occupancies.

{2 ( 120/240 V ) } x (60 A) = VA That's the same whether there are all 120V loads, all 120/240 loads, all 240V loads, or a mix of loads; its STILL JUST 60 A.

Finally when you "minus a minus" the "minuses" cancel out, the result is a function of positive values.

AC both voltage and Intensity are alternating. acceleration and deceleration in AC sinusodal.

Intentionally avoided peak and peak-to-peak as this would only further distract and confuse the majority (as well as a host of other issues), K.I.S.S. and kept it at elementary (4th-grade) mathmatics and 5th-grade Physics.

The limited capacity of the OP's question is sixty (60) amps based ONLY on the OP's information (limited) regrding the presence of the fuses. Whether or not the fuses are correctly determined, the unknown ambient conditions of the "room" hosting the fuses, the resistance, if the conductors run nything other than perfectly straight, the temperture rating and condition of the conductors (and insulation), ratings and conditions of contacts, and a host of other considertions, we cannot say.P.S. the likelyhood of the OP's 200-apartment-building's singular apartment's feeder supply being 120/240 VAC single-phase is SLIM.

Last edited by H.G. Watson, Sr.; 09-08-2013 at 10:47 AM. Reason: lost every dang paragraph. hopefully inserted enough carriage returns to make it readable. that auto save feature of the forum glitches!

62. Re: Determining the amperage mat a main disconnect fuse block

Nice Mr. Watson!! I was about to float Jim's rubber duckies down Vern's lazy river.

63. Re: Determining the amperage mat a main disconnect fuse block

I see Watson can't add 7200 + 7200 and come up with 14400 either.

64. Re: Determining the amperage mat a main disconnect fuse block

Originally Posted by Jim Port
I see Watson can't add 7200 + 7200 and come up with 14400 either.

I am calling you for a "FOUL". Apples and oranges again.

65. Re: Determining the amperage mat a main disconnect fuse block

I will leave you to wallow in your confusion. Professionals that work in the trade every day along with engineers for the generator companies have explained ad infinitum why you are wrong. Please stay away from the edges of the earth. I wouldn't want you to fall off.

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