I am not to familiar with residential wiring and I have a question about sub panel problem. I have a 200 amp main panel with a 125 amp sub panel. There is a 60 amp feeder from the main for the sub. My problem is I am getting an unbalanced loading problem. I tried balancing the load between the 2 phases and it worked for a while but its still tripping the 60 amp breaker, I replaced the breaker but still same problem. I am getting 63 amps on 1 phase and 47 on the 2 phase after I balanced it a couple of months ago. Can anyone lead me in a direction to look? Thanks

With the load you have, you need to take 8 amps off phase 1 and add to phase 2, and this will give you 55 amps per phase. Sounds as if you already know how to shift some load from phase 1 to 2, by measuring each branch circuit to find one with the right amount of load to move.


You have larger problems than unbalanced load.

A 60 amp feeder can only be loaded 80 % of the circuits rating, which is 48 amps. The load you currently have , if balanced, is 55 amps per phase, exceeds the allowable load of 48 amps. Even if you are able to balance the load, which is difficult as current changes in each circuit , you are overloaded on the subpanel feeder.

When I balanced the load last time it seemed to balance at around 42 amps with everything on in the house.With the same process done this time it seems that the current is higher than normal. Is it possible that their be a bad buss or a bad breaker the sub-panel?

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Originally Posted by then42

When I balanced the load last time it seemed to balance at around 42 amps with everything on in the house.With the same process done this time it seems that the current is higher than normal. Is it possible that their be a bad buss or a bad breaker the sub-panel?

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Did you pull 4 wires to the sub panel? 2 hot legs, neutral and a equiptment ground. If not I have seen this problem before.

It has #4 two hots neutral and ground.

The breaker is tripping due to overloaded amps, as stated measuring 63 amps on a 60 amp breaker, and that should not be loaded more tha 48 amps. Clearly something is a different or new load on the circuits causing the amp draw to be that high.
Can you tell me exactly how you balanced the load once before?

Well I swapped #1 & #3 and #5 &#7 circuits at the panel and seemed to work for a while.Their isn't anything new added to the panel.Could a loose connection cause higher amp draw?

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Originally Posted by then42

well I swapped #1 & #3 and #5 &#7 circuits at the panel and seemed to work for a while.Their isn't anything new added to the panel.Could a loose connection cause higher amp draw?

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A loose wire or bad connection could cause a problem but I am sure it would have over heated and be discolored by now.

A loose connection close to or on the circuit breaker will cause heat that will activate the breaker to open , since the circuit breaker is a thermal device.

A loose connection will not draw as much amps as you have over your original amp load.There must be something in the circuits that has changed or added. There may be larger wattage lamps installed, a different season cauisng heat to be on longer, and actually can indicate a two element water heater that only one heater is supposed to be on.

If you can take the time, measure each circuit amps, get back with a list of breakers, label, and amp draw and we can go further from there

I appreciate the advice, I will keep on searching for the problem. Thanks again!

If the main panel is 200 amp & the sub is rated at 125amp. He has a 60 amp breaker to the sub, can he replace the 60 amp sub feed w/ a 100amp breaker and proper sized wire?

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Originally Posted by skiberger

If the main panel is 200 amp & the sub is rated at 125amp. He has a 60 amp breaker to the sub, can he replace the 60 amp sub feed w/ a 100amp breaker and proper sized wire?

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Sounded to me that, he has a dual-pole breaker, 60AMP each, connected
To each side of the bus bar. i.e. each bus bar supplying 60AMP,
Which is total of 120AMP. The sub-panel is rated at 125AM, which is
In the correct ratings for his usage.

If my assumptions was correct, and he is supplying the subpanel
With 120AMP, then the question is what circuit be on which side
Of bus bar to balance the load. As I am thinking about this,
It can be very tricky to balance such a thing for a long term
If load on circuits changes often, which can be possible.

To understand this load balancing better, does anyone know on a
200AMP, which is 100AMP on each bus bar main panel, how does
The load work if one to use over 100AMP on one side of bus bar?
The town does not have a breaker on the line coming to the main service panel,
So there is no chance of tripping it. So can it be over heating the
Main 100AMP line coming to the house, and can it have voltage/AMP
Drop? How does this really work?
-Mike

The 60 amp 2 pole breaker supplies 60 amps per leg, not your assumed 120 amps. A 200 amp panel is 200 amps per each leg. Your 200 amp panel should have a 200 amp breaker.

What do you have so we can go from there?

Be careful swapping circuits around, 2 circuits sharing 1 Neutral, Need to be on opposite phases, or neutral can overload on those 2 circuits. Sounds like you have an Amprobe. No balancing needed on 240 Volt items. 100 Amp Breaker is a good solution.

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Originally Posted by tkrussell

The 60 amp 2 pole breaker supplies 60 amps per leg, not your assumed 120 amps. A 200 amp panel is 200 amps per each leg. Your 200 amp panel should have a 200 amp breaker.

What do you have so we can go from there?

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Seems like, I was not very clear on explaining my assumptions, or I do not
Seems to understand all the electrical terms.
I have a 200AMP main panel in our house. It's a Square D box with 30 breakers.
I was thinking of putting in a 50amp or a 60amp 2 pole breakers into the
Main panel, and then install a brand new 125amp subpanel, just like what was
Described on this forum. After I saw the problems that the person in this
Article had with load balancing, I started thinking that, maybe I do not
Quite understand the job at hand.

So, are you saying that, two 60amp in a 2 pole breaker inside main panel is only supplying
A total of 60 amp to the subpanel? That doesn't make sense to my electrical engineering
Background. But then again, I wasn't into the power-system branch of the degree.
I thought that each bus bar in the subpanel would supply 60amp. Isn't this incorrect?
Having said that, when I talk about 120amps total, I meant that, if you
Have left and right side bus bar in a subpanel, then the breakers on the left bus bar
Should get 60amp max. and the breakers on the right side should get 60amp max.
In other words, I should be able to buy a 60amp breaker and put it on the left side,
And buy another 60amp breaker and put it on the right side, therefore load balancing
Circuits that would be drawing a total of 120amp * 80% (safe capacity).

By legs term, are you talking about left or right bus bar? So are you saying,
In a 200Amp main panel, each bus bar is capable of supplying 200AMPs?
This is an important question to me, which I did not think that way if
I understand you correctly. In my main panel, I have 2 heavy black cable
(about 1/2 inch thick), and one same since cable with white tape (neutual).
Your answer makes sense that, each of the black cable is supplying 200 AMPs.
And seems like you are saying, you cannot add them to make it 400AMPS,
Like in the case of subpanel, I said 60amp 2-pole is total of 120AMP.

So why is the subpanel rated at 125amps? Would a subpanel of 60 AMPS
Be sufficient? By the way, where is a good place to buy subpanels?

Back to the load balance question:
When I asked a knowledgeable someone about the load balancing problem
Listed in this article, their response was, they must be way over loading that
Subpanel. How is it possible to overload a sub-panel in residential settings?
Should I be worried about this, and not install a subpanel for my new basement
Play room, and new attic room (both to be built soon), and just go off the
Main panel. My reasons for needing a sub-panel was due to lack of empty
Slots in the main panel. I only have 2 slots free in my main panel.
Any recommendations for this?

Lastly by not least, I like to thank tkrussell for his expertise and his time.
Thanks
-Mike

OK,technically a two pole 60 amp breaker is providing 120 amps at 120 volts, but a standard panel is 240 volts with a center tap on the transformer that creates the 120 volts. All panels are rated using the 240 volts as a baseline, so to speak.

Even though, practically each leg can feed all 120 volt circuits, and you can draw 200 amps from each leg, for a total of 400 amps, we still consider this as a 200 amp panel, since each leg of the breaker and panel is rated 200 amps.

Using a 2 pole breaker automatically connects to both legs, to deliver 240 volts, if a neutral is run, then 120 volts can be pulled off each leg.

Do not use two single pole breakers toe deliver 120/240 volts, as you suggested. A 240 volt feeder must use a 2 pole breaker, so there is a common trip between both poles. If one leg shorts or is overloaded, the tripping of one leg will automatically trip the other leg.

Load balancing issues is rare in residential, thou possible. If I have a 240 volt 60 amp feeder to a panel, and that panel, by coincidence,can have 70 amp draw off one leg and 50 off the other, this is a load balancing issue. Each circuit needs to be measured to find one or two single pole circuits that could be moved from the leg with 70 amp total to the other leg. Any 240 volt circuits will be closely balanced already ,and nothing needs to be done, thou a 240 volt circuit can contribute to an unbalanced load.

A typical residential dryer uses a 5000 watt 240 volt heat element. At 240 volts this draws 20.8 amps on each leg. But if you were to measure each leg feeding a dryer you will notice one leg drawing more current. Where does the difference come from? The 120 volt drum motor, which may draw 4 amps only off one leg, and causes a minor load imbalance.

Nothing can be done about this, only if there are 120 volt circuits that draw high current can be relocated from one leg to another to balance the total load at the main. Here is where Strat's advice may be important. If a high current circuit needs to be relocated, and if it shares a neutral, it cannot be put on the same leg as the other circuit. All you could do is swap legs for each circuit.

Balancing will never be exact, just get as close as possible. And this is only for full 100% current draw. In actual usage, each circuit current draw varies minute to minute.

Manufacturers only make certain panelboards. There may be a 60 or 70 amp panel available but it will only be 2, 4, or 6 circuits at best. The minimum size service allowed is 100 amps, so most subpanels used will be 100 or 125 amps. A smaller rated feeder can feed a larger rated panel. If I use a 125 amp rated panel and feed it with a 60 amp feeder, the panel can only handle 60 amps, as being limited by the feeder.

Panelboards can be found at the large box hardware stores, for the general public, or at electrical distributors, which many are only wholesale for contractors only.

Do not hesitate to use a 2 pole 60 amp breaker in the two empty slots you have, run a 4 wire 60 amp feeder cable to the new panel for your addition.

In a commercial setting , a good designer will know the total load of each circuit, and show which leg each circuit will connect to , and will know the total load of each leg to avoid any possible load imbalance on the main.

Great answer tkrussell. Thank you.

The question originator in this forum talked about using 4 wires of #4 wire for the dual 60A breaker. But he
Didn't talk about what kind of wire he was using from his main to the sub.

When I went to the home center near us, they said, the biggest wire they have
In a romax form, is the 4 wires of #6 wire. I like romax wires. In romax form, all
Wires are in one package, properly color coded and it's all rated correctly for the
Temperature and usage.

By the way, if I install a sub panel, it would be one feet away from main panel.
So I don't mind spending a few extra dollars to buy #3 or #2 wire, i.e. if it fits the
Dual 60A breaker openings. So here is the question: if I need to buy individual wires,
And I need 4 of them, two for HOT, one for nautual, one for Ground, What should
I ask for? There are so much choices at the home centers, and their sales
Don't seem to have the knowledge to be of any help.

Also, I like using those solid (not flexible) galvanized metal conduit, one to 2 inches diameter ones,
Can I put those wires from the main to the sub, inside the metal conduit?
Would conduit present a heat issue when wires are included in a conduit?
Do electricians like using metal conduit whenever possible, or they want to
Avoid using it whenever possible?

Another question is on the main panel itself. How many BIG breakers can you
Have in your panel? I have a 30 breaker Square D main panel. On the right side
Of the panel, It has dual 50A for the stove, dual 40A for the Air-conditioner, dual 15A
For another AC unit, plus, bunch of 20A and 15A. Is there a limit on how many
20A, 50A, 60A, 15A, and dual 20A, dual 50A, dual 60A, dual 15A can be
Placed in a panel?
So far the biggest breaker in our main is 50A, would I be able to put in a 60A
Without any problems?
Remember that we have a 200A feed to the main. Does bus bar get rated
On how big of a breaker you can put in?
This main panel is just about 20 years old. I don't have any documentation
Or any technical specs for it. So I am not sure what this panel is capable of.
Is there a way to know what model number panel we have?
Thanks again for your time tkrussell.
-Mike

Since the sub panel is only a foot away, use a piece of conduit, can be PVC with threaded fittings and locknuts. Then use #6 THHN wire pulled through the conduit.

Metal and PVC conduit is very popular.

The amount and size of breakers in a panel is not the issue, it is based on the total connected load as calculated by the National Electric Code Article 220.

The only place you may find a model number is on a label pasted on the cover.

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Originally Posted by tkrussell

The amount and size of breakers in a panel is not the issue, it is based on the total connected load as calculated by the National Electric Code Article 220.

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This is the breakers in my main:

(Please Note: I placed "d" after the breaker amp rating to show it's dual breaker
i.e. A 240 volt feeder with 2 pole breaker, with a common trip between both poles,
Also, I placed breaker # in () )

Left right
(1) 30d (2) 50d

(3) 30d (4) 50d

(5) 20 (6) 20

(7) 20 (8) 20

(9) 20 (10) 20 GFCI

(11) 15 (12) 15

(13) 20 (14) 15

(15) 15 (16) 20 <--- Unused - Like to replace this with 60d for a new subpanel

(17) 15 (18) 20 <--- Unused - Like to replace this with 60d for a new subpanel

(19) 15 (20) 40d

(21) 15 (22) 40d

(23) 15 (24) 20

(25) 40d (26) 15d

(27) 40d (28) 15d

(29) 15 (30) 15


Heavy loads breakers are with 240/2 poles as follows:
1,3 - dryer
2,4 - Electric range
20,22 - Central Air-Conditioner 1st floor, inside & outside unit
25,27 - Central Air-Conditioner 2nd floor, outside unit
26,28 - Central Air-Conditioner 2nd floor, inside unit

Would the A 240 volt feeder 60AMP with 2 pole breaker, with a common trip between both poles be OK to use to feed a sub-panel?
Would I still be within limits of total connected load as calculated by the National Electric Code Article 220 ?
Thanks
-Mike

I need the total square foot of livable space, including a basement that can be finished, no garage, attic, porch. Type of heat. Hot water?