Just a curiuos question. If you replace an electric service panel, where the circuits aren’t fully labelled, or there is skepticism that the labeling is even correct to begin with, then what’s the best way of figuring out how to balance the load?
For example, I did a panel recently where none of the circuits were labelled. Once you rip out the old and put in the new it’s hard to remember which bar the circuits were on to reinstall them the same way, which even doing so is an assumption the old panel was balanced which cant’ necessarily be proven anyways, its’ an assumption.
In such a situation as this should you just hook up the circuits randomly, then put an amp meter around one leg of the SE conductor ahead of the lug it attaches to and read the amps and hopefully the two are fairly equal? But if that is a right way, the until everything is on you really wouldnt’ get an accurate measurement.
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For residential lighting circuits it generally doesn't make much difference. Even if you balance for current usage characteristics, it's likely to change in the future. Larger loads are generally 240V (inherently balanced), and the ones that aren't should be easy to identify.
I THINK I understand what you're saying. Except, what will happen if one leg is unbalanced, that is, you're pulling WAY too much on one leg vs. the other leg? Will the main trip? I wouldn't think so, but wouldn't it cause the one SE conductor feeding that leg to potentially overheat?
If either leg draws more than the main breaker rating* then it will trip, period. Does not matter what the other leg is doing.* Note- that for "small" overloads (less than 500%) the breakers have a time inverese curve. Commonly they might carry up to 20% overload continuesly, 50% for a minute or two, and quicker as the overload increases.About the only loads that you can attempt to balance for the 2 kitchen small applicance circuits, bathroom circuit(s) and washcing machine.Even if you balance it so that 1 small applicance was on one leg, and the other on the 2nd. Washer on 1, bath circuit on the 2nd, etc, it is still possible that the first small appliance circuit is fully loaded, the washer is running, along with an iron on that circuit, and someone runs a laser printer that is on htat first leg.2 hours later all of the loads might be on the 2nd leg.If you have any 20 amp breakers balance them up. That is as good as it gets.
So, in essence what you're saying is, it's really no use to try and load balance in residential electric panels. That is, even on one leg you're VERY unlikely to pull 200Amps, and if you did pull 200A on one leg, the main WOULD trip irregardless if its 200A one one leg or across both legs? Of course DP breakers are, as previously pointed, inheritly balanced, so no need to worry about them. The double kitchen circuits should just be put one on each leg as a matter of an intent to form some balance between the legs.
Thing is, even with all the lights on and your toaster and vacuum going, you're likely not pulling as much current as your air conditioner, not to mention electric stove, electric water heater, spa heater, or any other such large electric appliances. Generally about 30 amps of service will supply all the lighting/radio/TV/toaster type loads for a moderately-sized house, while your typical service is rated 100-200 amps.And if all the lights are on then they'll be balanced anyway. You'd have to get pretty lucky to have a major imbalance with lighting loads.About the only way you could get into trouble is if you have a half-dozen or more 120V (plug-in style) electric space heaters. If you managed to get all those on one side you could have a moderate imbalance.A "moderate imbalance" will cause increased "voltage drop", but even then there would be no untoward effects (with properly sized entrance wires) beyond lights getting a bit dimmer on one side, brighter on the other.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
Hmmmm, well all of this is good to know. I have to admit, I never gave it much thought. What made me conscious of it today was a thread I saw elsewhere where someone said something about an imbalance on a leg. So basically, the way I've been doing it should be fine, and indeed it must be, because of all the panels I've installed/replaced, never once had a problem in the slightest. But it's good to hear someone elses take on it.
You would want to be careful if you had several known large 120V loads (more likely in a commercial setting). But general residential lighting loads are low and unpredictable, and so long as they're randomly assigned slots then there's virtually no chance of an imbalance problem.Do be wary of accidentally introducing a pattern. For instance, if one were to wire one circuit for lights and a second for outlets, doing these two circuits for each room in a house, and then assign lights, outlets, lights, outlets ... to the breakers, you could introduce a pattern that would increase the chance of an imbalance.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
good point. Not sure I'd ever do such a thing as lights, outlets, lights, outlets, and so forth, given that I always maintain some degree of thought in balancing the load. Still, it's a heck of a good thought, because I could see it'd be easy to fall into a pattern like that if you're not being conscious of any load balancing at all.
I'm not an electrician, but I had my 200A elec panel replaced several years ago. We had several breakers that would blow when all the lights were on in one room and the vacuum cleaner was being used, for example. I split the load on these circuits and had more breakers added which solved the problem.
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Yeah, that's a different kind of "balancing" -- reducing the load on individual circuits by transferring parts of the load to other new or existing circuits.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
I know.
"Let's go to Memphis in the meantime, baby" - John Hiatt.
http://grantlogan.net/
When you're running residential loads off a poco feed, it would be damn difficult to create a significant balance problem. I did once have a generator operator ask me to re-balance when I made a mistake and got a couple 10kW lamps on the same side, with nothing but little stuff on the other. It caused some vibration.
-- J.S.