How do i know how many amps to send to my subpanel?



Remove all sub panel covers or doors.


Measure about 5 feet (1.5 m) from the floor to mark the spot where you will mount the panel. This is a good height that is within comfortable reach of most adults.


Remove the lowest amp rated double pole circuit breaker or 2 low rated single pole circuit breakers from the main panel to make room for the new double pole circuit breaker that will supply the new sub panel.

The 2 circuits you removed will need to be re-fed from the new sub panel. If the sub panel is the same brand, you might be able to reinstall the original circuit breakers in it to re-feed those 2 circuits.

If you have breakers terminal screws that are serving more than one conductor, called double-lugging; consider moving circuits to the sub panel so that none are double-lugged - or combine the them with a short length of the same size wire (called a "pigtail") in a wirenut and use the pigtail to feed them.



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I'm building a workshop at my house, sort of a big garage. Anyhow, when I talk to BGE, I want to know what I'm talking about. Currently, I have a 100amp breaker box in my home. I posted another thread here about the cost to upgrade the box. This thread is about how many amps I should be looking for.

Is a 200amp box good enough? Would I just run my shop off of a 50amp breaker from my main service panel?

What are the suggestions on how to power my shop? Common practices?


Oh, the shop will be a basic wood working shop. I'll have a window air conditioner - probably on its own breaker. I'll be heating it with a wood stove. Many receptacles to run tools like a planer, band saw, table saw, etc... As far as lighting, I will probably go with a low energy LED setup. Shop will likely be about...

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The guy is sharp - this is a very good way to design a multi-story building for future expansions and it will cut your installation labor considerably as well.

You could have a dozen 100A feeders coming out of a 200A main - not a problem. These 100A panels could in turn feed a dozen more 100A panels each, etc, etc.

The key things to consider are what loads are likely to be on at the same times on each floor.

You may want to color code the hot legs of each feeder so you can keep the whole buildings hot leg loads distributed evenly easier. Haphazardly plunking stuff into the 100A panels without considering leg could load one of the 200A legs up more than the other and cause a main trip before it really needed to occur if things were located a little different.

Might also consider taking a 200A feeder all the way to the 3rd floor and tapping it at each floor for main breaker panels. If future needs ever called for a lot of power on one floor, it'll always be there....

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Hello, all,

I'm getting ready to have an electrician put some 220V circuits in my
detached barn workshop. (I only have 110V right now.) I'm hoping I have
enough power running from the main panel in the house out to the
sub-panel in the barn to do what I want.

When my electrician came out to check and make sure I won't need
another/heavier wire between the house and the barn, he opened up the
sub-panel in the barn and said it looked like I have 100A service at
the subpanel in the barn.

(He said that he wanted to check at the main breaker panel in the house
to make sure 100A service was going to the barn, but he forgot to do

I just took a look in the main panel in the house, and it looks like
there is a dual pole breaker feeding the barn (I think that's the
proper term -- it's like two breakers side-by-side with the switches
connected) and each switch of this double-pole breaker is labeled...

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This week’s question comes from Rick H. in Iowa:

Question: How can I tell what the maximum supported amperage capacity is for your cables?


Thank you for the excellent question Rick! Understanding the voltage and current limits of your cable(s) is absolutely critical to maintaining a safe transfer of electrical power between your devices. All cables feature some degree of resistance to electrical energy.

When electricity is forced to flow up against this resistance, it releases energy into the environment in the form of heat. When cables are very thin, i.e. 30 AWG or smaller, the cabling cannot dissipate that heat energy into the environment fast enough, leading to a fundamental breakdown (failure).

The electrical breakdown of a cable assembly is not a pretty sight. During my younger years when my electronics expertise was in its infancy, I once made the horrible mistake of wiring a 12V DC switch incorrectly on a project box. The switch...

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Panel to Garage sub-panel. How many amps can my sub-panel hold? (You are not my electrician.) I will be hiring a licensed electrician, I’m just curious as to what to expect.

The main house electrical service panel is connected to a sub panel in a detached garage.

The circuit on the main panel feeding the garage has a two pole breaker labeled 30 amps.

The garage sub panel has a one 20 amp circuit and one 15 amp circuit. There is room on the panel to add two more circuits.

My questions are:

It is my understanding that the circuit to the garage can be either a single 240 volt or two 120 volt. Is my understanding correct?

If this is correct, how many amps can I add to the garage sub-panel if it’s single 240?


How many amps can I add to the garage sub-panel if it’s two 120?


If this is completely wrong, let me...

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Dude, that's a great idea but I just don't know how to do that Rock. How is it done?

ASSuming this is an honest question, to find your previous threads you could:

a) on the Main Forum (or any other forum) there are several pages of threads since people start lots of threads... anyway you will see:

Pages: [1] 2 3 ... 438

in the upper left area of this page. To go to page 2, you'd click on the 2, 3 for page three, and so on. You could look through these pages one by one until you found your old post, then just post a reply to it...

b) you could go to the very top of the web page where there are buttons for: home help search profile calendar and logout. Click the profile one - it will take you to your profile (where you could add a picture to your nickname FYI). On the left of your profile page you will see:

Profile Info
Show Stats
Show Posts

... click on the Show Posts. That will take you to a list of all the...

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Household NM-B Wires are color-coded so inspectors/ electricians can easily identify which wire is used during construction Check if breakers are warm
Put hand on each circuit breaker. Including main breaker. No shock hazard touching circuit breakers when box cover is in place.
Always stand on totally dry surface when touching anything electrical. For example stand on dry boards.
Breakers should not be warm.
Warm circuit breaker indicates problem
Make sure cover is put over main breaker box and that box door is kept closed to protect against spark and fire

What does warm circuit breaker mean? It means breaker is Overheating
1) Breaker is going bad
2) Breaker is not big enough to handle Load, so amp draw is larger than breaker.
3) Breaker has been getting warm over time and is loose on the busbar.
4) There are loose wires causing arcs and heating

Vacuum cleaner cord gets hot
Put hand on extension cords, and household...
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In this how to install a sub panel installation I will guide you through the complete installation of a subpanel step by step.

The first question is why are you installing a sub panel. There are either one or two reasons to do this. One because you need more room in your existing panel and in that case if your existing panel is old this would be a great time to just upgrade your current service. Newer 200 amp main panels hold a lot more circuits/breakers.

Two, because you need to bring more power somewhere else like a garage you just built or an addition or even in some cases a finished basement. Either way, you want to install a sub panel. Ok. So let’s get going.

First: Where do you plan on placing the new sub panel? If it’s right next to you main panel that’s one thing, but further away like in that new garage you just built 100 feet away you will certainly want to figure in voltage drop. I can’t get too much into that because ever setup would be...

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You can find various types of small distribution hubs several places, including at many Wal-Mart's in the automotive audio section. Or order them from the internet sources in this article. (Try look in section 57, Cat# PDB-175-SIX, about $29). To build a "home made" combiner I use a plastic outdoor junction box, which has a removable lid, with a gasket. It is easy to drill the appropriate sized holes in the sides for routing wires. Use weather-tight wire clamps. I like to use hubs that have at least four outputs (which you will use as inputs for the wires from the panels). You can usually double the wires up, if required. You need one hub for + and one for -, or you can buy a dual hub, which is the one shown. Position it in the box so you can tighten the set screws. Epoxy it into the box, when you are satisfied with the layout.

The alternative to building your own is to buy a simple ready-made combiner box from AM Solar. Check...

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Most RV Manufacturer's in North America offer UltraHeat® systems as either standard equipment or a stand-alone option. Some offer them as a part of a Four-Season package upgrade option. Many European Manufacturers of leisure vehicles also offer UltraHeat®, similarly branded as "TankBlanket™" in some Euro Markets. Before you purchase your New RV or Leisure Vehicle, ask your dealer if the holding tanks have either of these anti-icing brands as O.E.M. standard equipment or in an upgrade option.

Just having "Heating Pads" installed doesn't mean they are UltraHeat® products. Because we're so popular, we have been flattered with overseas knockoffs that some RV Manufacturers are willing to use. These knockoffs have even gone as far as copying and using our same part numbers and label wording that we have always used, making them look like ours in most every way. They cost less, and are less effective because they produce a much smaller amount...

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Doesn’t the Electrical Service Panel HAVE to have a Main Disconnect Breaker?”

Main Breaker

The simple answer to this question is, “No—Probably not.”

Because most electrical service panels are NOT installed by homeowners or “Uncle Harry,” it is actually pretty rare to find a main panel without a main disconnect. There are a couple of ways where it might “appear” to be missing—but is in fact there after all. My goal is to keep this post simple enough that most readers can understand what I am talking about.

Real estate agents and home owners need to understand the basic principles so that when the inspector calls for replacement of what appears to be a perfectly good panel, they can understand why.

The first point I will make is that ALL electrical services to the home MUST have a means of shutting off all the power.

Being able to shut off all of the power is usually achieved by a Main Disconnect Breaker in the electrical service panel—and...

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Well said Tarheel.

Pulling 6/3 through condo into a nice 50amp sub panel will give you everything you could need. Id like to offer some advice, as a plumber by trade i just completed a similar project for my uncle. So i have been binging on electrical books, forums, and distracting electricians on the job with hand drawn diagrams to make sure I didn't become "that guy".

If you run 6/3 through conduit, your 50amp sub panel will have: 120v, 240v, (the extra conductor brings a second phase of 120v to the panel, which a double pole breaker can send both phases to a future 240v appliance like an air compressor/welder/heater), neutral and ground protection. This also distributes the load of your entire shed over the 2 120v phases, and not a single leg.

Refrigerators should really be on their own dedicated 20 amp breaker wired in 12/2.

Your lighting load is not too bad, so keep all your lights on one 15amp breaker. This way you eliminate switches, boxes,...

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