220v equipment

[alex grams]

I have a sub panel in my garage with 6 slots, and currently have 1 15amp 220v (2 slots) for my grizzly go513x2 bandsaw, and am going to purchase their 2hp G0548 dust collector soon. I want more room in the box to add more 120 lines in the future, but another 220 for the DC would max out the box.

The wire size for the current 220v (with the 15amp breaker) line can run 30 amps, so theoretically I could run two 15 amp plugs off of it, but grizzly recommends 15amp breakers for each individual piece of equipment. Does anyone have a setup like this or see any problems with running two 220v plugs off of the one circuit and replacing the 15amp breaker with a 30amp? I won't be turning on both pieces of equipment simultaneously, but i will be running them together, so i shouldn't have both hit their peak current on startup at the same time.

Thoughts, advice, suggestions?

Thanks in advance.

[Randy Cohen]

you would not be following the recommended amp ratings and therefore not providing the protection called for.

[alex grams]

thats what I thought, and the best I could come up with to meet their protection requirements would be to find a small 4 slot subpanel to run off of my other panel, then run the 220v 30amp line to the sub and split it into 2 220v 15amp lines, each with its own breaker. I just can't seem to find a small 4 slot panel.

[Daryl Upole]

I have a fair amount of knowledge in this area, but am not the expert. So, here's my input.

The breaker amps protect whatever is on that circuit to that extent. So, a 30 amp breaker would not protect two 15 amp pieces of equipment. Each piece of equipment could, potentially, draw 30 amps before the breaker trips.

It sounds like you could put in two 15 Amp 220 Volt breakers for your two pieces of equipment - this would occupy four of the six spaces. Then you could have two 120 volt circuits on the remaining two spaces.

As long as your total draw from this box does not exceed the capacity to it, you could add another sub-panel off of it if you just need spaces. For example, you could use a 30 amp breaker off your current panel to another sub panel with #10 wire. Then you could add your multiple breakers (i.e. 15 amp 220 volt to each machine) off of that as long as the total amperage used by everything off that sub panel did not exceed 30 amps simultaneously.

[Jack Briggs]

You should be able to run 2 15A 2-pole (220V) outlets on a single branch. The total draw should not exceed the 30 amp rating for the wire and breaker.

Alternately you can get a split breaker, which is in essence 2 breakers in one space. This way each machine would have its own breaker.

[alex grams]

I tried to find a double pole 15amp split breaker Jack, but all of the split breakers seem to be single pole.
That would be an ideal solution though if I could find one. I am somewhat a semi novice in these regards, but i would assume a 2 pole breaker such as the one referenced in this link (http://www.homedepot.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10051&langId=-1&catalogId=10053&productId=100003392&N=10000003+90008+503490+4294950611+523&marketID=8&locStoreNum=6506) would provide two 20 amp individual circuits of 220, but if either of them tripped, the other would trip also by virtue of the mechanical interlock on their switches?

[George Bregar]

You can run both off a 30A breaker. Breakers protect the circuit, not the equipment.

[Art Mann]

It has been pointed out many times on this forum, but bears repeating. Breakers are sized to protect the wiring in the wall or conduit, not to protect the devices to which they are attached. Many people use undersized breakers with the expectation that they are protecting their equipment, However, with modern thermally protected motors, this isn't necessary. In the case of an overload, the motor will shut down whether there is a perfectly matched breaker or not. In the case of a direct short, even a single strand of 26 AWG wire will conduct enough current to trip a 30A breaker. In practical terms, it is unlikely that a 20A breaker will protect a modern machine or prevent a fire when a 30A breaker won't.

The fact is, it is certainly possible to run two 240V motors on a 30A breaker at the same time. I know, because i do it routinely. If both motors are 15A and are under load, you may be pushing the limits and get unwanted breaker trips to deal with.

As always, obey the rules of the electrical code applicable to you area.

[alex grams]

The two pieces of equipment in question (bandsaw and DC) only pull 12 and 10 amps respectively, so with 10/3 wire, a 30 amp breaker would protect the circuit and the internal safe guards of the equipment would protect them.

[George Bregar]

The two pieces of equipment in question (bandsaw and DC) only pull 12 and 10 amps respectively, so with 10/3 wire, a 30 amp breaker would protect the circuit and the internal safe guards of the equipment would protect them. Really just need 10/2

[Art Mann]

You only need 10/2 with ground. The neutral wire isn't even used on nearly all 240V equipment.

[George Bregar]

it is 12amp and 10amp at 240, not 120, hence 10/3. I know it's 240. Two hots and a ground. 10/2. 10/3 is used on appliances that also need the neutral for 120.

[Mike Cutler]

I have a sub panel in my garage with 6 slots, and currently have 1 15amp 220v (2 slots) for my grizzly go513x2 bandsaw, and am going to purchase their 2hp G0548 dust collector soon. I want more room in the box to add more 120 lines in the future, but another 220 for the DC would max out the box.

The wire size for the current 220v (with the 15amp breaker) line can run 30 amps, so theoretically I could run two 15 amp plugs off of it, but grizzly recommends 15amp breakers for each individual piece of equipment. Does anyone have a setup like this or see any problems with running two 220v plugs off of the one circuit and replacing the 15amp breaker with a 30amp? I won't be turning on both pieces of equipment simultaneously, but i will be running them together, so i shouldn't have both hit their peak current on startup at the same time.

Thoughts, advice, suggestions?

Thanks in advance.

Alex

There are alot more questions that need to answered.

1. What is the breaker protection to the subpanel from the main panel?

2. What is the wiring size from the main panel to the sub panel?

3. What is the wire size of the current wiring as it exists?

4. Who manufactured the sub panel?

5. Can two seperate 220 loads be powered off of a single breaker?

Yes, BUT!!! There are rules to ensure compliance.

6. Can you replace a 15 amp breaker with a 30 amp breaker?

Physically you can. BUT!!!!!! uprating a breaker is not something that should be done indiscriminately. You need to know everything that that breaker protects, and know that uprating the breaker is in compliance with the code.

7. Can you add Tandem Breakers to your box to facilitate future expansion?

Yes. BUT!!! Once again there are rules. Not only with respect to the code, but with respect to the sub panel's manufacturers recommendations and use for the panel. Not every panel manufactured is even certified by the manufacture for the use of tandem breakers, and even though the breakers at a home depot may fit, and work. It doesn't mean that they are the correct approved breaker per the manufacture.

Rick Christopherson, here on the board, has a very nice website that contains excellent info for electrical principles and application in the woodshop. You can get to his site via his profile. A lot of good info on motors and theory. I highly recommend reading his work before you begin.

I'm not trying to disuade you, but messing around inside of a subpanel, or the main service panel in a home is something best left to experienced people.
Get a liscnesed electrician, and explain everything you want to do, or think you may want to do in the future, Let them set the panel(s) and all of the wiring up to meet your current needs and future expansion. Yes. It will be expensive, but down the line it may save you $$$ from trying to continually modify an exisisting electrical system.

Sorry to be the wetblanket.

[Rod Sheridan]

You can install a 30 A receptacle at each location, or use a fused 2 pole disconnect switch at each location to feed a 15 A receptacle (or hard wire the machinery if you wish).

Regards, Rod.

[alex grams]

I did install the sub panel from the main distribution panel in my house (with the help of my father who has years more experience in such things), but I do have knowledge of what the wiring and ratings of everything are.

1. What is the breaker protection to the subpanel from the main panel? 50amp

2. What is the wiring size from the main panel to the sub panel?
6/3 cu

3. What is the wire size of the current wiring as it exists?
10/3 to current 220 outlet

4. Who manufactured the sub panel?
Square D
5. Can two seperate 220 loads be powered off of a single breaker?

6. Can you replace a 15 amp breaker with a 30 amp breaker?
The wiring is sufficient to support 30amps, my main concern was the attached equipment.

7. Can you add Tandem Breakers to your box to facilitate future expansion?

I do not anticipate having any more major equipment, and the DC was the only piece that i anticipate running simultaneously with other equipment, any more large pieces will be run one at a time.

[Art Mann]

I'm not seeing anything unsafe or questionable based on those answers.

[Wade Lippman]

Your link doesn't work, but for some panels they make duplex breakers that are two 240v breakers that take up the the space of one. Is that what you were trying to link to? If so, they work just fine.

I wouldn't put two tools on a 30a breaker. It is legal and reasonably safe, but there are better ways; such as the duplex breakers

[George Bregar]

Your link doesn't work, but for some panels they make duplex breakers that are two 240v breakers that take up the the space of one. Is that what you were trying to link to? If so, they work just fine.

I wouldn't put two tools on a 30a breaker. It is legal and reasonably safe, but there are better ways; such as the duplex breakers What is unsafe about it? :confused:

[Daryl Upole]

It has been pointed out many times on this forum, but bears repeating. Breakers are sized to protect the wiring in the wall or conduit, not to protect the devices to which they are attached. Many people use undersized breakers with the expectation that they are protecting their equipment, However, with modern thermally protected motors, this isn't necessary. In the case of an overload, the motor will shut down whether there is a perfectly matched breaker or not. In the case of a direct short, even a single strand of 26 AWG wire will conduct enough current to trip a 30A breaker. In practical terms, it is unlikely that a 20A breaker will protect a modern machine or prevent a fire when a 30A breaker won't.

The fact is, it is certainly possible to run two 240V motors on a 30A breaker at the same time. I know, because i do it routinely. If both motors are 15A and are under load, you may be pushing the limits and get unwanted breaker trips to deal with.

As always, obey the rules of the electrical code applicable to you area.

Yes, I think Art hit it here. As a suggestion, it sounds like it would be safe enough and nothing to lose to simply put in a 30 amp breaker with the 10 gage wiring and run them together as such and see if there are unwanted trips. Another post points out that these two pieces of equipment would not draw any more than that. There is a clamp around amp measuring device (need to put it around a hot wire by itself - most likely in the panel) that you could borrow to see the actual amperage drawn by each machine if you felt that was necessary.

Also, the other day I saw some info on breakers that take up two spaces (i.e. the same as a 220 v double pole breaker) but actually functions and one double-pole breaker and one single-pole (i.e. 110v) breaker. I just thought this might be a simple solution for someone short on space.

[Wade Lippman]

What is unsafe about it? :confused:

Well, if it is "It is legal and reasonably safe" then there is nothing unsafe about it. Those long #14 cords on a 30a circuit isn't a great idea. (but please don't tell me how the breakers are only to protect the wiring and not the cords... that doesn't stop it from being inferior)

[Paul Simmel]

Well, if it is "It is legal and reasonably safe" then there is nothing unsafe about it. Those long #14 cords on a 30a circuit isn't a great idea. (but please don't tell me how the breakers are only to protect the wiring and not the cords... that doesn't stop it from being inferior)

Wade, with all due respect, many 15a appliances are plugged into 20a circuits. I don't have any outlets, home or shop, less than 20a #12. If the #14 cords are attached to 15a (or less) equipment, there is nothing unsafe about it.

[Steve Leverich]

I've been thru this entire thread and still can't find where anyone stated they were using #14 wire ANYWHERE. (nor would I do that in this case) - what did I miss? Steve

[Eric Haycraft]

I think that I have the same or similar square-d box in my garage. There are 6 slots total on mine, but only 2 allow the new tandem breakers. Square-D changed the mount on those so that they accept tandems (or regulars), but the other 4 slots won't accept tandems. Because of how these are spaced, you can only use 1 tandem if you have two 2-pole breakers set in it.

[Art Mann]

Well, if it is "It is legal and reasonably safe" then there is nothing unsafe about it. Those long #14 cords on a 30a circuit isn't a great idea. (but please don't tell me how the breakers are only to protect the wiring and not the cords... that doesn't stop it from being inferior)

What about all those 16 AWG and 18 AWG lamp cords that are plugged into 15A and 20A wall outlets in your own house? You haven't burned your house down yet have you? On the other hand, ther is nothing to prevent an idiot from attempting to run his 20A tablesaw through a 16 AWG extension cord either. A breaker will not protect the user against stupidity.

If you don't like someone telling you the purpose of circuit breakers, please ignore any posts with their name on it.

[Jason Beam]

Man these threads take on a nasty tone, don't they? Jeeze!!

I think the people who are in the know do a reasonable job of keeping their cool most of the time. The trouble is when those who think they know actually don't fully get it. I'm one of those people. I think I know, which is usually why I don't say anything. I know that I think I know ... i think.

My main reason for posting this is regarding the whole argument about the purpose of a breaker. Those who know are right, of course, a breaker is ONLY for the circuit - beyond the outlet, you're on your own.

I had trouble with this concept for a while, too, and I suspect it's a perspective issue, not that the people who disagree are lacking knowledge. Maybe I'm off base, but for me the "Aha" moment came when I figured out that my perspective about the basic nature of electricity was refined. I used to think that electricity was like flowing water. Shame on gradeschool for forming this opinion. Unfortunately there isn't really much out there that most people understand well to compare with electricity. Flowing water is the closest, but it's got some pretty fundamental diferences that I think people mistakingly apply to electricity.

Fundamentally, electricity isn't pushed. It's pulled by a load, not pushed. Breakers aren't valves that regulate the flow, by any means. They don't DELIVER electricity at all. That outlet won't feel ANY different with a 15a breaker or a 50a breaker on it until there's a load. And even then, if the load is below the outlet's rated amperage, that breaker won't make a lick of difference. More electricity is not pushed out of the outlet, period. Until the load actually requests too much electricity, that outlet's perfectly happy - no matter what breaker's on it.

I get the impression that some folks come from the perspective of pushing rather than pulling. It's easy to have that perspective - water works that way - and that's how we were all taught to think of circuits - valves were switches, pipes were wire, and it all made sense. Unfortunately, it isn't the way it works. A good exercise is to imagine the two wires of a 110v line sitting there, open - exposed - not touching anything - just hanging there in the air. Electricity isn't just POURING out of that wire - like it would if that were a water pipe. It's not being pushed at all. The only electricity leaving that wire is the amount that the air itself PULLS from it. If you change the load (touch it?) the electricity will match that load - your hand will pull considerably more amps than raw air (especially once a circuit is formed).

To the OP: If you have wired the circuit sufficiently (wire size, breaker size, outlets, etc), I am under the impression that, in most places in the US, you can legally place multiple 220v outlets on a single circuit - i do think, though, that you have to size every device in the circuit to match the breaker - that means 30a outlets, 30a wire, 30a breaker - everything should match. I think there are a handful of exceptions to that, though, like multiple 15a outlets on 110v 20a circuits - but that's off topic.

To be sure, though, you need to contact a local authority to ensure that your area allows such a thing.

I may verywell be absolutely wrong about what's legal. I'm a bit more sure about what I believe is possible, though there's always room for correction. :)

[Wade Lippman]

The tool has to be on a 15a circuit. What gauge do you think the cord is?

[Tom Veatch]

... you can legally place multiple 220v outlets on a single circuit - i do think, though, that you have to size every device in the circuit to match the breaker - that means 30a outlets, 30a wire, 30a breaker - everything should match. I think there are a handful of exceptions to that, though, like multiple 15a outlets on 110v 20a circuits - but that's off topic.... :)

You nailed it, Jason! That is correct.

Probably one of the most universal misconceptions is that the protection provided by the circuit breaker extends beyond the outlet. It doesn't, pure and simple.

Plugging a 100watt light fixture (appx 1 amp) into a 15 amp household circuit (or a 50amp circuit for that matter) doesn't mean the fixture is going to explode from all those excess amps, nor is the breaker on that circuit responsible for protecting the fixture or for trying to keep it from drawing more than it's normal current - as long as that current is less than the breaker rating.

[Allan Froehlich]

First Post (wOOt!)

I heard somewhere that running two motors on the same breaker is a bad idea.

I think it has something to do with both motors running out of perfect sync with eachother and the way the sinewave of AC can lead to very high, yet short, amperage spikes. Supposedly, this will cause a big problem for you.

Has anyone else heard of this before?

[Thom Sturgill]

Ok. In a prior life I worked as an electrical engineer, and trained my BIL to pass the licensing exams as a journeyman electrical worker. When talking about wiring, there is the concept of 'ampacity' or the capacity to carry current. The larger the wire the higher the ampacity. As long as the ampacity of the building wiring is greater than the demand it is ok. This also applies to the rating on the outlet itself and any extention cords and the tail on the machines. It is fine to use a 20A recepticle, and #10 wire to wire a 15A circuit. Its just overkill, but it would allow you to upgrade the circuit if needed for heavier loads.

On the otherhand, the rating on the circuit breaker tells you what amperage or draw, it will cut out or trip at. If you put two devices on a single 30A circuit, and one draws 10A, the other could draw as much as 20A (possibly causing the motor to let the smoke out) before the breaker tripped. The amperage rating of the breaker should ALWAYS be equal OR LESS than the rating on the house wiring and recepticles to protect them, and equal or less than the rating of largest single draw to protect it.

[Tom Godley]

I also find that some of these posts get a little raw -- Most on the forum are just trying inform or be informed. These electrical issues always raise hair!

My new shop is going into an area that the previous owner (an artist) used as his studio. He must have been afraid of 220 plugs - most of the tools were just powered by running the Romex out of the wall and straight to the tool -- he did at least use the correct wire for the breaker size. So I have a lot of long "pigtails' in the shop area :)

The one place he did have a plug was for his table saw -- It was in his old welder location - so he had his TS plugged into a properly installed 50amp outlet using the correct 50amp plug all going to a 50amp breaker. The wire to the TS was 16/2. More than likely replaced at one point- as I would think that it would have originally had at least 14/2 cord.

One of the things I do for a living is work with traumatic injury claims. This makes me afraid of things - high places -- fork lifts - assorted industrial equipment -- And a lot of stuff we live with every day.

About five years ago I was forced to go to an industry convention - and by chance - since it had nothing to do with me - went into an electrical demo run by an insurance company. Now, my term may not be correct- but he was showing the "shock/spark/fire" of different power lines and breakers. The point was to show the "loss potential" of what look like normal electrical installs. He had a "mock up" of a few panels installed with normal breakers - he then shorted out a 12g line attached to 20amp breakers -- the difference in the reaction time of the breakers was surprising. The Square D was the best and the GE was the worst. When he went to the older breakers (I believe at least 10y) and those that had been used as "switches" some failed totally -- he was especially not fond of "Pushmatics". When he started to use lighter gauge wire (shorted) on the older breakers -- many burst into flame.

My point with this post and a previous one in another thread -- is that as the table saw install above -- It is not a good idea to have 14g wire attached to in this case a 50amp breaker. Also, I have come to learn first hand, not all breakers - even new ones- react to a direct short the way we think they should.

Sorry if I sound like I am preaching

[Eric Haycraft]

I had a similar dilema when setting up my garage. I needed a hefty 220 to run my 3HP planer and jointer, but my TS is smaller and only draws 7.5 amps in 220. I also didn't have room in my subpanel for 3 or 4 220 circuits with 3 or 4 different amp ratings. So, what I did was install 1 - 30 amp 220 with a common (I will add another when I get a real DC) and put a separate breaker box on every machine that plugs into the 30 amp 220. So my TS has 7.5 amp fuses, my planer has its own 20 amp breaker attached right to the machine, etc. Since I added a common, I can also add 110 outlets with their own breakers to the machine itself.. so my TS has 2 - 20 amp outlets attached to it for running the router in the wing or as a convenient place to plug in other power tools.
The other advantage here is that all of my plugs can be the same no matter the size of the machine. It is the breaker on the machine that limits the amps drawn and really simplifies things if I want to move machines around later.

[Mike Cutler]

I'm not seeing anything unsafe or questionable based on those answers.

Me neither Art. There is more than enough margin.

Alex.
Sorry to be so late getting back. We've been without power since 1PM.

I apologize if my previous post was insulting. It wasn't intended to be.
It is very difficult to help someone out on an electrical question when you don't know all of the variables involved. That was why I asked the questions that I did.
You have more than adequate capacity to accomplish what you are trying to do, and there are a number of ways it can be done.

There is nothing in the NEC that prevents, or precludes have multiple motors on a single branch circuit as long as the branch circuit wiring and breaker are sized correctly.

Once again. I apologize if I came off as a little over the top. It wasn't my intent.

[Jon Bonham]

Posts like these are why people like me will always have work. ;)

[Mike Cutler]

Posts like these are why people like me will always have work. ;)

I hope it's because you have a liscense,and aren't an insurance adjuster or a fireman.;) I send the 345KV out.It gets stepped down considerably on the way to the tablesaw.;)

15,000 HP, 12ft tall and 8' in diameter, with a weight of 22 1/2 tons, running off of 6.9KV. Now that's a motor.:eek:,;)

[Jon Bonham]

I hope it's because you have a liscense,and aren't an insurance adjuster or a fireman.;) I send the 345KV out.It gets stepped down considerably on the way to the tablesaw.;)

15,000 HP, 12ft tall and 8' in diameter, with a weight of 22 1/2 tons, running off of 6.9KV. Now that's a motor.:eek:,;)

220, 221, whatever it takes.

[Eric Haycraft]

Posts like these are why people like me will always have work. ;)

And what specifically do you think is wrong with my wiring?

[Jon Bonham]

And what specifically do you think is wrong with my wiring?

It wasn't aimed at anybody in particular, just a general statement because of the 20 different opinions in the 30 posts in this thread.

I'm not an AC electrician, although I have a good working knowledge and have done a lot of the work. I'm a low voltage electrician. I mainly do boats, hot rods and sand cars from scratch. A monkey could do AC, no offense to monkeys. ;)

[Rick Christopherson]

I didn't respond to this thread earlier today because at the time the answer was already given and everything was copacetic. Why did this simple question have to degrade into a lot of mumbo jumobo and speculation in the mean time?

There is nothing wrong with doing what the original poster suggested with one exception. You cannot install 15 or 20 amp outlets on a 30 amp circuit. If you are going to install a 30-amp breaker, then you need to use 30-amp receptacles.

[Mike Cutler]

. A monkey could do AC, no offense to monkeys. ;)

Jon.
This statement is completely uncalled for. A fully qualified Journeyman Electrician is a highly skilled individual. There is a more to wiring, and being an electrician than "black to black", and "white to white". It just looks that easy.There is a lot more to being an electrician than meets the eye. You have my absolute, 30+ years experience, guarantee on that.
While there is nothing wrong with what the OP wants to do. there is more than one way to accomplish it, depending on physical layout, future expansion, code compliance and ease of installation.
It's more than "black to black" and "white to white" to do it properly.

[David Wilhelm]

I have the same issue. No more breaker room so I'm just going to add another panel. You could perhaps change all your breakers to the half size ones if they make them for your box and gain room. That would be around the same expence. Check your codes

[Chris Friesen]

A good exercise is to imagine the two wires of a 110v line sitting there, open - exposed - not touching anything - just hanging there in the air. Electricity isn't just POURING out of that wire - like it would if that were a water pipe. It's not being pushed at all. The only electricity leaving that wire is the amount that the air itself PULLS from it.

To be precise, with standard wall sockets electricity is being pushed from one wire and pulled from the other...but it can't actually flow anywhere unless the two wires are connected somehow. It has the "potential" to flow, but until you connect a load it won't actually flow. Its like blocking the hose of a running vacuum--there is suction, but no airflow.

This is why voltage is also knows as "electrical potential". It indicates how strongly the electricity is being pushed/pulled.

To complicate things, which wire is pulling and which is pushing flips back and forth 60 times/sec (in North America, 50 times/sec in Europe).

[Greg Funk]

I used to think that electricity was like flowing water. Shame on gradeschool for forming this opinion. Unfortunately there isn't really much out there that most people understand well to compare with electricity. Flowing water is the closest, but it's got some pretty fundamental diferences that I think people mistakingly apply to electricity.

Fundamentally, electricity isn't pushed. It's pulled by a load, not pushed. Breakers aren't valves that regulate the flow, by any means. They don't DELIVER electricity at all. That outlet won't feel ANY different with a 15a breaker or a 50a breaker on it until there's a load. And even then, if the load is below the outlet's rated amperage, that breaker won't make a lick of difference. More electricity is not pushed out of the outlet, period. Until the load actually requests too much electricity, that outlet's perfectly happy - no matter what breaker's on it.

I get the impression that some folks come from the perspective of pushing rather than pulling. It's easy to have that perspective - water works that way - and that's how we were all taught to think of circuits - valves were switches, pipes were wire, and it all made sense. Unfortunately, it isn't the way it works. A good exercise is to imagine the two wires of a 110v line sitting there, open - exposed - not touching anything - just hanging there in the air. Electricity isn't just POURING out of that wire - like it would if that were a water pipe.
Jason,

Actually, the electricity and water analogy holds up very well for resistive loads.

Electric potential is analogous to pressure. In your example consider the wires as pipes that are capped on the ends. Bigger wires are like bigger pipes. A resistive electrical load is like a smaller diameter pipe. The higher the impedance of the load the smaller the diameter of the pipe. Connecting the wires to a load is like connecting a short length of pipe between the capped ends of the main pipes. If you were to measure the water pressure at various points in the pipes it would match exactly the voltage on the wires.

A circuit breaker is the same as a valve that shuts off when the flow rate is higher than a set threshold. Current is analogous to flow rate through the pipes.

Greg

[Josiah Bartlett]

First Post (wOOt!)

I heard somewhere that running two motors on the same breaker is a bad idea.

I think it has something to do with both motors running out of perfect sync with eachother and the way the sinewave of AC can lead to very high, yet short, amperage spikes. Supposedly, this will cause a big problem for you.

Has anyone else heard of this before?

Complete bunk. You have my word on that as an electrical engineer with a master's degree (I am not an electrician). If that were the case you wouldn't be able to run more than one motor in your entire house. The feed side of the breakers are all shorted together by the bus bar in the panel, and the impedance of the breakers has to be extremely low or they would get hot with use.

You may find, however, that when running multiple motors that starting one while the other is running trips the breaker. Motors require more current to start than run.