Home Electrician info needed!?

[Dragon Tamer]

When it comes to electricity, erring on the high side can also bring you disaster. Heavier wire will not create any problems but too large a breaker sure can. Too much protection in that area means that in case of minor problem that would have just blown the proper breaker and warned you of a problem, it won't happen. The breaker will fail to see the problem and the smoke (that all electrical devices run on) will leak out of the device and we all know that once the smoke leaks out the device will no longer function.

For a device that pulls approximately 30 amps a 40 amp breaker would be just about right. Should you go up a step and install a 50 amp breaker you may discover that in the case of a problem the smoke will start leaking at say 45 amps and that would not be enough to trip the breaker.

[DGXSER]

Yes, the breaker should never be rated for MORE than the conductors connected to it, but you can put a lesser rated breaker in. If it were me, I would put the 2-pole 30 AMP breaker in to properly protect the device in a single purpose circuit like this one.

[Rooster]

power to the garage

Being as I have contracted for 10 years in the electrical business and am in Canada where the prices are much higher for everything I can tell you straight up that this isn't a big deal. Get three electrical companies in your area to give you a QUOTE not estimates on how much to do the job, and yes you will have to walk them through the idea or you may get three totally different prices based on their personal interpretation of what you want. Then you select not the cheapest but the guy you thought was the most honest of them, a one or two man company likely will do a better job as those outfits are closer to the action and also are more picky about quality. And if your going to all the trouble of putting 240 volt power to the garage have the electrician just run a 120/240 feed to the garage with a medium sized panel and run your welder, compressor, and everything else off of that panel. Discard the old feed so that there is no complication between two separate power supplies going into one building. By the way if I were to do the job and from panel in the house to the new panel in the garage the distance was under 100' i would charge $1100 for anyone not an XS11 member and that is at Canadian prices (labor rate here is average $75 an hour for contractor and alot of our material cost are double yours) for an XS11 member I'd spend time BSing while getting a hand doing the install and at the end of the job if I made a friend all I care about is the money for the material. SO if there's a electrician in top cats neck of the woods get your ass over there bail him out and thank him for being instrumental in starting this great web site

[TopCatGr58]

Hey Rooster,

I truly appreciate the info and sentiment. However, I'm not the one who created this site, I am just one of the folks that helps to manage it, along with the fine Mods, as well as the members themselves that often contribute their time and ideas for great tech tips, as well as just helping out their fellow Xsives with tech help posts here in the forums!

The Electrician that I'll be working with is a friend of a coworker's husband, he's an older fellow and I'm sure is well experienced and have been told he does like to do/work old school style, and that he'll definitely give me a decent "friendly" price deal on the work. And him being a licensed electrician should also allow me to not worry about an inspection.

Regrettably he's come down with the flu, otherwise he would have worked on it this weekend. I'm not in any hurry/rush so no problem there. I did some window shopping and found the 30/50 amp 3 prong 220/240v plugs and receptacles at Lowes for less than $20.00 for both. The Garage is attached to the house, it's just a matter of running the lines from the existing fusepanel in the garage about 6 feet towards the center of the wall, either thru the wall, or even external conduit, with copper wire, to a receptacle in the wall, and then just put the better plug on the welding machine cord, and that's it!

The compressor is only 110, but with the welder on the 220 line, then it frees up the 110 to be able to be run at the same time the welder is running on 220, so that I'll be able to keep it pumped up with plenty of pressure to feed the hungry PLASMA CUTTER's CFM/70psi appetite!!

Once I get everything wired and working, I'll be doing some test cuts and welds and such, and will take photos/videos to show you the "FUN" I'll be having!

No worries about the modest cost of this project, got to stimulate the local economy somehow!!

T.C.

[DiverRay]

TC,
If your compressor will run on 220, DO THE CONVERSION! The motor runs cooler, and you WILL notice a difference in output. IF you are putting in 220, just add the second 30A. breaker and put in a pair of 220 20A. plugs in. Cheap, and your ready for the next toy!
I hope put in more power later here, but I'm using the dryer plug for my TIG as of now, so I'm happy.

[TopCatGr58]

Hey Ray,

AFAIK the compressor is only a 110v motor, Central Pneumatic/HF 21 gal machine...label states 115V only! Most everything that I have toy wise is 110v, not anticipating any other toys with the 220v requirement.

From what I've recently read and been told, be careful with your dryer plug, you may want to turn off the breaker and inspect the plug/wiring...IF it uses Aluminum wire..they don't tolerate the vibration and manipulation of being plugged/unplugged alot, and can come loose at the terminals. Most folks don't plug/unplug their dryers/stoves alot so there's not much wear involved with their use, but if you're using the plug for several 220v devices, you may be in for trouble!? JAT.

T.C.

[crazy steve]

From looking at some of the replies here, there's considerable confusion on how to size a breaker and/or wire and/or device for a load. A few simple rules....

First, your wire ampacity should always be equal to or higher than the breaker rating; i.e. a 40 amp breaker should have at least 40 amp wire connected to it. Bigger is fine, smaller is a no-no. Don't go too big or you won't be able to fit the wire into the termination lug.

Next, breaker size. A given size breaker is designed to trip at it's marked rating, that's NOT the size load it's designed for. If you operate a breaker within it's top 20% of it's rating, you can suffer nuisance tripping and markedly increase the chances of it failing, sometimes with disastrous results (fires, burned-up panels). The basic rule is to size the breaker by multiplying the full-load current of the device or circuit by 125%, so a 30 amp load X 125% = 37.5 amps. You won't find a breaker that size, so you go up to the next 'standard' size. The one major exception to that is motor loads; a motor can have a fairly low 'full load' current (amps), but it's starting current can be up to 800% of it's full-load current (if only for an instant) so you have to increase the breaker size (and wire/outlet ratings) to prevent tripping. For these applications, the basic rule is 300% of the full-load current; nearly all breakers are inverse-time thermal trip designs, so the instantaneous current drop-off is fast enough that the breaker won't react to the overcurrent and trip. A lot of 'consumer' items (like small compressors and such) will give a circuit size, so use that number, but otherwise you should calculate it for safety. If it shows an 'odd' size, always go up to the next standard size.

Wire rating. There's been several mentions made of different ampacities for a given size wire depending on it's type/temp rating. The catch here is every part of the circuit has to be rated for that temp, all the way to the breaker/panel. While commercial gear is almost always rated at 75C, that may not be true of all residential panels; some are only good to 60C. So unless you know that your panel is rated to 75C, use the 60C numbers for safety. The cost difference is small, a cheap price for safety.

Device ratings (outlets, cord caps). Same thing applies here; use a plug that's rated the same as the breaker size. Yes, sometimes you'll find a piece of equipment with a 'small' cord on it. If the item has a UL or CSA sticker on it, it's OK. But you'll run into import stuff or equipment without those labels, so that's when you should pay attention. Beware EC or EEC labels, that's a 'international' spec and not the same thing.

Now, I'm not going to argue with those who say 'but I did this or that and it works fine' because it very well may. After 30+ years in the electrical trade, I've seen plenty of sub-standard installs that worked for years with no issues. But I've also seen more than a few that failed, sometimes at large expense for repairs. All of the above is out of the National Electrical code, there's no 'opinion' here, just the facts.... and using these rules will give you the best shot at having a safe installation.

I will note a warning for those of you that may have Zinsco or Federal-Pacific panels; both of these brands are no longer made (both lost their UL approval) because these breakers were notorious for not tripping under high-but-not-quite-max loads and getting hot enough to damage the panel buss to the point the panel would fail. The original manufacturers are out of business and there's some 'off-shore' replacement breakers being sold for these that don't have UL approval. Have somebody competent look at your panel before installing any breakers, and make sure you follow the above rules...

[b.walker5]

Excellent advice Steve. The only thing I would add would be to point one, and that is to remember that the breaker is there to protect the circuit wiring, not what's on the end of it, as we have no control over what's plugged in.

We start our installations with a maximum demand calculation, based on the type and number of outlets, then the cable de-rating factors such as length of run and heating factors i.e. in conduit, bunched cables, enclosed in insulation etc, and this determines our final cable selection. We then select a breaker rating to suit the cable rating.

However, all to often I have seen the breaker changed (up sized) by the homeowner/handyman because they've bought a bigger gizmo that kept tripping the old breaker, and all too often I've seen melted and burnt wiring as a result.

IMHO untrained/unlicensed people shouldn't be allowed any where near the stuff.

[crazy steve]

....remember that the breaker is there to protect the circuit wiring, not what's on the end of it, as we have no control over what's plugged in..

Good point; cord-and-cap connected devices are assumed to have their own internal protection, or that a failure will simply trip the supplying breaker. Some hardwired equipment may be depending on the supply breaker for protection, but again, most will have their own internal protective devices. The breaker isn't there so much to protect the equipment, but to keep from burning down the building....

[DGXSER]

Steve, the only thing I think is debatable is the sizing of the breaker. If the device says it is to be on a 30 amp circuit, then you should protect the circuit with a 30 amp breaker. Not a 40 amp breaker. Oversizing a circuit because you don't want nuisance trips is also a great way to cause a fire and burn up electrical systems. Seen it happen, and yes it is ugly at best. For typical circuits, yes you never want to go past 80% of its rated capacity, basically that same 125% you mentioned, that rule is for distributed loads. As you indicate dI believe, you also need to look at the rating of the receptacle being installed on a dedicated circuit liek this. If you put a 30 amp rated receptacle on the other end, you better dang well put a 30 amp breaker on the circuit regardless if you ran 0000, #6, or #8. If a circuit is dedicated, and the device states to protect it with a 30 amp breaker, I would not recommend you upsize it to 40.

[crazy steve]

Steve, the only thing I think is debatable is the sizing of the breaker...

Nope, sorry, no debate. With only some exceptions (other than the already-mentioned motors, none of the rest would be applicable to anything you'd hook up to a standard house panel), the 125% rule is the last and final word. BUT, you may find equipment with a 'recommended' or 'minimum' breaker size listed on it, which if it's UL or CSA-listed means you can use that size because the manufacturer has already figured the proper size for a safe install; but there's nothing to prevent you from using a 'bigger' circuit to supply this, and it's no less safe than the smaller choice. If the item lacks a UL or CSA approval, you'll still need to check actual full-load and do the calculation. I've never seen a piece of equipment with a 'maximum' breaker size listed, at least not anything that's approved by UL or CSA.

A common misconception is that the breaker feeding a specific item is there to protect the device it supplies. With rare exceptions (again, nothing you'd find hooked to a house panel), that's not true. If the device needs protection, it's either already built-in or you install secondary protection devices in-line feeding the device. The panel breaker is there to protect the wiring system, structure, and personnel from damage or harm, that's it, nothing more.

Another thing to think about is circuit breakers aren't designed to be tripped and reset except in response to a fault, which if the system is correctly designed should never happen. They're not rated as switches either (so if you're using one as a switch, stop it or buy a breaker that's rated for switch use; not cheap or easy to find), and as few as ten 'trips' can damage a breaker enough that it can fail. I've personally seen larger breakers blow up (with the force of a bomb) when being turned back on after being tripped, and this is after the fault was cleared...

I'll note that this is true for 'normal voltage' wiring (over 50 volts/under 601). Get into those low/high voltage systems, and there's a quite a bit of difference but none of it applies to residential.

[b.walker5]

A common misconception is that the breaker feeding a specific item is there to protect the device it supplies.

Which is why I say again, "Untrained/Unlicenced people should NOT be allowed anywhere near this stuff"

Sorry Don, but the breaker has absolutely nothing to do with whats plugged into the outlet. It's sole purpose in life is to protect the cable. Nothing More, Nothing Less. Your argument that a 30 amp device should not have a 40 amp breaker simply doesnt hold water, because of the above. If the cable is rated for 40 amps then its absolutely correct to have a 40 amp breaker. What you plug in is in no danger whatsoever because unless it's faulty it's only ever going to draw its rated current, which may be 2A or 32A. In the event of a fault causing a short circuit the fault current will quickly (milliseconds) exceed the breaker rating and trip it anyway. Granted your 2 amp load may be damaged by the instantaneous fault current, but the supply cable is under no danger because the breaker is rated correctly for it's size. For my money I'd certianly prefer a blown up whizbang over a burnt down house.

[cywelchjr]

Which is why I say again, "Untrained/Unlicenced people should NOT be allowed anywhere near this stuff"

Sorry Don, but the breaker has absolutely nothing to do with whats plugged into the outlet. It's sole purpose in life is to protect the cable. Nothing More, Nothing Less. Your argument that a 30 amp device should not have a 40 amp breaker simply doesnt hold water, because of the above. If the cable is rated for 40 amps then its absolutely correct to have a 40 amp breaker. What you plug in is in no danger whatsoever because unless it's faulty it's only ever going to draw its rated current, which may be 2A or 32A. In the event of a fault causing a short circuit the fault current will quickly (milliseconds) exceed the breaker rating and trip it anyway. Granted your 2 amp load may be damaged by the instantaneous fault current, but the supply cable is under no danger because the breaker is rated correctly for it's size. For my money I'd certianly prefer a blown up whizbang over a burnt down house.

I will take exception with the "unlicensed" portion of your statement only. As long as the person has the proper training either through proper self study or coursework, and is allowed by code to do so, and proper inspections are done, then it's fine. In most U.S. jurisdictions the homeowner is allowed to do must any work themselves, as long as they have a permit to do the work, and that it's inspected when completed (and anything that can create a safety problem generally requires a permit). To do work for someone else generally requires a licence from the state or locality, but it's a part of our culture that generally the homeowner is considered able to be smart enough to go out and learn how to do their own improvements and do them themselves, but they at least do require that the work be inspected upon completion, even if done by a licensed contractor. Now I may be a bit of an exception, I worked in construction in high school, so I have some experience in the field, just enough to know the basics, and to know what I can do and when to call in a pro. Then again I know how and where to look up what I need to know to LEARN how to do the more complex things, and my son in law is an electrician, so I have an unfair advantage .

[crazy steve]

Yeah, I don't really have a problem with an owner doing his own work, but too many of them don't know what the hell they're doing and it can be dangerous. And beware free help sometimes; I've seen some scary stuff put in by so-called 'electricians' who hold some sort of 'specialty' license (marine, telecom, linemen) who don't have full knowledge of the trade. Good example, I got a weekend panic-stricken call from a neighbor a few years ago to come down and look at his well pump. He'd gone out to do some mechanical maintance on it and while he was out there his wife got knocked on her ass (literally) when she put her hands into the kitchen sink to wash dishes. Seems there was 90 volts to ground on the sink... woohoo... Couldn't figure out what he did, as he hadn't touched anything electrical on the pump, but that sink was hot as a pistol. Problem? His 'electrician' buddy (who it turned out was a fire alarm tech, and knew just enough to be dangerous) had installed a light in the pump house, and used the ground because he couldn't find a neutral. Turn the light off, everything was fine. Turn the light on, hot plumbing... she had both hands in the sink when he turned on the light.

When I left, she was screaming at him about 'no more saving money you cheap a$$!!!'....

If you're not 100% sure of what you're doing, get a pro. And don't try to cut corners; the life you save may be yours or a family member!

[ddragon63]

Which is why I say again, "Untrained/Unlicenced people should NOT be allowed anywhere near this stuff"

Sorry Don, but the breaker has absolutely nothing to do with whats plugged into the outlet. It's sole purpose in life is to protect the cable. Nothing More, Nothing Less. Your argument that a 30 amp device should not have a 40 amp breaker simply doesnt hold water, because of the above. If the cable is rated for 40 amps then its absolutely correct to have a 40 amp breaker. What you plug in is in no danger whatsoever because unless it's faulty it's only ever going to draw its rated current, which may be 2A or 32A. In the event of a fault causing a short circuit the fault current will quickly (milliseconds) exceed the breaker rating and trip it anyway. Granted your 2 amp load may be damaged by the instantaneous fault current, but the supply cable is under no danger because the breaker is rated correctly for it's size. For my money I'd certianly prefer a blown up whizbang over a burnt down house.

I'm just gonna assume there's another Don in this thread or you've confused me with someone else. I don't recall talking about breakers....