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RussZHC
04-23-2012, 07:37 AM
Don't have "big" power in the garage but many homes have either a dryer, stove or A/C, I am not above running an "extension cord" out a window for a welder, how long can I make it before its just pointless or stupid heavy?

MotorradMike
04-23-2012, 08:03 AM
It's all about voltage drop.

Problems are these:
Connectors add voltage drop and can melt causing fire.
Smaller gauge wire is worse than heavy gauge wire.
Longer wire is worse than shorter wire.
Higher current is worse than lower current.

Extension cords are meant for hand drills, trouble lights, and radios.

Things like welders, water heaters, and driers need to be wired properly to the distribution panel.

vpt
04-23-2012, 08:17 AM
I use a 25' extension cord for my welder ALL the time. In fact my TIG has been plugged into the extension cord for the last 10 years. I want to get some adapter plugs for it so I can run my stove and stuff from it as well.

So long as you get a good size wire and good plugs there is no difference between running 100' of wire in the wall or 100' of extension cord on the ground.

My 25' was over $100 by the time I got plugs and stuff.

J Tiers
04-23-2012, 08:21 AM
As an alternate to the foregoing..... consider:

What is the difference between an extension cord and "proper facility wiring"?

Answer.....(s)

Extension cords tend to be undersized for wire gauge

Extension cords lay on the floor where they can be tripped over.

End of story......

if the extension cord is properly sized for the load, and some precautions against tripping over them are used, there is NO real safety difference.

Furthermore, there is some relaxation of the "properly installed facility wiring" wire size allowed in the electrical code for welders, in consequence of the "duty cycle" they are used at (not 100% "on").

An extension cord will likely be more expensive because it should be "SO" cord, meant for extra heavy service, with a jacket, padding, properly rated connectors, etc.

The power got to your house on wires, it can get to your welder in wires also.

garagemark
04-23-2012, 08:29 AM
What MM says is true. BUT... cords are often used for welders and large loads. There are many voltage drop calculators on the Internet, or you can look at the NEC (National Electric Code) chapter 9, table 9 for conductor properties. You also will need table 310.15 to find the ampacity for a given wire size.

First you need to know the current draw of whatever you are going to power from the cord. Then you need to size your cord accordingly (i.e. 30 amps= #10 wire). Then you can calculate the voltage drop of that wire size. 3% voltage drop is about the limit; then you will need the next size up conductors. I have copied a voltage drop example to follow from Mike Holt's web site. Just plug in your own numbers.

240 volt Single-Phase Example: What is the operating voltage of a 44 ampere, 240 volt, single-phase load located 160 feet from the panelboard, if it is wired with No. 6 conductors, Figure 5?

(a) 233.1 volts (b) 230.8 volts (c) 228.4 volts (d) 233.4 volts

Answer: (a) 233.1 volts

Voltage Drop = I x R

I is equal to 44 amperes

R is equal to 0.157 ohms (Chapter 9, Table 9: (.49 ohm/1,000 feet) x 320 feet

Voltage Drop = 44 amperes x 0.157 ohms

Voltage Drop = 6.9 volts, (6.9 volts/240 volts = 2.9% volts drop)

Operating Voltage = 240 volts 6.9 volts

Operating Voltage = 233.1 volts

EVguru
04-23-2012, 08:47 AM
There's an oft forgotten problem with long extension leads.

What do you do when you don't need a lead that long?

Using one coiled up has been the cause of many fires.

Sometimes just plugging in a coiled up lead, even with no load, is enough.

vpt
04-23-2012, 08:58 AM
There's an oft forgotten problem with long extension leads.

What do you do when you don't need a lead that long?

Using one coiled up has been the cause of many fires.

Sometimes just plugging in a coiled up lead, even with no load, is enough.


Many say that is myth. However I never "wind/coil up" my cord when I'm not using the full length. I somewhat fold it up in a out of the way corner of the floor.

I forget what size my cord is but I do know it is OVERSIZE for what the welder needs. When it comes to electrical cords I found that bigger is better than that one time "its not big enough".

bborr01
04-23-2012, 09:58 AM
I have a couple of #6 ga extension cords that I use for welders, etc. Never have had a problem with heat buildup in them either. They are about 30' long and work just fine.

Brian

wb2vsj
04-23-2012, 10:06 AM
1) My wife didn't want to fully unwind a 100' cord one day (only needed 10' or so). The next day I want to put it away for her - it was still plugged in. It was wound on one of those cord reels. It was definitely warm. I didn't believe it myself until that day.

2) I think insurance will come into play here too if something goes awry if it's plugged into an extension cord and shouldn't have been. Any reason not to pay out...


Walt

philbur
04-23-2012, 10:10 AM
It's not a myth, you can run it coiled but the maximum load capacity is down-rated. Some shop bought reels (maybe all) have the down rating printed on them.

Also I have a 25 meters of extension cable with significant heat damage to prove it.

Not sure about the no load senario though. No load generating heat sounds like over-unit to me.

Phil:)


Many say that is myth.

flylo
04-23-2012, 10:15 AM
I always use bigger than recomend. 10 ga is my smallerst also 4 6,8 ga. I use a 4 ga for 3 phase but it hard to handle as it's close to 11/4" in dia. But it works well until I get the big tools set in they're permanent place in the shop. Soon I hope.

garagemark
04-23-2012, 10:15 AM
Just stick a decent size piece of ferrous metal through the coil. Problem solved.

RancherBill
04-23-2012, 10:36 AM
Russ

What is the current rating of your welder and how long do you want the cord to be?

EVguru
04-23-2012, 11:31 AM
Not sure about the no load senario though. No load generating heat sounds like over-unit to me.

It's because of the inductance. Energy is being stored and withdrawn. If there was no resistance in the cable, there would be no power being drawn and no heat.

If you've got one of those energy consumption meters that will display watts and VA, you can see the VA go way up as you coil the cable.

fjk
04-23-2012, 11:41 AM
I use a 100' 8ga cord for my Lincoln AC225 and have no troubles.
It might not get the swoopiest bestest welding at the high end, but
I don't do stuff that needs every last electron of welderizationing...

For the most part, it's used uncoiled --- because I need the distance.
The last 10-20' might be sort of coiled up somewhat, ish, kinda sorta,
but I'm also outside there, so any heat is very quickly dispersed.

Welding machines are a special category in the NEC, they allow a higher
current draw for a given wire size than they otherwise would, everything
else being equal. The reason, so I've been told, is that welding machines
are highly intermittent in their load, so the wires can cool off. This is
allowed, though, only when the machine is hard-wired to the circuit.
If the circuit is pluggable (i.e. you could plug something other than a
welder into it) then it has to be rated for the continuous load. (I don't
have an NEC, I'm not an electrician, but that's what I've been told
independently by a couple of real live electricians ... ymmv)

Frank

Black_Moons
04-23-2012, 12:02 PM
Since AC cords have both a 'hot' and 'neutral' (return wire), the inductance cancels out and you won't even get any 'transformer/inductor action' should you have a large coil of wire.

inductors also work on a basis of:
Voltage = Current Change Per Second * Henries
Meaning no current (no load) = No voltage = no power.

That said, a coiled up cord that *had* a load on it, could stay warm for a very long time. Basically all electrical insulators are also good thermal insulators. Hence why you should not coil up the cord in the first place: you are burying heat making wire in several layers of heat making wire covered in insulation. Nowhere for heat to go = Heat builds up = wire overheats long before it would in 'free air'

The same thing would happen if you just wrapped your wire in lots of house insulation.

That cleared up, theres no diff between an extension cord and house wiring as far as your appliance is concerned. 3% voltage drop is *exceptionally* conservative as well. I highly doubt you would notice 10% voltage drop in basically any appliance.

One problem you may encounter is startup currents for compressors (insanely high startup torque needed) may actually cause enough voltage drop to reduce startup torque below whats needed to spin the compressor up before pressure builds, resulting in a stalled out compressor.

Other then that, most power tools will just take slightly longer to spin up and it may be slightly worse for the motor since start up currents cause high dissipation.

Welders likely won't see much diff since they are more or less a constant current load and I doubt 10% voltage makes more difference then say, holding the torch 10% further away.

http://www.prototypemachining.ca/Articles/WireCapacityCharts.html
Gives ohms per foot on the first chart (And melting limits of the insulation), and the 2nd chart is the NEC limits for 3 conductors in a raceway/cable/direct burial. a good starting point for extention cord limits with a decent safty factor.
(Note that the 90c wire rating is the most common you will find)

darryl
04-23-2012, 12:24 PM
You can find a table that shows the recommended wire size for lengths and current levels. You could have 1000 ft of extension cord, and as long as the gauge was heavy enough you wouldn't lose enough voltage to worry about.

As far as the coiled up cord getting hot, I'm going to have to do that experiment. I won't leave home with it plugged in :)

For whatever reason, this reminds me of the utube video showing a guy setting a magnet on a lens, which is placed on a mirror, then surrounded by 9v batteries and AA's. None of the batteries or cells are connected, but the magnet rotates.

garagemark
04-23-2012, 01:30 PM
3% is the National Electric Code rule of thumb for sizing long wire runs to loads using voltage drop calculations. We, as hobbyists in our own home, are not really bound by the "code", but some folks like to stay within certain published parameters.

10% drop of 120 volts is only 108. Some electrically powered items can withstand that... some will not. I have seen undervoltages wreak havoc on electronic speed controls in portaband saws and drill motors. I've also used undersized cords on a little 110 volt wire feed welder. It does NOT perform well at all, and I won't do it again.

Mark

brian Rupnow
04-23-2012, 02:17 PM
When I was young and poor (which seemed to go on for an awfull long time), I had a 220 volt air compressor. I made up a heavy gauge extension cord for it, 50 foot long. This gave me a portable compressor which travelled around in the back of my pickup truck. I was heavily into my "auto painting phase" at that time, and if you had prepared your car for paint and bought the paint and reducer, I would come to your house, plug my extension cord into your stove or dryer receptacle, and paint your car for $50.00---In your garage, under a tarp, under a tree, in your breezeway, even just setting on your lawn. This lead to many hilarious incidents which I won't get into here. Then later, when I was into my "wrought iron" phase, I did the same thing with my 180 Amp Lincoln buzz box. Neither the compressor nor the welder ever seemed to suffer ill effects from running on a 50 foot extension cord.

Tony Pratt
04-23-2012, 02:51 PM
A coiled up extension lead catching fire or melting in my case is not a myth, it happened to me many moons ago! I can't remember the details but the lead was completely ruined.
Tony

darryl
04-23-2012, 02:57 PM
Typical ac motors do take a lot of current at start-up. If there's a lot of voltage drop in the supply, the motor will take longer to come up to speed, and will lose rpms earlier when loaded down. Neither situation is good for it.

If you do the math and figure out the minimum size of conductor for an acceptable loss, then there isn't a problem. Well, cost of the cord might be a problem. Of course the connectors have to be good as well. Those pre-made molded-end extension cords are usually not what you'd choose where there's going to be high currents. The two-wire triple-socket molded end types are the worst and should never be used for anything more than a night light- maybe not even for that. They are garbage in my opinion. If one is looking at that kind of thing as an extension cord, then yes it would be a no-no to use it for anything more than a trouble light, basically.

For a real extension cord to run motorized equipment, you should use cabtire and ends that you put on yourself. None of this is cheap, but a fire is a lot more expensive.

Paul Alciatore
04-23-2012, 02:58 PM
It is really all about the Voltage drop in the cord. All electric conductors have a certain amount of resistance and that resistance translates into a Voltage drop as per Ohms law: E = I x R. Notice that E, the Voltage drop is proportional to both I, the current and R the resistance. I is determined by the device you are operating and can be found on the nameplate. For your extension cord, R is determined by the length and size of the conductors used in it. R is proportional to the length and inversely proportional to the cross sectional area of the conductors. The longer the cord, the more the resistance and therefore the greater the Voltage drop. The bigger the conductors, the LESS the resistance and the less the Voltage drop is. So larger size conductors are needed for longer cords.

The Voltage drop is important because each electric device has a certain operating Voltage range that is needed for proper operation and long life. Any Voltage that is lost as a Voltage drop in the cord is not available for the device. Thus, if you start with 115 VAC and there is a 20 VAC drop in the cord, then your device (welder, drill, hair dryer, etc.) will only be operating on 95 VAC. As a general rule, a 10% Voltage drop is considered the most that many/most devices will accept and still operate satisfactorily. But some can tolerate more and some will not tolerate that much.

Here are some sites that discuss actual applications:

http://www.homedepot.com/webapp/catalog/servlet/ContentView?pn=Extension_Cords_Reels

http://home.mchsi.com/~gweidner/extension-cords.pdf

http://home.mchsi.com/~gweidner/extension-cord-chart.pdf

I searched for [ "extension cord" length table ] and there are many more results. I have personally used extension cords and cables up to 4-0 gauge to extend power with complete success. Connections are important as mentioned above because they can also add resistance which translates to Voltage drops AND heat which can melt or vaporize them. Most tables stop at 20 Amps and if you need a higher current than that, you will probably need to do the calculation yourself. It goes something like this:

1. Determine the Voltage and current you are working with.

2. Determine the length of cordage needed.

3. Determine the maximum allowable Voltage drop for your equipment. If no other criteria is obvious, use 10% or 11.5 Volts for a 115 VAC circuit and 23 Volts for a 230 VAC circuit.

4. Calculate the allowable resistance from Ohms law: R = E / I where E is the Voltage drop from step 3 and I the required current from step 1.

5. Tables like shown below will show the resistance of various gauges of wire per 1000 feet. So we must translate our resistance to an equivalent value for 1000 feet of cable. Since the current travels both ways through the extension cord, coming and going, we must use twice the desired length so multiply the length in step 2 by a factor of 2 (double it).

http://hyperphysics.phy-astr.gsu.edu/hbase/tables/wirega.html

6. Multiply the allowable resistance from step 4 by 1000 and then divide it by twice the length of your extension. This gives you the allowable resistance for 1000 feet of wire/cable. R x 1000 / 2L.

7. Go to the wire table and find the smallest wire size that has the same or a LOWER resistance per 1000 feet as found in step 6. This is the gauge of cable needed for your application.

Black_Moons
04-23-2012, 03:13 PM
I was heavily into my "auto painting phase" at that time, and if you had prepared your car for paint and bought the paint and reducer, I would come to your house, plug my extension cord into your stove or dryer receptacle, and paint your car for $50.00---In your garage, under a tarp, under a tree, in your breezeway, even just setting on your lawn. This lead to many hilarious incidents which I won't get into here.

Hahahha, I can just imagen.. I seem to recall one story from a friend about painting a car shortly before a good gust knocked lots of cotton wood seeds down into the paint... Fuzzy car anyone?

Paul Alciatore
04-23-2012, 03:17 PM
Re: Coiled up cords.

Coiled up cords are generally safe at the current levels normally seen in homes and home shops. If such a cord had a heat problem, it is probably due to the fact that it has undersized conductors for the current level and the heat developed in the cord was not able to dissipate into the surrounding air efficiently due to the coiling. Inductive effects for an AC extension cord should be very minimal because the current is traveling in both directions in two conductors that are in very close proximity. The AC field will cancel almost completely. Resistance and resistive heating is the thing here.

But frankly if an extension cord failed, coiled or not, I would first suspect physical damage, like a nick or kink which would generate a higher resistance area and local heating. Often evidence of such prior damage is lost in the smoke making event.

Now, a coiled DC cable may be different, I don't know. But first analysis fails to show any mechanism other heat that could result in such a cable failing. It would generate a magnetic field, but such a field would only heat a nearby magnetic material, like steel. And that would only happen if the DC current was an unfiltered one (pulsating DC). Again, physical damage would be a far more likely source of failure.

Peter.
04-23-2012, 03:27 PM
Standard length for a power cord is 1.5" short of reaching.

darryl
04-23-2012, 03:32 PM
Speaking of the conductors, these days I'm very wary of ratings and country of manufacture. I have yet to see copper coated steel wire show up in anything but lamp cord and speaker wire, but if it ever showed up in cabtire or any industrial type of supposed copper wire, it would be quite dangerous. A same-gauge steel wire will have at least ten times the resistance as a copper wire. I always take a magnet with me when buying wire. If it shows any attraction to a magnet at all, I'll take it up with the store clerk, but I'll never buy it.

By the way, someone mentioned a while back about poor quality rubber coated wire. Yup, some of that crap is here, and it doesn't last- it hardens and cracks prematurely. An old section of proper cabtire will still be soft and flexible decades later, and will continue to outlast some of the new crap for decades yet. I'm hoping that the american made cabtire doesn't go cheap on the rubber compound.

Paul Alciatore
04-23-2012, 03:54 PM
The only steel cable I have ever seen was Army comm cable for field telephones. If I recall correctly, it had 3 steel strands and 4 copper ones. This was done for durability, the steel made it a LOT harder to break while the copper strands maintained conductivity. It was great as it was strong enough for a large range of other uses. Like towing your Jeep.




Speaking of the conductors, these days I'm very wary of ratings and country of manufacture. I have yet to see copper coated steel wire show up in anything but lamp cord and speaker wire, but if it ever showed up in cabtire or any industrial type of supposed copper wire, it would be quite dangerous. A same-gauge steel wire will have at least ten times the resistance as a copper wire. I always take a magnet with me when buying wire. If it shows any attraction to a magnet at all, I'll take it up with the store clerk, but I'll never buy it.

By the way, someone mentioned a while back about poor quality rubber coated wire. Yup, some of that crap is here, and it doesn't last- it hardens and cracks prematurely. An old section of proper cabtire will still be soft and flexible decades later, and will continue to outlast some of the new crap for decades yet. I'm hoping that the american made cabtire doesn't go cheap on the rubber compound.

sasquatch
04-23-2012, 04:37 PM
House wiring can easily be 100ft long to a recepticle, and usually the pannel is installed on the front corner of the house etc.

So, here we have a few runs to different distant corners of the house, that could be 100ft long (after sneaking around all the corners , through the walls etc, ) and that wire is usually #14, then i have to shake my head as i see people buying 50-75 or even 100ft extension cords, and plugging them into that recepticle that is only #14 wire, and is already 100ft from the pannel.

There must be a LOT of burnt out power tools, and electric whipper snippers/ lawn mowers !!

RancherBill
04-23-2012, 05:32 PM
Since AC cords have both a 'hot' and 'neutral' (return wire), the inductance cancels out and you won't even get any 'transformer/inductor action' should you have a large coil of wire.

This a 230 volt cable, he said he would plug into a dryer plug etc.

So does the inductance cancel here also? They 180 degrees out of phase from each other.

Lew Hartswick
04-23-2012, 05:43 PM
This a 230 volt cable, he said he would plug into a dryer plug etc.

So does the inductance cancel here also? They 180 degrees out of phase from each other.
The electrons still go out one wire and have to come back the other .
Come ON!!! :-)
...lew...

RussZHC
04-23-2012, 07:09 PM
Thanks for all input...there is no specific/exact welder just keeping eyes open, I still don't have a gloat :D
BUT there is a Miller CST 280, used, available at what is an OK price for me. Connection would be a bit of a hassle, so thought I'd ask.

I am just learning MIG (a bit of a thread over on the welding forum) but, if I understand correctly, the above model is capable as "stick" as well as TIG, is in a "suitcase" format. So it, or something like it, would make me "capable" of the most usable forms of welding (for me).

The issue is the voltage supply. At some point it may come down to extension cords, better supply to the garage (I know that is best but only solves the issue in that one spot), or something engine driven (for me the latter, right now, is the extreme but it could also solve the compressor issue)


There are a few Youtube videos featuring this particular welder (CST 280) and they only add to my question as some feature ship repair where cables are literally running all over the place.

Clevelander
04-23-2012, 07:30 PM
Be generous in your wire selection...too large a wire just means your machine will have a better voltage supply, at more power available. Your extension cord will run cooler if it is a larger gage. Yes it is better not to run the wire in a coil, particularly on a holder where the wires are held close to each other on a reel, basically you are heating the wire and then putting a heater around it so it can't dissipate properly. If the wire is cool to the touch you have nothing to be concerned about PROVIDED you have used an adequate sized connector in the system. Quite often the connectors tend to be the weak link. Wire is typically rated to run at a maximum of 60 degrees celcius. Easy check...if it's uncomfortable to touch it's the load is too heavy.

J Tiers
04-23-2012, 10:42 PM
The coiled cord thing is no joke.....

It is the same thing as the NEC...... the table you usually see for current capacity.... most people don't realize that is for 3 or fewer wires in a cable or a single "raceway"....which means one conduit or wireway, etc.

When you put several additional wires in, the current capacity is decreased according to a derating table. The reason is that the insulation temperature may be exceeded.

I have personally seen extension cords at our trade show booth get overheated when coiled. The regular orange type.... must have been 50 foot of wire coiled up , 6 of them in a row inside a section of the display, powering lights behind big photos. Nobody was there for some reason (just after hours maybe). Were not turned off due to union rules (only union folks were allowed to shut off or turn on power).

They were so hot they stank, couldn't be touched, and the jackets were starting to melt a little. I came back to the booth just as a facility electrician walked by sniffing the air. I asked him if he smelled what I smelled, and he did, so we poked into the matter and found the cords. We unplugged the lot, (no union fuss when I did some of them).

We also spread out the coils , which were just laying on the concrete floor.

Your Old Dog
04-23-2012, 10:52 PM
You mean between substations?

I haven't read the entire thread but based on JTiers post I'll offer this one. Cord heat is one of the main cause of fires at Christmas. Extension cords get snugged up tight around table legs and when the current starts to climb the insulation starts to melt and walla you got a fire. Don't pinch insulation if there is any chance a cord will be pulling some serious current.

dave5605
04-25-2012, 12:16 PM
One thing you don't want to do is coil your extension cords on a steel spool and then just unwind what you need. If you keep it coiled you will induce voltage on the ground and the ground(and the machines steel frame) could be at 90v (out of 120v) and no breaker will trip. Then if you get between that machine frame and one properly wired with no extension cord you can get zapped. Two grounded frames with 90v between them.

Needless to say I threw out my metal spools that had all my 100' cords wrapped on them.

You can actually watch the voltage on the ground go down as you unwind the cord from the spool. Simple transformer action at work.

Btw, I have a 50' cord made from #4 wire/cable that originally powered a double wide trailer/home. 50 amp plug/receptacle for my welder in those unique situations where what I'm welding can't get close to the power source.

J Tiers
04-25-2012, 09:59 PM
Dave.... that makes no sense to me..... maybe I don't get what you are driving at...

There isn't enough metal in most any metal reel to do a dang thing, and the reference to voltage on ground also doesn't make sense to me. there is no net field, for the reasons given above.

Black_Moons
04-25-2012, 10:05 PM
One thing you don't want to do is coil your extension cords on a steel spool and then just unwind what you need. If you keep it coiled you will induce voltage on the ground and the ground(and the machines steel frame) could be at 90v (out of 120v) and no breaker will trip. Then if you get between that machine frame and one properly wired with no extension cord you can get zapped. Two grounded frames with 90v between them.

Needless to say I threw out my metal spools that had all my 100' cords wrapped on them.

You can actually watch the voltage on the ground go down as you unwind the cord from the spool. Simple transformer action at work.

Btw, I have a 50' cord made from #4 wire/cable that originally powered a double wide trailer/home. 50 amp plug/receptacle for my welder in those unique situations where what I'm welding can't get close to the power source.

... Insulation leakage through the cord, Not transformer action. Won't even be more then a few 100 uA unless the cord is damaged and wet (or damaged and shorting out to the reel)

J Tiers
04-25-2012, 11:58 PM
... Insulation leakage through the cord, Not transformer action. Won't even be more then a few 100 uA unless the cord is damaged and wet (or damaged and shorting out to the reel)

probably less than that...... BOTH wires are on the reel, plus ground in many cases, so the net voltage is unlikely to be over half the hot wire voltage.

I bet it isn't leakage, but capacitive coupling that is being described, anyhow.

Evan
04-26-2012, 01:24 AM
About the fake copper wire Darryl mentioned, it's around. Here is some I bought at a local dollar store. Looks like copper but it is a few microns of copper on iron. It is sold as "speaker wire" but if it were used as lamp cord there could be a serious risk of fire with a high wattage load. It looks like they made the strands really fine so it would bend as easily as real copper.

http://ixian.ca/pics9/scamcopper2.jpg

This is the entire coil hanging from a magnet stuck to the fireplace poker.

http://ixian.ca/pics9/scamcopper3.jpg

dp
04-26-2012, 01:39 AM
This topic reminds me of a story I wrote a long time ago. http://hawglydavidson.com/vbgstories/how_hard_could_it_be.html

I needed to reduce the current draw of the welder to prevent the breaker popping so plugged it into a long extension cord.

It worked!

vpt
04-26-2012, 08:34 AM
The guys that had problems with coiled wires, are these cheap walmart cords? Overloading the cords? For over 25 years now we have had multiple cords coiled at the outlet for our pond agitators. These are 1/3hp motors that run 24/7/365, have 150' cords on them and anywhere between 75-25' of cord is coiled. Maybe we are just lucky?

garagemark
04-26-2012, 09:26 AM
The amount of heating is directly proportional to the amount of current passing through the conductor, the conductor size, and the number of turns in the coil. A cord with no current passing will exhibit no heating. A light load will create some amount of heat, and a heavy load is where the trouble could begin.

As a general rule, it's always going to be best to keep cord lengths as short as possible and use as heavy conductor cord as required for the intended load.

We use very heavy 480 volt extension cords here at the plant constantly to run large cooling fans over our aluminum casting sow molds. We keep the lengths as short as possible, and slightly oversize the cable to the fans (the magnetic starters are mounted on the fans). Never a heating problem yet.

Evan
04-26-2012, 07:30 PM
The type of insulation is also very important. Real rubber insulation won't melt at all. It has to be set on fire by the wiring which takes a very high load. Low temperature plastic insulations which are really common on cheap cords will melt long before the wire is hot enough to affect rubber and allow the wires to short a strand or two which will then rapidly heat to fire starting temperature. The plastic insulation also ignites easily at relatively low temperatures.

The bottom line is that an extension cord will work fine. However, for it to be safe the cost of proper 40-50 amp wire will make your eyes water.

sasquatch
04-26-2012, 07:38 PM
Those cheap orange cords are a real bad buy. I see them all the time in 50-75ft lengths.

They shouldn't be sold in any length over 12ft. Most i see are #16-#18 wire.

Back a few years ago i bought a Large diameter yellow cord 75ft length, it was the diameter of at least a #12.

Had moulded ends on it, and one was messed up, so i went to put a new end on it, and it was only #16 wire. (there were no outside markings on the cord, which i guess should have been a clue.)

So i cut it up into 12ft lengths put ends on a couple and used it for light applications.

Boostinjdm
04-26-2012, 09:00 PM
This topic reminds me of a story I wrote a long time ago. http://hawglydavidson.com/vbgstories/how_hard_could_it_be.html

I needed to reduce the current draw of the welder to prevent the breaker popping so plugged it into a long extension cord.

It worked!

That's ass backwards. Adding cord length results in voltage drop which increases amp draw for a given wattage.

dp
04-26-2012, 09:12 PM
That's ass backwards. Adding cord length results in voltage drop which increases amp draw for a given wattage.

The given wattage dropped and the breaker quit popping.

Evan
04-26-2012, 10:31 PM
That's ass backwards. Adding cord length results in voltage drop which increases amp draw for a given wattage.

That can happen with an induction motor but not with a transformer welder.

J Tiers
04-26-2012, 11:01 PM
That's ass backwards. Adding cord length results in voltage drop which increases amp draw for a given wattage.

Only for a "negative resistance" device...... anything which draws on a "power" basis ....... Things like motors, and some types of switchmode power supply.

If power is constant and voltage goes down, current MUST go up.

vpt
04-27-2012, 08:33 AM
Those cheap orange cords are a real bad buy. I see them all the time in 50-75ft lengths.

They shouldn't be sold in any length over 12ft. Most i see are #16-#18 wire.

Back a few years ago i bought a Large diameter yellow cord 75ft length, it was the diameter of at least a #12.

Had moulded ends on it, and one was messed up, so i went to put a new end on it, and it was only #16 wire. (there were no outside markings on the cord, which i guess should have been a clue.)

So i cut it up into 12ft lengths put ends on a couple and used it for light applications.


I like to buy the cheap cords to replace worn or broken power tool cords. When I can find the black cheaper extension cords I get a little smile on my face and grab a few.

I have a few good extension cords in the shop that I use daily, one of them is a yellow one but a good one, not that sub $20 stuff. Nothing beats a 'good' cord! That seems to be the case with most things though, like the saying "you get what you pay for".

Black_Moons
04-27-2012, 09:16 AM
osha recommends that all extention cords be exactly 2 feet too short for the job at hand to prevent coiling. :rolleyes: