Friends:
The temperature and voltage drop tables are the basis for selecting wire sizes for various usage (and you can download simple software that will speed the process up. However, they do nothing to help you determine the aperage needs of the building in question. I have a guide for residential use that shows how to factor in HVAC, stoves and ovens, ligting circuits, fans, etc., but nothing that would help with workshops and barns.
I have a workshop with medium duty band saw, scroll saw, heavy drill press, 2 1/2 horse router, etc., as well as the normal lighting and so forth. Also have a barn which WILL have a lighting circuit with 10 or 12 lamps, a 20a general purpose circuit including window unit and ceiling fan, and another 20a tool cirsuit that will be rarely used.
Any suggestions on sizing wire to feed these?
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First question, is this strictly a one man personal shop, where you'd only use one machine at a time? Or is it likely that you'll have other people using multiple machines simultaneously?
With the price of copper somewhere between astronomical and obscene, for big feeders running a long distance you may have to resort to aluminum.
-- J.S.
For a workshop or barn you want to look at the large set of combined equipment that you will be using at one time.
And include what you might like to have.
For a typical woodshop that might be:
3 hp tablesaw, 2 hp dust collector, lights and heat/AC.
Saw 4400 watts
DC 2900 watts
Lights don't know how big a space or the type of lights, but 1000 watts is large amount
1000 watts.
Again I don't know what the size or climate is, but maybe 3500 watt utility heater.
3500 watts.
That is total of 11,800 watts or 50 amps at 240.
In answer to both of your kind responses:Shop will usually be one-man with someone else in there on occasion -- but certainly not a production shopLighting is provided by seven fluorescent troughers with two 48" tubes each at about .43 amp each, for a total if all are lit of about 6 amps.Heat is provided by a small plug-in oscilating table unit when needed (about two months a year). Not sure of the wattage, but well under 15 amps current draw.Possibly a window a/c unit for use about 2 months a year.The saw and DC load as you show it would be about 30a.So we are still in the range of between 40 and 50A at 240.If we say 50a at 240, and we balance the load at the panel, am I correct that each leg should be sized for half of that? If so I can use 6awg copper for the feeders (about 120 ft). Does this make sense?
"The saw and DC load as you show it would be about 30a."Yes, if you are talking about 240.Again depends on the specific equipment, but if you are probably talking about 1000 watts for heat and also for small to medium size window AC.So that is a little less than I used.So 50 amps is a good working number for a shop.But when you talk about 50 amps is 50 amps in each leg.#6 copper will be good for that distance.And #6 AL will work, but marginal. Also you will need to use wire and connections that are rated for 75* C (and most are).But #4 AL would give you a little better margin on voltage drop.
50 a at 240 volt (if that is your estimate) is at minimum 8 ga copper. (it would be 6 ga aluminum. That is EACH wire is 6 or 8 GA. don't chintz out here.
In metal conduit this is the factor people use to determine voltage drop.
Voltage drop on 8 ga. wire is about .15 ie 100 foot at 100 volts supplied yields 85 volts at the end.
6 Ga is .095 or 100 foot is 90.5 volts on a 100 foot run.
4 ga is .062 or 93.8 volts.
3 ga is .048 or 96.2 volts.
now understand no one runs 100 volts. it is 120 or whatever variance you have locally. the length of the run if 200 feet is doubled. etc.
Use big wire, make good connections.Jack of all trades and master of none - you got a problem with that?
Voltage drop on 8 ga. wire is about .15 ie 100 foot at 100 volts supplied yields 85 volts at the end.
'might want to check your math on that one. 8 AWG copper is 0.0764 ohms per 100'. At 50A, thats a voltage drop of 50 x 0.0764 = 3.8 volts in each leg, or 7.6 volts total voltage drop.
Where do you get 4400 W for a 3 HP TS? 746 W = 1HP. I thought Ohm's Law for power was P=IE. 240 x 50 =12000. C'mon, show your work.
"I cut this piece four times and it's still too short."
I don't have the wire handy right now to see the type -- do plan to run it in tightly laid conduit -- would that make a difference to your concerns?I know the code "has it all," and even that Code Check Electrical has a lot of it. However, to someone like me who has a significant electrical project no more than once or twice a year, the prospect of buying and studying the code is a little daunting. I am grateful for the advice I get here, and hope you don't get tired of my questions.
You don't need to read and remember the whole book, just look up the sections that apply to what you need to do i.e., wire gauge, how many can occupy the different sizes of conduit, what kind of conduit is needed to particular applications, recepticle types, how many can be on one circuit, etc.
I just had some work done by someone who normally works in industrial situations and he referred to the manual several times because it was a residential job. I would rather have him look it up than think he knows it all, but is wrong.
Don't worry about my concerns, worry about whether it's up to code and satisfies the inspector.
"I cut this piece four times and it's still too short."
As it happens, there IS no inspector out here.The wire in question does not seem to have a type stamped on the jacket. However, it is 6 awg fine stranded with a silicon rubber insulator and a braided fibreglass protective outer jacket. Seems I have about 500' of it, and unless there is a safety issue, with the price of copper these days, I'd like to use it.Any thoughts?
Joe,
I will catch a lot of grief on this! If the cable is not rated for UF moisture. Oversize your conduit and pull interduck thru to keep the moisture out. It works for moisture sensitive telecom cable.
Cost of copper! I would use it for my shop!
What do you need this wire for, exactly? If it's total overkill, I would consider selling it for scrap and buy what you really need. You may come out ahead.
"I cut this piece four times and it's still too short."
Highfive:Very simply, I need the wire to feed an outbuilding. We have already determined that I need 4awg for the workshop, but the barn (a completely separate building) just has two light circuits, a general 20a tool circuit and a small a/c window unit. There is hardly anything ever pludgged in or turned on except for a vacuum cleaner, power hand tools, or the window unit. Right now we run power when we need it over a 12 awg cord set with 20a connector and plug, and use battery power for lights.I am going to run 240 down there but don't need more than about 30a max (which would give me plenty to spare).
it definitely sounds like SRML
Silicone Rubber Motor Lead wire
it has three temp ratings too
200C...180C....and 150Cit is used in high temp settings,
motor leads
transformers,
HID lighting,
steel mills,
foundriesjust not underground as feeders.....its the wrong stuffyou need wire with a W in the designator
TW,
MTW,
THW,
THW-2,
THWN,
THWN-2
RHW,
RHW-2
XHHW,
XHHW-2,or a U.........UF, or USE.
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Finally got good light and a magnifying glass (hard to reed black stamped on grey braid). Turns out the wire is pretty much what you thought, but designated differently. It is 6awg SFF-2/SEWF-2 rated for 150c and 600 volts. I take your point about using wet-rated wire. Just as a matter of curiosity, what about SFF causes it to fail in damp conditions?
It is not shown in the NEC.Apparently it is only listed for used in fixtures and equipment wirings.http://www.firstcapitol.com/sff2_sewf2.htmhttp://www.tevelec.com/CatalogProducts.asp?nProductsID=262
I found the same thing, and asked my electrician last night -- who of course also failed to find it in the NEC. So, his answer was that the NEC forbids it because it is not listed for damp.OK, I am fine with that.I am still curious as to why that type of wire is unsafe in wet conditions. Doubtless there is a reason, but no one seems to know it.
Mainly that is not what it was designed for. Thus no one looked up the specs and tried to evaluated for a wet application.It is designed for high temp work. And is probably much, much too expensive if someone wanted to buy it for use in wet areas.
Exactly -- It sounds like a low volume product, and a more expensive one to make. If it's in good condition, he may well be money ahead to sell it off and buy the right stuff.
-- J.S.
that wire is intended for some very specific uses and for industries that need that degree of insulation.... it is used mostly as short leads and not feeders....I routinely use it for re/wiring highbay lights, motors,controls, ..... and heating elements along with some situations that benefit from the flexibility of both types....the conductor is simply not rated for immersion .....although it could in all probability last a long time without problem..... I personally am not in the habit of experimenting with electricity and and would not suggest that to anyone the call is all yours since there is no inspector around !!your dillemna is still one of the gauge being borderline with the NEC requirement of 3% VD for a 50A load.
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I wonder who would buy it?
BTW, the 50a feed is to the workshop, and I will go ahead with the original plan to use #4 -- the 30a feed is to the barn and that is where I was considering using the #6 hi-temp wire.
...30A load........that sure got lost in the conversation .who would by it ? motor repair shop
an industrial supplier ?????
e-bay
the scrapmanthat stuff is VERY expensive, you may want to spend some time trying to unload itOR
you could run GRS and dope the couplings,seal the ends, add Schrader valves, a pressure gauge, a PS with an ASCO valve and keep the pipe pressurized with dry nitrogen...that would keep moisture out.........).
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Edited 10/31/2006 6:17 am by maddog3
How expensive is it? Any idea the price per spool in today's market?I like your idea about the the pressurized pipe, but, as this is for a barn, I wonder if I could use methane instead? I might be able to put a ball-cock pressure valve on the barn end and develop a sort of collection device to attach over the tails of the natural sources of pressurized methane, and connect it to the the pressure value with a long flexible armored tube. As I see it, that would be a truly green, sustainable use -- of course, an arc in the pipe might lead to unfortunate consequences, but risk the price of progress. It is the nature of science to probe the unknown.This concept, though advanced, sophisticated, and environmentally pro-active, is probably not in the NEC, though...
Yeah, unfortunate consequences. Reminds me of the story about the lightning strike that went thru a septic tank and leach field.... ;-)
-- J.S.
I will check the $$$ tomorrow....but you are somewhere in the 0000.00...probably $4 / ft...." This concept, though advanced, sophisticated, and environmentally pro-active, is probably not in the NEC, though..."yeah but neither is your wire, so the whole electrifying your barn thing could be one big noisy experiment..... consider using PVC coated GRS ...the couplings have long flanges on them...for a better seal
and don't forget the high dollar gas compressor you will surely need andjust need to know where to send the flowers, hope your not in Indiana !
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Actually, if I tap into the natural source of the methane, it comes out pressurized. The big promlem would be for the methane generators to step on the gas pipeline tubes.
another problem would be the chunky , or semi-solid methane .........
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Well, yes that's true. I'd have to devise some kind of a separator, which might be a simple, gravity-operated device. I have thought of another challenge As anyone who has been around the oil and gas business knows, bottom-hole pressure is important to the percentage of recovery, consistent pipeline operation, etc. , In this case, I fear that bottom-hole pressure will be quite inconsistent. Of course, as the plan is to use the methane as a nitrogen substitute in the conduit, rather than to transmit gas fuel to some third-party end user, perhaps a the ball check valve will be all that is needed and consistency is not critical.Of course, if sufficient pressure can be generated, it might be feasable to install a flexible storage unit that taps into the conduit, and to draw off of that for gas lights and heat -- but perhaps not for cooking...BTW, where in Indiana do you hang your hat?
Just in case you wondered, bottomhole pressure in an oilfield engineering sense is defined as follows in Schlumberger's on-line Oilfield Glossary. It would be an interesting exercize to translate this into the terms of my methane generators, wouldn't it? Think of "mud weight" and especially "fluid friction in the annulus." ____________________________________________________________________The pressure, usually measured in pounds per square in. (psi), at the bottom of the hole. This pressure may be calculated in a static, fluid-filled wellbore with the equation:BHP = MW * Depth * 0.052where BHP is the bottomhole pressure in pounds per square in., MW is the mud weight in pounds per gallon, Depth is the true vertical depth in feet, and 0.052 is a conversion factor if these units of measure are used. For circulating wellbores, the BHP increases by the amount of fluid friction in the annulus. The BHP gradient should exceed the formation pressure gradient to avoid an influx of formation fluid into the wellbore.On the other hand, if BHP (including the added fluid friction pressure of a flowing fluid) is too high, a weak formation may fracture and cause a loss of wellbore fluids. The loss of fluid to one formation may be followed by the influx of fluid from another formation.
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well......my first pun of the evening,depth, in your example, could remain constant.
the only variable then would be MW !
which if I understand the equation would vary from feeding to feeding..
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Hmmm.Actually I think there would be two variables in this case. One would be MW as you point out, and the other would be the actual methane content of the reservoir. However, both would seem to be affected by the same feed factor, so perhaps with a bit of calculus we could develop a fairly predictive formula.
the resevoir(s) cyclic nature could perhaps be supplemented by connection through a surge tank to a secondary source of methane...a rice paddy perhaps.... co-generation ? I think so, effluent could be pumped into the (flooded) paddy increasing the root density of the plants through anaerobic digestion, providing larger yields and a constant source of fuel for the generator(s)and at the same time thumb our noses at Kyotowhere are you located?
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Edited 11/1/2006 5:09 am by maddog3
Located in North Texas -- in a drought -- which makes the otherwise excellent rice paddy solution somewhat problematic...
well It sounded like a crazy enough idea at the time. ...it snowed here today, wind chill = 24FYI, your #6 wire was @ $2.98 / ft...or $1490.00 for 500' with the discountOTC would be significantly higher though.
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That is indeed expensive. Around here a 500' spool of 6 awg THHN retails for between $.80 and $.90 to walk-in traffic with no volume or contractor discount. So, my wire is about 4x more expensive.I have just listed it on eBay. We'll see if anyone wants it.
Edited 11/2/2006 11:40 pm ET by Joe Sullivan
...NW Ind. near the Mich. line, about an hour East from Illinois, near the southern tip of the Lake.
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Aha. That's why you are familiar with the needs of steel mills and foundaries. I once worked at a steel foundry in Milwaukee. It is a dying business, but I must admit, there is something molton steel and the casting business that really gets into your blood.Electricians who know their trade are critical guys and not easy to find in that business.
Thank you, that is nice of you to say.I work in an Iron Foundry that pours large engine blocks ,and wind turbine hubs ..primarily....
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The 2005 NEC may be accessed online on the NFPA site for free.
Whether the conduit is tightly laid or not makes no difference. The inside of conduit is not a "location" for the purposes of the NEC; what counts is the location of the conduit. If it's underground, then the wire type must be listed for wet locations.
where/how can I access the 05 code for free? nfpa.org doesn't seem to give a full free view of the code...or does it?
Homer, I took them up on it and went and looked. It took quite a while to figure out, but you have to find this page :http://www.nfpa.org/aboutthecodes/AboutTheCodes.asp?DocNum=70Once you are at the Code 70 page, you must scroll down to the bottom where there is a read heading that says "Additional Information About This Document." At the top of the section with that heading, you have to click on "Preview This Document." After you do that, it will take you to a page where you have to agree to their limited use policy. You click "I Agree." You will be taken to a page full of explanitory type. On that pace is a hyperlink that says, " Open National Electrical Code 2005 Softbound Edition." Click that and it will download in a bit.Once you have it, be sure and click on the Table of Contents Icon. It is a grey button that looks like a list. Usig that you can page through the table of contents and jump to sections. WIthout it, you have to turn one page at a time.You can't download, copy, or print anything. It is not honor system. It just will not do those things. There is also no index function that I can find.They say they have put it up for public participation, but they certainly make it an involved, time-consunming nuisence. Bottom line, they want to sell $75 code books -- not that I blame them.
The online NEC does have an index function - click on the little button at the bottom right of the cover page, the one with
1.____
2.____
3.____
on it.
Edited to add: I should say, it's a table of contents and not an index...
Edited 10/29/2006 10:21 am ET by Stuart
It is tricky to find. At the NFPA home page, click on Publications at the top of the screen. That opens up a drop down menu. Scroll down to necdigest, then go to Review the NEC Online.
"I thought Ohm's Law for power was P=IE. 240 x 50 =12000"Ohms law has to do with ohms. V = IR. Nothing to do with power.Although to be completely accurate I should not have used the term watts, but rather VA (volts amps)."Where do you get 4400 W for a 3 HP TS? 746 W = 1HP."Watts and HP are measurements for power, just using different units. And the conversion factor 1HP = 746 W.But that only has a limited relationship with the INPUT power to the motor. You have ineffectancy and losses in the motor.But also, while you only pay for real power (watts) the wiring and service needs to also include reactive power.That is why I said that the I should have used the term VA instead of Watts.Now the NEC say for a 3 HP motor you should use 17 amps. I used 18 as WW machines often have import motors that draw a little more and then rounded it up.And to be real accurate I should have use 230 volts as that is where the motor is speced.
Sorry, I actually meant that the Power Formula is P=IE, not Ohm's Law. I know 1HP = 746 W, that's why I stated it, although that's actually output, not input as you said. Remember the thread about compressor ratings? I saw you there, don't try to deny it!. lolWanna convert the power to BTUs? JK. From ttp://everything2.com/index.pl?node_id=1311867"For most power consumers, Volt-Amp (VA) is simply another term for Watt. The majority of the power draw for the average person is used up in such items as light bulbs, power supplies for electronics, heating elements in cooking appliances, and other such uses. These power draws are basically resistive, that is, they can be modeled as resistors in a circuit.
Inductive LoadsFor larger power consumers, however, Volt-Amps are a more complicated matter. Large factories will have a number of machines which are mostly powered by electric motors. Electric motors represent a large inductive load, that is, they must be modeled in a circuit using inductors, because their operation depends on the creation of a rotating magnetic field. (The relatively small motors in ceiling fans, vacuum cleaners, and clothes dryers in a typical household are not a significant enough source of inductance to worry about.) "And, since you obviously have a technical background, here's a link you will probably find pretty amusing. http://www.youtube.com/watch?v=W1kxfG57-_4
"I cut this piece four times and it's still too short."
That is a good one.
Good thing they eliminated the side fumbling.
"I cut this piece four times and it's still too short."
I would suggest using larger wire, because the VD on the 50A load using #6 leaves very little room for additional equipment later on.
adding just ten more amps would put you over 3% total VD
install more than you think you need, as it has been my experience that panels can fill up very quickly
....... especially when tools are involved
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OK, #4 it is. I was trying to talk my way out of it, as I have a good-sized spool of hi-temp (fiberglas cover) #6 copper fine-strand machine wire. Have been shopping for a decent price on #4 (4 conductors needed) but am finding it hard to best the $0.80/ft at big orange on a 500 ft spool.
hi-temp wire ...is it SRML ?it has many excellent uses,
but IMHO underground feeders is not one of themif you are running underground the stuff would be in water almost constantly and it doesn't take abrading too well either..
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Years ago I had the exact same quandry when I was converting my 2 car garage to a single person woodshop which was a separate building about 100' from the meter. Not knowing as much about it ,nor caring at the time, I ran #6 to a small sub. I did regret not using #4 or even 2 as the drop was just signifigant enough. It ran all my 240 equip ok , but there was no room to expand anywhere. Good thing it was only me there.
Why don't you get a copy of the National Electrical Code? It's all in there.
Oddly enough, you actually pay a professional for his training and experience- as well as his time and tools. You really ought to sit down with an electrician and discuss this.
By "electrician," I mean someone with a license or a journeyman' card- not some self-taught handy type the 'can pull wire.' Only those who went through the training will have the bookwork needed for this discussion.
I do mean "electrician;" not 'engineer', 'architect', or the guy at the parts house.
In far more general terms, I highly recommend feeding the barn with buried pipe. Bury it deep. Make it big. That way, if later you want "more power," you can replace the small wires with big ones.
Likewise, I suggest a panel no smaller than one able to take 8 full size breakers. A good arrangement is to have a disconnect outside the building, with the panel inside. I'd still prefer to use an "outdoor" panel inside. If you mount a "gutter" either under, or next to, the panel, you will have plenty of space to connect your circuits.
You will need to run four wires- a ground wire is a must, as you will be keeping the grounds and neutrals separate from each other. You will also need a ground rod out at the barn.
At a bare minimum, I'd run #8 in a 1 1/2" pipe.
Look, I am a professional, in a different field (NOT a lawyer)and I don't mind paying for professional advice. In fact, although he is out of pocket right now, I had worked with a master electricial on some elements of this re-wiring, especially grounding -- after someone on this forum mentioned that there were possible problems with the equipotential plain in animal shelters.I am with you completely about pipe, buried deeply, and well oversize. That is already in the plan. I understand about the need for four wires, and we have a way above code grounding system at the servie panel with 2 awg wire, and an array or four properly placed electrodes connected to the ground wire using Cadweld.The whole issue here was wire size. I don't want to pay retail for hundreds of feet of copper. 6 awg is much easier to find, and cheaper than 4 awg. Also, I have 500 feet of the 6 awg wire that became so controversial earlier in the thread. So I was trying to decide if I wanted to reach for 4 awg, or settle for 6 awg. That's why I asked if anyone knew a formula for rating workshops. There is one for residences, one for agricultural buildings, and one for many other special purposes. The usually do something like rate the highest expected load at 100%, the next at 60% and so on.At the time the thread started, it had never occurred to me to ask anyone about my silicon rubber/woven fiberglass coated wire. When the subject coma up, I was of course concerned and the guys who brought it up sounded like they might know what they were talking about.So I asked more questions.
the closest thing I could find was 220.103 and tables...but it is for an actual Farm...
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When I post to any forum, I try to address related issues, as well as explain things so that anyone can understand them; my answers are more for the general public (who might read this next year), than just the original poster. Nor do I try to define "code minimums" for the application. The code quite plainly states that it is not to be used as a design manual; far better to try to design for the actual use. Now, what you are asking for is a "load calculation." This is done based upon your specific loads. These generally break down into three categories:
- An amount based upon the size of the place, it's use, and a multiplier (usually) found in the NEC. Since this use is not specifically listed, and workshops usually like lots of light, I would suggest assuming a lighting load of 3 watt/ sq. ft if you're using T-8 florescents .... 4 watts/ sq ft. if you're using "recycled" fixtures; - An amount basted upon 125% of any fixed loads, such as water heaters, space heaters/ air conditioners, etc.; and, -An amount based upon the highest combination of shop equipment likely to be used at any one time. For example, the table saw + the dust collector + the air compressor. For the last two items, the loads are based upon the full load amps on the equipment nameplates. The procedure is essentially the same as that used for a home- or any other structure. Since there are a number of "value judgements" to be made, having an electrician do the math is well advised.