What size plasma cutter?

I am getting a new plasma cutter. I have decided on HyperTherm ONLY. I have a Victor smoke wrench for big stuff now, and am considering this for small stuff, including some 20somethingish gauge paintlock, which I shall shape into sculptures and works d' arte.
I was wrestling with what size to get. I tend to overbuy on stuff, but I think with this, I can go with what I need. The larger ones need more air, hence bigger compressor. It already looks like I'll need a compressor to go with this anyway. There is a huge difference in price for each jump in capacity, so one of those jumps could easily pay for the compressor. I would be doing a lot of cutting, so wonder if a 30 would be hearty enough for high duty cycle. Or would a 45 be better, or just overkill, which I like?
How about used units? Are gently used units a good risk? Is there a lot that goes out on these things when used correctly?
I would have to say that one with 3/8 capacity would do the work I want to do, and for all the extra money, I can live with my gas rig for thicker cutting.
TIA
Steve

Steve - Good choice on the company - If you cut metal, I would get the larger one.
Saying that, what voltages and cables do they support ? 3Phase generally means better duty cycle. But might not be handy.
IIRC, those are user level plug in power cables and can switch. Look into it - if one has it and the other doesn't - might be useful for resale or relocation.
e.g. portable means tote it from place to place. I roll mine if needed, got a 50' torch cable instead. I have a metal core unit. A 600 with the torch upgrade.
I press it to the limit some times and it comes through for me.
Martin
On 12/5/2011 5:44 PM, Steve B wrote:
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Now you got me thinking. The brochure says a 13.5amp draw. My line going to the shop is 165' of 8/3 /grnd., iirc. Maybe 10/3 w/grnd.
My wirefeeds have been run at high amperages and I have not popped a breaker out there yet. I haven't had anything else of a 220v. flavor hooked up out there.
Any idea of how close that is to the limits of the main wire? Or what the ideal wire size would be, although it's too late now if the wire's too small. I need to go look at that cable and get the exact size, and consider it before making choice of machines. The job was done by a licensed electrician, so, I know it's done right. Still, any feed will only provide so much juice. At the time, I did not think I'd ever have a plasma cutter.
Steve

Make that input current 13.5a. Output current 15-30a.
Steve

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Even an 8-3 line out 165' from the house is WAY too small for a home shop garage , barely enough for lights and plugs, and a drill press or other very light power tools. When you strike an arc, the lights should NOT dim very much...
If you plan to run a real compressor (5-HP or better) and a welder or plasma cutter at the same time - I'd be looking at a minimum100A 120/240V line and sub-panel out to the shop building, and #2 Copper or 2/0 Aluminum headed out there in a 2" conduit.
Or even another step bigger (both wire and 3" or even 4" power conduit) to allow for voltage drop - it adds up fast.
If you aren't "visual blight averse", you can always go with overhead wire out there - it needs to be XLPE insulation, and you need Quadplex wire being after the House Main - 3 insulated wires (hots and Neutral) wrapped around a bare ground strand. After the House Main you aren't allowed to combine Neutral and Ground.
http://www.cmewire.com/catalog/power/servicedrop/09serviceDrop-XLPE-600v-Quadruplex.pdf
This is the one time where Aluminum wire is perfectly acceptable, overhead or underground, because it's point to point. And you leave some slack at both ends for the inevitable bad connection where you have to cut off three inches and terminate it again.
While you have the trench open, put in extra conduits - a few 1" for Phone or CATV with a good 1' horizontal separation from the power line, and a spare 2" for when you burn up the old wire and it won't repull - and it's February and you really don't feel like digging trenches when the high will be -20F.
Plus one conduit to send PEX Pipe with cold potable water out to the garage, and another with compressed air feed back to the house for doing Honey-Do's (nailers and caulking guns) without 300' of hose. Same thinking, if it goes bad it's easy to pull a new one through the sleeve, rather than get out a shovel.
Plastic conduit is cheap, manual labor is expensive.
--<< Bruce >>--

"Bruce L. Bergman (munged human readable)"
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The cables are R 2 600 V. aluminum 7/16" dia. , one slightly smaller one (neutral?) 3/8", and one insulated copper ground 5/16. It is buried in 2.5" electric conduit made for underground with UV protectorant.
The box is a huge Seimens that came out of a hotel. I know it is all down to the size of the breaker, and I would have to go out there to look at that, but it is cold. I do know the breaker at the house is 100A.
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It's a done job.
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http://www.cmewire.com/catalog/power/servicedrop/09serviceDrop-XLPE-600v-Quadruplex.pdf
I'm already at that kicking my own butt stage for not including the ag water line, potable water line, and a couple of cat5 cables in another 2.5" PVC in the same ditch, but what is done is done. Maybe this next one will go over head, or at least slightly subsurface.
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Bought a pancake for that.
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Used the 2.5 for that reason, just didn't put two of them.
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The smaller cable is R 4.
Steve

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Going out there again after looking at my Glover's Pocket Ref, I see XLPE on the cable, which I do not see in Aluminum Wire Amp Capacity, p. 140. The #2 single aluminum wire shows a range of 110-150 amps, if I am reading it correctly.
The sequence of numbers and letters on the cable are:
Alcan 2 AWG AL XLPE 600 V USE - 2 Sun Res (UL) 2009 Aug 30 09:52 454
Thanks to any electrical types who can decipher this. I am sure this will dictate which size of a plasma cutter that will work out there. This is the deal breaker right here, I believe.
Steve www.heartsurgerysurvivalguide.com

On Tue, 06 Dec 2011 09:53:59 -0800, Steve B wrote:
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Those are the ratings for #2 aluminum, single conductor in free air, NEC Table 310-17, not applicable to wire in conduit.
Applicable table 310-16, not more than 3 current carrying conductors in raceway (conduit) cable or earth (buried) - lists for #2: 75 amps for 60 C rated wire, 90 for 75 C and 100 amps for 90 C rated wire. Presumably your wire is rated for 90 C (it should be marked with an insulation temperature rating somewhere) but ...
The lowest temperature rated component in the circuit governs, normally the circuit breaker, not available rated for 90 C wire, 75 C wire rated is the max available so the circuit must be rated for the 75 C rating max per the code, with the extra 10 amps at 90 C useful only for meeting the correction factor requirements listed at the bottom of the table ...
But some inspectors will let this slide, even though it is not strictly in accordance with the NEC, hence your 100 amp circuit on #2 aluminum, not quite proper, but close, not too likely to cause problems.
2-1/2" conduit is *way* oversize for a #2 feed, are you sure it isn't 2/0? That is what I would put in for a 100 amp shop subfeed, but I doubt if you could have missed the /0 unless the markings are munged.
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Alcan - manufacturer 2 AWG - size AL - aluminum XLPE - cross-linked polyethylene insulation 600 V - max service voltage USE - Underground Service Entrance rated wire 2 - size agaun? sunlight resistant UL listed date manufactured lot no ?
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I know it won't be the best route, but one could have a new set of cables built for the plasma - and have them shorter and larger. Then have a long torch cable - have the machine in the middle. Or have the torch work closer.
I got a long torch cable - so I could leave my unit installed next to my CNC table - but cut steel on trailers that pulled in front of my shop. I have an overhead that keeps most of that another 20' away.
Martin
On 12/6/2011 11:53 AM, Steve B wrote:
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Steve B wrote:
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No, your circuit capacity will dictate how high an output level you can run a plasma cutter and to some extent for how long. The circuit capacity does not dictate how large a plasma cutter you can get since all that I have seen have adjustable outputs and draw far less that their max rated input when operated at a lower output. I've run my 100A input rated Syncrowave 250 on a 30A circuit with no issues when only running the output to about 50% power which was plenty for 14ga steel tubing. In the case of your circuit, it would seem you have plenty of capacity for something like a 50A input Powermax 1000 and a compressor to go with it (20A input).

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If that's correct, #2 AL in an underground run 165' should give you at least 50 Amps at 240V before voltage drop starts kicking in - which will be fine for a compressor in the 3 - 4 HP range (5 Sears HP), and a mid-sized plasma cutter or welder drawing around 30A at 240V. at the same time. But don't go crazy with the lights and three other people working with power tools.
Going down a size or two to #4 for the Neutral is fine, since you don't put nearly the load on the Neutral as you do on the hots.
You must make sure they didn't put in the bond strap between the Neutral Bar and the Safety Ground bar out in the shop sub-pane - they must remain separate, so if the neutral ever does go open you know it immediately.
You can plant a supplemental ground rod out at the shop and attach it to the panel ground, as insurance for the Ground in the conduit going bad on you..
Now the only real restriction on the plasma cutter is your Machismo and your Wallet. How often will you really want to cut steel over an inch thick? Or two inches? (Though I think those will be out of the amperage available range.)
I would go for the pilot-start options, for when you make interrupted cuts like expanded and perforated metal sheets.
--<< Bruce >>--

"Bruce L. Bergman (munged human readable)" wrote:
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I thought an additional ground rod for sub panels in detached buildins was code somewhere.
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The Powermax 1000 takes a 50A feed and will sever 1" steel.
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Hypertherm, Hypertherm, Hypertherm, or if you're a true blue addict, one of the blue models that is OEM'd be Hypertherm.

"Bruce L. Bergman (munged human readable)"
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I went out today, and as inquired about by a poster, looked for other lettering except for XLPE, but could find none. I took away the cover panel on the Seimens control panel. There is a 100 amp main feed with a 60 amp to the 220 line that feeds my less than 30 amp wirefeed. I do not run any welding machine off my 60 amp circuit, but never say never, and like the plasma cutter, one may be on the event horizon. What it looks like to me is that I have a 60 amp circuit available for a plasma cutter. Like I said originally, this will be for less than 3/8", and in most case 12 ga. or thinner, which will fall waaaaaaaaaay under the 60 amp limit.
IOW, I think that what I have will run a HyperTherm 30 or 45 all day long. And if it pops a breaker, I'll just fire up the smoke wrench and git'r'done.
Steve

On Wed, 07 Dec 2011 14:41:50 -0800, Steve B wrote:
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Out of curiosity I looked up your cable on Alcan's web site:
<http://www.cable.alcan.com/CablePublic/en-US/Products/Energy+Cables / Service+Conductors/600+Volt+Underground+Service+Cables/600+Volt +Underground+XLPE+90C+Service+and+Secondary+Cable+Full+and+Reduced +Neutrals.htm> Which has all the specs including a 90 C temperature rating.
Also found there, discussion of various interpretations of the code ratings of SE being made by inspectors since 2008 code changes:
<http://www.cable.alcan.com/CablePublic/en-US/Information+Center / Specifications+and+Standards/Codes+and+Standards/FAQS/Now+that+SE+Cable +used+as+a+branch+circuit+or+feeder+is+restricted+to+60C+how+does+that +affect+the+s.htm>
text content pasted below - 4 applies to an exterior feed to a shop, but note that type USE is permitted underground, unlike plain SE discussed here (I think that is the only significant difference):
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Now that SE Cable used as a branch circuit or feeder is restricted to 60C, how does that affect the size of the conductors in different applications?
Since the language in 310.15(B)(6) changed in the 2008 NEC, there has been a great deal of confusion on how to size SE Cable for branch circuits and feeders. Even jurisdictions that have adopted the 2008 NEC are enforcing it in a variety of ways. Here are some common interpretations of the new language:
1. If the SE Cable is being used as a service cable, there is no change from previous practice. Continue to use the 75C column of Table 310.16, or use Table 310.15(B)(6) if it is a dwelling meeting the requirements of that section.
2. If the SE Cable is being used as a "main power feeder" for a dwelling, use Table 310.15(B)(6). Note, however, that the language has changed in 2008, and this only applies to a single cable feeding a single panel that serves the entire dwelling and all associated loads (swimming pool, shop, etc.). This interpretation seems to be the most common, although many inspectors disagree with this restriction. Check with your local inspector if you need a formal interpretation.
3. If the SE Cable is being used for any other type of interior feeder or branch circuit, the ampacity is limited to the 60C column of Table 310.16. However, note that 215.2(A)(3) states that: “Feeder conductors for individual dwelling units or mobile homes need not be larger than service conductors. Paragraph 310.15(B)(6) shall be permitted to be used for conductor size.”
4. If the SE Cable is being used as an exterior feeder or branch circuit, the ampacity is limited to the 75C column of Table 310.16. (Remember that SE Cable can not be used underground, even in a conduit.) However, note that 215.2(A)(3) states that: “Feeder conductors for individual dwelling units or mobile homes need not be larger than service conductors. Paragraph 310.15(B)(6) shall be permitted to be used for conductor size.”

Steve B wrote:
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I'm quite happy with my Powermax 1000. The finecut consumables are also very good to have for detail work. In the shop it runs off a CH 60g compressor and never runs out of air. I've used it in the field cutting doors and windows into cargo containers running off a small Dewalt portable compressor and I didn't run out of air before I completed each cut up to 80" or so long and the compressor caught up while I setup for the next cut (moved straightedge).

I would also get a Powermax 1000.
i
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What I gotta get is my cable sizes and breaker sizes. That will tell me a lot. Probably tomorrow if the wind isn't blowing too bad. I may just have to settle for a small one because of the install I already did. I didn't figure for doing anything heavy, and had the SA200 for thick welding.
I know the big plasmas kick ass. It's just that for the increase in cost ($3,000 for the 1000 vs. $1,000 for the 30, or $1500 for the 45) plus a big compressor. I do not do a lot of heavy cutting, nor do I plan to. For the occasional thick job, I think I can handle up to 1" thick very well with my gas rig. And it's paid for. I cannot remember the last time I cut 1" thick metal. But I have had a lot of call lately to cut 1/4" and less. And had I had a plasma cutter, I would already have a lot of hours in on ideas I have on the drawing board. And a $5000 toy would be fun, just not cost effective.
I've done all the big repairs I am going to do. I'm building in a rolling I beam hoist system, as well as different lifts and davits so I don't have to pick up stuff a lot any more. My broken back doesn't work very well any more. But my brain does, and rigging to a hoist is easy.
We're decking the roof Saturday if it is calm.
Steve

I just looked at the cables. There are two R 2 AWG aluminum 600 volt cables, one slightly smaller one with a yellow stripe, and a separate insulated copper ground. That makes FOUR separate cables going out there, not one that has four wires in it. The outside diameter of the R2 is 7/16" including the black insulation. The smaller one is 3/8" diameter, and the ground is 5/16".
Can anyone give me more about capacity with that information?
Steve

On Tue, 06 Dec 2011 09:24:27 -0800, Steve B wrote:
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It depends on the size of the branch breaker feeding that wire. The wire could be good for up to a 75 or 90 amp circuit depending on other factors, but it is more likely on a smaller breaker like a 60 (good for 48 amp continuous load max), with the wire over-sized from minimum code requirements for reduced voltage drop.
You need to limit the continuous load on all molded case circuit breakers under 600 amps to 80% of their rating, both per the code and per the breaker trip curves, for example:
http://www.altestore.com/mmsolar/others/QO-QOB_Circuit_Breakers.pdf
The time-current trip curves shown are for the standard test temperature of 104 F, but when the temperature inside your panel hits 140 they will trip at as low as 80% rating as shown on the figure 1 ambient temperature rerating curves. The inside of a heavily loaded panel will be a lot hotter than the outside.
Peak and intermittent loads can exceed continuous loads by an amount which is overly complicated for a quick post.
Glen