Electrical Expert Help Please

[jolane]

I am trying to figure out whether I can safely run a Plasma cutter in my garage. I feel I might not have enough power at the panel, so I would really appreciate some suggestions.
The main breaker is 150A. I have a 20A 220V (table saw, Dynasty, possible plasma with upgrade) and a 50A 220V (air compressor, Ingersoll Rand True 5HP Two Stage). I am looking at the Miller Spectrum 625, and it is rated at 30A 230V. I am considering upgrading the 20A to a 30A circuit anyways for the Dynasty, but don't want to get that done and then need to install a 40 or 50A additional circuit for a plasma.
We have a gas dryer (breaker switched off) and electric stove. I will remove any and all 220V circuits I install when I move, but I want to do this to code if possible. I don't want to swap out panels if I don't have to (Service company says that I have 220A available if I want to upgrade the panel).
I measured one leg of the Air Compressor circuit for current draw, and noticed that it draws ~113A when switching on, then while running is drawing ~26A. My tank is 60 gallon, 175 psi maximum, so while decent size, I expect that while I am using a plasma cutter, the compressor WILL kick on. If I have a Spectrum set to maximum (~30A input draw), and the compressor kicks on, and I going to trip the main breaker? What if the microwave, or worse yet the stove is turned on? Any ideas?
Finally, if I do have to upgrade the panel, does anyone know if I can simply buy the same brand (Siemens) 200A panel and swap only the guts. The walls are finished, and the outer case looks like it has some sort of universal hole pattern. The case itself is really much larger than the buss bars, MUCH larger, like it is universal in size. I am not trying to get out of code requirements, or having it inspected, merely trying to minimize the work to change the panel.
Thanks so much for any input...I really want a plasma but am worried about this power thing.
Joshua

BTW: another rec from a friend was to get another compressor just for the plasma, but then that takes up precious space and money...I would rather not do that.

[Thumb Clip Pull]

I am in the same boat....

I have an old style ITE circuit breaker pannel. It is full, and I need to run at least a one hundred amp circuit to the shop to power my Syrcrowave 300.

In my case, I am going to have to upgrade to a 200 amp service to my house. I am going to remove the existing breaker box, and install a Cutler Hammer panel with copper buss bars and new circuit breakers.

In your case; you could turn off and tag out the circuit breakers for your household appliances. (Turn them off and tag them "Do not turn on while I am welding!"

The high "start current" of your air compressor is only momentary. The current should spike, then fall back to "run current" as you already know.

You could stop the plasma cutter when you hear the air compressor come on, then resume cutting after the compressor is running smoothly. (Provided that both the plasma cutter and the air compressor are not on the same breaker.)

I think that I would up grade the service if you own the home. It will increase the value of the home when you decide to sell. (At least that is my opinion!)

Yours,
Thumb Clip Pull Pin.

[INTP]

I'd be REALLY surprised if the momentary surge from the compressor, even with the plasma running full-tilt, affected the main breaker. Breakers generally trip at their rated value for a continuous load, and will accomodate a surge of some factor like 2:1 or slightly higher (check your brand's rating).

For reference, I have a square D homeline panel in my garage. I measured my 120V single stage compressor as surging at around 55A on startup. It was tripping the 20A breaker that was there, but has never tripped the 30A that I put in when I upgraded the wire (to 10 AWG). This is just an example. Your mileage may vary.

[tooldude56]

If it comes down to changing the panel to a 200amp.,and you do'nt mind a little extra work,you might consider doing what I did,I have never regretted it.I eliminated the 100 amp service at the house,installed a complete new 200 amp. service in the garage and ran a 100 amp. branch circuit to the house.My house has mostly Nat. gas appliances,so 100 amps. is more than enough there and I now have a lot of room for expansion in the garage.Since then, I have also added a 3-phase service,but at the time 3-phase was not in the forcast.

tooldude56

[ASKANDY]

I'd say if you upgraded the 20A to a 30 and used that for the plasma, you should be in great shape if the wire running to the breaker can handle 30A.

Andy

[rb455ho]

I agree with Andy. Upgrade the #12cu wire, 20 amp circuit to #10cu wire, 30 amp circuit. If by chance the circuit is in EMT switch to stranded wire which has a higher ampacity than solid. It is most probably not so 10-2 with ground romex will work just fine. Do not use the start current as once the start windings are out of the circuit the run current is your only concern.

[jolane]

Thanks Everyone for the help,
I tried to find out more about breakers, and how they trip, but couldn't find anything useful. If I had a general current versus time load for a breaker, I guess I should be able to figure out a given current load at a point in time.
The 20A circuit I have is immediately below the panel, which is in the garage already. No more than 2 feet away...and I believe I used 10-2 Romex for the circuit already (have to check to make sure).
As for upgrading the panel, this is by far the ideal situation, but unfortunately I don;t think it will add any value to my house. My neighborhood is the type where people pay others to do things...not very hands on. Not the right environment to make a lot of noise. Also, I hope to not be in the ssame house in a year or two... I am currently looking for land/a shop/etc...but for now I have what I have. I will upgrade though if required...just don't want to for the reasons above.
Andy, so do you think that the Spectrum 625 will run full tilt on a 30A breaker? The manual lists 35A time delay. This is going to be used in a home shop environment, NOT a production shop of any kind. It may see 1-2 hours a weekend at peak usage time in the current garage (running out of space to work any longer).
Thanks again for all the input!
Joshua

[hankj]

Jolane,

Look at the nameplate data on the compressor motor. Whatever the current is listed at is all the braker it will ever need. I vote for the 20 - 30 amp upgrade and cut away!

Hank

[jolane]

Thank You Hank! After looking around at breaker data, as much as I can find, it looks like they usually will withstand ~5-600% the rated current for ~10 sec, rough figures. With that in mind, I don't think that the current draw of the compressor will be a circuit breaker "popping" issue. The only concern now is voltage drop when it kicks on. It does dim the house lights a little. I guess I can try to measure it though.
This is starting to get exciting now...I could really use a Plasma..I am getting tired of cutting with a 4 1/2" grinder...
Thanks Again Everyone!
Joshua

[fun4now]

Plasma Oh Boy He He He !!!!

PLASMA is the BOMB BABBY!!!! you will be looking for excuses to cut stuff up when ya get it. besides being great tool's they are great fun too.

[hankj]

Ther is another resort: The poor mans plasma by Victor Equipment. Zero current draw!

Hank

[fun4now]

hankj

hummmm fire, look at all the prity collors he he he flame good

[jolane]

Yep Hank, that is an option also. Actually I have a nice set with rosebud and the such, brand new in the box...but am hesitating with the bottles. They take up so much room (I already have a K size C25 and Argon). They are also rather expensive... I would like the heat though for bending.
Actually though, I expect that my cutting will consist of a good mix of sheetmetal (automotive related, building a resto rod right now) up to 3/8" type stuff. I want the ability to cut thicker though, and have a need to cut aluminum (fuel tank, intake manifold, etc). So, while the O/A would work for some things, I don't think it is the best thing right now. I only bought the set because it seemed like a good deal. It will now sit there for a year or two before it gets used...
Joshua

[hankj]

Hey, Bud, they won't go bad on ya! Just do your thing, and keep on grinnin'.

Hank

[TheRealSpinner]

I must say that I have not had a lot of experience in cutting, but the first thing I bought for cutting (after a crappy all in one rotozip-waste of money, don't know what I was thinking) was an O/A setup. I was renting for a while because I didn't have the money to buy, then realized how much money I was wasting and bought the bottles, anyway, I just have a medium sized (nothing fance) cutting torch with welding tips also. The shop I bought it from said that the tip that came with it would cut through 5" thick material. Right now, the only thing I try to cut is 16 or 18 ga. sheetmetal or 1/4" round stock. It's great for roundsock (with finishing required), but sucks for sheetmetal that thin, but there are ways around that.

I would look into buying a O/A set-up. Couldn't hurt (except the pocket book).