ac electrical question

patooyee · Mar 29, 2014

As some may already know I recently acquired a Miller Syncrowave 350 TIG welder. The welder pulls 150 amps max. The shop I got it from, which used it on heavier stuff than I probably will, was running it on a 125 amp breaker without issue, so I suspect I may never pull the full 150.

My shop has 100 amp service. I've discussed getting 200 amp service at length with the power company and it is looking like it will be either very expensive or flat out impossible to accomplish. They say the lines going to my meter are capable of 200+ amps but the transformer that feeds my pole would need to be upgraded. The problem with that is that the current transformer is already encroaching on a Mediacom line that is mounted on the same pole and they may not be able to install a physically larger one. So now I am looking for backup plans.

I have access to another meter on my building, also 100amps, that is currently not being used, probably will never be. I am contemplating the possibility of activating that meter and tying its two 100-amp lines into mine to get a 200-amp box capable of feeding my welder. To my lame mind it seems like this would work. I would go straight from both 100-amp fuse panels into my own 200-amp box and feed the welder with either a 125 or 150 amp breaker. Does anyone see any issues with this? I know its kind of ghetto and redneck but it may end up being my only option unless someone else can think of something else?

The last option is to just run the welder on a less-than-100 amp breaker coming from my current panel and never be able to use it to max capacity. Yes, I know it will be rare that I am welding anywhere near max capacity, but its always nice to know I can if I want to.

John Galbreath Jr. · Mar 29, 2014

i would run it and see if it trips the breaker, then go from there.

patooyee · Mar 29, 2014

I know it will eventually trip a breaker welding 1/4" aluminum because my buddy has the same welder and his does. I feel like I will be messing with 1/4" enough to justify the trouble right now. Plus, it is currently wired with a really nice massive cord designed for high amperage. To wire it up to the 100-amp panel I would have to first un-wire the current cord, buy a long piece of smaller cord, and re-wire it all in the name of testing something that I am fairly certain I already know the results of.

mitaker · Mar 29, 2014

If it were me I would do this:
Check the incoming wire size to your electric meter.
Is it #2 Aluminum? If yes skip to answer 2. If it's any size larger go to answer 1.
1. Whatever the incoming wire size is rated for, I would install a new main breaker panel sized to match your incoming wire size ( 1/0 AL - 125 amp, 2/0 AL - 150 amp and so on). Then install a 125 amp breaker to feed the welder. Also keep in mind that the shorter run for power will keep voltage drop to a minimum thus keeping amperage draw lower. Using copper conductors will also be to your benefit. Lastly, use good stuff Square D QO (not Home line), or Cutler Hammer CH (not BR). It doesn't cost much more and it will be better for running loads at or near the capacity of the equipment.

2. You are screwed. Look into a portable generator (probably a trailer mounted unit) used on the interwebs might be able to pick one up for $3500-5000 for the size you need.
You cannot jump two electrical services together. This will almost certainly blow up the transformer that feeds your building.
Hope this helps.

patooyee · Mar 29, 2014

mitaker said:
You cannot jump two electrical services together. This will almost certainly blow up the transformer that feeds your building.

This statement seems illogical to my uneducated brain. They are jumped together 5 feet above the meters by the power company. (One line coming in that breaks out to 3 meters on the wall.) Can you please explain how jumping them back together further down the line = transformer destruction? To me this seems akin to using 2 smaller wires going from an alternator to a battery instead of one big one. Yes, its inefficient but sometimes its the only option.

As for answer #1, the service comes in at 3 lines (One 120v, another 120v, and a ground) to a pole that goes down the building exterior wall that goes to a switch. The 3 lines then split off into 9 smaller lines from the switch to the 3 meters, only one of which is in use right now. (The one in use is mine, another is for the aforementioned office that will likely never be used again, and the third for a small store that went out of business a while back and is shut off due to non payment.) From each meter the lines go to a 3-gang 100-amp fuse box and from there to the individual panels. A power company engineer came out and looked at the main line going to our pole, which is aluminum, and said that it is capable of much more than 200 amps. If I had to guess what size it was I would say #1. But the line going from my fuse box to my breaker box, which is at least a 50 foot run, is small-ish copper stuff. What I think you are eluding to in suggestion #1 is that I could replace the 100-amp fuses in my fuse panel with something higher and then draw more amps at the panel? Knowing the line that feeds my panel is small-ish though, wouldn't I rather just run my own separate line branching off from the fuse box going to my own small breaker box that was dedicated to the welder? That way I could size my line properly for the welder circuit and not deal with the main breaker line?

I guess what we are saying here is that there really isn't anything keeping me from drawing more than 100 amps from the transformer other than the line sizing and the installed fuses. I don't really need 200 amps anyway. In reality 125 is probably plenty. So install 125 amp fuses assuming the line going from the pole to my fuse box is capable of it (Knowing the power engineer already said the main line is.) and rock out assuming I can get the amps to the welder in a safe manner?

jp · Mar 29, 2014

did you talk to the engineer from the power company because what you've just stated sounds like bs about you wanting to upgrade and the power company I work for want charge you nothing if your upgrading your service

patooyee · Mar 29, 2014

Re:

Yes. As I've already stated, he came out to my location and has given me an estimate on the upgrade. Next week he is sending a pole truck out to measure the space on the pole to determine if the upgrade will be possible at all. He has been very helpful and is down with the project and doing all he can to work with with me. I have had other friends I know upgrade service and they have all had to take part in the cost. Maybe different power companies do stuff differently?

What are you saying is b.s.?

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rideright · Mar 30, 2014

Jumping the two meters together is a safety issue. If the power company disconnects one meter the other can back feed. Then some pore sole who thinks the power is off, because the meter has been pulled, will get hurt. You can size your panel to the feeder size from the transformer to the top of the meter base. All you should be responsible for is the wire and conduit from the meter base to your panel. All of this is without seeing your setup so it is an educated guess.

wimpykid · Mar 30, 2014

I'm with JP on this one as I also work for a power company. If someone wanted to give me more money, I would be all over it.

Can you see what numbers are on the transformer? If you're not familiar, there are company #'s and kva ratings normally visible. 5,15,25,37 etc. being kVa ratings. 25 and 37 kVa are not much different physically in size. 37 kVa is probably what you need, but the wire size of your service, what's going into your weatherhead, may be your problem.

halcat · Mar 30, 2014

Keep in mind, if they pull your meter and you do any re- wiring, the electrical inspector will more than likely have to insect it again. If it ain't to code, you won't get your meter back until you bring it back to code.

patooyee · Mar 31, 2014

Re: Re: ac electrical question

Pulling my meter was never an option. The plan was to add 2 poles and another meter to get a dedicated welder circuit. They emailed me today to say that adding the new transformer is possible. My cost is $1300 + I have to install my own pole in my yard. The price itself is not a deal breaker. It's throwing that money at a rental property that is. I guess I just have to think about this a little more. I'm on vacation right now so nothing is happening until next week at the earliest.

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BlackYJ · Mar 31, 2014

I'm no engineer but I would think tying to different services together would also pose problems with the frequency along with what was previously stated about the safety issue of backfeeding. I don't feel like flipping through the code book but I'm 99% sure that this would never pass inspection either. That being said I think utilities has priority over telephone and cable so I don't see why they couldn't make them move their lines to make room for a larger transformer if needed.

BlackYJ · Mar 31, 2014

Just noticed you had that issue solved ..sorry bout that :dunno:

Puppy · Apr 2, 2014

Don't worry about the power company service entrance. It is their responsibility to size the secondary conductors on an overhead service. They are generally under rated and fall under a completely different set of rules than what is inside the building.

I would install a true 200 Amp servies at the building and take it from there. This would give you a 200 Amp. main circuit breaker and capacity to feed your welder with a 150 Amp. branch breaker.

Most residential services are 200 Amp., 120/240 Volt, single phase and are being fed from a 25 KVA transformer rated at 104 Amp. capacity at 100% duty cycle. They are responsible for sizing the transformer that feeds the customer owned service and most times they are undersized for peak demand. They just allow them to run over 100%, which is not uncommon.

jp · Apr 2, 2014

puppy is right put you in a 200 amp service and let your power company worry about sizeing there side if you burn the triplex or open wire secondary or what ever they got feeding you and the pot up then that's there problem but they must have a really small pot there if they saying it's to small we run one house 200 amp service off a 15 kva house without any problems and there's a lot of 25 kva pots out there running 3 to 4 houses with no problems

patooyee · Apr 4, 2014

Sorry I've been kind of vacant on this thread, been on vacation but am back now.

All the figures the engineer at the power company was running were based on max load 100% of the time at all feeder locations coming from that transformer. That is 4 total meters. (The 3 on my building and one on a small single bed apartment next to my building.) Of the 4, only 2 are currently in use, mine being the highest usage. After talking further with the engineer about how little power is actually being used he seems EXTREMELY confident that I could basically do whatever I wanted with the existing power without negatively affecting anyone. So the plan to upgrade transformers, etc is out for now so long as half of the meters continue being out of service. (Which they will be, haven't been in service for years.)

I need to head over there and pay some more attention to the wire sizing feeding the fuse boxes after the meters. I have many options now that I have the go ahead to do what I want. I can either pull more amperage from my current service or activate one of the other meters and pull new service from it.

But one thing I am researching now is how to size the wire that will be feeding my welder circuit from the main. Can anyone help here?

And thanks for the input everyone.

patooyee · Apr 6, 2014

This is finally coming to an end result.

My 100 amp service and the unused meter's service both have a 2-ga aluminum cable feeding to the fuse boxes. Going by NEC table 301-16 that means the max amps I can pull is about 100. The weird thing is that from the fuse box to my breaker box it is all 4-ga al and the other box is all 2-ga al. That means technically the cable in my shop is not rated for the service, yet it does fine. I found this funny since my service powers my massive shop and office whereas the other one powers an office the size of a small closet. So rather than trying to tax my tiny 4-ga wires with even more amps than they are already feeding, I am having the unused meter activated. This is convenient because its 2-ga cable actually runs through my shop right where I want the welder service at. The plan is to replace my 100-amp fuses at the meter with 150, install a breaker box inside that is fed through a 125-amp breaker which will feed the welder. Yes, I know technically the cable is not rated for that mush, but it seems there is a large safety factor built into those ratings based on my shop's service cable.

Even so, I still won't be able to feed the welder everything it wants, but it will be enough for me. There is also a power factor correction capacitor set for the welder that brings max draw down to 125 amps should I ever want it.

Puppy · Apr 7, 2014

Without knowing the specifics or your situation, I really can't comment further. However I am curious. I am assuming this as an overhead service drop form a pole mounted transformer bank. There should be (typically) a splice point at the building mounted weatherhead that the power company splices into the customer supplied service entrance conductors that go to the meter and then into the breaker panel. Are you saying that the #2 AL is the wire size in the conduit from the weatherhead, thru the meter, and into the panel?

patooyee · Apr 7, 2014

Puppy said:
Without knowing the specifics or your situation, I really can't comment further. However I am curious. I am assuming this as an overhead service drop form a pole mounted transformer bank. There should be (typically) a splice point at the building mounted weatherhead that the power company splices into the customer supplied service entrance conductors that go to the meter and then into the breaker panel. Are you saying that the #2 AL is the wire size in the conduit from the weatherhead, thru the meter, and into the panel?

No. That is much bigger than #2. That is what the engineer was pointing at when he came out and said that it was capable of "way more than 200 amps." From there the service goes down to the 3 meters and from each meter it goes to a fuse box via #2 at each. From the fuse box it goes into the respective building units. My unit is the largest but has the smallest cable coming from the box, #4. The small office space that isn't being used and I am now paying for has #2 going to it from the fuse box and happens to run through my shop before it goes into the office. So I'm just going to cut the cable to the office and put my own box at the cut. If the office ever gets used again I'll reassess.

Oh, and for whoever initially mentioned to look at the big number on my transformer, it is 50kwh.