Electric Service Rating vs Reality

[Jared Sankovich]

I have 200amp that really should have been 400amp for the size of the house (needed a sub panel just to fit all the circuits) Never tripped the main though.

[Jacob Reverb]

Never tripped my 200A breaker, but if you have an "instant" electric HW heater, or if you like tig welding heavy aluminum, as I do, you're gonna occasionally gobble up some beaucoup kW, and 300A service is probably more prudent than 200.

[John K Jordan]

... or if you like tig welding heavy aluminum, as I do, you're gonna occasionally gobble up some beaucoup kW, and 300A service is probably more prudent than 200.

Yikes, I use TIG but I haven't welded aluminum. My Miller TIG and MIG machines both plug into a 50 amp circuit. Are you saying AL welding will use more current than I do for mild steel or do you mean using a much bigger machine? What kind of machine do you use?

And to further hijack this thread, what's a good way to learn aluminum TIG welding, is it considerably different than steel? Any particular type of electrodes? I have an argon cylinder.

Would an aluminum spool gun for the MIG be an easier way to get started? I'm mostly interested in smaller things, 1/4" or less.

JKJ

[Andrew Seemann]

I think part of the reason for 200A vs 100A is that the cost difference isn't that great to go from 100A to 200A in parts at installation, but upgrading from 100A to 200A after the fact is rather expensive. 200A boxes typically have more breaker spots in them as well.

My shop has a 100A subpanel and 100A wire, but I have just a 60A breaker feeding it in the main panel, mostly because I had one handy at the time. I've never tripped it.

I've never tripped a main breaker, although I lived in a 12 unit apartment building that had 100A service that blew one of the cartridge fuses in the 1930's vintage knife-switch service main. And that was only a on a hot day when everyone had window ACs running. I remember having to explain what was wrong to the maintenance guy and how to fix it. He was confused why only half the power was on in the the building. I was quite furious (and hot and sweaty) at the time and laid into him about the wiring being inadequate and a fire hazard. My tirade must have made it to the owner (or his insurance company) because the service was soon upgraded to more llke 400A and the place rewired.

[Alex Zeller]

I'm not an electrician either but I do lots of electrical work at my job. I work with people who are also not electricians but think they are. I wired my house after taking the time to learn the codes (we have plenty of sub contractors at work who are electricians). Here's a story I often tell people who think about trying to wire their house or shop without any knowledge.

A coworker (who will remain nameless) wired up his barn. At the back of the barn was a metal gate. While he never had a problem both his wife and son said they kept getting a shock. That went on for 6 months (with me saying he had a real problem). Finally one day one of his bulls went to take a drink out of the water tank. It was winter and he had a device in it to keep the water from freezing. As soon as the bulls lips touched the water it dropped him to his knees. That's when he figured there was really a problem (apparently the bull was more valuable than his wife or son). After shutting off circuits one at a time until he figured out the one with a problem he found he put a staple through a wire and it was shorting out the hot and ground wire. He pulled the staple and said the problem was solved.

Now if you know electricity and basic electrical red flags should be going off. And this is my point. No matter how many times I tried to tell him he had a much bigger problem. He didn't believe me. It wasn't until 3 or 4 actual electricians were almost screaming at him how dangerous his barn was that he finally figured I was right again. He could not understand when I kept saying that he should have tripped a breaker the moment he turned that circuit on. Turns out he used an old panel he had, the screw in fuse type. Someone had put a penny behind a good fuse. Since it wasn't blown he never checked.

I'm a do it yourself kind of guy but I do try to listen and understand advice given. Most everything you will do at a house is very much common sense stuff. But if you aren't sure find out. If you think something isn't right then assume it isn't. Electrical fires are by far and away the 1# cause of houses burning down.

[Rollie Meyers]

The only time my main circuit has "tripped "is when I shut it off to install something in my panel.

A breaker only "trips" during a fault, or overload, merely turning it off is not tripping it, larger frame circuit breakers not normally used in residential commonly have a push to trip button on them though.

[Jason Roehl]

A breaker only "trips" during a fault, or overload, merely turning it off is not tripping it, larger frame circuit breakers not normally used in residential commonly have a push to trip button on them though.

And you should stand to the side when you push that button. We've shut down our 2000A main service breaker at work before. The first time I went to shut it down for the electrician, he all but shoved me out of the way before my finger hit the button. He's in his early 60s, and has plenty of good stories from doing lots of work in commercial/factory settings. I've learned a lot from him...

[Jacob Reverb]

Yikes, I use TIG but I haven't welded aluminum. My Miller TIG and MIG machines both plug into a 50 amp circuit. Are you saying AL welding will use more current than I do for mild steel or do you mean using a much bigger machine? What kind of machine do you use?

And to further hijack this thread, what's a good way to learn aluminum TIG welding, is it considerably different than steel? Any particular type of electrodes? I have an argon cylinder.

Would an aluminum spool gun for the MIG be an easier way to get started? I'm mostly interested in smaller things, 1/4" or less.

JKJ

John.

The reason welding aluminum takes so much more power and heat than welding steel is aluminum's thermal conductivity. The only metals more thermally conductive than Al are gold, copper and silver -- so the heat "wicks away" faster than you can dump it into the workpiece, so you need a machine that can really put the coals to 'er To weld 1/4" aluminum, 250A is about the minimum, and 400A is better. It you try to weld aluminum slow, or with a smaller machine, what happens is that the whole workpiece gets hotter and hotter until, instead of a tiny, focussed puddle of molten aluminum, you get a big pancake PLOP. The whole thing melts at once and collapses.

I use an old Miller transformer that puts out 465A of AC, but being a transformer, it gobbles up the current. It's on a 100A circuit, but 150A or more would probably be needed to dial it up to 465A (never have opened it wide-open). If you use an inverter-based machine, you can feed it considerably less power (they're more efficient) but those machines are a lot more expensive and generally not as long-lived. If you occasionally want to weld something bigger than your machine can handle, you can punch it up by using helium instead of argon. This makes the arc far hotter for some reason, and allows you to weld things that you couldn't manage with straight argon, at least not without a lot of preheat. But helium is expensive, and floats away, where argon is cheaper and mostly stays put.

The other thing about tigging aluminum is that al develops a protective oxide on its surface (alum oxide) whose melting point is something like 3500*F whereas aluminum melts at around 1700* ... and you need AC welding current to "clean" off this oxide layer. The + part of the sine wave cleans/lifts off the oxides and the - part of the sine wave melts the workpiece. On machines newer than about 1975, you can vary the % of the wave that is pos and neg and thereby change how much "cleaning" versus penetration the arc will have (this is called "AC balance."). You will also want continuous high frequency on an alum welding machine to help keep the AC arc lit (it tends to extinguish as it crosses zero V).

Don't know much about mig in general or spool guns in particular, but hope this helps.

J.

[John TenEyck]

My house was built in 1961 with 60 amp service. I limped by on that until I wanted to get central AC. I actually thought the service was 100 amps and ran a 60 amp subpanel to the basement to power my woodshop. Never tripped the main breaker, miraculously, but to Tom's point, as I was running at least a combined 4 hp sometimes. Anyway, upgrading to 200 amps was as much about having enough breaker spaces in the panel as available amps. I could have gotten by with a 150 amp panel, but 200 gives me some room to grow w/o having to add a subpanel. And I filled it some with a two welder outlets and a couple of new 120V circuits. I installed a 17 KW generator a couple of years after the new panel was installed. It can produce something like 75 amps and is just capable of running everything in the house, minus the welders. It's really curious how the power company tried to convince me to only go up to a 150 amp panel. They had to install new lines to the house anyway. Wouldn't they want me to use more power and pay them more money? The gas company had no qualms when the gas meter needed to be upsized to handle the generator.

I do remember my parent's 1924 house had a 30 or 40 amp service when I was little; wire and tube in some places, too. Yikes. Fuses blew regularly until they finally upgraded to 100 amp service and installed new circuits.


John J. , I've never welded Al but I'm pretty sure it takes a lot more power than for mild steel. The thermal conductivity of aluminum is far greater than steel so the heat wants to run away from where you are trying to weld. So you have to dump a lot more power into it to raise the temp. enough to weld.


John

[John K Jordan]

Thanks for the tutorial! I might be happy welding things considerably smaller than 1/4"! I'll check my manuals. I thought I read in one manual that that machine uses a reverse pulsed DC for Aluminum which is supposed to blast the oxide off the surface with every pulse. But it's been years since I read it and I might be totally confused, not necessarily a rare thing.

O do love the TIG for small things made from steel. I never tried it before I got the machine but I did previously weld thin sheet metal with a torch so maybe that helped.

Things like this little hand saw that fits scroll saw blades is my idea of fun.
saw.jpg
Repairing farm and shop things is my justification for the little weld shop (and the plasma cutter).

Thanks again.

JKJ

John.

The reason welding aluminum takes so much more power and heat than welding steel is aluminum's thermal conductivity. The only metals more thermally conductive than Al are gold, copper and silver -- so the heat "wicks away" faster than you can dump it into the workpiece, so you need a machine that can really put the coals to 'er To weld 1/4" aluminum, 250A is about the minimum, and 400A is better. It you try to weld aluminum slow, or with a smaller machine, what happens is that the whole workpiece gets hotter and hotter until, instead of a tiny, focussed puddle of molten aluminum, you get a big pancake PLOP. The whole thing melts at once and collapses.

I use an old Miller transformer that puts out 465A of AC, but being a transformer, it gobbles up the current. It's on a 100A circuit, but 150A or more would probably be needed to dial it up to 465A (never have opened it wide-open). If you use an inverter-based machine, you can feed it considerably less power (they're more efficient) but those machines are a lot more expensive and generally not as long-lived. If you occasionally want to weld something bigger than your machine can handle, you can punch it up by using helium instead of argon. This makes the arc far hotter for some reason, and allows you to weld things that you couldn't manage with straight argon, at least not without a lot of preheat. But helium is expensive, and floats away, where argon is cheaper and mostly stays put.

The other thing about tigging aluminum is that al develops a protective oxide on its surface (alum oxide) whose melting point is something like 3500*F whereas aluminum melts at around 1700* ... and you need AC welding current to "clean" off this oxide layer. The + part of the sine wave cleans/lifts off the oxides and the - part of the sine wave melts the workpiece. On machines newer than about 1975, you can vary the % of the wave that is pos and neg and thereby change how much "cleaning" versus penetration the arc will have (this is called "AC balance."). You will also want continuous high frequency on an alum welding machine to help keep the AC arc lit (it tends to extinguish as it crosses zero V).

Don't know much about mig in general or spool guns in particular, but hope this helps.

J.

[Rick Potter]

My reality:

In 2005, I rehabbed a rental my brother owns. It was a 750 sq ft house from maybe the '20's that had been moved to it's present location. I had a bit of trouble trying to run a benchtop table saw, and discovered it had a panel with no main, just three glass 15A fuses that fed knob & Tube wiring, some of which had been replaced by zip (extension) cord wires. And my bro wanted to install an electric stovetop.

Ended up putting in a panel with rewire.

I currently have a rental house with a 60 Amp panel, and 6 circuits. I really want to put in a big wall A/C, but it will have to wait until I can get the place rewired.

My house has a 225A panel that was put in when we did the solar. We also have 4 sub panels. Hard to keep track.

[Ole Anderson]

I would think that the reason for 200 amp panels has more to do with the number of available circuits rather than the actual total load on the panel. Theoretical load, yes. When I built my house in 1975, my buddy's dad was an electrician and he convinced me to go with a 200 amp panel in a 1550 sf house. So glad he did as that panel is now full. Wired it under permit myself.

[Ronald Blue]

And to further hijack this thread, what's a good way to learn aluminum TIG welding, is it considerably different than steel? Any particular type of electrodes? I have an argon cylinder.



Would an aluminum spool gun for the MIG be an easier way to get started? I'm mostly interested in smaller things, 1/4" or less.

JKJ

I'm rusty at this because it's been so long since I TIG welded aluminum John. You definitely need the Argon. Once proficient you can get much prettier welds with the TIG. At least in my experience. Aluminum behaves much differently as well. The "puddle" isn't so obvious. As I recall I used AC and continuous high frequency but it's been over 25 year so I could be wrong. Get some aluminum rod and some odds and end pieces to practice on. New metal welds much better than used. By this I mean a repair weld is challenging on used parts because it seems you never get the impurities all out of the weld area. A water cooled torch head is nice if you are doing a lot of it. It will be hotter than you weld steel at.

[Tom M King]

The best way to learn to weld aluminum is to pay someone to teach you, whether a school, or individual. You just can't do it well with cheap equipment. A cylinder of Argon is a very small part of the investment. A spool gun works, but still needs a good machine running it, and it gets heavy, and awkward pretty fast, depending on what you want to weld.

Talking about upgrading a service, I'm getting ready to upgrade a 1974 200 amp to 400 amp. The service entrance is coming in to the house with the 200 overhead, and we're changing that to feed the 400 underground. The second 200 amp panel will feed a couple of car chargers, other stuff like a couple of RV hookups, and a 100 amp sub panel that will be far enough away that the cable to it will have to be upsized enough that the conductors will be too large to go in the 100 amp breakers, so there will be junction boxes with pigtails from the breakers to the larger cable. That subpanel will feed another subpanel another 300 feet away, so there is some serious cable sizing calculations to do.

We already have four meters running here, and I don't want to run another main service where the 100 amp sub panel is going.

[Steve Demuth]

So here's my question; Who has had main circuit trips and under what circumstances?

Once, at the pole, when an idiot drove a steel post through the underground cable to the house.