Metal welding and test equipment

[tkamiya]

I am thinking of getting into welding metal.  One of my major concern is possibility of generating huge power spike and destroying my collection of test equipment.  Welding will be done outside or in garage (with plenty of ventilation) and my test gear are in my lab, but they ultimately connect to the same utility feed to the house.  I do have whole house surge protector at breaker panel.

Say I use a stick welder and connect it to dryer socket.  Would this pose any risk to my test equipment?

[Benta]

Extremely unlikely. If you used the welder a couple of feet from the TE, the measurements might be cr*p, that's all.

[jpanhalt]

Check the wiring to the dryer outlet.  Much older homes might not have a true ground, but rather a "grounded" lead (white) and just 3 wires to the outlet.  If not, then running a second ground to a ground rod is covered in our code.  For an adjacent garage, I would just be sure everything was off.

[tkamiya]

Do you mean "neutral" and two hots?  Indeed that is the case.  Code did not allow separate ground wire but I heard it was amended recently, and now allows separate ground wire going with 3 wire 240V connection?  Do you know what part of code says this?

I do have an electrical license but it is from Japan, and I live in US now.

[geggi1]

If you have expensive sensitive test gear you should not have it connected to the grid permanantly anyway!
The simplest and cheepest solution is to unplug the test gear whewn you are not using it.
The other option is to get an online UPS between the grid and your test gear. The UPS will clean up your voltage and any dips in the voltage will keept away from the gear.
You should also looking into some surge arrestors if you got conserns.

[jpanhalt]

Yes, "neutral" is referred to as the "grounded" as opposed to "ground" wire in the NEC.  Neutral is not usually switched.  So your household wiring might be carrying the ground potential from the welding.  I am assuming your welder is 220-230V.  Right?

Any relatively current NEC will discuss grounding and ground rods.  In fact, a local public utility commission may not follow all of the details. 

As for your situation, I would not run any welder without a good earth ground.  Get an abridged NEC at Home Depot. Menards, Lowes, etc., figure out what you want to do, then check with your utility provider.  You may be able to do it yourself, assuming it is a single family residence you own.   

[tkamiya]

Ah, I see.  Yes, I am aware Neutral is grounded but is NOT a ground.  At the time I installed whole house surge protector at service entry and breaker panel (which happens to be a sub panel), I beefed up the grounding system.

I don't have a welder, yet.  I'm doing a pre-purchase research to make sure I buy a suitable machine that I can actually use.

[BILLPOD]

Good Morning Tkamiya,  I had a 240V stick welder before I got my 120V wire feed welder, now I hardly ever use the stick welder.  And wire-feed is easier to learn on.  In my case it was even cheaper to buy.  Get wire feed first, is my recommendation.

[jpanhalt]

Be aware that some manufacturers (e.g., Hobart, Lincoln) have different grades, one for the welding market and the other for home improvement sales.  One difference is the transformer if it has one.  I have no direct experience.  Both of mine are 1984 vintage (Linde 225 MIG, Miller for TIG/stick).  The newer pulsed MIG welders are nice.  I am horrible with stick, but nothing beats TIG for fine control.

[rstofer]

3 wire 30A dryer outlets have 2 hots and a ground.  There is no neutral present!  It was thought, at the time, that the miniscule neutral current required by the interior light and timer could just run over the grounding conductor.

The 50A range outlet may also be 3 wire with the same logic.

30A 3 wire outlet: https://www.amazon.com/Legrand-Seymour-3860CC6-125-volt-250-volt/dp/B000BQSU8C

The dryer outlet and the range outlet were changed to 4 wire devices in the '96 version of the National Electric Code

[jpanhalt]

I don't think your assertion applies to knob and tube installations prior to about 1955.  If you disagree, come visit Parma, OH for some post war tract homes.  There is no ground.

[rstofer]

Knob and tube isn't all that common and I have no idea how they wire dryer outlets.  I would suspect they have neither ground nor neutral.  I have only worked on one house that had knob and tube.  There should be a lot of pre-war houses still standing.

Houses built prior to around 1950 may have knob and tube even though NM cable was invented by the Rome company in 1922.  That's why it is called 'Romex'.  I wouldn't make any bets on how knob and tube houses are wired.

Open wiring is still common in many countries.  I saw individual conductors laid parallel on the wall surface heading toward a light switch while visiting in Malaysia.  The house wasn't all that old but all of the wiring was insulated individual conductors stapled to the wall surface.  It was done neatly so it wasn't some hack job.  That's just the way they did it.

The house was a brilliant piece of engineering:  It rains pretty heavy so the beds were mounted on pedestals about a foot above the floor so the water flooding through the house wouldn't get to the bedding.  There was a one foot screened air gap at the top of all the walls for natural ventilation.  It gets hot over there!  It was fun to see a house built for the environment.

[Ground_Loop]

I weld all the time. Never had a problem. Stick, gas MIG and plasma cutter all on 240 VAC 3-wire 60 Amp service about 100 feet from the lab.

[BrokenYugo]

The welder is likely only using the third pin as a safety ground, regardless of the third pin's intended use in legacy outlets. I think that's a code thing, hence welders using a plug different than the range/dryer type.

The only old (I'd guess ~1960) 50A 3 wire 240 dryer outlet I've messed with, and used to burn at least a few pounds of welding rods without any mysterious failures in the house, doesn't have a proper third wire at all. It uses the aluminum wires in the armored jacket of the cable twisted up into a wire of roughly equal size. I don't think that was ever a legal neutral, as rstofer says, it was just once common practice to make it do double duty as a relatively low power neutral, since both eventually go to the same bus in North American wiring. Only trouble is that only works until it doesn't, hence the eventual outlawing of the practice.

[tkamiya]

I was actually trained on knob and tube wiring....   old days....

[jonpaul]

Bonjour à toutes, I am on Old  EE, not a welder, but in 1980s my lab was in a warehouse building with welding and arc lamp testing 12 kW métal halide lamps for cinéma  up to  55 KV. 

Often computer and electronic instruments were disturbed or damaged by welders and arc lamp ignition.
The best protection is unplugging instruments  or never use both electronic and welding at same time.
Earthing and wiring safety are related,  but a different issue.

Many industrial line transient protectors are available in all voltage and KVA ratings, from the usual electrical suppliers, eg Square D, Holt, Eaton.

Finally, regardless of the type,  MIG, TIG, etc, the welding arc is a copious generator of EMI, conducted and radiated.

Just the ramblings of an old retired EE

Jon

[JohanH]

Often computer and electronic instruments were disturbed or damaged by welders and arc lamp ignition.

Jon

Short anecdote.

My late father in law used these ancient Asea DC generator arc welders (could be as old as from WW2 time, not sure). These were three phase 380/400V (could be driven from a tractor, too). They had a habit of destroying fluorescent lamps in his workshop. The shop was properly grounded. I never figured out what the main issue was. It could've been that the arc welders did induce some currents through ground. Fortunately he didn't have any electronics that could have been destroyed.

Picture from the Internet, but this was the type of welders he used until about five years ago. He'd honed his skills with these ancient monstrosities and welded even aluminium and cast iron. Built all kind of farming equipment from scratch and repaired tractor engine blocks etc. He had the largest and thickest skinned hands and fingers I've ever seen, permanently brown from oil and dirt from the machines (rarely used gloves). We used to joke he didn't need a sledgehammer, he used his fists (because he did actually on occasion to dislodge some large metal part).

[tszaboo]

If you have expensive sensitive test gear you should not have it connected to the grid permanantly anyway!
The simplest and cheepest solution is to unplug the test gear whewn you are not using it.
The other option is to get an online UPS between the grid and your test gear. The UPS will clean up your voltage and any dips in the voltage will keept away from the gear.
You should also looking into some surge arrestors if you got conserns.

Nonsense. We had equipment that wasn't even turned off for a decade. You want to have stable environment for voltage references, and for a high end multimeter it could be 30 minutes to settle within specification.

OP: Place a surge arrestor, which has warranty for the plugged-in appliances. I see there is a surge arrestor sold at Conrad for 25 EUR, that covers up to 50000 EUR.

[tkamiya]

Just FYI....

I live in Florida, the lightening capital.  I have "whole house surge protector" at main feed entrance/panel and at a subpanel.  My ground system is 3 times the requirement.  All test gear are connected to industrial rack mount UPS.  I took care to pull direct connection to the subpanel with particular attention to ground wires solidly connected.  I did all I could do practically.

We are now bit deviating from the main topic, but unplugging isn't enough, if that's your method.  You'll have to remove all cable connections as current can be induced.  By the way.... in summer, tall skyscrapers get hit multiple times a day by direct lightening.  Yet, nothing blows up. Same thing for tall towers.  Good single point grounding is the key.  At place of my former employment, we got direct hit.  Nearby hits were common.  Yet all computers kept working.

Welding is a new area for me.  Hence my original post asking for opinions.  I can use expertise of people who has done this.  I know there are many on this board.

[Gyro]

OP: Place a surge arrestor, which has warranty for the plugged-in appliances. I see there is a surge arrestor sold at Conrad for 25 EUR, that covers up to 50000 EUR.

Does anyone know of one one of these plug in / power strip surge protectors manufacturers with high payout figures actually paying up? I bet there are all sorts of wiggle clauses in the small print, probably including welders / workshop equipment in the vicinity. It just sounds a bit like the Durahell equipment replacement guarantee. Just Curious.

[mansaxel]

Often computer and electronic instruments were disturbed or damaged by welders and arc lamp ignition.

Jon

Short anecdote.

My late father in law used these ancient Asea DC generator arc welders (could be as old as from WW2 time, not sure).

They were built into the sixties at least. I've not had the opportunity to try one out, but they're said to be very, very good current generators (as alluded, it's a three-phase induction motor driving a DC generator) and a dream to weld with. The comparison at the time of course was simple AC-only welding transformers, not even DC. And welding (stick, of course stick, that's the True Form!) using DC is a whole different experience than fighting an AC transformer.

For starters, you've got the rotational inertia of the motor-generator set, so you can count on continued current delivery when resistance dips in the arc, and paradoxically, it becomes easier to weld using low current settings, because the welder will back that low current like nothing else; it will be what you set it to, and no fluctuation.

This is something they share with the better examples of the next generation heavy-duty welders, like the 20kW (3-phase 30A 400V) variants from ESAB and Kemppi. They're DC, courtesy of the then-invented high-power silicon diode rectifier, and they retain some of the niceties of the motor-welder. When you use one, again, you can go lower in current, because there's all this solid backing of power, and it feels like you can make your welding seam like a knife in butter, it's just effortless.

Compared to this, the PFC / SMPS ones are nowhere near as fun. But an ESAB or a Kemppi still will make that experience better than most.

[JohanH]

For starters, you've got the rotational inertia of the motor-generator set, so you can count on continued current delivery when resistance dips in the arc, and paradoxically, it becomes easier to weld using low current settings, because the welder will back that low current like nothing else; it will be what you set it to, and no fluctuation.

Yes, this is what he basically explained. They also had a terminal, so you could use an external resistor to tune the excitation current. He had a long wire that he used as a variable resistance.

[jonpaul]

Rebonjour: We had decades of work in HV and transient/EMI/ESD protection, mostly for medical, avaionics, lighting applications.

We did work with Furman Sound and other power quality firms....

Most of the power strips use small cheap MOVs that deteriorate and are underrated. WWe have had MOVs that caught fire.

Transient Absorbing Zeners and other types of power transient protection can handle the voltages and cuerrents in industrial environements.


Whole House protection needs very careful installs inside the service entrance or main breaker panel.

Also must have a  dedicated safety breaker and very short direct earth.

#8 Cu bus and several 20' x 1/2" Cu ground rods are a good start.

Needs a licensed electrician to do this properly.

Expect cost ~ $500...$5000 depending.


Jon

[tkamiya]

Whole House protection needs very careful installs inside the service entrance or main breaker panel.
Also must have a  dedicated safety breaker and very short direct earth.
#8 Cu bus and several 20' x 1/2" Cu ground rods are a good start.
Needs a licensed electrician to do this properly.
Expect cost ~ $500...$5000 depending.

Jon

Jon,

I'm all ears. 

Would you mind elaborating what "careful install" does it require?  My install at main utility entrance was connected to mains on both legs via 30A circuit breaker per instructions.  Neutral was connected to bus bar.  Ground went to grounding point in the panel per instructions.  Ground wire, I believe is #6 to 6 standard length grounding rod spaced few meters a part.  (code requires 2) 

One at inside of the house sub panel (distribution panel) was connected to 30A circuit breaker and grounding point in that panel.  Having separate ground to nearest point will be against the code.  Since there is long way from this point to the actual grounding point, I'd expect impedance is quite high, but again, doing anything else will be against the code.

I have an electrician's license in Japan but I'm in US, and in my state code allows anyone to work on their own houses.

Did I get this right?  Do you have any opinion or suggestions?

[jpanhalt]

My understanding of the code is that a single ground rod with a maximum resistance of 25Ω is required.  Since that is not so easily tested, most inspectors allow two rods at least 6 ft apart without need to validate resistance.  Two rods is not much more expensive than a single rod and may offer a safety margin, so I would just go the two-rod route. In fact, I am thinking of retrofitting my current home (built in 1993) with two rods.