TIG torch water cooler on the cheap??

[FlyFishn]

Wow, not trying to talk you into it...different subject, but why a 220 chiller? Just b/c your rig is 220, that doesn't mean you need to run a 220v chiller does it?

I pulled the trigger last night and ordered the coolmate 300 220v. I wanted to go with the 220, since I already have welder hooked up to 220, I can just plug cooler right into back of welder and they both turn on and off at same time.

I'm late to the party - but just a thought. If you run 4 conductor wire to where the welder plugs in (NMEA 14-50 plug for example) you have both voltages. It feeds off the same breaker. Your "4th wire" is neutral.

However, if you want to get technical - on service entrance panels in North America neutral and.... take a guess here... earth ground are bonded together. That means if you check continuity on a 120v outlet your neutral wire and ground have continuity - because they are tied together at the breaker box.

Sub panels are a different story. They may not have bonded neutrals (meaning bonded to ground). However, that sub-panel is pulling power from a main panel that eventually will tie in to service entrance where ground and neutral are bonded.

So, technically speaking, because neutral and ground are bonded together you can reverse the theory and say that your "ground wire" on a 3 conductor pair (note that I didn't mention voltage - as the power lines don't matter - if you get hot and neutral or L1 hot and L2 hot, doesn't matter) is your neutral. So by taking either of your L1 or L2 hots across ground you have your 120v.

The catch to the above is that in romex the ground wire is paper wrapped, and when you get to larger conductor wire (likely 10g and up) the "ground wire" is reduced in size. It seems to me that 8/3 and 8/4 (fixed install building wire, not SO cable for equipment hook-ups) size wire uses only 8g for hots and neutral, whereas ground is 12g or 14g. So by theory of wire gauge the smaller gauge wire would be current limited. So for a light bulb on a drill press or a coolant pump you might be able to get by.

Though, for big machines (like lathes) that have 120v accessory power - such as to run digital readouts - they have a secondary winding on an input transformer that supplies the accessory power. The good thing about this is sometimes the inputs of those transformers have a few taps to meet various line voltages - that keeps your control voltages much closer to spec.

But for a work light or a small pump motor where the voltage isn't critical and the amperage is very low - even on a 240v grounded circuit you should be able to get 120v if you need to.

The catch is if you end up needing to draw current later it wouldn't be a smart idea to run off the ground wire as neutral...

To each their own, and if it were me I wouldn't want to use a ground wire as neutral normally, but the theory is here to do it and if it were temporary or to prove a concept it would be possible.

 

[jmkasunich]

I'm late to the party - but just a thought. If you run 4 conductor wire to where the welder plugs in (NMEA 14-50 plug for example) you have both voltages. It feeds off the same breaker. Your "4th wire" is neutral.

However, if you want to get technical - on service entrance panels in North America neutral and.... take a guess here... earth ground are bonded together. That means if you check continuity on a 120v outlet your neutral wire and ground have continuity - because they are tied together at the breaker box.

...snipped the details...

To each their own, and if it were me I wouldn't want to use a ground wire as neutral normally, but the theory is here to do it and if it were temporary or to prove a concept it would be possible.

Some folks here are probably very familiar with electrical stuff, and some others aren't. I want to make it clear that using ground as a neutral is NOT legit per code. Yes, you'll probably get away with it for some light load like a light bulb. But if that ground conductor ever opens up between the machine and the panel, then the frame of the machine is going to be hot through the light.

Back in the day there was an exception in the code for electric kitchen ranges and electric dryers - they were allowed to use three prongs even though they had some 120V loads (the light inside the oven, the motor in the dryer). That was changed, I think in 1999.

Other than kitchen ranges and dryers, it has pretty much never been legit to run anything that has both 120V and 240V loads on a three-pronged plug. You need both ground and neutral.

 

[Janderso]

However, if you want to get technical - on service entrance panels in North America neutral and.... take a guess here... earth ground are bonded together. That means if you check continuity on a 120v outlet your neutral wire and ground have continuity - because they are tied together at the breaker box.

I always thought that was weird.

 

[FlyFishn]

I always thought that was weird.

Ah the lessons learned the hard way. I was troubleshooting a transformer-based DC power supply trying to check the waveform at the rectifier. Chassis ground and neutral being the same here... I clipped the 'scope probe ground to one of the input rails to the rectifier set (AC side) and created a dead short through the 'scope. Luckilly the only smoke that blew was from the small lead to the shield of the 'scope probe. In fact, I opened up the alligator clip, cleaned up the wire, and put it back on. I still use it today.

 

[royesses]

Ah the lessons learned the hard way. I was troubleshooting a transformer-based DC power supply trying to check the waveform at the rectifier. Chassis ground and neutral being the same here... I clipped the 'scope probe ground to one of the input rails to the rectifier set (AC side) and created a dead short through the 'scope. Luckilly the only smoke that blew was from the small lead to the shield of the 'scope probe. In fact, I opened up the alligator clip, cleaned up the wire, and put it back on. I still use it today.

An isolation transformer is a good way to prevent this.

Roy

 

[FlyFishn]

There is a method of using an oscilloscope to measure DC amperage. The way you do it is you put a very low resistance resistor (a wire with known value, in the milliohm range, works also). Then you sample the voltage going in to it and the voltage coming out of it. The difference in the voltage across the resistor calculates out to the amperage through it.

You might recognize the theory as a current shunt. It is, but it doesn't have to be a ready-made shunt.

Shunts are typically placed on the negative lead of a DC power circuit, not the positive lead.

The down-side is that on DC systems the negative side is chassis ground. Chassis ground is at the same potential as the ground pin of a 120v outlet. If your power supply and Oscilloscope are plugged in to the same outlet then the chassis ground of the oscilloscope is at the same potential as the chassis of the power supply....... which is the same potential as the negative wire in your DC power circuit.

Since you sample your DUT (device under test, or circuit) with the probe tip - not the ground side of a probe - the tip of the probe is what you are trying to measure the voltage drop of the shunt with. That negative lead is already at chassis ground. So all 3 wires - the negative wire where the shunt is placed, thus the probe tip, and the probe ground/shield are at the same potential.

Problem number 1 - the probe tip and ground are at the same potential. You can't measure across shorted out probed - there will be nothing to measure.

To bring the potential of the DUT to something that can be measured you can reverse the polarity of the probes. Since the tip of the probe is measuring across the shunt on the negative side that means you would need to raise the ground lead to positive. That gives you reverse polarity and a difference in potential to measure across, right?

What happens when you connect the negative probe lead (at ground potential through the power outlet) to the positive lead of the DC power supply? Keep in mind chassis ground on both the power supply and 'scope are at the same potential.

Problem number 2 - You short out the power supply through the ground of the 'scope.

An isolation transformer is a good way to prevent this.

Roy

Somewhat correct. You need to float the power supply AND disconnect the ground loop.

The way I did the above was with a DC to AC power inverter run off another AC to DC supply. That gave me the floating power supply and break in ground (the inverter chassis ground was not connected to service ground, otherwise I would have reconnected the ground loop).

Then I swapped the shunt to the positive lead and the hooplah of the floating power supply requirement went away. But I did learn something. Better than staying in a Holiday Inn Express and I didn't electrocute myself. Its all good. A few sparks and smoke won't hurt too much, sometimes....

 

[royesses]

an elegant expensive option is a differential probe. But it is hard to justify the cost if you are not making a living at it.

Roy

 

[homebrewed]

Not to be a wet blanket, but personally I detest chillers. I worked in a high-tech lab with million-dollar tools, some of which required a chiller. Even highly-rated chillers didn't seem to last very long, a few years and bye-bye. Hopefully the $400 chiller failure didn't damage the $1M tool as a result (!). Like the choice of a $.25 fan on a motherboard that fails and kills your much more expensive computer, sometimes I just don't understand the mentality of saving every last millicent regardless of what the final application is.

We had a stack of dead chillers in the back room waiting to be dispositioned. And, BTW, our luck with refurbished chillers was even worse.

Personally I'd go for the lowest-tech approach, either single-pass from your house supply or if hard water is a real problem, a coolant loop with distilled water, a bucket and pump.

Also, unless you are vigilant about using glycol or other (usually nasty) anti-algae additives like Chloramine, you will get algae growth in your hoses (and bucket). Using black hoses and an opaque reservoir to keep out light can help prevent algae growth.

 

[pontiac428]

@homebrewed, a chiller is a phase-change device, whereas a radiator is simply a water loop with a pump, radiator, and fan. TIG coolers are usually the latter, multiplying the available surface area for convective cooling without any electronics to speak of. Like I said above, not much to go wrong with these systems.

For preservation, you can make your own coolant with non-toxic propylene glycol and a squirt of child-safe benzalkonium chloride (polyquat) disinfectant from the hot tub aisle. That's what Miller sells for $30 a gallon, pre-diluted.

 

[Weldo]

Regarding water choice, I've heard before that distilled water can be very aggressive in attacking metals. The idea is that since it lacks any sort of trace amounts of metals and minerals that it will try to remove metals and minerals from its vessel at an atomic level. Municipal supply adds in minerals to prevent this from happening.

Can anyone confirm or deny this?