Is this safe or legal? (Safety experts will love this)

Status
Not open for further replies.
ronaldrc said:
I said loose connection and I meant a arc fault. And current across a resistive load such as an electric heater
doubles when you double the voltage.

I know, but on a loose connection the arc would have a greater chance of not self extinguishing? Current would double, but keep in mind the same radiator or heater would burn up. A heater of the same wattage would have half the current when the voltage doubles from a re-designing standpoint. Unless you mean that circuit can take a bigger heater or more heaters?




I did not say the EMF would be fire hazard, but some believe it is a health hazard.

I know that, I agree that it is a Health hazard. I was adding that in addition to the Health hazard we both agree on that when conduit is used net currents will cause major inductive heating even more so than a grounded neutral does due to a 100% imbalance. 20amp will indeed produce 20amps of magnetic field with many feet of conduit to compliment that. If you have ever touched conduit with a circuit where absolutely no current is returning on another conductor you will learn fast:lol::)

Thanks for the reply: Ronald
Click to expand...


Answers in red
 
Fundamental Law of Thermodynamics

Fundamental Law of Thermodynamics

Every job site location has the ability to provide plus or minus 230/240 volts. If you use 15 amp 115/120 volt circuits then you will only be able to operate 15 amp 230/240 volt equipment.
Click to expand...
There seems to be a problem with this statement. 1800 watts in equals 3600 watts out? i don't think so.
 
mbrooke said:
I know, but on a loose connection the arc would have a greater chance of not self extinguishing? Current would double, but keep in mind the same radiator or heater would burn up. A heater of the same wattage would have half the current when the voltage doubles from a re-designing standpoint. Unless you mean that circuit can take a bigger heater or more heaters?
Click to expand...

No had nothing to do with the size or voltage of the heater. I was merly stating at double the voltage at 240
volts as apposed to 120 volts the arc in the loose connection on the knob and tube wiring would be a lot worse.

Ronald
 
ronaldrc said:
No had nothing to do with the size or voltage of the heater. I was merly stating at double the voltage at 240
volts as apposed to 120 volts the arc in the loose connection on the knob and tube wiring would be a lot worse.

Ronald
Click to expand...



But you did say this: "And current across a resistive load such as an electric heater
doubles when you double the voltage." Which lead me to believe you were talking about a heater. Perhaps my misunderstanding.




Pachensen kicks law governs all arcs, and a higher voltage means more difficult to extinguish. Think switches with a voltage rating. But wouldn't load also play a role?
 
photo correct

photo correct

Based on the photo how can it work? Does the photo show the two cords plugged into the same duplex receptacle? How do you get 240 out of that?
 
so if the two outlets are via two breakers on the same pole, you get 240v how? its single phase neutral center tap, no? perhaps why there's that dummy switch?
 
Last edited:
FionaZuppa said:
so if the two outlets are via two breakers on the same pole, you get 240v how? its single phase neutral center tap, no? perhaps why there's that dummy switch?
Click to expand...
No. It requires that the two receptacles you plug into be supplied by different bus bars in the panel, and therefore different phase voltages. (Hence the need for long feeder cords sometimes.)

For a demo they could use one duplex receptacle with the jumper(s) broken out and the two receptacles connected to opposite sides of an MWBC.
 
mbrooke said:
My only gripe is that if someone pulls a plug while the 240 volt machine is plugged in it can back feed the male cord cap. And the extension cord should be at least #10.
Click to expand...

I had to build one of these once (don't ask; it was silly). I set it up with two relays. Each relay coil was driven phase-to-neutral from each source. The contacts switched the OTHER phase. that way, if you lost one phase, both sides would shut off. It also prevented the "live male end" problem.


SceneryDriver
 
I personally like the disclaimer:

Note: User assumes all responsibility on use. It is the users responsibility to check
the inbound voltage, outbound voltage, and total amp draw to verify these are not
going to be overloaded. The user agrees to test the amp draw of any appliance or
machine that they plug into these converters to ensure they are not being overloaded.
Meters are cheap and mistakes are expensive. You can purchase a meter at
http://www.steam-brite.com/voltage-meter-mulitester-p-6259.html
User agrees to hold Steam Brite, its employees, and agents harmless in the event of
any use of said use of converter. The user agrees to not hold SteamBrite and all
employee against any problems that arise out of the use of said converters.
Remember, just because it plugs in does not mean it is OK to use!
 
edward said:
When you double the the voltage the current doubles?
Click to expand...
For resistive loads yes, remember the wattage will quadruple though if the resistance remained the same and the voltage doubled. -- 10 ohm resistance element @ 120 volts will draw 12 amps put out 1440 watts, keep everything same except apply 240 volts instead of 120 and you will draw 24 amps and put out 5760 watts.

Put a loose connection somewhere in the 240 volt application and it will be able to sustain an arc more easily then it typically will in the 120 volt application.

ronaldrc said:
That old myth is mainly from the way a dual voltage motor works by paralling the windings for a lower voltage or putting them inseries for a higher voltage.

Nothing to be upset about.

We all do that from time to time.

Ronald :)
Click to expand...
If you have a dual voltage motor, something with dual voltage heating elements or even many transformer windings are series or paralleled depending on applied or derived voltage - you are changing the resistance or total impedance of the load so it does match up with voltage and you have same net volt amp output from the application. A dual voltage motor has same output at either voltage, but at different current levels accordingly. Again similar to what I wrote above - if motor happens to have (at a specific output) an impedance of 10 ohms when 240 volts is applied the amps drawn will be 24 amps, the input VA will be 5760. This motor has two halves to the windings that are connected in series. Each half of the windings will see a voltage across it of 120 volts and a current of 24 amps.

Somewhat of a bad real world example as you probably will not find a motor very easily that draws that much that is designed to be connected to 120 volts - but the 10 amps was easier to do most of the math in my head.

Reconnect same motor for 120 volts by paralleling two halves of windings and you still have 120 volts across each half of the windings and each will still still have 24 amps through each coil - for a total of 48 amps @ 120 volts for the whole thing. 120x48 is still 5760 VA.

ronaldrc said:
No had nothing to do with the size or voltage of the heater. I was merly stating at double the voltage at 240
volts as apposed to 120 volts the arc in the loose connection on the knob and tube wiring would be a lot worse.

Ronald
Click to expand...
Knob and tube, NM cable, THWN in raceway, all are going to have similar response to same resistance in a bad connection. I actually find K @ T that has not been tampered with after initial install to have better connections then some of today's wiring methods. The guy that comes in later and splices on and doesn't use either solder or a positive mechanical connection device is what is concerning.

SceneryDriver said:
I had to build one of these once (don't ask; it was silly). I set it up with two relays. Each relay coil was driven phase-to-neutral from each source. The contacts switched the OTHER phase. that way, if you lost one phase, both sides would shut off. It also prevented the "live male end" problem.


SceneryDriver
Click to expand...
The "live male end" problem is a big problem and would be one of my first reasons to reject such a setup if it didn't have a method of preventing that.
 
GoldDigger said:
No. It requires that the two receptacles you plug into be supplied by different bus bars in the panel, and therefore different phase voltages. (Hence the need for long feeder cords sometimes.)

For a demo they could use one duplex receptacle with the jumper(s) broken out and the two receptacles connected to opposite sides of an MWBC.
Click to expand...

residential service is single phase 2-pole (bus bar) center tap.
 
kwired said:
Put a loose connection somewhere in the 240 volt application and it will be able to sustain an arc more easily then it typically will in the 120 volt application.


If you have a dual voltage motor, something with dual voltage heating elements or even many transformer windings are series or paralleled depending on applied or derived voltage - you are changing the resistance or total impedance of the load so it does match up with voltage and you have same net volt amp output from the application. A dual voltage motor has same output at either voltage, but at different current levels accordingly. Again similar to what I wrote above - if motor happens to have (at a specific output) an impedance of 10 ohms when 240 volts is applied the amps drawn will be 24 amps, the input VA will be 5760. This motor has two halves to the windings that are connected in series. Each half of the windings will see a voltage across it of 120 volts and a current of 24 amps.

Somewhat of a bad real world example as you probably will not find a motor very easily that draws that much that is designed to be connected to 120 volts - but the 10 amps was easier to do most of the math in my head.

Reconnect same motor for 120 volts by paralleling two halves of windings and you still have 120 volts across each half of the windings and each will still still have 24 amps through each coil - for a total of 48 amps @ 120 volts for the whole thing. 120x48 is still 5760 VA.



The "live male end" problem is a big problem and would be one of my first reasons to reject such a setup if it didn't have a method of preventing that.
Click to expand...


This is like comparing apples to oranges. In manufactured appliances and equipment if designed for a higher voltage it will pull less current than one designed for a lower voltage.


We where talking about using a higher voltage or double the voltage on something that was designed for a lower voltage and so the amps. would be more.

The motor example was not a good example I shouldn't have used it.

kwired said:
Put a loose connection somewhere in the 240 volt application and it will be able to sustain an arc more easily then it typically will in the 120 volt application.
Click to expand...


Please explain I don't understand.
 
The current in an AC arc goes through zero twice in each cycle.
Something has to happen to restart the arc when the voltage comes back up again.
One way for this to happen is if the parts are so close together that the voltage will be high enough to cause a spark to jump the gap, starting a new half cycle of high current arcing.
If the peak voltage is twice as high, the gap can be roughly twice as wide and still support a continuous arc.

If the arc is hot enough to generate a plasma or a cloud of molten metal, then restarting will be much easier, but is the kind of arc you see in arc flash videos, not the slow arc that can cause fires without tripping a breaker.
 
kwired said:
The "live male end" problem is a big problem and would be one of my first reasons to reject such a setup if it didn't have a method of preventing that.
Click to expand...
The SteamBright documentation suggests that they do have such a provision in their equipment.
Have to open one up to see just how they designed it.

(The chicken versus egg problem of how to get one circuit to energize the other before the first circuit has been energized by the second can, if necessary, be handled with a momentary push button to start the unit up.)
 
GoldDigger said:
The current in an AC arc goes through zero twice in each cycle.
Something has to happen to restart the arc when the voltage comes back up again.
One way for this to happen is if the parts are so close together that the voltage will be high enough to cause a spark to jump the gap, starting a new half cycle of high current arcing.
If the peak voltage is twice as high, the gap can be roughly twice as wide and still support a continuous arc.

If the arc is hot enough to generate a plasma or a cloud of molten metal, then restarting will be much easier, but is the kind of arc you see in arc flash videos, not the slow arc that can cause fires without tripping a breaker.
Click to expand...


Wait just a minute when you said sustain I thought you meant the circuit could stand a arc better than a 120 volt circuit.

Then we are in agreement you are saying the 240 volts would do more damage by being sustained for a longer length of time?

And why not talk about Single Phase I think its a great subject. :)
 
ronaldrc said:
Wait just a minute when you said sustain I thought you meant the circuit could stand a arc better than a 120 volt circuit.

Then we are in agreement you are saying the 240 volts would do more damage by being sustained for a longer length of time?

And why not talk about Single Phase I think its a great subject. :)
Click to expand...

1. I was not the one who said it (but I might have given the chance.)
Unfortunately sustain does have the two meanings of a. maintain and b. withstand without damage. You takes your choice based on context.
2. I did, BTW, deliberately say phase voltage (as in instantaneous) rather than phase.
My only other comment on "single phase" at this point is "ground pin down"!
 
GoldDigger said:
1. I was not the one who said it (but I might have given the chance.)
Unfortunately sustain does have the two meanings of a. maintain and b. withstand without damage. You takes your choice based on context.
2. I did, BTW, deliberately say phase voltage (as in instantaneous) rather than phase.
My only other comment on "single phase" at this point is "ground pin down"!
Click to expand...

Well since you did quote my post " uh B?

As for the phase leg used on single Phase I Have learned to ignore it.

Thanks:Ronald
 
Status
Not open for further replies.
Top