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Posted by dan on August 24, 2008, 10:09 pm
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I am going to get a hypertherm powermax30 soon.
It can run on 120v ac(reduced power) or 240v ac(full power).
I will use it mostly at work where I can use 240v, but I might need to
use it at full power at home.
If I make up a cord set that has two 120v plugs feeding one 240v
receptacle, and plug each of the 120v plugs into outlets that are on
different legs of the service could I then get 240v at up to 15 amps?
--
Dan H.
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Posted by Curt Welch on August 24, 2008, 10:46 pm
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notme@privacy.net (dan) wrote:
> I am going to get a hypertherm powermax30 soon.
> It can run on 120v ac(reduced power) or 240v ac(full power).
> I will use it mostly at work where I can use 240v, but I might need to
> use it at full power at home.
>
> If I make up a cord set that has two 120v plugs feeding one 240v
> receptacle, and plug each of the 120v plugs into outlets that are on
> different legs of the service could I then get 240v at up to 15 amps?
Yes. Assuming you wire the cord set correctly, and assuming the outlets
you plug into are wired correct, and assuming nothing else is drawing power
from the circuit (which will just reduce the max load) and assuming neither
15 amp circuit is GFCI protected. If it's a GFCI, it will trip when you
pull the current from the hot leg but not the neutral leg on the same
circuit.
This arrangement of course is not up to any code and is dangerous for
multiple reasons. If the circuit breaker trips, most likely only one of
the two will trip leaving the outlet and the equipment half-hot. There's
the risk some equipment will malfunction (or be damaged) in a odd way if
powered like that, but mostly, it's a safety issues because the equipment
will seem dead most likely when in fact there is still power applied to it.
If you plug it into two outlets which are on the same leg, you will get a
very low voltage across the hots (just the few volts that result from
different amounts of voltage drop assuming something on one of the two
circuits is drawing some power), but you will get 120 from either hot to
ground. There's always the risk that that error could end up damaging your
equipment. I wouldn't expect to to damage most things, but it's a
possibility.
But other than those sorts of safety issues, it should work. Just don't
blame me when your house burns down or someone gets electrocuted.
--
Curt Welch http://CurtWelch.Com/
curt@kcwc.com http://NewsReader.Com/
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Posted by dan on August 25, 2008, 12:00 am
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What's that Lassie? You say that Curt Welch fell down the old
rec.crafts.metalworking mine and will die if we don't mount a rescue
by 25 Aug 2008 02:46:32 GMT:
>> If I make up a cord set that has two 120v plugs feeding one 240v
>> receptacle, and plug each of the 120v plugs into outlets that are on
>> different legs of the service could I then get 240v at up to 15 amps?
>
>Yes. Assuming you wire the cord set correctly, and assuming the outlets
>you plug into are wired correct, and assuming nothing else is drawing power
>from the circuit (which will just reduce the max load) and assuming neither
>15 amp circuit is GFCI protected. If it's a GFCI, it will trip when you
>pull the current from the hot leg but not the neutral leg on the same
>circuit.
I forgot about GFCI breakers and miss-wired outlets.
>
>This arrangement of course is not up to any code and is dangerous for
>multiple reasons. If the circuit breaker trips, most likely only one of
>the two will trip leaving the outlet and the equipment half-hot. There's
>the risk some equipment will malfunction (or be damaged) in a odd way if
>powered like that, but mostly, it's a safety issues because the equipment
>will seem dead most likely when in fact there is still power applied to it.
>
Yah, I had thought about that. If the load was all 240v it should be
OK, but many 240v things still have some 120v stuff in them. In that
case it may be damaged, seem dead but still be live, or just not work
properly.
>If you plug it into two outlets which are on the same leg, you will get a
>very low voltage across the hots (just the few volts that result from
>different amounts of voltage drop assuming something on one of the two
>circuits is drawing some power), but you will get 120 from either hot to
>ground. There's always the risk that that error could end up damaging your
>equipment. I wouldn't expect to to damage most things, but it's a
>possibility.
>
>But other than those sorts of safety issues, it should work. Just don't
>blame me when your house burns down or someone gets electrocuted.
I probably won't do this, but I thought of it and wanted to hear what
others here would say.
Thanks,
--
Dan H.
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Posted by Bruce L. Bergman on August 25, 2008, 4:33 am
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On Mon, 25 Aug 2008 04:00:04 GMT, notme@privacy.net (dan) wrote:
>Curt Welch 25 Aug 2008 02:46:32 GMT wrote...
>>> If I make up a cord set that has two 120v plugs feeding one 240v
>>> receptacle, and plug each of the 120v plugs into outlets that are on
>>> different legs of the service could I then get 240v at up to 15 amps?
>>
>>Yes. Assuming you wire the cord set correctly, and assuming the outlets
>>you plug into are wired correct, and assuming nothing else is drawing power
>>from the circuit (which will just reduce the max load) and assuming neither
>>15 amp circuit is GFCI protected. If it's a GFCI, it will trip when you
>>pull the current from the hot leg but not the neutral leg on the same
>>circuit.
>
>I forgot about GFCI breakers and miss-wired outlets.
On modern houses in the last 20-ish years, all garage, bathroom,
wet-bar and laundry sink, and outdoor receptacles are on GFCI
circuits.
If you try splitting the circuits, it will trip.
>>This arrangement of course is not up to any code and is dangerous for
>>multiple reasons. If the circuit breaker trips, most likely only one of
>>the two will trip leaving the outlet and the equipment half-hot. There's
>>the risk some equipment will malfunction (or be damaged) in a odd way if
>>powered like that, but mostly, it's a safety issues because the equipment
>>will seem dead most likely when in fact there is still power applied to it.
>>
>Yah, I had thought about that. If the load was all 240v it should be
>OK, but many 240v things still have some 120v stuff in them. In that
>case it may be damaged, seem dead but still be live, or just not work
>properly.
There's a reason they call that kind of a lash-up a "Killer Cord".
Because you unplug one of the cords, and the male pins you are waving
around are energized....
Two-year-old boys love to mess with things they don't understand,
especially if those things can kill them. And since Daddy is over in
the corner working, he can't supervise Junior every second.
Now then, where is your laundry center in the house, in the garage?
Or a service porch right inside the garage door? Do you see that big
30A 240V receptacle there for an electric dryer? <Hint.>
They usually put that 30A 240V receptacle there, even if you use a
gas dryer - and you should, it's rare when electricity is cheaper than
natural gas as a heat source, and with Propane it all depends on
market prices but usually gas has a slight edge.
And where is the main power service panel for the house - On the
outside wall of the garage, perhaps?
That seems to be a very popular place to put it, and it's real easy
to poke a hole out the back of the panel and mount a 30A or 50A 240V
receptacle right there.
And if not... Run some heavy gauge AL service cable between the
main and the garage, Place a small 100A 8/16 sub-panel on the
inside wall of the garage - one circuit for the welder, one for the
Hypertherm, one for the 5HP air compressor, one for the lathe and
mill. Just don't try running them all at once, or the main breaker
will let you know.
--<< Bruce >>--
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Posted by dan on August 25, 2008, 8:30 pm
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What's that Lassie? You say that Bruce L. Bergman fell down the old
rec.crafts.metalworking mine and will die if we don't mount a rescue
by Mon, 25 Aug 2008 01:33:27 -0700:
> There's a reason they call that kind of a lash-up a "Killer Cord".
>Because you unplug one of the cords, and the male pins you are waving
>around are energized....
Yah, I thought of that after my last post.
>
> Two-year-old boys love to mess with things they don't understand,
>especially if those things can kill them. And since Daddy is over in
>the corner working, he can't supervise Junior every second.
Thankfully I don't have any kids, 2yrs old or otherwise.
> Now then, where is your laundry center in the house, in the garage?
>Or a service porch right inside the garage door? Do you see that big
>30A 240V receptacle there for an electric dryer? <Hint.>
Nope. Don't have any laundry center. Two room apt. over a two car
garage(I get 1/2 of the garage).
>
> They usually put that 30A 240V receptacle there, even if you use a
>gas dryer - and you should, it's rare when electricity is cheaper than
>natural gas as a heat source, and with Propane it all depends on
>market prices but usually gas has a slight edge.
>
> And where is the main power service panel for the house - On the
>outside wall of the garage, perhaps?
In my landlords basement. And the feed from the pole is on the other
side of the house. But there is a sub panel in the garage that feeds
my apt. But I will have to have an electrician run conduit to my side
of the garage. Should be easy.
--
Dan H.
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> It can run on 120v ac(reduced power) or 240v ac(full power).
> I will use it mostly at work where I can use 240v, but I might need to
> use it at full power at home.
>
> If I make up a cord set that has two 120v plugs feeding one 240v
> receptacle, and plug each of the 120v plugs into outlets that are on
> different legs of the service could I then get 240v at up to 15 amps?