Simple question for the resident electricians

cgrabe

cgrabe

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Jun 1, 2004
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NOTE: This is a repost from the SW Products & DIY board where I accidentally posted it. Mods can feel free to delete that post.

I want to build a float switch to cut power to the pump in my sump if the water level drops too far. I'm leaning toward using one of these (30A/250V) mercury switches to cut power to an Ehim 1048 pump (120V/10W). I would assume that since the power source (US Home) is AC, it doesn't matter which wire I put the switch on. Is that correct? Do I only need to break one line to safely stop the pump, or will both lines need broken?
 
When A House Is Wired 110 There Is Typically These Three Wires
Black
White
Copper

Basically The White And The Copper Is Tied To The Ground In The Box. The Black Being The "Live" Side If It Were Me I'd Take The House Plug Apart And Find Out Exactly What Side Of The Plug In Has The Black On It. Then I'd Cut That Side Of The Circuit With The Switch.

I'm Not A Electrician But I Have Wired Including The Mains 3 Or 4 Homes.

Just Make Sure You Kill The Power To The Plug Some Older Homes Have Metal Gang Boxes And It's Easy To Short The Plug Against The Side Of The Box Pulling It Out...
 
Thanks for the reply. I was under the impression that there was one ground, and the remaining two wires alternated between positive and negative at 60Hz. That, though, would beg the question of why some plugs are polarized. Oh well. I really should study up on these things; they're good to know.
 
Very true. The copper is the ground and cutting that gets you noware. the white is similar but different. and the black is where the "current" is persay. the way the plug is wired is always different, and remeber this: it may be one way on one plug but different on another plug if you chose to move the switch. you do know that they have these kind of things for sale that hook up to a power strip. look in Fosters and Smith i saw it the other day
~:cool:
 
If You Have A Volt/Ohm/Amp Meter You Can Put The Black "Ground" Of The Meter In To The Ground "Roundish" Hole On The Plug And The Stick The "Red" Lead In To Either Side You Will Find On One Side There Will Be 110-120 Volts And On The Other Maybe .5 If You Get Say 5 Volts Or Greater There Is More Then You Have A Bad Ground On That System Or On Another In Your House. This Can Lead To Other Things IE Shaking Pic On Your Computer Monitor.
 
Originally posted by Murdock
If You Have A Volt/Ohm/Amp Meter You Can Put The Black "Ground" Of The Meter In To The Ground "Roundish" Hole On The Plug And The Stick The "Red" Lead In To Either Side You Will Find On One Side There Will Be 110-120 Volts And On The Other Maybe .5 If You Get Say 5 Volts Or Greater There Is More Then You Have A Bad Ground On That System Or On Another In Your House. This Can Lead To Other Things IE Shaking Pic On Your Computer Monitor.
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I do have one. Thanks, I'll try that.
 
Originally posted by aquaguy1331
you do know that they have these kind of things for sale that hook up to a power strip. look in Fosters and Smith i saw it the other day
~:cool:
Click to expand...
I thought about that, but those things cost close to US$50 whereas I can get a mercury switch for $2.50 and make my own.
 
<repeats what murdock said>
Yes, it is VERY important, I say again, VERY VERY VERY important that you cut power to the BLACK(live) wire. the white and bare copper both have the same potential to ground, your house, you, everything else. 0. the black wire has some potential to everything else all but .001% of the time. if you cut the neutral(white) wire, yes the pump will stop but the parts inside will still be energized. therefore if anything touches it while the neutral is cup, the thing touching it is suddenly dead or in a lot of pain.
 
Thanks. This thread makes me seriously question my understanding of AC/DC, but that's a good thing. Better to find out now than have it dawn on me as I go into cardiac arrest.
 
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