Does a switch like this exist?

[guy99]

If so, what is it called and where can I get one?

Right now I have the electric portion of the water heater in our 1984 310 Limited MH wired to a three prong cord. When we are parked somewhere with full hook ups, we plug it in and use electricity to heat water.

I would prefer to have it permanently wired to a dedicated 120 V circuit and controlled by a switch. I would like the switch to 'release' if power is lost. It would then be necessary to turn the switch back on when power is restored. Thus the switch would go 'off' when we disconnect and not go back on if I start the generator or hook up again until and unless I manually turned it back on. It would also be nice if it had a light to indicate that the circuit is activated.

Surely such things exist (my table saw has a switch which performs this function) but I don't know what to ask for or where to look. I've browsed the big box stores with no luck.

TIA

[wkerfoot]

Guy99,

Try a local hardware store or electric supply store.

Bill

[TomW]

Originally Posted by guy99

...Surely such things exist (my table saw has a switch which performs this function) but I don't know what to ask for or where to look...

Your table saw has a "magnetic" switch.

Once energized, a magnetic field keeps the switch contacts closed until opened by the red button or a power failure.

Check a Grainger catalog.

Tom

[overlander63]

Sounds like a magnetic switch, like used to operate heavy machinery. Push the button, and as long as power is supplied to hold the magnet, it will stay on. When power is lost to the magnet, it will release, and turn off whatever it is controlling. Every one I have seen has been a two push button affair.

[tfm37]

You can do this with a normally open pushbutton switch and a normally closed pushbutton switch and a 120 volt ac relay with at least two normally open contacts. The coil of the relay is wired thru one of the normally open relay contacts. The pushbutton of the normally open switch is wired around (parallel) to this contact. When the pushbutton is pressed, the relay closes the contact and keeps the coil energized. The normally closed pushbutton is wired in series with the relay coil and when it is pressed, it deenergizeds the relay. The remaining normally open contact of the relay is used to switch the heater element on and off. Lots of words to describe this, but it is pretty simple to do.

[guy99]

I'd sure like to find a single, packaged component to do this.

I've done some web searches and will check grainger. Seaching on magnetic switch gets lots of hits, but not what I'm looking for.

Anyone else have an idea about a source or what search terms I should use?

[markdoane]

Look for "Magnetic starter" rather than switch. Here's a cheap one: G8291 Magnetic Switch, Single-Phase - 110V Only, 2 HP

edit: you can also get a remote on-off pushbutton, and a indicator light.

[Loren]

guy99,

Here's one, but you won't like the price:

McMaster-Carr

search for catalog # 8230K24

They also have some others on that catalog page that may suit your purpose and cost a bit less.

Loren

[bobchevy89]

hello the one markdoane has listed is the one you want.$53.00 is a good price.
Bob

[markdoane]

Uh, the one in McMaster-Carr won't even do the job, it's just a pushbutton non-magnetic switch.

[Poprivet]

Yes, the switch you want is available. Go to your local electrical industrial supply warehouse and describe what you want. They will be able to help you.

[zamboni]

What about a On-off-On switch, you could add/wire the indicator light yourself.

[Loren]

guy99,

Sorry, I thought I had found one, but after closer reading of the description I see that Mark's right. The McMaster-Carr switch isn't magnetically held. It won't do what you want it to do.

Good deal, huh? Just think of all the money you saved.

Loren

[Fyrzowt]

If you like the one on your table saw, order one from that saw manufacturer.