Turn off a electrical circuit (plug) when water is detected.

No.

sywink ... I don't know the answer to your question. (I think the best answer is for you to check with a licensed electrician.)

No, I'm just here to tell you that the poster above me is a dumbass, and you should not listen to a word he utters.

That is all.

True.

What leads you to think that a GFCI outlet hooked up to two random wires will cut the power, Sywink? A GFCI is a "switch" of sorts, but that is most definitely not its intended purpose, nor could you expect it to work as you intend.

Those two "currently unused wires" are almost certainly unused because they are not tied in electrically to what is operating at the moment. You could put a switch onto the outlet that powers the dehumidifier, but to be honest, and I'm not intending to be rude, it sounds like it REALLY would be best for you to contact an electrician.

Doesn't the dehumidifier have its own shut off switch? Is there no, likely balck or white toggle switch anywhere on the unit? Or if there is an access panel there might be a switch inside.

That would be the best and easiest place to put and wire a switch in. Can you take some pictures of the unit?

Why can't you just pull the dehumidfier plug from the outlet?

For those of you with helpful intentions, thanks for your answers. I was however hoping for a knowledgeable electrician to render an idea rather than advice on the wisdom of pursuing an idea. Whatever I get however, this is a pretty good forum for having to explain my idea, and perhaps I will find a flaw in my logic just by having to explain it.

As for unplugging, etc., I can't monitor the system 24 by 7 unless the monitoring is automated. As for hiring an electrician, they live and die by municipal codes, not the needs of the customer, and I'm sure I can comply with those codes by buying a hot water heater overflow switch, except I will be paying 90% of the cost to shut off the water supply I don't have. I want a $20.00 switch, not a $200.00 switch. But I do want to do it with the safety of the $200.00 switch.

So to elaborate a bit on my original posting: if I understand ground fault correctly, the circuit is interrupted because the current flow from the source to the "hot" terminal in the GFCI is different (and presumably less) than the current flow from the "common" to ground. Also, I am pretty certain that the "unspecified" wires of the water detector are intended to turn off a low voltage thermostat. Well, I thought I might be able to simply short out the common and the ground with the water detection circuit. I wouldn't need to go anywhere near the hot side of the GFCI, so what could I hurt? The shorted common to ground not working, I could supply a low voltage with a normal DC battery (1.5v, 9v, 12v etc.) connected through those wires to the ground and the common terminals of the GFCI. Until such time as the circuit is closed, which the the presence of water would effect, there would be no voltage across those terminals and the GFCI would provide unimpeded ground fault protection, just as it is designed to do. When and if the circuit closes it would apply that DC voltage between the ground and the common terminals. I think this is the opposite of what a GFCI is supposed to detect, but it is certainly a disruption, and I'll bet the GFCI will trip on any disruption, so it seems to me that it might work. It would just be sort of nice to have a 2nd opinion before I go spend $20.00 building something to test my theory.
The worst thing I can think of is that the battery would be drained if you didn't dry up the water, however, since the GFCI would interrupt the 120 supply, the dehumidifier would turn off until the GFCI was manually reset, which you couldn't do until such time as you dried up the water.
Does that make sense?

The simple answer is no.

GFCI has a circuit breaker that blows when the current on the 2 lines are not equal. It is designed to break the circuit when it senses when any other circuit to ground opens.

If you wanted to try to make the GFCI work the way you are asking you could try the following but I wouldn't recommend it. Put a pan underneath the system and make sure the cord is plugged into an outlet in that pan. If the pan fills with water, it would hopefully cause a short that would blow the GFCI breaker.

You would be better off buying a water alarm such as this -
http://www.walmart.com/ip/First-Alert-Water-Alarm-3pk/14710711

There may be one out there that can be wired to turn a switch off but you would have to search for it.

This is similar to what you are looking for:

http://www.farnell.com/datasheets/1295505.pdf
It can be set to turn circuit on or off depending on fluid level.

Try the electronic places online for others.
Newark, Digikey, Allied Electronics should call carry this or something similar.

Your right, this is close, except I have the water sensor already as an integral part of the condensation pump. This also looks like it is an international - 220V - component. At any rate, I need to substitute my detection switch for theirs.

If the wires you state exist turn a circuit on or off based on water being present then it would be a simple process to simply attach them to a relay which can turn off power.

Digikey relays

You would need a wiring diagram to know what the wires do. Do they provide power if the circuit opens or are they simply a switch. What voltage/amperage are they rated for?

Could one not simply wire a switch [water activated] right into the cord that goes from the wall outlet that supplies the power for that same humidifier?

That was my first suggestion. OP wants to use sensor in existing equipment.

Any indication as to why the sensor in existing equipment isn't doing its sensing job and shutting down the dehumidifier?

Actually OP the situation you described is exactly the intended purpose of a GFCI and you can go ahead and install it. The CEC tells us that an GFCI receptacle must be installed near any wash basin, sink and receptacles exposed to weather, among other things.

By installing the GFCI you would be effectively protecting the circuit and device from a short circuit if water would to be become a conductor between the hot and neutral or hot and ground.

The sensor consists of a float and two wires. When the float gets too high an internal connection between the wires is completed, when it is lowered, the connection is broken. The other end of the two wires is available to control something. I'm trying to define that something.

Where did "OP" come from?

Thanks, Placid Carcass, that was my initial thought, but it seems sort of like an abuse of a GFCI, thus my original question was effectively "could I achieve the same result by shorting the "ground" and the "common" within the GFCI and thereby keep control on the common (not hot) side of the GFCI? I was asking this because the available switchable circuit is intended to be low voltage, nominally 24V DC, over about an 18 gauge wire.

At some point in my life I tried to use a shared "common" and a shared "ground" with 2 separate "hots" to control 2 outlets connected to two GFCI switches connected to two breakers using a 3 wire plus ground wire. I could (and do) share the "common" and the "ground" between the GFCIs, but had to use two distinct 2 wire plus ground between the GFCIs and the outlets. I have never understood why.

Humph - on 2nd thought I believe that I could set and use either GFCI, but couldn't keep them both set - so I built a mutually exclusive switch. Still, my memory isn't what it once was.

Thanks

Then you only need to connect the wires to a relay.
Power of some kind to one wire, the other wire to control signal on a relay. When the float is too high it will turn the relay off. Simply run the power to the dehumidifier through the relay.

Depending on the amperage required, a relay and socket should run about $20.

OP stands for orginal poster.

I've spent a good part of my day trying to educate myself on relays. Unless I am mistaken the following fan control module from White/Rogers economically fills the bill. Since I want to shut the AC circuit off in the presence of water, which to me means "DC circuit on", I believe that I would want a SPDT-NC, or "normally closed" module. In the enclosed flyer, that would be a model 90-113 or 90-118e. As I understand it, this module would also supply the 24vDC requirement.

Would you take a look at this PDF and give me an opinion?
http://s3.pexsupply.com/product_files/White%20Rodgers%20-%2090-113%20-%20Brochure.pdf

Thanks.

OP means Original Poster.



How is this completed? Does this shut off the dehumidifier?

Are you trying to have an auto shutoff so the water from the DeH doesn`t spill over?

Isn`t the description above what is already doing thatÉ

You seem to be on the right track.