Float switch top-off with relay?

[Ermin]

I have two float switches to control top-off level in my sump. One is for the actual level to start the refill pump. The second is a backup to cut the circuit in case the first float switch gets stuck.

After using the setup for several months, both switches failed together causing a small overflow.

I hooked up a powerhead directly to the float switch running off AC current. The plastic float switch is rated for 15A purchased from Grainger. However, I've heard that this is not safe at all, supposedly, the float switch can't handle direct AC current and will get stuck. Is this true?

How do I hook up a relay to the circuit to make the system "low voltage"?

Also, I want to add a timer relay to the circuit. In case both flow switches fail again, I want the timer to only permit refilling for 5 minute and delay the pump from continuous operation. I know there are timer relays used in air conditioning units. Those relays prevent the AC compressors from flipping on/off constantly. Any suggestion for a cheaper solution?

Thanks in advance.

[Geoff]

sorry, i just do not know.

all of my auto top off are valves and not switches. i tend to trust mechanical devices more than electrical. i have only had one overflow since i started using these, and it was caused by the UV from the bulbs breaking down the vinyl tubing to the valve and not the valve itself.

G~

[Goofy]

Kent float valve has made me a less frustrated man. IMO no other way.

[David Grigor]

I was researching this exact thing about a month ago and saved the link with the Radio Shack part # for the relay: The relay mod looks easy to do:


http://www.reeffreaks.com/viewtopic....er=asc&start=0

[Phishnoob]

Feel free to PM me with any questions on this.

The best thing about a DPDT relay is that you can wire it to cut the connection on the loss of power. Use the 12V wall transformer as mentioned with the relay in the circuit to stay on unless the power goes out and it will cut everything.

Basically what a relay does is use a tiny bit of current flow to drive an electromagnet which pulls on a contact letting the bulk of the current flow through the main circuit. When power is lost the contact goes back to the NO (normally open position).

A good relay to use is a Bosch that is used for car fog lamps and stuff. This is probably good for 15A, you can connect it up how you like, and it is ten bucks or so at an auto parts place. Get some spade lugs while you are there and some 18 gauge wire and you are all set.

If you have a voltmeter you can test this out. Put 12V across the coil then see if the other contacts have zero ohms across them and you are all set.

[newerthannew]

I was able to find relays at RadioShack that are normally closed and can handle 120VAC, then I simply wired a float switch to a 12v power source to energize the coil which will then interupt a circuit to a pump.

I chose this way as it seemed more elegant to power the relay only when nesc.

Tom