Confused, rely, do I need it for top off?

[whirley]

I'm confused.

I want to run a top off system with float switches. I was planning on using a pump/powerhead in my water reseviour to 'push' the water into the sump. I bought float switches from http://www.floatswitches.net.

I thought all I needed to do was buy an extention cord, cut it, wire the float switches in serial with the plug, plug in the powerhead and bingo...good to go.

My confusion is that now, some people are saying to use a rely (sp) to lower the current (?). Huh?

From what I gather, if something was to happen that this will prevent current (alot of it) to go into my fishtank, if something bad was to happen. Is that correct?

I'm a little confused. Can I get away without the rely?

whirley

[Ereefic]

You don't need one, but it is a good idea to use one. Besides not letting the full 120v into the tank if something were to go bonkers, it will also reduce the chance of the floatswitch sticking by sending 120v to power the switch.

I don't know how you are running the switchs, but I am running 2 switches. The main switch is the power on/power off switch. The second switch sits higher than the main, and if for some reason the main switch fails in the on position, the second switch when raised by water level will cut the power to the pump.

If you wanna do it this way, check out the wiring diagram i've attached.

Relay can be gotten from Radio Shack for around $8 and you'll need a 12v power supply also, around $10.

Relay Part# 275-218 DPDT Plug in Relay

[MarkM3]

Yes, and no. The reason people use a relay is to prevent electrocusion in the event that water comes in contact with the metal conductor of the wire. It is possible to wire directly to the float switches, but it is not as safe. The main issue is checking to see if the float switches are rated for the current that the pump draws (i.e. the pump will say X watts, float switches are rated at Y watts; as long as Y>X you are in business)

[whirley]

"12v power supply "
Is that like a battery?

From floatswitches.net:
"Maximum Switching Rate 20W Maximum Switching Voltage 200V Maximum Switching Current 0.6A Contact Withstand Voltage (DC) 250V Contact Resistance 0.3W max Temperature Range 122-F. "

So, if I use a MaxiJet pump (1200),would that be ok? It states it uses a 120v, but maximum consuption is 20 watts.

Is there another pump that I can buy that would make this safe?

Thanks for the help!
whirley

[Ereefic]

12v Power Supply: http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&category%5Fname=CTLG%5F009%5F001%5F001%5F001&product%5Fid=273%2D1776

With this wired in like the diagram I supplied, the 12v will power the floatswitch, and the 120v will go to the pump.

A maxi-jet 1200 will be fine, that is what i'm going to use.

[whirley]

btw, I do plan on running at least 2 switches for each 'circuit'.

whirley

[whirley]

Hey, I plan on running two 'circuit's, one for the solenoid attached to two float switches, another circuit to the pump (maxijet) in the water reserve, again attached to two float switches.

Would I need to buy 2 Relays?

thanks again.
whirley