how to choose a relay for a float switch?

[drkwoods]

I want to control my sparge with a float switch. But I see running 120V thru the switch is a bad idea. I have 24volt in my control panel already (for my Gas Valves) could I run that through the switch and then use a relay to turn on/off a march pump as needed?

I like the idea of this SS Switch http://www.ebay.com/itm/Liquid-floa...aultDomain_0&hash=item1c1d98112b#ht_500wt_969



I was thinking this was the proper relay? any advice?
www.ebay.com/itm/Plug-in-Relay-5-pole-120v-Coil-Lamp-Actuator-SPDT-24v-/190626832527?pt=LH_DefaultDomain_0&hash=item2c623ea08f#ht_1044wt_1185

 

[day_trippr]

If this image is to be believed, the coil on that relay is actually 120VAC.

Cheers!

 

[audger]

could I run that through the switch and then use a relay to turn on/off a march pump as needed?

yes. one problem though, is that when the pump is off, nothing prevents backflow. so when the pump turns off, its possible that it will loose prime and not start pumping when power is turned back on. the best thing to do would be to use a relay to control an electric ball valve, and leave the pump constant on.

and obviously, you dont want to use that 120v relay coil because you dont want 120v going to the float switch. use low voltage, 24v should be ok. i would use a low-current resetable fuse on anything over 12v though. 24v is borderline high enough to flow thru a human, 12v is normally too low.

 

[drkwoods]

yes. one problem though, is that when the pump is off, nothing prevents backflow. so when the pump turns off, its possible that it will loose prime and not start pumping when power is turned back on. the best thing to do would be to use a relay to control an electric ball valve, and leave the pump constant on.

and obviously, you dont want to use that 120v relay coil because you dont want 120v going to the float switch. use low voltage, 24v should be ok. i would use a low-current resetable fuse on anything over 12v though. 24v is borderline high enough to flow thru a human, 12v is normally too low.

I currently turn my March pump on off during the sparge and fortunately dont lose prime, so Im ok there. Plus All my vessels are bottom drain (no pick up tubes) and I set up the pumps with help from the manufacturer and its been good that way.

I just have no idea how to buy a relay or know which one I need. I suppose it needs to be 24v coil and then have a switch able to handle a 120volt pump. but how do I read that on the description.. or maybe a link to one on Ebay that will work?

 

[drkwoods]

this better?
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=300651873350&fromMakeTrack=true#ht_1200wt_908

 

[OneHoppyGuy]

Wire it like a neutral safety on a transmission - switch the ground side.

 

[spearko520]

if you want to run 24v through the float switch and use that to pull in a 120v circuit, i have some contactors which would work. the made 24v circuit would energize the magnetic coil on the contactor and close the switch to your 120v pump circuit. I use a similar setup to run a pump for a chilled glycol system that i use to keep kegs cool. If you PM me your info, i will mail you one. If you want to power a solenoid valve or a ball valve with an actuator, make sure you use a 24 v actuator and then you can just use 24v for the whole circuit. I think all the actuators i have are 0-10vdc, but i might have a 3/4 ball valve that needs an actuator that you could have too. Let me know.

 

[OneHoppyGuy]

A contactor is serious overkill for a pump or valve. A simple relay would suffice.

 

[drkwoods]

well I just bought the relay I needed, but I like the idea of controlling a 24v Ball valve instead of the pump on/off. Although my system stays primed well, I think im going to test weather I like the pump to be controlled or the flow. My system is all 1/2" spearko520 and I do appreciate your offer that's awesome!~ I'll let you know after I test. Thanxx