Float Switch (Electronic?)

R

Reefugee

New member
In this thread , Warren had a float switch for sale. Like Steve pointed out - the float switch looks like it is directly connected to120V (a potentially dangerous setup). Anyway - I questioned that the float switch was expensive, but Warren responded that they were "electronic" float switches.

I am wondering - what is the differences between an electronic float switch and the magnetic (?) float switch that you can get at aquahub for under $10.

http://www.aquahub.com/store/madisonm8000.html

BTW - I started this thread because I didn't want to clutter up Warren's FS thread with too much discussion.

Minh
 
I don't see the electronic portion nor a relay on the picture from warren's thread. Which means electric current can pass thru the water and I don't think the contacts on the float switch is good enough to support 110v application.

-perry
 
Electronic float switch = magnetic float switch

The one shown in the pic of the other thread is a electronic float switch, which is a magnetic float switch. all electronic float switch have a magnet inside the floating thingy, moving up and down will cause the switch inside the stem to either close or open, hence letting current go through the circuit.

Another kind of float switch is the mechanical ones, like the Kent marine ones or the one in your toilet.

also, some of the electronic float switch can handle maximum of 400mA, 120VAC, going through it depends of spec. which means it should be ok if you run the float switch inline with an extension cord like the one selling in the other thread with a maximum 48W of electronics. although I would rather keep it under 40W, but it should be safe to use it. if you ever need to control something larger then 40W, then u have to go though a high current relay switch in addition with the float switch. as the one from aquahub above can have a maximum of 30W, but I would only run a max of 24W electronics.

I don't know if this mean anything, but I have been running an inline float switch with a small 5W pump as top off for couple years now, never had a problem. anyways, good luck.
 
Last edited:
<a href=showthread.php?s=&postid=9116374#post9116374 target=_blank>Originally posted</a> by xinumaster
I don't see the electronic portion nor a relay on the picture from warren's thread. Which means electric current can pass thru the water and I don't think the contacts on the float switch is good enough to support 110v application.

-perry
Click to expand...


I don't understand why ppl keep saying no "relay or electronic portion" is equal to "electric current can pass thru the water" sorry for my ignorance if I am wrong, but how can a relay help with current and water? do you even know what is the reason behind "a relay and electronic portion" in this application?

"contacts on the float switch" is different in each case, there are different specs for each float switches. in which, there are heavy duty float switch out there which will take 120V applications. As again, sorry for my ignorance if I am wrong, but I have done my homework when I first build my auto top off.
 
DarkDevil,

The whole purpose of the relay is so that you are running a low voltage/current through the switch, which is submerged underwater. The relay is what makes the connection to the high voltage pump. I wish I had taken a picture of one that I built for someone recently. Maybe if I get motivated tonight, I will try to draw a diagram so you can see.

Without a relay - you are running 120V directly through your sump. If your wiring breaks, you are in serious risk of being electrocuted. With 12V 500mA, there is no risk of shock. Some may argue that people already have 120V in their sump with pumps and such. But those pumps usually well tested, well insulated, waterproof, and UL certified. A DIY does not have the same level of care. But then again - everyone should have a GFCI outlet for their tanks.

BTW - thanks for the explanation of "electronic." I guess when I think of electronic, I think that it has some sort of circuitry built into it.

Minh
 
actually I know very well why and how a relay works and how the diagram should look like, those comments are meant for sarcasm. all I am trying to say is, for any reason if a newbie read this thread, they will just see "relay or electronic portion" is equal to "current pass through water", which is definitely not the case, and they just keep going on and on with that idea in their head, which most of the comments from RC are kept that way anyways.

I totally understand the concern of wires breaking under the water, to my worst luck that I always have, anything can happen to me or my tank. as u have mentioned, of the 10 other electronics that is running inside the tank, any of them may have failed. heck, I have heard more of the Rio pump cook the tank then someone saying their top off fried the tank.

for whatever DIY, you should do it with utmost care and design definitely, i.e. insulate all the wires, all connections are secure, no wires touching or rubbing, no wires should be hanging on the water, anything close to water should, actually it's MUST run GFCI, on and on and on. so IMO, as an engineer, careful/luck is not equal to engineering spec/facts. just my $.02, thanks
 
Here is a question that maybe someone can answer. When I build an auto topoff with a relay switch, I wire it so that the hot (black wire) is on the relay. When the relay is in the open position - the is still a very small amount of current flowing. Why is that?
 
the float switch will not allow you to use a certain amount of wattage. I am not at home now but it says to only use a certain amount of wattage. These types of switches sell everywhere. if it was a hazard I dont think online vendors would sell them.
 
With such a device I would never put 120 through it.
It says "nominal VA: 30"
That's volt amps or (Volts x Amps)
So if you put 120 though it you have already exceed 30 VA and you haven't even put a load or device on it yet.

This also explains how extremely small solenoids rated at a mere 3 watts can melt these switches together.

http://www.aquahub.com/store/curingspik.html

Straight from Aquahubs website
<I>

"Let’s say you want your float switch to turn a pump on when the water level in a tank falls below the level of your float switch. Your pump draws 15 watts and your float switch is rated for a 50 watt load. You know that a 15 watt pump could spike to 150 watts (up to 10 times the pump rating) and destroy your float switch, so you would wire the float switch so that it turns on the relay when the water level falls and you would wire your pump to the contacts of the relay"
</I>

These switches are sold for with the intent to have a knowledge of how to use them.
Just because someone sells them, does not make the fit for an unsafe purpose.
While yes there are heavy duty Float switches, these are not one of them.

I also checked the wire on those switches. They are not rated for 120volts
AND
It's only 20AWG wire which IS NOT LEGAL in the USA to be on a circuit breaker of 15 amps (most homes) or even worse a possible 20 amps.


I'm actually starting to work on an entire MARS meeting with the sole subject being "Electrical Safety in the Aquarium Hobby"

They wanted me to have this together by next meeting, but I told them I needed more time to get together a really good presentation. So it will be either March or April's meeting
<b>
I will actually be drinking a glass of water with a 120VAC cord in the glass, plugged in, in the water.
This will be one meeting you won't want to miss!
</b>
I used to teach for an electrician school "WECA" here in Sac.
~Steve~
 
Ooo... Steve with a live wire in a glass of water? I am so there!

Seriously though, I think this is an excellent topic often overlooked in the hobby, and would love to get the 'real deal.' In the meantime, no electronic float switches for me.
 
Yep live wire in a glass of water, and then drink it while it's on.

Granted I will have controlled environment setup, but to prove a point that water is not conductive, and even when it is, sometimes it's still ok if the right conditions exist.

I would have to say "Do NOT try this at home!"
;)


I use electronic float switches in all 3 of my tanks, however they all have a relay installed on each one, and the voltage is only 12VDC that goes into the tank.
 
a volt-amps is equal to the product of the root-mean-square of the voltage and root-mean-square of the current in amperes. although you're plugging into a 120 volt outlet, it doesn't necessarily mean you're exceeding the rated 30 VA. you have to determine the root-mean-square of the voltage running through the powerhead or device plugged to the switch. you also have to know the current running through the device.
 
for powerheads i think the wattage rating is determined by rms volts multiplied by rms amps of the resistive load. in that case 30VA= 30 watts
 
just to clear up my part, I use something similar to this , rated for 150V AC / DC and 1A AC/DC, 25 VA with 20awg lead wire, which can hold maximum of 1.5A when used as a power transmission, is it legal? maybe not. other things I do illegally? hell yeah :D anyways, my point is, there are heavy duty ones out there, good luck
 
Cool topic!!
Can someone tell me what kind of relay I should use? Where to get them that would be great too :) ..
 
Does it come with the instruction on how to wire it?? Sorry for the dumb question. I only know how to replace the wall outlet cover :D ..
 
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