Autotopoff float switch schematics (Please Review)!

[rufio173]

Hi everybody,

I've been trolling the sites for information on how to wire up an auto top off system with two float switches. One to backup the other one.

I've found some good threads, but most of them just mention how to wire up an auto top off system with a latching relay system. I don't want and don't need to do that so I've kind of tried to assimilate all this information and make my own circuit for a simple relay setup that hopefully will work. I also wanted to use a relay since I've heard that splicing the floatswitches directly into the line can be hazardous to your health :smokin: . Right now I don't need that kind of grief so I decided to use a 120VAC 10A relay that will lower the amperage that is drawn through the floatswitches.

I tried to make my diagrams as he to understand as possible since I know when I was first assaulted by these electrical wiring schematics, I didn't know what was going on.

So, let me tell you how I envision this will work. The lower floatswitch will control the water level while the upper switch just acts as a backup.

With a few modifications to the circuit, you could set up a latching relay and also have a backup floatswitch for the upper float switch in your latching relay assembly. I however don't think it is necessary since I'm not going to be using a solenoid controlling my RO/DI output but just a reservoir with a powerhead in it.

Here are the schematics... please you electrical guys out there, please comment on any flaws to the set up:

http://reefcentral.com/gallery/data/500/4686DPDT_circrelay_.jpg

http://reefcentral.com/gallery/data/500/4686DPDT_physrelay__bmp.jpg

Peace,
John H.

[Wallygator]

Hey, Great schematics! :)
I'll assume that the first is the same as the second.
One small flaw in the second drawing... the power that is feeding the common on the relay should be before the float switches as in the first drawing. If it's after the float switches you will be drawing all of the current through the float switches.
I think I would do a start-stop setup with two float switches, that way you would have broader control over the water level. Otherwise one is fine if you don't need the larger water level control.:D

[rufio173]

Hey Wally Gator,

Thanks for pointing that out. I'll fix it immediately. I'm just starting to learn this stuff.

I don't want to go the latching circuit route because I don't need it, but if I were to go that route, I'd simply include a third float switch to backup the latching top off assembly and change up the circuitry a bit. I think that would be better than just having the one set of upper and lower floatswitches.

Peace,
John H.

[rufio173]

Hi all,

This is the fix suggested by Wally gator that will keep the current from frying/melting the floatswitches.

http://reefcentral.com/gallery/data/500/4686DPDT_physrelay_.jpg

If anybody wants to know why a relay lowers the current through the switches, I was told that it was because that it takes a lot of current to align the ferromagnet of the coil relay to produce the magnetic field so that it somehow drains the current. Please somebody with a physics background chip in on why this occurs.

All you have to know is that relays will help save your floatswitches when using 110VAC.

Peace,
John H.

[xrunner1234]

For safety, I would switch both legs, not just the 'hot'.

[xrunner1234]

For safety, I would switch both legs, not just the 'hot'.

[Runner]

Originally posted by xrunner1234
For safety, I would switch both legs, not just the 'hot'. I'll second this -- especially since you have the other switch readily available.

[rufio173]

hey guys,

Could you extrapolate a little more on why I should put a float switch on both leads. Explain to me why that would be safer.

Remember that I am not an engineering student and have only taken beginning physics courses that are needed for chemistry majors so you will have to explain in layman's terms. :)

Thanks,
John H.

[xrunner1234]

Originally posted by rufio173
hey guys,

Could you extrapolate a little more on why I should put a float switch on both leads. Explain to me why that would be safer.

Remember that I am not an engineering student and have only taken beginning physics courses that are needed for chemistry majors so you will have to explain in layman's terms. :)

Thanks,
John H.

First, you totally disconnect from the line. You can't argue that.
Second- if you just switch the hot, then you must use a polarized plug, either a 2 prong with one side bigger or a plug with a 3rd grnd lead. The polarization is to ensure that the 'hot' is really the 'hot'.

[rufio173]

Hey Xrunner,

Makes sense. Thanks for the input. I will definitely do that then. If it works better this way and is a little safer than it's worth doing, plus it doesn't really take any longer.

Peace,
John H.

[rufio173]

Hey Xrunner,

Can you comment on this:

"with the way you have it drawn, the lower float switch will stay submersed and only the top one will turn the pump on. if you're wanting redundancy so that the lower switch is constantly turning the pump on and off, and the top one is a fail-safe to turn the pump off in the instance that the lower switch fails, then the lower should be NO and the upper NC. and yes, you're bottom circuit is the right one for power routing, not the first pic."

Looking at my circuit, it seems like it will work fine the way I have it set up, but this is what Electric130 (JR) says that I must do to have the first one act as the switch to keep my sump level and the upper switch to act as a backup. It doesn't make sense to me. Is he right on this one? You guys all seem to think that the circuit will work for what I want.

Peace,
John H.

[xrunner1234]

Originally posted by rufio173
Hey Xrunner,

Can you comment on this:

"with the way you have it drawn, the lower float switch will stay submersed and only the top one will turn the pump on. if you're wanting redundancy so that the lower switch is constantly turning the pump on and off, and the top one is a fail-safe to turn the pump off in the instance that the lower switch fails, then the lower should be NO and the upper NC. and yes, you're bottom circuit is the right one for power routing, not the first pic."

Looking at my circuit, it seems like it will work fine the way I have it set up, but this is what Electric130 (JR) says that I must do to have the first one act as the switch to keep my sump level and the upper switch to act as a backup. It doesn't make sense to me. Is he right on this one? You guys all seem to think that the circuit will work for what I want.

Peace,
John H.

Short= fill (NC)= energize relay= turn pump on: When the sump is at the right level the float should open. If that fails shorted, your sump will continue to fill until the top float (which is NC) opens, shutting your pump down. Looks good to me.

[rufio173]

Thanks Xrunner,

I talked to JR about it. He was confused and it seemed allright to him after I explained it a little more thoroughly. Thanks for all the input though. I definitely am very excited at the possibilities of these relays. Hehe... so many DIY projects you can use them for. :)

Peace,
John H.

[electric130]

Originally posted by rufio173
Thanks Xrunner,

I talked to JR about it. He was confused and it seemed allright to him after I explained it a little more thoroughly. Thanks for all the input though. I definitely am very excited at the possibilities of these relays. Hehe... so many DIY projects you can use them for. :)

Peace,
John H. what confused me is the contacts on your floats. they're drawn as NO. you want NC. i just didn't think all the way through it before i posted last time.

[electric130]

Originally posted by xrunner1234
First, you totally disconnect from the line. You can't argue that.
Second- if you just switch the hot, then you must use a polarized plug, either a 2 prong with one side bigger or a plug with a 3rd grnd lead. The polarization is to ensure that the 'hot' is really the 'hot'. in actuallity, it really doesn't matter. plugs never used to be polarized and electrical equipment worked just fine. if you reverse the wires, a pump or relay will work just the same. if you notice, a lot of power head cords aren't polarized. also, i don't see the added safety of switching both hot and neutral. house light switches and industrial switches only disconnect the hot. can you explain why disconnecting the neutral adds any safety and where it adds it? thanks.

[Runner]

Originally posted by electric130
... can you explain why disconnecting the neutral adds any safety and where it adds it? thanks. Because a neutral can still pack a punch if it is not solidly connected to ground. And because the switches are going in the water where such problems will be amplified. Sure, it is double-failure protection. But since the relay has a spare contact available, you might as well do it.

The local utility is requiring me to install a 4-pole transfer switch on our backup generator to prevent bad ground connections from killing their guys. The same thing on a larger scale...

[electric130]

Originally posted by Runner
And because the switches are going in the water where such problems will be amplified. Sure, it is double-failure protection. But since the relay has a spare contact available, you might as well do it. but only the float switches will be in the water. only hot will be flowing through them. the relay and outlet will be outside the tank and water. it's no different than an outlet in the wall then. an outlet on a light switch in your house only switches the hot. i still don't see the safety added with switching neutral too. the neutral shouldn't be anywhere near water.

[Runner]

The neutral will feed through the relay coil to the float switch in the water.

[rufio173]

Ok,

So, I'm wondering what I need to actually do. If I will be putting the switch on the neutral. Do I just put the switch actually in the path of the neutral lead? It's that simple right?

You keep mentioning an extra contact on the relay and using that but I don't know what you are referring to.

Peace,
John H.

[Runner]

The relay you are using is DPDT, which has two seperate contacts that act together. You are using one of them to switch the power leg. Simply place the other contact on the conductor between the relay coil and the neutral. The two sets of "C", "NO", and "NC" terminals are two seperate contacts -- not duplicate terminals of the same switch.

The only time you are allowed to switch the neutral is in an instance such as this -- where the "hot" legs are switched simultaneously.

[rufio173]

Hey Runner,

Ok, so do you mean like this. I'm sorry, but diagrams help me out a whole lot more :)

http://reefcentral.com/gallery/data/500/4686DPDT_physrelay_-alternate.jpg

Thanks!
John H.

[rufio173]

Like this?

http://reefcentral.com/gallery/data/500/4686DPDT_physrelay_-alternate.jpg

Peace,
John H.

[rufio173]

Runner,

I don't think this is what you are suggesting, but if you could take my picture and add in your connections and change mine, that would be great. It's easy to just open up the image in the paint accesory and dabble around with it.

Thanks,
John H.

[electric130]

Originally posted by Runner
The neutral will feed through the relay coil to the float switch in the water. true, but that's not the neutral that would be switched by the contacts based on what you've said in past posts. if you put that neutral on the contacts (the one going to power the pump), the circuit would never get completed. switching the neutral on the powerhead through the contacts of the relay would have no added safety. just as much potential in the floats as the hot, and there's no way around that.

[Runner]

I'll sketch and scan a circuit for you tomorrow.

[rufio173]

Thanks runner,

I just don't get what you were trying to explain. I'm not sure how it will close the circuit that is.

Peace,
John H.

[rufio173]

Hey Runner,

Thanks for the offer, but since there hasn't been a sketch posted, I'll say that you lost interest and go about wiring it the way I've done it.

The other way doesn't seem to be much better and I'll ask my dad what he thinks. He's got a pHD in Biomedical engineering and he definitely understands circuits so I'm sure he'll understand what you are talking about.

Peace,
John H.

[Runner]

Oops. I forgot about you. Sorry about that. I just started to sketch it out and realized that I was wrong about the second switch being able to be used the way I said. electric130 was correct about that.

You should be fine without switching the neutral, anyway, so long as all your stuff is hooked up to a GFCI receptacle or breaker.

[electric130]

Originally posted by Runner
You should be fine without switching the neutral, anyway, so long as all your stuff is hooked up to a GFCI receptacle or breaker. good point. i think everyone should have at least one GFI on their tank's electrical. i'd even take it a step further and have a GFI receptacle at the tank and an Arc-Fault breaker in the panel. maximum protection!

[rufio173]

Thanks guys,

Will do!

Peace,
John H.

[Runner]

I was a little fuzzy on how you were running your circuit, anyway. Here is how I would wire it up. I use both contacts on the DPDT relay -- one to seal in around your upper float switch and one to energize your receptacle. Is this what you were looking for?

<center>http://reefcentral.com/gallery/data/500/14962PumpDownCircuit.gif</center>

If you have any questions, I'll try to be more responsive this time.

-Scott

[electric130]

that diagram will only work if you were pumping water out of the sump. to fill the sump with the pump, you'd need to make the floats NC. this is what i use on my setup. the relays are shown as the same, but they should be CR1 and CR2, independent.

http://reefcentral.com/gallery/data/500/10832FLOAT_CONTROL_SYSTEM-Model.jpg

[Runner]

Here is my circuit modified to show control for pumping into the sump. The float switches do need to open when water rises.

<center>http://reefcentral.com/gallery/data/500/14962PumpUpCircuit.gif</center>

Keep in mind that you should probably use a third float switch in the "upper-upper" position as your HIGH alarm should the upper float switch freeze and fail to stop your sump from overflowing.

[xrunner1234]

This is similar to what I have but it is on a 12VDC system so it should work. It is not a latching type, so there is no large hysterysis on water fills and I believe that the poster wanted 2 floats, 1 lower and 1 for a safety backup.

I have a similar setup to the latching ones shown before on my reservoir tank for my RO/DI, but for my sump it's not needed.

http://reefcentral.com/gallery/data/500/36214float_setup.jpg


Short= fill (NC)= energize relay= turn pump on: When the sump is at the right level the lower level float should open. If that fails shorted, your sump will continue to fill until the top float (which is NC) opens, shutting your pump down. Just make sure that a qualified Electrician/person checks, builds, and installs your setup.

[electric130]

Originally posted by xrunner1234
It is not a latching type, so there is no large hysterysis on water fills that hysterysis is what prevent a powerhead or pump from burning out prematurely by limiting the number of times it's cycled on and off. the hysterysis can be made as large or small as you want depending on the placement of the float switches. my sump fluctuates about 1", or about 1/2 gallon. that's more than acceptable IMO. especially considering it used to fluctuate 2 gallons per day before i installed an auto top-off. even then, i had no ill effects from salinity swings. the salinity difference wasn't even detectable.

[xrunner1234]

Originally posted by electric130
that hysterysis is what prevent a powerhead or pump from burning out prematurely by limiting the number of times it's cycled on and off. the hysterysis can be made as large or small as you want depending on the placement of the float switches. my sump fluctuates about 1", or about 1/2 gallon. that's more than acceptable IMO. especially considering it used to fluctuate 2 gallons per day before i installed an auto top-off. even then, i had no ill effects from salinity swings. the salinity difference wasn't even detectable.

True, but just make sure you have an overflow float. And floats do (at least on the ones that I have) have about 1/4-1/2" play before they switch states. So there is a 'built-in' hysterysis.

Did we confuse the snot out of the rufio yet?

[rufio173]

Hey guys,

No, I'm still with you guys.

Runner, thanks for the input, but like I stated before, I didn't want a latching relay setup. But thanks for the additional diagrams and the time you put into it.

I don't need the hysteresis, because I'm pretty happy with the 1/4" difference. It shouldn't turn on my maxijet 600 more than once every 15 minutes or so considering my tank size. That is far below the cycle times that I have my maxijets on with my wavetimer. I would only use this setup with a maxijet pump due to their reliability with quick cycling times.

Once again, thanks to all you electrical guys for helping me figure this all out, now I feel like understand a little bit more about how electricity works and how to use a simple relay.

Oh yeah, one question, what do you guys use to draw circuit schematics... any good free programs out there?

Peace,
John H.

[Runner]

Heh. I just used Paint for those above. I normally use AutoCAD at work. And that ain't free.
:)

[rvitko]

I can't help you along the lines of what you are working on but I can suggest an alternative. Here is what I used to use. I took the mercury switch out of a thermostat and wired the positive leg of a 12v DC transformer through the mercury switch so when down the circuit was closed and when up it was open. I sealed this inside a PVC pipe with both wax and the glued on end caps- this was my float mechanism and note it was 12V DC for safety. The + lead coming from the float and the negative straight off the transformer were wired to a 12V DC air pump available from Schego as the Schego Triumpf. The air pump kicked on when the float dropped and pressurized a 5 gallon glass carboy with a two hole stopper. One hole just fed the air in and the other had a tube which went to the bottom of the carboy and out to the sump. The air pressure from the pump pushed out the fluid. It was very simple and absolutely safe and accurate to within about 1" of water level. The air pump is the only hard part to acquire- you will need to contact Hawaiian Marine the US distributor as he only brings them in for fishing buddies who use them to aerate live wells. They are quite strong for a DC pump. Mercury switches aren't so easy to find nowadays either but search for old thermostats at salvage yards.

[electric130]

i have autocad also. it's free if you've got about $5000 laying around that you're not using ;)

[rufio173]

Haha guys,

I think I'll stick with paint... the poorman's schematic tool!

Hey Roger, thanks for the additional info. Sounds like a real safe setup, but I don't want to use the carboy. I have one that I just use gravity with, but right now, I don't want to use the carboy since I'd have to pull it out whenever I wanted to fill it and the hole is so small. It's just a pain in the *** even though it is really simple. 12V is definitely not going to kill anyone, but I like dabbling with my life :) Haha...

But seriously, if you properly wire and seal everything in this setup, there should not be a problem.

Peace,
John H.