Wiring a float and relay to protect your ATO pump and more

[gregzz4]

I had read about people destroying their ATO pumps by running them dry, and I wanted to add a powerhead and heater to my holding tank, so I decided to install some floats that shut off the powerhead and the heater, and eventually the top-off pumps
After running this setup for almost a year, and having it run low enough on more than one occasion that it nearly ran out of water, I decided to add a flashing led to let me know when I was not paying attention to the level before the Tunze pumps are shut off

The Osmolator will squeal if the level gets too low due to an empty ATO holding tank, but I don't want that happening when someone is sleeping, or I'm out of the house

My 10g ATO tank



Better shot of the floats, but before the second Osmolator was installed



My relays



The LED mounted in a project box and where I will see it right away when I come in the room, or am looking at the sump





I have Tunze Osmolators on both my DT and QT, plus the led, so I used 4 relays

My total cost, with 2 floats and a hanger, 4 relays, 4 sockets, 2 power supplies, 1 led, 2 duplex outlets, 1 GFCI, and various wire and connectors, was about $200 +tax, give or take, so do you really want to do it?
I'm anal about redundancy and protection, so I was stupid enough to spend the money but I’m glad I did it

My ATO holding tank consists of a heater and powerhead, 2 ATO pumps, a ground probe and 2 floats. The floats are mounted on a DA hanger with the upper float pointing up, and the lower pointing down and resting on the glass. This is perfect as the pumps are still wet at the lower shutoff point, and both the heater and powerhead are still totally covered at the higher shutoff point

Also used are; 4 relays and 4 sockets, 2 12vdc power supplies, 1 12vdc flashing red led, 2 120vdc 3-conductor power cords, and 3 duplex outlets
With the 3rd outlet for the heater/powerhead circuit, I used a GFCI.
This not only protects me, but all the 12v circuitry including the Osmolator. It’s money well spent.

If you don’t run a heater or powerhead in your ATO tank, you can skip the process of adding it’s circuit, but the top float also controls the flashing led, so modify my setup to suit your needs
I like the heater and powerhead as, even though it’s only a cup at a time, I don’t like dumping cold water into my system, and I don’t like the idea of the ATO sitting stagnant. But this is just me …

You can, of course, buy all this stuff wherever you want
I’ve linked all the stuff I used only for ease of understanding and to give you an idea of costs

The parts list

Relay
Socket
Float hanger kit and a second float
12vdc power supply
12vdc flashing red led
Project box Not required, but is great for mounting the led
3-conductor power cord You can get this at Home Depot etc
Duplex outlet if you don’t know what one is by its name
You’ll also need boxes for your outlets. If exposed to your tank/splashing etc, waterproof are the best to use

Electrical connectors and tools to do the job are needed, plus some handy-skills or someone to help you are a must. After all, we are dealing with electricity here SMILEY
If you have a multi-meter/electrical tester, that’s a bonus.

For this project, regardless of how many ATO pumps you want to run, we need 3 duplex outlets

1 outlet provides power to the 2 12vdc power supplies, and it’s powered from your house

1 outlet for the heater and powerhead – this is not connected directly to your house power

1 outlet will be split – it provides power to the heater/powerhead circuit, and also gets house power
Below is a pic on how to ‘split’ a duplex outlet
Break off the ‘tab’, and be sure there is no contact between the upper and lower outlets, on both sides of the outlet!!
To make this clear, break off the tabs on both the ‘silver’ screw side, and the ‘brass’ screw side
Failure to do this is not a good thing, and I’ve warned you, so I’m off the hook!!
What you are doing is creating 2 different paths – one upper and one lower. One outlet will be used to power the circuit from the house, and the other will be used to power the ATO circuit that goes through the relay.
Snap off a breakaway tab
Grab the tab with pliers and wiggle it back and forth until it breaks off


Lets get started!!

If you don’t know much about electricity, you’ll need some help, but if you’re even a bit handy, this is easy enough.

The relay socket is labeled 1 through 8
7 and 8 are where voltage is connected to power the relay
5 and 6 are where you connect the incoming signal/power you want to control
3 and 4 or 1 and 2 are where you connect the accessory you are controlling
1 through 4 are N.O. and N.C. circuits
Without power to the relay, 1 and 2 are closed/powered
With power to the relay, 3 and 4 are closed/powered

Wiring a float to control a relay

Cut the end off a 12vdc power supply and strip it. Neither the relay nor the float are polarity sensitive, so positive and negative have no bearing here.
Connect one wire to either terminal 7 or 8 on the relay socket. Connect the other wire to one of the float wires. Connect the other float wire to the other terminal of either 7 or 8.
This is what controls the relay.

Connect your ATO pump controller’s pump power wires to terminals 5 and 6. Connect your ATO pump to terminals 3 and 4. If it’s polarity sensitive, make sure you match them across the socket. It’s pretty straight forward when you look at the socket. 6 powers 2 and 4 and 5 powers 1 and 3.
If it’s like the Osmolator 12v pumps, they’re not sensitive, which means there’s no positive and negative to worry about matching up.

That’s it for controlling your pumps.

Wiring a relay to control a 120vdc outlet

Controlling the heater and powerhead is a bit trickier.
The relay is wired the same as above for the 12vdc supply and float.
Here’s the fun part.
Wire a duplex using one of the 3-prong power cords, essentially creating an extension cord. The black (HOT) wire goes to the brass screw, the white (NEUTRAL) wire goes to the silver screw, and the green or bare copper (GROUND) wire goes to the green screw.
Take one duplex outlet and split the circuit as pictured above. I prefer to break of both tabs as there’s less chance of voltage leaking.
At this point you’ll need to decide where you will be mounting everything as we are now going to cut some wire.
Take the other 3-prong power cord and remove the outer jacket far enough that you can cut the HOT and NEUTRAL wires, but still have the GROUND intact. Connect the GROUND to the duplex. Connect the HOT and NEUTRAL wires coming from the plug end to the relay socket terminals 5 and 6. Now connect the loose HOT and NEUTRAL wires to terminals 3 and 4. Make sure they match up with the other HOT and NEUTRAL wires – if HOT goes to #6, then it must also go to #4.
Wire the other end of the loose HOT and Neutral wires to the half of the split duplex that is not going to be wired to your house power.
Insert the 3-prong plug of this cord to the half of the duplex that you will wire to your house power.
The float/relay circuit will now control the power going to your heater and powerhead outlets.

OK, last steps.
Insert the relay to the socket.
Wire the other half of the duplex you split to your house power, and that’s it.
It wouldn’t hurt to make labels for the split outlets. Maybe on could read 120vdc, and the other could read switched. Or whatever makes the most sense to you.
If you have a multimeter, now is the time to test your new circuit. If not, plug in a lamp to your new heater/powerhead outlet, plug in the 12vdc power supply and play with the float to make the light go on and off.

If you don’t like the way the float is switching, you can flip it by removing the clip. Now it will switch the opposite way.

If you haven’t yet mounted the socket, unplug the 3-prong power cord and 12vdc power supply and mount that socket somewhere safe and solid

Wiring a warning led

The particular led I bought is polarity sensitive. The orange wire is +, leaving the yellow wire as –
I tapped into one of the existing 12vdc power supplies, before it connects to a float. These wires go to terminals 5 and 6
I then made a jumper wire that connects from terminals 7 and 8 on the relay that is controlled by the float that in turn controls the heater/powerhead circuit. This is what turns the led on when the water is low
Next, I connected the led to terminals 1 and 2
Lastly, I used a small project box to mount the led and also added a grommet for the wires.

It works as planned and with a long wire on it, I can put it almost anywhere.