DIY auto Shutoff for a return pump

[chuckdallas]

I have an empty tank (except fresh water to test if it leaks) and have set up the overflow box (sides & bottom tempered) and wet-dry filter and return pump. I want to develop an auto shutoff system for the return pump. Someone said to purchase a "float valve" and then go to Radio Shack to get a relay and then wire up the whole thing.

I saw a single switch auto shutoff on "Autotopoffs.com" for $40. It looks well built and much better than anything I could design for $40 (plus S&H).

I know a lot of you are Do-It-Yourselfers, so what do y'all recommend (Southern Virginian upbringing)?

Build it or buy it?

[LaOtIn]

+1 on buy it, install it and forget about it!

i am planning on buying their single switch kit and a small pump because the way my sump/stand is i do not have room to put my top off reservoir above the sump. their pumps are dirt cheap and u can look on usplasics.com to find a container, they have just about every size/shape you can think of.

:thumbsup: on setting it up

[DustinB]

The easy way to make a DIY auto-shutoff would be to use the float switch to break a leg on the AC line coming into the pump. However, this is a bad idea to have AC running through the switch like this. The person online that was showing this method online must have a death wish.

The proper way to do it would be to build a simple circuit using a mechanical relay. You would need a 10A 120+V relay with a 5v DC control, a basic 5v DC power supply, and a cheap float switch.

You would use the relay to break one AC leg of the pump. Then you would use the float switch to break the 5v DC leg to the control of the relay.

When the float switch is activated or deactivated, depending on how you set it up, it would trigger the relay to turn the pump on/off.

This would cost you probably around $30 in parts or so. It would really be up to you on how you want to do it, you can get a basic auto-topoff setup for $50, maybe cheaper if buying used.

Figure out which way you want to go, I can probably get you a list of what you will need if you decide to make it.

[BeanAnimal]

A simple float switch and relay will NOT work...

You need to build a latching circuit. Here is why:

If the float in the sump senses a low water condition, it will turn off the return pump. This action will allow the water in the plumbing to drain back into the sump, raising the float switch and turning the pump back on. This will cause the water level to drop again, turning off the pump...

...Over and over until the pump burns up!

You need a latching circuit (a simple double pole relay) with either a single float and a manual reset switch or two floats (a trigger float and a reset float). I don't have time to post the circuit... but if you can't make any headway, let me know.

[DustinB]

I didn't even think about that, I was looking at it in an auto-topoff sense. Thanks for catching that!

[TheBends]

Why couldn't you run a check valve in the return line so that when the pump shuts off water does NOT syphon back which keeps the water level at the same height in turn keeping the pump turned off and also not causing your sump to overflow? :hmm2:

[BeanAnimal]

Why couldn't you run a check valve in the return line so that when the pump shuts off water does NOT syphon back which keeps the water level at the same height in turn keeping the pump turned off and also not causing your sump to overflow? :hmm2:

Check valves fail (when you least expect it)
Check valves reduce flow
Check valves should ALWAYS be avoided when there is a more elegant option :)

Let me rephrase:
A) Without question, you need a float switch, optical, pressure or similar sensor to detect low sump level.

B) It is best practice to use a low voltage sensor and a relay to switch line level voltage in an aquarium. It is a must for a return pump.

If you are already using a relay, then why not use it as a latch instead of a simple contactor? The operation is fail-safe, unlike the check valve that fails-unsafe. You get more bang for the buck and avoid the use of a check valve and its problems.

[dots]

I'm still on "why" in the first place? Why do you want to "auto shut off" the return pump?

[BeanAnimal]

I suppose some folks with small sumps would like a "low water" safety feature to prevent the retun pump from running dry due to evaporation.

[Pickupman66]

I ahve thought about something like this. sorta like an emergency if the overflow gets clogged. that said, i want it to only be able to reset manually.

[chuckdallas]

I have tempered glass all over, so I can't drill a hole. I also have a single u-tube siphon from the internal overflow box to the external overflow box without an aqualifter, so everyone has warned me that during a temporary power outage to the house or pump, say 30 minutes, the siphon will break when the water stops going into the internal overflow box and then, when the power resumes, the pump will turn on, so the aquarium will fill up and overflow. I thought the float switch would go into the Display Tank (yeah, not pretty), but I've also heard you all say put it in the sump. I have seen the float switches from autotopoff.com ($40 for a single switch) and I'm not sure that it will fit in the bottom of my sump. The return line has a siphon break about an inch from the top of the water line. I had a check valve in the return line clear rubber tube, but I'm going to take it out, since it restricts my flow.

[BeanAnimal]

Get a new tank :)

You can use a mechanical or optical float switch in the display tank to prevent overflow using the latching method but there are some gotchas to consider. Setting the float to the proper height in the sump (to prevent overflow display tank overflow) will take some work and be dependent on the evaporation level of the sump and the effectiveness of the autotop off.

The problem with a float in the display (driving a latched circuit) is that a power outage will also collapse the latch. Not ideal at all. The latch needs to be a bit more complex to auto-set after a power outage but collapse during a high water event. If I get a chance later, i will draw the circuit up.

[dots]

Get a new tank :)


Yeah, those tanks that are converted like that, should be a temporary thing for those not sure they want to commit to the hobby.

Sounds like a perfect reason for an upgrade to me......safety always is a good rationalization.

[BeanAnimal]

Now to convice her that the 75 is not safe, but a 110T or a 120 standard would be MUCH safer :)

[uncleof6]

I don't know bean, I think the 120 is safer than the 110T by far..... ;) (Better footprint)

Jim