"Low Tank Water" switch ?

[bcarwell]

Could somebody point me to the right type of 110VAC float switch(es) for turning on and off a basic 1 1/2 inch 10 GPM water pump for a 1000 Gallon tank, e.g. a switch that turns it the pump on when the water is low in the tank and off when its filled. I know there are plenty of "float" switches at Tractor Supply that sit at the top of the tank to turn off the pump when the tank is full. But what kind of switch senses when the water level is at the bottom to turn it on ? And is there a pair of switches in an assembly for both the "on" and "off" levels ? Or do you just kludge something together once you have the switches ?

Bob

 

[aczlan]

On the sewage holding tank at the hotel I work for we have 4 switches, they are (from top to bottom):
1. Overflow switch - 2' from the top of the tank - Turns on an alarm when it is floating and the sewage is within 2' of the top of the pit
2. High level switch - 4' from the top of the tank - Turns on pump 2
3. Pump on switch - 4' from the top of the tank - Turns on pump 1
4. Lower switch - 2' from the bottom of the tank - Turns off the pumps when the tank is empty

I think that they are all "On when floating, Off when hanging" type float switches. They all go to a relay box which chooses which pump to turn on and when to do it

Aaron Z

 

[Kays Supply]

I use these type switches for sewage pits. I use an on when down switch to turn the water supply to the building off if it water level in the sewage pit gets too high so the second floor idiots don't flood out the down stairs idiots. Oh , this on a 3 plex for college students. You can wire two floats to a relay and expand your range of pump up[ or down. Granger is an online source or a local plumbing/ pump supply.

 

[bcarwell]

I don't know anything about these "floating" switches and how they work. Do they ride along some sort of vertical pole like a piece of PVC and have a toggle switch toggled by stops at the top and bottom of the pole or what ? Do you have to kludge the assembly together yourself or are there inexpensive switch and pole assemblies you can buy ?

Bob

 

[Car Doc]

Some pond pump switches are floating type and I believe they have a mercury switch in the bulb that floats but I could be mistaken.

I know they just hang from the top or side of the pump depending on model.

 

[Kays Supply]

They are a ball on a wire. You put a weight on the wire to set the travel of the float. It hangs in the pit on the wire. They were mercury switches but they have "saved us from the evil mercury". They are now mechanical. They have a ball that rocks back on a microswitch. They don't last as long as the old ones, but do better than anything I have come up with. I will have to do some thinking to get a wiring diagram on how to wire a double set up. A single can have a couple feet of pump down/up it will take a double if you want more . I just looked, Google Grainger float switch, several types will come up.

 

[F1520]

You can accomplish this with a single float switch. I have a water system that works exactly this way. Install a float switch tethered to a length of 1 1/2" PVC pipe that stands inside the tank:

Phoenix Pumps, Inc. - Goulds Float Switches

You need a NC/Normally Closed switch to turn on the pump when the tank level is low and shut it off when the tank is full.

Some switches of this type have very long cords. Where you attach it to the PVC and how much slack you let it hang by will give you enough travel to have the pump kick on when the tank is just under half full and kick off when it's full again.

 

[schmism]

You can accomplish this with a single float switch.

as he said the single float switch is tethered in the tank. generally the tether is half the tank fluid level movement and tethered in the middle of the vertical fluid travel. (a 10' tall tank... tether is 4' long attached 5' down the side of the tank. this means the fluid level moves 8' leaving a foot at the bottom and a foot at the top) the switch can tell the difference between a vertical down position ( hanging by the tether out of the water....water to low) a horizontal position (floating on the surface) and standing on end (submerged underwater... water to high)

depending on the position of the switch (normal open vs normal closed) will dictate what the pump does at ether end of the float operation (aka will the pump come on when low off when high or vise versa shut off when low come on when high)

 

[Kays Supply]

I am used to having a smaller diameter tank than it is tall. With piping and wiring to deal with a long cord on the float doesn't work for me. It can
get tangled up. In a water only tank the longer cord may be fine.

 

[Raspy]

Float switches are rather clumsy and can get hung up or fail in repeated use. Better is a boiler low water cutoff. These have a single hole that a probe goes through and senses water. I'm setting one up now. When the water gets down below the probe it turns on the pump with a time delay relay that shuts off the pump after a set time that is enough to fill the tank. It only has one hole, no moving parts, all electrical is outside the tank.

My tank takes about 1/2 hour to completely fill, so I can set it up to come on and remain on for 20 minutes or so after the probe is covered.
This system also allows for various safeties or warnings if the pump fails, if you want them, such as a delay on warning light or buzzer that will tell you if the tank is not filling for some reason.

This technology is very reliable and is also used for boat bilge pumps in addition to boilers.

 

[schmism]

Float switches are rather clumsy and can get hung up or fail in repeated use.

I suppose that depends on the quality of the switch. As every municipal facility that has sewage lift station relays on a series of float switches. If they are good enough for commercial 100% duty sewage lift stations .... why reinvent the wheel. aka KISS

 

[aczlan]

I suppose that depends on the quality of the switch. As every municipal facility that has sewage lift station relays on a series of float switches. If they are good enough for commercial 100% duty sewage lift stations .... why reinvent the wheel. aka KISS

Ayep. We have (knock on wood) never had an issue with the float switches in the pit at the hotel. We have had a lightening strike take out one leg of the 220 circuit that the pumps run on, we have had junk jam up the grinders and we have had a pipe break and allow the slurry to backfeed into the tank instead of going out.
But (knock on wood) in the 5 (almost 6) years that they have been in operation we have never had an issue with the float switches.

Aaron Z

 

[Raspy]

With sludge systems you pretty much have to have a float of some kind because of the conductivity and foreign material in the mix. Whatever works is fine.

I've had the "bulb on the end of a cord" system fail by getting hung up on things in the tank, the "sliding float" get stuck and fail, and the floating PVC tube that operates an out-of-the-tank switch, let in contaminates and become covered with growth to where they become stuck. I've also had a number of float systems fail because of turbulence over time that wore them out. All of these required a hole in the tank somewhere and I try to keep that to a minimum. No bugs or dust in, no friction with movement through the hole and no electrical cords passing through a tank wall. Also, the slider or bulb systems have a pre-determined differential between off and on. This works for sumps, but not so well for tank filling. But, again, whatever works in your case is fine. I consider a sludge system to have far different needs than a fresh drinking water system. Hot tanks and insulated fiberglass tanks are even harder to make work well. And, for me, the system needs some kind of warning system, if it's not working right, to protect the pump. This can be a system that shuts off the pressure pump, or turns on a light, or something. The one I'm working on now will simply run the pressure pump until it burns up if the tank runs out of water. That has to be fixed.

Either way, the cooler, cleaner and less turbulent the better. If it only gets very occasional use, like a sump pump, it should have a way to get exercised occasionally. I just found one the other day that runs fine but won't pump because of a stuck and dry check valve. It's a flood waiting to happen.

 

[Egon]

And is there a pair of switches in an assembly for both the "on" and "off" levels ? Or do you just kludge something together once you have the switches ?

Bob, you have a plethora of switches to choose from. It comes down to your level of expertise, availability of instruments and money available. The type of tank and access points is also to be considered.

The float switch may be the simplest. By using two you can start and stop for low and high levels.

Then would come the electrical probe type. These are usually installed on the side of a tank on a nozzle.

Another would be a pressure sensitive switch installed at the bottom of the tank. they will come in a version that has stop/start capability and again may require a nozzle at the bottom of the tank.

There are lots more as a Google search would show.

And don't even think of ultra sonic.

Consider checking in with your local farm supply store or electrician for specifics on what seems to work for them.

 

[tommu56]

some thing like this

GE 2900B3S1C1-20 Open Tank Float Switch note this one closes on rise (wrong type for filling tank)

You can adjust the weight position and the length of the cable to turn on and off minimum is about 9" of travel.

another choice

http://www.grainger.com/Grainger/SJERHOMBUS-Float-Switch-3HCV1?Pid=search

Float Switch, Mechanical, Tether, Normally Closed, Max. Amps Running 15, Voltage 120/230, Cord Length 30 Ft., Wire Gauge 14, Pumping Range Min./Max. 7 to 36, Tether Length Min.-Max. 3 1/2 to 24 In., Float Length 3 9/16 In., Float Dia. 3 3/64 In., Max. Temp. 140 F, Max. Temp. 60 C, Float Material PVC, Includes Mounting Clamp Assembly
Grainger Item #3HCV1

you need it to closed in the down position open when it floats up
tom

 

[pat32rf]

A float switch is definitely your easiest way. They do come with contacts to start on drop but they might be hard to find. There will also be no "diferential" (high-low level) adjustment. A boiler "high voltage" probe arraingement is more adjustable as you just put a probe at the high and low points. Easier than it sounds. Ask about a boiler condensate pump switch....

 

[grsthegreat]

float switches work fine. mines been working 100% for 14 years (hope this post doesnt jinx it).
If your worried they have piggyback switches.... meanine 2 floats that do the same ting. if one fails the other kicks in.

Or you can install an alarm float that rings alarm if level gets too hogh or low.

you can find any of these switches at wholesale plumbing and/or well drilling shops. there not too expensive.

Heck, our Home Depot used to carry them till a few years ago.

 

[mmurphy]

The next question is, is this temporary set up or a permanent? If it is a temporary, I would go with a plain simple float. The pedastal type sump pumps worked on this easy set up for many years. I have been in water plants that use it also. A stilling well for the float will keep float running consistant up and down. A stilling well can be made simple as a PVC pipe anchored in place with an opening at bottom that allows water to slowly enter.