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Float switch

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Float switch

Postby RogerS » 25 Jun 2022, 11:29

Is anyone familiar with how these float switches work? Scant information on eBay.

What is the point of the different lengths ? I'm after a float switch that will turn on when water reaches a certain height and then off once the level has fallen sufficiently.

float switch.png
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Re: Float switch

Postby 9fingers » 25 Jun 2022, 11:41

Different lengths for different hi/lo differentials.
Almost certainly magnetic and reed switches in the tube as confirmed by the miniscule current handling of the switches. Each float only has a limited travel. You can see the circlips if you look carefully.
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Re: Float switch

Postby AJB Temple » 25 Jun 2022, 11:42

If they are similar to the ones I have (not sure) then they are contained loosely in a tube so they slide up and down. Different lengths allow different trigger points and access. The one in our terrace sump is quite long.
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Re: Float switch

Postby AJB Temple » 25 Jun 2022, 11:42

Bob was there first and better informed as usual :oops:
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Re: Float switch

Postby Lurker » 25 Jun 2022, 11:43

I think that the different lengths are more to do with the fixing above the water level.
Also you can have two floats on and off to avoid rapid recycling.

Edit: posted before reading Bob’s.
Note well the point about the reed switches.
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Re: Float switch

Postby Mike Jordan » 25 Jun 2022, 11:47

It is rather strange,My guess is that they are intended to maintain a level of water rather than to pump out unwanted water. I have a pump used for emptying a garden pond, that has a float switch in the power lead. It turns the pump on when the switch is upright but when the level falls the switch drops out of the vertical position and turns off the pump.
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Re: Float switch

Postby 9fingers » 25 Jun 2022, 12:03

Roger I suspect you may well need a little extra logic in the wiring between the two switches and won't find out until you get the item and experiment.

Depending on which way up you fit the guide rod, the function of the two switches will reverse. Nothing that can't be fixed with a handful of components and a relay to carry the current of the pump.
The extra circuitry will be worth it just avoid drilling the tank below high tide level to get the function you want with the wires at the top.
This will be left as an exercise for the OP! :lol:
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Re: Float switch

Postby Cabinetman » 25 Jun 2022, 12:15

If you do go down the DIY route with wiring Roger it’s handy to remember you can waterproof things using a hot glue gun. Ian
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Re: Float switch

Postby RogerS » 25 Jun 2022, 12:39

Thanks guys. That confirms my own gut feel.
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Re: Float switch

Postby Woodster » 25 Jun 2022, 14:00

Have you already bought a pump? The one I’ve got has a float switch built in. Not sure of the on/off water depth as it’s buried in the shed somewhere. :lol:

Edit: Not mine but it looks quite similar as I remember.

https://www.amazon.co.uk/MEDAS-Electric ... 58066&th=1
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Re: Float switch

Postby RogerS » 25 Jun 2022, 14:31

Woodster wrote:Have you already bought a pump? The one I’ve got has a float switch built in. Not sure of the on/off water depth as it’s buried in the shed somewhere. :lol:

Edit: Not mine but it looks quite similar as I remember.

https://www.amazon.co.uk/MEDAS-Electric ... 58066&th=1


No I gave up on those. I've got a cheap fountain pump. Also those floats have got too much hysteresis.
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Re: Float switch

Postby 9fingers » 25 Jun 2022, 14:45

What is the tank material Roger? If non metallic then capacitative sensors might be an alternative worth looking into as you can stick them on the outside where you wish.

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Re: Float switch

Postby RogerS » 25 Jun 2022, 17:42

9fingers wrote:What is the tank material Roger? If non metallic then capacitative sensors might be an alternative worth looking into as you can stick them on the outside where you wish.

Bob


Brick ! It's the surround at the top of the well in the cellar. What happens is that the water table inside the well is higher than the floor and so water gradually weeps through cracks etc ((I think). Tanking not practical because the inside is always full of water and outside would look awful. So opting for the high tech solution.

I've got a relay but need to see what the coil voltage requirements are. That's for tomorrow. Omron LY2NJ. Hopefully it's 240v.

This is what I've come up with.
float switch cct diagram.jpg
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Assumption is that when the water level reaches the float, the contacts close. Distance between the two floats needs to be small and so shortest float switch I think.

Operation...

Water at required level...Upper and Lower OPEN. Pump off

Water gradually rises and Lower CLOSES and feeds mains to Upper float and also latching contacts on relay. Pump off.

Water reaches 'bail out time' Upper CLOSES. Completing the circuit, relay energises and contacts C close thus latching the relay on. Pump ON.

Water gradually falls, Upper OPENS but relay still held on by the latching contacts.

Until water level falls below Lower which breaks the circuit.
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Re: Float switch

Postby RogerS » 29 Jun 2022, 10:11

Here's a video of those float switches in action.

https://youtu.be/M2psgNC5kiE

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Re: Float switch

Postby Cabinetman » 30 Jun 2022, 10:30

Hi Roger, CT1 can be used to stick things underwater if you wanted to go gown the tanking route. Ian
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Re: Float switch

Postby RogerS » 30 Jun 2022, 10:50

Cabinetman wrote:Hi Roger, CT1 can be used to stick things underwater if you wanted to go gown the tanking route. Ian


Thanks Ian but think I'll pass !
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Re: Float switch

Postby RogerS » 30 Jun 2022, 14:48

Life is never simple. Received the float switch today. Supposed to be able to be operated from either top or bottom. I can't see how? :eusa-think: Maybe you have to take the floats off and turn them the other way round ? At the moment, the contacts only close with water level if it is fitted from the bottom...not what I want.

EDIT:

Yup...that's a relief. Turn the floats over
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