Pump float switch

[assegayer]

Diagram attached shows what I believe could work for a well pump used on a farm. Basically the pump has been burning out and I have found the cause, its because they turn the pump on then forget and the water runs out in the well thus its dry pumping. So i was thinking of introducing this sort of system. Any thoughts?

Thanks

 

[Marvo]

Depending on the size of the circuit supplying the pump the MCB might be overrated for the float switch. It's better to have your controls on a separate 5 or 10A circuit. Wouldn't a 24VAC float switch be a safer option?

 

[Deleted member 72666]

You can purchase submersible pumps with built-in float switches very cheaply these days without the need to be messing about with control ccts.

 

[Deleted member 72666]

What's the max lift height and how much water are you wanting to move (flow rate)?

EDIT:
I've just noticed that this is in the non UK section, what voltage are we talking here and what location?

 

[Richard Burns]

A separate control circuit with a NC float switch and latching start might be a better idea, but not better than a float switch controlled pump, though it does depend on the application.
This would seem to meet the operation as it appears to be from your post.

 

[assegayer]

What's the max lift height and how much water are you wanting to move (flow rate)?

EDIT:
I've just noticed that this is in the non UK section, what voltage are we talking here and what location?

They dont really want to change the pump now as they just purchased a new one. and richard the diagram your talking about seems to be good...maybe as marvo suggested a 12v one maybe better like this 24V 16A 35mm DIN Rail Mount 2 Pole Definite Purpose AC Contactor | eBay just purely because 230 volt underwater is a bit dodgy.

Basically the system is on a farm its a fresh water well thats used for watering crops. but every now and then the well takes a bit more time to naturally build up water inside therefore the pump maybe dry pumping burning out the pump. if theres any other system please do reccomend to me....THANKS ALOT FOR YOUR REPLIES

 

[Richard Burns]

You know the pump power and loading and you know what ELV supplies you have, match the contactor to these items and you will be away.
Obviously such a contactor as you have shown does not have auxiliary contacts to allow latching.

However the float switch could just start and stop the pump and the user just switches on an isolator to enable the pump.
So it would keep watering whenever there was water until someone stopped it; as opposed to my first possibility, where if someone starts it, once the level drops the pump stops until restarted, even if the level rises back up in the intervening time.

 

[Darkwood]

They dont really want to change the pump now as they just purchased a new one. and richard the diagram your talking about seems to be good...maybe as marvo suggested a 12v one maybe better like this 24V 16A 35mm DIN Rail Mount 2 Pole Definite Purpose AC Contactor | eBay just purely because 230 volt underwater is a bit dodgy.

Basically the system is on a farm its a fresh water well thats used for watering crops. but every now and then the well takes a bit more time to naturally build up water inside therefore the pump maybe dry pumping burning out the pump. if theres any other system please do reccomend to me....THANKS ALOT FOR YOUR REPLIES

They are IP rated for submersion ... think about the motor voltage!....

These pumps as mentioned can come with integral float control - ' just put permanent supply to pump and the float will control', volts free float switch where the user brings their own control voltage through the fitted float or stand alone pump where the user fits a independent float control system.
All are IP rated for submersion and there are no immediate restrictions on voltages for control but certain situations may warrant extra low voltage on the control side which would be more to do with the rest of the set-up and not the fact that it is underwater.

 

[Darkwood]

Be careful here you need a two point level set-up, if you have an immediate action float switch you may get a chasing effect caused by rippling water or just fast fill, your contactor will just be chattering on and off all the time which isn't good for both the motor or the contactor.

If you can get a delayed action float or intergrate a timer to avoid 'chasing effect', alternatively 2 floats doing the pump on and pump off switching so there is a set volume that is removed once pump is on and it has to fill the same volume before it cycles again.

 

[Deleted member 72666]

]They dont really want to change the pump now as they just purchased a new one.[/B] and richard the diagram your talking about seems to be good...maybe as marvo suggested a 12v one maybe better like this 24V 16A 35mm DIN Rail Mount 2 Pole Definite Purpose AC Contactor | eBay just purely because 230 volt underwater is a bit dodgy.

Basically the system is on a farm its a fresh water well thats used for watering crops. but every now and then the well takes a bit more time to naturally build up water inside therefore the pump maybe dry pumping burning out the pump. if theres any other system please do reccomend to me....THANKS ALOT FOR YOUR REPLIES

I bet by the time you've done it'll have been a lot cheaper for the client to have 'chucked' in a submersible with integral float switch! Just saying!

 

[Marvo]

You can also go with a pump protection controller that detects dry run by monitoring phase angle and run current. ACDC Dynamics - Rhomberg Products - Pump Protection Relays

Lots of ways you can skin this particular cat. There's also a 'pres control' available that sits in-line in the discharge pipe, it provides pump control, pump dry run safety etc etc here's the Grundfos version but there's others available.

The best solution will depend on the existing bore hole pump, booster pump and irrigation installation and how it's configured.

 

[shanky887614]

you could simply have two float switches.

one dropping a N/O contactor on low water then a high level float switching the coil voltage to the contactor

quite simply it will drop out when the water gets low.

then there will be no coil voltage to operate the contactor to start it again till the water level is high enough