Question about float switch wiring.

[Mduncan60]

I'm planning on setting up a well storage tank for my well. I have learned a lot on this forum. More than on any other website. But I just want to clarify something. The well pump is currently controlled by a pressure switch. The pressure switch opens and closes both the L1 and L2 circuits. I have always assumed that was necessary. But it seems that a float switch opens only one circuit. Am I understanding that correctly? That only one circuit needs to open and close to start and stop the pump.

 

[Reach4]

Yes.

 

[Sponsor]

 

[Valveman]

You can use a float switch to control the pump. Or, you can use a pressure switch and tank if the float switch controls a solenoid valve.

 

[Mduncan60]

Yes.

I do like a simple answer.

 

[Mduncan60]

You can use a float switch to control the pump. Or, you can use a pressure switch and tank if the float switch controls a solenoid valve.

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View attachment 86300

By solenoid valve, do you mean a relay or contactor?

 

[wwhitney]

I'm planning on setting up a well storage tank for my well. I have learned a lot on this forum. More than on any other website. But I just want to clarify something. The well pump is currently controlled by a pressure switch. The pressure switch opens and closes both the L1 and L2 circuits. I have always assumed that was necessary. But it seems that a float switch opens only one circuit. Am I understanding that correctly? That only one circuit needs to open and close to start and stop the pump.

A circuit is a loop of wire, which typically includes both a power source and a load. So I believe you mean the pressure switch opens and closes both the L1 and L2 wires. But to interrupt a circuit it is sufficient to open one wire.

Cheers, Wayne

 

[Mduncan60]

A circuit is a loop of wire, which typically includes both a power source and a load. So I believe you mean the pressure switch opens and closes both the L1 and L2 wires. But to interrupt a circuit it is sufficient to open one wire.

Cheers, Wayne

Totally perfect answer. Exactly what I was thinking and now confirmed. Thank you.

 

[Mduncan60]

So Wayne, Im seeing that people are using a contactor or relay ? To interrupt the circuit, and others say you can wire it directly. What is the best way? And if it is to use a contactor, do you have a recommendation.

 

[wwhitney]

My comments are generic and not specific to this application, as I have no experience with float switches, etc.

Often there's a requirement for both a disconnect and a controller. A disconnect should break all the ungrounded (hot) conductors, while a controller only need to break the circuit. So you'd use a disconnect to make things safe before working on it, but your controller (e.g. float switch) can leave a wire energized as long as there's no complete circuit.

For a 120V load, there's just one ungrounded conductor, so breaking a single wire works for both purposes. But for a 240V 2-wire load on a standard residential 120V/240V system, there are two ungrounded conductors, so your disconnect would need to break both, while a controller could get away with breaking one. Often when a disconnect is required, the breaker supplying the circuit can be the requisite disconnect, possibly with a requirement for permanent means for attaching a lock to the breaker if the breaker is not in site of the equipment.

As to a relay, it's useful in a couple cases: (1) one is that your controller has a load limit, and you want to control a larger load. So the controller controls power to the coil of the relay, and then the relay controls power to the load. (2) you're limited for whatever reason to one type of incoming control signal (say making/breaking one pair of wires), and you need another type (different logic, or multiple sets of wires). The few times I've needed one, I've used something from "Relay In A Box" as it was very conveniently prepackaged for me.

Anyway that's the general background, now you can try to figure out how the above applies to your application.

Cheers, Wayne

 

[Valveman]

If the float switch is rated for the max amps of the pump being used a relay is not needed. If the motor draws more amperage than the float switch is rated to handle a relay or contactor is required.

 

[Fitter30]

Will using a float switch cycling half the power yes. But i don't want the potential of 120vac going to ground. Two pole 25 amp 120vac coil contactor and a box would take care of it.

 

[wwhitney]

Will using a float switch cycling half the power yes. But i don't want the potential of 120vac going to ground.

It won't, the float switch just needs to be rated for the current and voltage it is interrupting. Once the circuit is interrupted, it won't matter that the two sides of the switch are 240V to each other and each 120V to ground.

Cheers, Wayne

 

[Mduncan60]

This is all great knowledge. Different opinions but that's OK. I think I am able to make an educated decision. Thank you all for your input. More opinions are always welcome.

Marvin

 

[Mduncan60]

My comments are generic and not specific to this application, as I have no experience with float switches, etc.

Often there's a requirement for both a disconnect and a controller. A disconnect should break all the ungrounded (hot) conductors, while a controller only need to break the circuit. So you'd use a disconnect to make things safe before working on it, but your controller (e.g. float switch) can leave a wire energized as long as there's no complete circuit.

For a 120V load, there's just one ungrounded conductor, so breaking a single wire works for both purposes. But for a 240V 2-wire load on a standard residential 120V/240V system, there are two ungrounded conductors, so your disconnect would need to break both, while a controller could get away with breaking one. Often when a disconnect is required, the breaker supplying the circuit can be the requisite disconnect, possibly with a requirement for permanent means for attaching a lock to the breaker if the breaker is not in site of the equipment.

As to a relay, it's useful in a couple cases: (1) one is that your controller has a load limit, and you want to control a larger load. So the controller controls power to the coil of the relay, and then the relay controls power to the load. (2) you're limited for whatever reason to one type of incoming control signal (say making/breaking one pair of wires), and you need another type (different logic, or multiple sets of wires). The few times I've needed one, I've used something from "Relay In A Box" as it was very conveniently prepackaged for me.

Anyway that's the general background, now you can try to figure out how the above applies to your application.

Cheers, Wayne

Thank you for the detailed breakdown. And yeah, I would never not have a disconnect, and in sight of the equipment. I do understand the concept of the relay. It's the same as in an automotive application which is my line of knowledge. Use of a relay is always the safest way to go in automotive which is why I'm leaning in the direction.