# Float switch with contactor and pump



## ismat143 (Apr 10, 2010)

*contactor with coil and aux contacts*

Hi,

i want to run 3 phase pump with contactor.

The contactor have A1,A2 coil(220 volts), L1,L2,L3 and T1,T2,T3 with NO NC

i want to run the pump automatic when the water level in the tank reaches half, as i know i required cable type float level

My question is,

1. if i supply Line to A1 and netural to A2(220volts) then coil will energise and pump will start continously, but how to use NO and NC to control the contactor?, with rotatry switch(on/off).

Can anyone explain with schematic.


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## nap (Dec 4, 2007)

nevermind, I see in the title you say they are aux contacts. With the system you have I see no need to use the aux contacts for anything.


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## micromind (Mar 9, 2008)

The NO and NC are used only with momentary devices, like start/stop buttons. If the float is a maintained contact, just wire it in series with the coil. 

NO and NC are not used with maintained contacts.

If there are two floats (one to start the pump, the other to stop it), then the NO and NC are needed.

Rob


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## ismat143 (Apr 10, 2010)

Model no. LC1D32 TeSys


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## micromind (Mar 9, 2008)

I recently installed a bunch of similar contactors in a process controller. They were Telemecanique (just like yours), but LC1D09s. A bit smaller. 
They can be mounted to a flat surface with screws, or they'll clip on to a DIN rail. 

Rob


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## ismat143 (Apr 10, 2010)

You wrote,
The NO and NC are used only with momentary devices, like start/stop buttons. If the float is a maintained contact, just wire it in series with the coil. 

NO and NC are not used with maintained contacts.

If there are two floats (one to start the pump, the other to stop it), then the NO and NC are needed.

my question,

if two floats then how to use NO and NC, please explain


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## beenthere (Oct 11, 2008)

Ismat143:

Please don't use the round red button with the explanation point in it, to respond to a post.
That is the report post button. It sends an email to all mods, and the Admin. And is used to tell use an improper post has been made.


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## ismat143 (Apr 10, 2010)

Hi,

According to attached schematic, If i connect Float and pump with contactor is it correct?


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## williswires (Jul 21, 2008)

Try again...

Only looked at the left one--

If you are asking if it would work, I would say it _could_ work, as long as the float leads are brown = common, black = N.O. (normally open when hanging), and blue = N.C. (normally closed when hanging) BUT your pump motor is three-phase, and you typically don't use the full line voltage to control the motor.

Keep in mind the following for the left one:
Upper float turns the pump ON when it floats
Lower float turns the pump OFF when it drops
The N.O. contacts on the contactor are open when the coil is not energized (pump is off), and closed when the coil is energized (pump is on).

Proper:
A1 and A2 are your control voltage, and must be kept separate from L1, L2, and L3. Therefore, say, for 120VAC control voltage (because you have a terminal called N, or neutral) your voltage comes in through A1, has to go through the lower float, then a set of wires through the upper float to the coil (other side of coil connected to N). Then you need a parallel set of wires that leaves the lower float and goes through the contactor's N.O. contacts and goes to the coil to hold in the contactor as the upper float drops out. The contactor will drop out when the lower float drops.

Note: You can switch the order of the devices if you want, meaning A1 goes to the upper float first with the contactor's N.O. contacts wired in parallel, then both join up and go to the lower float, then to the coil.

Draw it again and we'll see how you do...notice I didn't tell you which float contacts to use. If you know the actual functions of the float connections, please post them along with any other info about this.


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## williswires (Jul 21, 2008)

...just found your other thread...




It's best to keep the original thread going for all related questions instead of creating a new one. That way all the info is in the same place.

If this is directly related to your other thread, please ask the MODS to move it over there...


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## J. V. (Jun 1, 2007)

ismat143 said:


> You wrote,
> The NO and NC are used only with momentary devices, like start/stop buttons. If the float is a maintained contact, just wire it in series with the coil.
> 
> NO and NC are not used with maintained contacts.
> ...


The float switch connected in series with the contactor coil will fill on low (close contactor) and stop (open contactor) on full without using anything but the float switch and the contactor coil.


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## williswires (Jul 21, 2008)

I don't know which thread to respond to - another one was started with a schematic.


Please identify ALL info for your question

what is the purpose of your pump? is it to empty a tank once it gets full? is it to fill a tank back up once it gets low? is it to maintain a constant level in the tank?

how many floats will you have?
what do you want your rotary switch to do? (auto/off/manual or something else?)
what voltage is your pump?
is your control voltage 220V as you mentioned?
where will your control voltage come from?
what are the color codes of your float wires?how many floats will you have?


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## ismat143 (Apr 10, 2010)

Answers for the questions,

1.what is the purpose of your pump?
ans. Its pumping water from well(submersible pump),it is to fill a tank back up once it gets low.

2.how many floats will you have?
ans. i have only one float(with three wires brown,black and blue)

3.what do you want your rotary switch to do?
ans.its purpose is to (auto/off/manual).

4.what voltage is your pump?
ans. 380 to 420 volts(3 phase)

5. is your control voltage 220V as you mentioned?
ans. yes it is 220 to 230 volts

6.where will your control voltage come from?
ans. from supply line(L) and Netural(N)


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## beenthere (Oct 11, 2008)

ismat143 said:


> Answers for the questions,
> 
> 1.what is the purpose of your pump?
> ans. Its pumping water from well(submersible pump),it is to fill a tank back up once it gets low.
> ...


You should list what country your in.
In most/many countries, 220 doesn't use a neutral. Are you calling 277, 220? 277 does use a neutral. 

Sounds like your using 50hz.

Both of your drawings are incorrect, and would have the pump running continuous.


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## AllanJ (Nov 24, 2007)

It will not work properly unless the float(s) operate one float switch using a loose linkage.

1. As the water level drops, the pump should be off.
2. When the water level gets low enough, the pump turns on.
3. As the water level rises, the pump stays on.
4. When the water level gets high enough, the pump turns off.

Two (separate) pump switches each with its own float tightly linked, and NO/NC switches on the contactor unit, are unable to fulfill both conditions 2 and 4 with a fairly large distance between the turn on and turn off levels.

For a 220 volt coil and 220 volts from phase to phase, you can get the control (coil) current from any two of the 3-phase legs.

Example: Phase leg to float switch to coil A1 then coil A2 to another phase leg. Choose the float switch terminals (two of the three wires black, blue, brown) that close when the float drops far enough and that open when the float rises far enough.


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## micromind (Mar 9, 2008)

This is a 220/380 3 phase wye connected system. There is 380 volts phase to phase, and 220 volts phase to neutral. If the neutral is present, a 220 volt coil will work.

A contactor will control the motor, but it will not protect the motor. For that, you'll need an overload block. The Telemecanique LRD series will work, and it'll mount right to the contactor. You'll need the full-load current of the motor as well as the service factor (S.F.) current to get the right one. For a submersible pump motor, use class 10.

A single float can be used to control the contactor, but the 'dead zone' might not be enough. The 'dead zone' is the distance the float moves between turning on and off. It's usually less than an inch. 

To fill the tank more than that, you'll need two floats. One will start the pump, the other will stop it. For this set-up, you'll need to use the NO contact. 

It's pretty simple to hook up either type, but we'll need to know whether you're using one or two floats, and whether or not there's an overload block.

Rob


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## 3 legged dog (Dec 21, 2009)

If you want the tank to go from full to half and back, then you will proably need two float switches and use the N/O side switch.

If you use only one switch then you will not need the side switch.


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## ismat143 (Apr 10, 2010)

Thanks for replys,

I think my above explanation is not correct,

just a simple question,

I have the following things,

1. Contactor(lc1d32) - 3 phase 400 volts( with NO,NC and coil A1,A2 220 volts)
2. Float switch with 3 wires(Brown,Black, Blue) 220 volts, in which brown is common
3. Selector switch (auto/off/hand)
4. Submersible pump - 3 phase 400 volts*
5. Power source 3 phase(L1,L2,L3) 400 volts with netural

I have 5000 gallon of tank and water is filling in it from the well(with submersible pump) and every time i have to fill manually when its get empty, to avoid this i want to make it automatic filling. i have the following above things to do it automatic but iam not sure how to wire(connect) all together , can any one explain me how to connect the above things together?.

Thanks
*


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## micromind (Mar 9, 2008)

Assuming the power in and out are done, connect the incoming neutral to A1. 

Pick any one of the incoming hots, and connect it to one side of each block on the H-O-A switch. 

Connect the other side of the 'hand' block to A2.

Connect the other side of the 'auto' block to the common of the float switch. I don't know which color it is, if you don't have a diagram of it, post back, we'll help you determine what colors go where.

Connect the NC side (also known as 'close on fall' or 'open on rise') of the float switch to A2. (Two wires on A2).

This control scheme will result in the pump running when the switch is in hand. It'll ignore the float. When the switch is in auto, the pump will run only when the float tells it to. When the switch is off, the pump won't run at all. 

Note: Unless there's properly sized fuses or an overload device somewhere between the power source and the motor, there isn't any protection for the motor. If voltage drops too low, or phase imbalance is too great, the motor will burn up. Depending on the size of the fuses or circuit breaker ahead of the contactor, the control circuit might not be protected. 

It's also possible, depending on what type of float you have, that the float will start the pump, it'll run for a short time, then the float will stop the pump. If this is not good, you'll need two floats, and the control wiring will be a bit different. Also, if waves in the water cause the pump to start and stop rapidly, it'll burn up either the motor or the contactor. Two floats will solve this as well.

Rob


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## AllanJ (Nov 24, 2007)

Protection for the pump motor is a brand new topic.
Protection for the motor is normally not achieved using the contactor or the coil circuit.
The motor may include a built in thermal circuit breaker to protect against overheating.

If a second float switch is used to turn off the pump, that switch will exert total control over the pump by turning the pump back on when the water level drops just a little.


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## nap (Dec 4, 2007)

you might want to check the action of the contacts in the float. There are such things as a wide angle action that would work well for you. It closes the contacts when down and opes when up but it is designed to extend the "dead zone" as micromind called it.


If such is not available to you, you sill most likely want to use 2 float switches and a relay to control on and off actions of the control circuit so to allow the pump to pump until the tank is full enough for you.


If you use just one float switch with a typical "dead zone", depending on how much water you use and the size of the tank, you may end up cycling the pump too often and cause undue wear from frequent starts.


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## spark plug (May 5, 2009)

micromind said:


> The NO and NC are used only with momentary devices, like start/stop buttons. If the float is a maintained contact, just wire it in series with the coil.
> 
> NO and NC are not used with maintained contacts.
> 
> ...


Some models of float switches DO come with NO and NC contacts. But they're optional. It could be wired for NO or NC. But not both. The float switch has Three terminals. One is COMMON. (Hot) The others are (1) NO; (3) NC.:yes::no:!


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## micromind (Mar 9, 2008)

The NO an NC contacts I was referring to are located on the motor starter contactor, not the float. 

Please read each post very carefully, including context before you criticize a reply.

Rob


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## AllanJ (Nov 24, 2007)

The schematic for the contactor as shown here has three normally open contacts for the 3-phase power to the motor, a fourth contact that is normally open (marked NO) and a fifth contact that is normally closed (NC). (portion deleted)

The float switches mentioned have three wires each so they also probably have contacts you can call NO and NC. I don't know which one should be labeled which. You need the 3 wire float switches for a generic pump that might be used to either fill up a tank or basin or empty out a sump (water collecting pit).

(portion deleted)


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## micromind (Mar 9, 2008)

The NO contact on the starter is usually used with start-stop pushbuttons. It serves as a latch to hold the starter closed once the start button has been pushed. It remains energized through the stop button.

If two floats are used, the bottom one is used as the start button, and the top one is used as the stop button. 

This way, once the liquid level has triggered the bottom float, it energizes the coil, and is held in by the NO contact. 

When the liquid level reaches the top float, it de-energizes the circuit, and the NO contact opens, thus releasing the latch. 

The contact of the bottom float has to be open, and close on falling liquid level. The contact of the top float has to be closed, and open on rising liquid level.

Rob


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## spark plug (May 5, 2009)

micromind said:


> The NO an NC contacts I was referring to are located on the motor starter contactor, not the float.
> 
> Please read each post very carefully, including context before you criticize a reply.
> 
> Rob


I've read your reference to the Motor Contactor (a/o) to the float switch, and my comment wasn't meant to criticize, just to throw that in. If the implication was that I criticized, my strongest apologies to you!!!:yes:!


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## micromind (Mar 9, 2008)

I have to apologize too, it was kind of a lousy day, I didn't mean to take it out on anyone. 

Rob


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## Kharwa (Feb 10, 2015)

Hi, The float switch is there to switch on the pump when water level drops and shut off the pump when the tank is full


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## Kharwa (Feb 10, 2015)

Sorry for the inadequate info. The float switch is to work on a single phase borehole pump.The connection is to be made at the control box. The float switch has a brown, a blue and a yellow wire. I hope that might help.


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## Bob Sanders (Nov 10, 2013)

Kharwa said:


> Sorry for the inadequate info. The float switch is to work on a single phase borehole pump.The connection is to be made at the control box. The float switch has a brown, a blue and a yellow wire. I hope that might help.


I would hope the problem is solved (It's a 4 year old thread)


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