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Old 07-07-2017, 07:52 AM   #1
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Wanting the GFI to trip.


Good Morning everyone!

Here is my situation. I have a 7.5 hp single phase electric motor that drives my irrigation pump. And to make the story short, our canal situation is completely screwed to where anyone can take all the water they want and usually do. Problem with this is it leaves my pump/motor cycling on and off searching for water.

Here is how the system is set up. The pump sucks out of the bottom of a tank. The tank has a float ball in it where the electrical is hooked up on a normally closed position if it is floating on it's side.

The float controls the electrical current that controls the contactor for the main power leads for the 7.5 hp motor. When the water runs low, this contactor will kick on and off for quite a while and I just lost the motor due to this situation

All the power for both the motor and the contactor runs thru a 60 amp breaker. Here is my thought on how to correct this situation so I don't end up with another $1700 electric motor getting fried.

I am thinking about establishing another circuit on a 20 amp GFI breaker. The float ball has 3 wires to it. One is the power source lead. One is normally closed while on it's side, the other is normally open in the same position. When the float vertical, the leads reverse. So, if I run my contactor control power from this GFI breaker and have the normally closed to the contactor and the normally open to the grounding bus, that in turn would trip that breaker as soon as the float lets power to the normally open side, right? then in turn would keep my motor from re-starting until I reset the breaker.

Hope that didn't come out too confusing! Basic question is does anyone see an issue with making the GFI breaker trip by feeding voltage to the common buss bar?

Thanks for any and all replies!

Hope I did
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Old 07-07-2017, 08:21 AM   #2
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Re: Wanting the GFI to trip.


I think I would wire it with two floats and a standard on/off motor control circuit. Instead of start & stop buttons, you would have start & stop floats. When the water gets low it turns off the motor contactor. The contactor can not turn back on until the on switch(second float) activates. Then it will run until the off(lower float) is triggered.

If you want a manual restart the use a normal push button start switch instead of a float for the start.

Last edited by joed; 07-07-2017 at 08:31 AM.
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Old 07-07-2017, 08:26 AM   #3
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Re: Wanting the GFI to trip.


Here is a simple diagram I found

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Old 07-07-2017, 08:32 AM   #4
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Re: Wanting the GFI to trip.


The way the rest of the water system is set up consist of 2 sediment settling tanks (Much bigger than the pump tank) and after the water is gone out of the canal, the water in these tanks keeps filling the final pump tank until the level equalizes. and that is where the problem lies. Those bigger tanks will re-fill the final tank for at least a half an hour where the pump just kicks on and off the entire time

To protect this second pump, I would rather just have it shut down once and the water will equalize thru the overflow and no damage to the pump will be done.

A 2 float system would still allow the pump to cycle on and off which is the cause of the current motor to fry and fail.
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Old 07-07-2017, 09:16 AM   #5
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Re: Wanting the GFI to trip.


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Originally Posted by Dajain View Post
The way the rest of the water system is set up consist of 2 sediment settling tanks (Much bigger than the pump tank) and after the water is gone out of the canal, the water in these tanks keeps filling the final pump tank until the level equalizes. and that is where the problem lies. Those bigger tanks will re-fill the final tank for at least a half an hour where the pump just kicks on and off the entire time

To protect this second pump, I would rather just have it shut down once and the water will equalize thru the overflow and no damage to the pump will be done.
Can you put in a float switch in one of the two larger sediment tanks? Set the off where your pump drains its tank dry. Set the on high enough to allow the tanks to equalize and not short cycle the pump.
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Old 07-07-2017, 11:01 AM   #6
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Re: Wanting the GFI to trip.


Or, another option I will probably try before anything else is use the common wire on the GFI breaker and run that thru the float. When the float goes vertical it would break the grounding circuit and also cause the breaker to trip.

I like the thought of that better than using the hot side to trip the breaker.
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Old 07-07-2017, 12:19 PM   #7
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Re: Wanting the GFI to trip.


Trying to intentionally is not something you want to do.
Are you going to be there every time it trips to reset it?
How long do you think the breaker will last before it quits?
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Old 07-07-2017, 01:08 PM   #8
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Re: Wanting the GFI to trip.


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Trying to intentionally is not something you want to do.
Are you going to be there every time it trips to reset it?
How long do you think the breaker will last before it quits?
Yes, intentionally is exactly what I want to do. I want to eliminate any chance of the pump restarting without me looking at the situation to see if there will be no damage when the pump is re-started.

When I am running the pump, I go to check on it 2x a day. So, yes, I would be resetting every time.

When the pump costs almost $1800, I can buy a lot of GFI breakers at $30 each before it becomes unjustified. If I wanted to do it correctly, I would get a micro commander with a float system, program it with a motorized flow gate and call it done, but the situation wouldn't justify that expense either

Now, keep in mind that the pump doesn't run dry everytime we use it. It mainly happens when water is low in the canal. So, this system (or safety) would only be necessary maybe 3x a year.

Last edited by Dajain; 07-07-2017 at 01:19 PM.
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Old 07-07-2017, 01:54 PM   #9
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Re: Wanting the GFI to trip.


Quote:
A 2 float system would still allow the pump to cycle on and off which is the cause of the current motor to fry and fail.
Simply replace the second float with a manual push button. The pump will not restart until someone goes and pushes the button.
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Old 07-07-2017, 02:27 PM   #10
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Re: Wanting the GFI to trip.


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Simply replace the second float with a manual push button. The pump will not restart until someone goes and pushes the button.
I don't have a second float. And the way the system is set up, a second float would do no good because the other tanks fill my pump tank several times before the water level would get low enough in the bigger tanks to trip that second float. Meanwhile, the pump would be kicking on and off draining the smaller tank faster than the big tank can fill it because there is no water source to keep up with the demand.

Last edited by Dajain; 07-07-2017 at 02:32 PM.
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Old 07-07-2017, 06:13 PM   #11
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Re: Wanting the GFI to trip.


I meant the second float in my first post. A simple motor start-stop control is all you need. I already posted the diagram. You already have the contactor. all you need is a auxiliary contact and start button. Use the existing float as the stop switch and a manual start button to restart the motor.
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