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Help with a 240v time delay relay setup

Discussion in 'Power Electronics' started by HiroProtagonist, Dec 14, 2019.

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  1. HiroProtagonist

    HiroProtagonist

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    Dec 14, 2019
    I own a livestock operation that has a well supply line that crosses a deep creek. After 8 years, the line finally broke despite significant reinforcement. Fortunately, I was nearby ( and the cause); so, I could run shut off power to the well before it ran it dry or burned out the pump.

    When the water level in the creek drops (rained a lot lately), I plan on repairing/and reinforcing hte supply line similarly to last time. But, I fear it will break again and burn out well pump. I would like to put a time delay relay in between the pressure tank and the well pump which will shut off the power if it has run continuously for 15 minutes. I am unfamiliar with the nomenclature of relays and have also noticed that most advertised time delay relays max out at 10A. I need 20A.

    Any input on the relay that I require and wiring diagrams would be greatly appreciated. Thank you.
     
  2. Bluejets

    Bluejets

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    Oct 5, 2014
    Usual arrangement for this type of protection is to look at "loss of prime".

    Is the pump "start" operated manually or automatic...?

    When you say the "line broke" is that the water supply suction line..?
     
  3. HiroProtagonist

    HiroProtagonist

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    Dec 14, 2019
    This is a deep well submersible pump. A loss of prime protection is not really what I am after.

    The pump is started by a pressure switch attached to the pressure tank. Once the pressure in the tank drops to 30 or 40 psi , the pressure switch actuates and closes the contacts which triggers the pump to operate until the pressure in the tank gets to 70 to 80 psi.

    The line that broke is a supply line that feed automatic livestock waterers. The line runs approximately 1/2 mile long underground and across the botttom of the creek. So, if it broke the pump would run continuously until the pump burned out or the well was exhausted.

    I am open to other options. But, from my limited knowledge an interval on time delay relay appears to be what I need. The "limited knowledge" and "appears" led me to ask those more knowledgeable and more experienced in this field.
     
  4. duke37

    duke37

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    Jan 9, 2011
    You did not say what the line is. I assume it is a water supply pipe.
    A pressure switch is unlikely to be man enough to switch your pump directly and a contactor is possibly used and can be controlled with another input.
    I would consider restricting the feed to the supply pipe and use a pessure switch so when the pipe is broken and the pressure drops to near zero, the pump can be turned off.
    It would help if you said what country you are in and the type of electrical supply you have. Pictures are often a help.
     
  5. Bluejets

    Bluejets

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    Oct 5, 2014
    This is exactly why we need all the info otherwise we are just guessing.
    Loss of prime is actually a pressure switch arrangement used to detect broken feed water lines so your comment about it not being suitable is incorrect.

    What does make it more complex is this the pumping is a pressure call arangement.

    As Duke37 says, you could add a protection "loss of prime" pressure switch, set to drop say at 20psi with it's contacts in series with your existing pressure switch.
    Whatever arrangement currently in place may or may not be adequate regarding the pressure switch contact rating but I have found them to be more than enough at around 16 to 20 amp rated.
    It won't be operating (open/close) under any sort of what you might call load, as it's switching when there is next to none.

    You would also need to add a "start-up" bypass manual push button only across the new "loss of prime" pressure switch contacts to allow you to get the pipe pressure above 20psi to begin with.

    So, under normal operation, the added switch just sits there (closed) monitoring the (more than 20psi) pressure line. Pressure drop from 70 down to 40 calls the existing pressure switch which now starts the pump and stops it again above 70.
    If your feed water liner breaks, pressure drops,pumps starts @ 40, and so long as it cannot maintain 20psi, it will drop out, only to be restarted again , manually via the "start bypass button".
     
    Last edited: Dec 15, 2019
  6. Ylli

    Ylli

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    Jun 19, 2018
    Sounds to me that the OP simply needs a 'time out' circuit. Apply 240 VAC to the box, and it passes that 240 VAC through to the pump and starts a timer. If after 15 minutes, the 240 VAC is still present, then the timeout circuit shuts off its output and sounds an alarm. If the input 240 VAC drops before the 15 minutes passes, then the timer resets and waits for the next cycle.

    I'm pretty sure there are simple 'time delay' relays that can do this, but I'm not familiar enough with them to make any specific recommendations.
     
    HiroProtagonist and duke37 like this.
  7. duke37

    duke37

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    Jan 9, 2011
    I know the tank as a hydraulic accumulator. This has a sealed rubber bag inside a steel cylinder. They are used to pressurise central heating systems.
     
  8. Bluejets

    Bluejets

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    Oct 5, 2014
    Timer is no good.
    If the pump cuts in and only runs for say 1 minute, then you have a timer running the pump dry for the remainder.
    Loss of pressure or detection of flow is only way.
     
  9. HiroProtagonist

    HiroProtagonist

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    Dec 14, 2019
    I apologize for not providing sufficient information. I live in the SE US. The power supply to this water system is a two wire 110V-120V ea. providing 220V-240V total. The supply of power is constant to an actuator that a spring loaded pressure switch. Once the pressure drops to <30 psi, the contacts are closed by the spring which provides power directly to the submersible well pump. The electricity supply is constant until the pressure in the system raises to 50 psi.

    A "loss of prime" pressure switch is commercially available from Square D that will cut out <10 psi. In this application, the pump could be running for many days before that occurred. In other words, the pump could likely keep up with the leak until either the pump burnt out or the well supply was exhausted. That is precisely what I am trying to avoid. Perhaps, I could fiddle with that to raise the cut out to 20 psi.

    Ylli described what I believe would work, but stated it more succinctly than I did. Anyone have ideas of where to find the relay Ylli described?
     
  10. HiroProtagonist

    HiroProtagonist

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    Dec 14, 2019
    If the relay is in between the pressure switch and the well pump, the power supply to the relay is cut when the pressure tank is refilled and the timer should restart the next time the pressure switch is activated.
     
  11. Ylli

    Ylli

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    Jun 19, 2018
    Last edited: Dec 16, 2019
  12. Tha fios agaibh

    Tha fios agaibh

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    Aug 11, 2014
    I agree that a timer isn't ideal but it would work.
    My preference would be to use a flow switch with a built-in time delay to stop the pump.

    Many timers would work, but you need 2 poles for switching 240v and higher contact ratings than available on most timer relays.
    Alternatively, you could use a small off delay timer to switch the coil of a contactor which would do the switching of the pump motor.
    The Pressure switch would feed both the timers coil and a normally closed timed open contact that would cut off the motor after the timer times out.
     
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