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Thread: Jet pump rapid short cycling at cut-out

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  1. #1
    DIY Junior Member FRS's Avatar
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    Default Jet pump rapid short cycling at cut-out

    My jet pump (1/2hp) has started cycling very rapidly at the cut-out (40psi). Cycles perhaps 4 or 5 times in the space of a few seconds...pressure guage fluctuates rapidly with it and then shuts off and sits happily at 40psi. It will do this every minute or so without any demand in the system. Lights in the cottage flicker wildly and the pump gets, of course, quite hot until it shuts itself completely down, cools off and starts doing it again.

    New 25 gal pressure tank last summer. 18psi charge in it.

    Cut in on the motor is 20.

    New pump last summer.

    No leaks anywhere.

    Foot valve is ok.

    There is no check valve on the system.

    We're pulling water from the lake (cottage system).

    I started the system up this past Thursday (today is Sunday) with no issue (had everything running in 10 minutes flat). I winterised the pump properly....poured plumbing antifreeze directly into it as I do every fall. Rest of the system I blow out. Anyway, it started cycling on Saturday. Normal cycles have been the 2 to 3 min range...normal in my opinion.

    Wondering one of two things....
    1) the pump is about 135 ft away from the panel....running 14/2 wire. Am I getting too much resistance? But if this was the case why would it cycle like this only at the cut-out. I have noticed that this pump does dim the lights very briefly when it cuts in where the old pump didn't (we burnt out the old pump because the tank failed....don't ask!)
    2) at every start up in the spring it does take a day or two to have the water come "clean" and not be spitting up dirt etc. after I drop the foot valve back in the lake. Has there been some grit hurt the impeller or better yet, the pressure switch.

    Any ideas out there before we go back up this weekend? I really don't want to be buying a new pump!

    Thanks!

  2. #2
    DIY Senior Member craigpump's Avatar
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    There is a loss of pressure someplace most likely at the footvalve

  3. #3
    DIY Junior Member FRS's Avatar
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    Thanks. I did pull the intake out of the lake and checked....no leaks or obstructions on the foot valve and there are no leaks anywhere in the system. Pressure does not dip from 40 before the pump decides to bizarrely cycle...but as I describe, the pressure then swings wildly as it quickly cycles. And besides, if there was a leak, the pump should be waiting to dip to 20 for it to cycle.

  4. #4
    DIYer, not in the trades LLigetfa's Avatar
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    Where is the pressure switch in relation to the bladder tank? It sounds like there is too much distance between them. It also sounds like the tank is getting waterlogged so maybe a busted bladder.

    As for losing pressure when no water is used, that can only be a leak or footvalve issue.

  5. #5
    DIY Junior Member FRS's Avatar
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    75 feet away and 15 feet vertical. Has never been an issue.

    Tank is brand new and reads 18 lbs. Trust me, aside from leaks that's the first thing I checked. Again, the system is NOT losing pressure. Therefore no leaks. And, I have checked the entire system for leaks.

    Silly thing just spontaneously turns on and off and on and off and on and off and on and off (say that reallllly fast and you'll get a sense of what I'm talking about) every minute or so at 40lbs pressure and no demands on the system.

  6. #6
    DIYer, not in the trades LLigetfa's Avatar
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    Quote Originally Posted by FRS View Post
    75 feet away and 15 feet vertical. Has never been an issue...
    Just cuz you got away with it this long doesn't make it right. Move the switch up to the tank Tee where it belongs. There is probably some sediment in the line somewhere or at the tank Tee letting the pressure build up faster than the tank can take it.

    Also, a bladder can be bad and it still hold pressure. A drawdown test would be required.

  7. #7
    DIYer, not in the trades LLigetfa's Avatar
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    Quote Originally Posted by FRS View Post
    My jet pump (1/2hp) has started cycling very rapidly at the cut-out (40psi). Cycles perhaps 4 or 5 times in the space of a few seconds...pressure guage fluctuates rapidly with it and then shuts off and sits happily at 40psi.
    That description suggests that there are pressure pulses brought on by having the tank too far from the pump. The pressure pulses cause the contacts to bounce open and close. A waterlogged tank can present a similar symptom.

    That also suggests a switch that now does not latch open when it should. There is a fine balance point where once the contacts open, it should cross the point of no return, latching open until the pressure drops to 20 PSI.

    The fact that a minute later the cycle repeats is another symptom which suggests that either the pump went into thermal shutdown for the minute, OR there is enough of a pressure drop for the unlatched contacts to close.

    Sediment in the nipple can affect switch behaviour in a broad way. Sediment under the diaphragm usually affects the low pressure kick-in side of the operation.

    As I suggested before, abandon the switch on the pump and install a new switch at the tank Tee where it belongs.

  8. #8
    In the Trades Texas Wellman's Avatar
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    Gauges are not always accurate, even when new.

    The pressure the gauge "sees" may not be the same pressure the switch "sees". Sediment could be blocking one or both, but affecting each differently.

    You can put a larger line to the switch, but you'll still have 1/4" inlet/outlet piping. I've even seen where a large piece of pipe, 2" diameter, was used to subdue the pressure waves caused by cyclying.

    Good luck. My bet is that your gauge is sticking and not reading the pressure when it falls off through the footvalve or similar.

  9. #9
    DIY Junior Member FRS's Avatar
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    Thanks guys.

    Heading up tomorrow....new switch and new 3/4hp pump (maybe I'll just install it anyway...5.5 amp instead of 8.5 should get rid of my light dimming issue....) is in the truck (pain in the a** to run for stuff). I'll clean out the line to the switch and we'll see where we go from there....if I have to run for a small tank to install beside the pump i will....i know i have a new foot valve somewhere in the shed...

    Stay tuned....I'll get back to you Monday.

  10. #10
    Jack of all trades DonL's Avatar
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    Quote Originally Posted by FRS View Post
    Thanks guys.

    Heading up tomorrow....new switch and new 3/4hp pump (maybe I'll just install it anyway...5.5 amp instead of 8.5 should get rid of my light dimming issue....) is in the truck (pain in the a** to run for stuff). I'll clean out the line to the switch and we'll see where we go from there....if I have to run for a small tank to install beside the pump i will....i know i have a new foot valve somewhere in the shed...

    Stay tuned....I'll get back to you Monday.

    It sounds like you are going to replace a 120 Volt Pump with a 240 Volt Pump on a 120 Volt electrical feed.

    The current difference that you listed tells me this.

    240V is much better. The bigger the motor the more current at the same voltage it will require, not less.


    Good Luck
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  11. #11
    DIY Junior Member FRS's Avatar
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    Rocket....if I switched it over internally to 240 (keeping it on the 120 line) would my light dimming go away?



    Anyway guys, I tore the switch apart...membrane had a couple cracks in it (like what you would see on the sidewall of an old tire)....replaced the switch....in retrospect, cracks are probabably from all the switching on and off....but who knows.

    was marginally better.

    interesting though....now that I was able to sit in the daylight and watch it (without a 3 yr old and a 6 yr old buggin me) it was actually losing some pressure....would dip to say 36 or 37 lbs.

    had a new pump in the back of the truck (3/4 hp) :-)

    hesitated to open the box and actually spend the money when I knew I had a good pump sitting right in front of me....

    ran to town

    got a 5 gallon pressure tank

    mounted it directly on top of the pump. ya, i know the switch next to the other tank....meant farting around with electrical and i really didn't feel like it.

    anyway...problem solved.

    happy wife too.

    :-)

    guys, thank you for your wisdom regarding the location of the switch in respect of the tank....would have still been messing around with it and in the meantime would have spent 4 or 500 bucks trying to solve the issue (and not accomplishing).

    hats off to this forum!

    Cheers.

    so tell me something....plumbing guy at the hardware store (Home Hardware for you Canadian folk) tells me that PEX is no longer recommended for well applications??
    Last edited by FRS; 05-05-2013 at 06:13 PM.

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