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Help with a good relay for well pump switch

Discussion in 'General Electronics Discussion' started by TimF, Feb 13, 2017.

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  1. TimF

    TimF

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    Feb 13, 2017
    I need to move the pressure switch on my water well system but need to keep the power supply, controler and load line to the pump in the same location. I hope to set up a relay or contactor at the old site to switch the well on and via a low voltage circuit switched by the pressure switch at the new location (about 50' away) actuate the relay or contactor. Having read some on relays and contactors it seems many have built in or onboard transformers which seems like the cleanest way to go. It's a 240vac single phase pump, probably about 300' run on #12 wire.

    I guess I'd like to know if a relay is fine, or should I look at a contactor (I gather they are more heavy duty), what low voltage should I use for the relay (I am guessing 24vac) and most importantly a specific suggestion of a particular relay. I think what I need is a 2 pole, single throw, NO, 10amp or greater (per my meter the pump draws slightly over 9amps and close to 10 on start up) contact rating and, if wired, #12 wires for the input and out put. I think a lot of these types of relays are used in the HVAC and refrigeration industry.

    Any advice, suggestions or input would be greatly appreciated.

    Thanks!
     
  2. Minder

    Minder

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    Apr 24, 2015
    You can get heavy duty relays, although small DIN style contactors are quite prevalent on ebay etc. Telemecanique etc.
    I prefer to use a DC coil as you do not suffer some of the problems of AC, if you have a 24vac supply all you need is a suitable bridge rectifier for the coil.
    M.
     
  3. TimF

    TimF

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    Feb 13, 2017
    I'll check it out, thanks for the input.
     
  4. Bluejets

    Bluejets

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    Oct 5, 2014
    As a side note, 300' on 12 g cable at motor full load 10 amp seems a bit on the light side given motors tend to draw quite a bit more at start-up.
    Curious though why you think it necessary to shift the pressure switch.
     
  5. Minder

    Minder

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    Apr 24, 2015
    The ampacity of #12 cable is rated at 20amps, the DC resistance per 1000ft is 1.06 ohms.
    M.
     
  6. TimF

    TimF

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    Feb 13, 2017
    So Minder, by that you are saying the #12 is sufficient?

    The 300' is a guess. I don't know how deep the well is but I believe in the area they range from 120-200 feet. The run from the well is about 60' and the run from the breaker to the supply is about 30 so I used a worst case guess. The well was professionally done by a reputable co. and works good and has for many years so I am confident that the wire is heavy enough but Bluejets, to your point, that is another reason I don't want to move the pressure switch and extend the load run to it. The wire may be heavy enough for the set up as is but if I add 50' it may not. So my thinking is, if I don't add run I am likely in good shape with regard to wire size.

    I spent a fair amount of time reading about various relay options and called some manufacturers. I think I am going to use this track mount relay setup. It's all in one and fairly simple to set up.

    http://www.functionaldevices.com/building-automation/display.php?model=RIBM02ZNDC

    I will mount the track in a box at the existing site, wire it with the 240 and run #22 from it to the pressure switch at the new location. When the pressure switch closes it will actuate the 24vac transformer and close the contacts. When full pressure is reached the pressure switch will open and release the contacts. At least that is the idea.

    My plan is to wire it up with the configuration I have now (without moving my pressure tank or switch) and, if it works, let it operate for a while (a week or two) to make sure there are no issues. If not, I'll consider it "tested" move my tank and pressure switch and plan to actuate it with the relay.

    Thanks for the input. If you see a major flaw with my plan (or a minor one) please advise.
     

    Attached Files:

  7. Bluejets

    Bluejets

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    Oct 5, 2014
    I was referring to the voltage drop over the route length at the maximum motor draw.
    By my calculations @ 10A there will be approx. 8% drop or 9.5V (not to mention start-up Vd).....I'm assuming OP resides in 110V territory? (always open to correction....)

    TimF...if you are using a relay in the same location as the original pressure switch there will be no difference to your motor cabling run surely.
    Also if the motor is already running with no problems then the above voltage drop maybe not an issue for you.

    I still don't get the guts of why the pressure switch needs to be re-located.o_O
     
    Last edited: Feb 14, 2017
  8. Minder

    Minder

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    So you are using the P.S. to switch the primary of the transformer?
    What are you going to use to close the dry contact on the relay board?
    That board set up seems a little OTT just to pick up a relay.
    If you do intend energizing a transformer with the P.S. then why not feed the 24vac secondary to pick up the relay, and fit a bridge either at the transformer or the relay to use a 24vdc coil.?
    M.
     
  9. tedstruk

    tedstruk

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    Jan 7, 2012
    Little problem with that idea. the switch is connected to a pressure sensitive switch that is installed in a tank that the switch sits on. without the pressure from the tank, the switch doesn't know when to turn on and shut off. What you need is a wireless remote, or a pressure sensor, which is very sofisticated....

    I had consided this idea with a second tank idea I had, where a holding tank maintained a second pressure and the main tank was simply a bypass sump...

    It failed because any amount of pressure, is infinite, unless it is valved.

    Moderator note: I was always told that if you can't say something nice, say nothing. And so, that would be my reply if asked how much weight people should give to anything tedstruck posts.
     
    Last edited by a moderator: Mar 4, 2017
  10. TimF

    TimF

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    Feb 13, 2017
    The board is relay and 24vac transformer. The continuous power to the board is supplied by the same input power for the pump pigtailed to the board continuous power input so everything can be inside of a small housing at the old switch location. The connectors to actuate the primary are top right of the board. I will run a light wire from one of those to one pole of the pressure switch and then a wire from the other side of the same pole back to the other connector - basically a switch leg. Then, when pressure in the tank reaches the low pressure setting the contacts on the pressure switch will close completing the circuit and actuating the primary and thus closing the contacts for power to the pump. When the pressure reaches the upper cutoff setting the pressure switch will open, opening the circuit and killing power to the the primary and opening the contacts to the well turning it off. At least that is the plan.

    While the board may be a bit OTT, I think it makes is much simpler than buying and mounting the components separately and heavy duty enough to operate trouble free for a long time. Also, it's fairly cheap ($25).

    I'm with you Bluejets on the "do I really need to move the switch at all?" It seems that, being basically a horizontal system that the pressure everywhere in the system is the same so the pressure switch anywhere should work (actually, leaving it was my original plan and may be what I end up with). But in reading practical experiences posted in well forums the consensus seems to be that the further from the tank the pressure switch is the more erratic the switching is and it often leads to quick cycling which I don't want. I'm not sure I buy it and actually will leave the switch where it is at first. If it works fine I may just leave it there. Buuuuuutttt, if there is a problem I need to have a backup plan in place that I can quickly execute for moving the switch to near the tank. Otherwise I will have a lovely wife and 3 wonderful daughters without running water for a couple of days, maybe more, as I sort it out. That is never a good thing (they like their showers and water to their horse's tanks - I kinda do too). I can set it up to run via the relay as it sit's now, just changing the wiring (which and can change back in minutes) to trouble shoot it so if and when I do move it I will know it will work.

    So, I think I am on track for that but understand I could be way off base too so I do appreciate the input! At the very least it's interesting and educational.
     
  11. Minder

    Minder

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    Apr 24, 2015
    I don't seem to see a transformer on the relay board?
    M.
     
  12. TimF

    TimF

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    Feb 13, 2017
    I assumed it was under the relay. I called the manufacturer's tech support just now and asked about it. Helpful and informative guy. He said there is an electromagnet that that actuates the relay but it is high voltage (208-277) and the input to actuate it (my switch leg) has the voltage stepped down to 24vac via the components on the board. So effectively the same net result but without the transformer. The way I selected this relay was by calling Functional Devices Tech Support and telling them what I wanted and asking what they suggested. The gentleman said this would be most simple and easy as well as not overly expensive. I had said that I was looking at a 24vac "switch leg" to actuate it and he said this had that. I assumed the voltage was stepped down via a transformer and that was wrong but not particularly critical. All of this punctuated with a big "I think" of course. :eek:) When I receive it. I'll play with it before installing it of course.

    If indeed this is correct does the rest of the layout (using the pressure switch etc.) make sense to you?
     
  13. Minder

    Minder

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    Apr 24, 2015
    Deciphering the board and components, it looks to me like there is a small bridge rectifier and a voltage dropping circuit.
    If so there is no galvanic isolation between the 240v and the LV DC.
    Personally it would not be a device I would chose.
    I would tend to prefer a SSR over that.
    M.
     
  14. Bluejets

    Bluejets

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    Oct 5, 2014
    Can you enlighten us on the reason why you believe it is necessary to relocate the pressure tank/ switch in the first place.

    Very unusual requirement.
     
  15. TimF

    TimF

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    Feb 13, 2017
    Hummm.... So I gather you are saying that if a or some components failed you would be concerned that the low voltage leg could be energized with the 240vac supplying the board? I am not an expert or even knowledgeable on boards or electronic components so I guess I sort of have to assume that a large company that has been manufacturing electronic components for power management for almost 50 years knows what they are doing and they will function as designed. When i get it I will call them and ask the question though - is the low voltage portion isolated or not and if so how?

    I didn't say it was a requirement and I don't think it's code, just the norm and best practice because it's the way it works best. As I think I mentioned above, I did an online search for potential issues with having the pressure switch and found many instances where homeowners and professionals said it was a bad idea and led to problems. There were also instances where people said it was not an issue. As for a definitive scientific answer I could not find one but did not do an exhaustive search. The truth is the physics behind the flow of liquids is extremely complicated and very few people truly understand it. I am going to have a pressure tank, and from there run the water through a filter, then through a softener, it will T-off to a guest house and then into the main house. As I mentioned, while I think it will work where the pressure switch is currently located I'm not sure. I am sure (or as sure as I can be) it will work with the pressure switch near the tank so want to be able and ready to move it there in a timely fashion if I need to.
     
  16. Bluejets

    Bluejets

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    Oct 5, 2014
    There are many devices around which incorporate non-isolated power supplies.
    One which comes instantly to mind are some types of PhotoElectric cell operated daylight switches.
    The difference here is , you are taking this (possibly)non-isolated supply outside of it's immediate environment and placing it in a situation where it could possibly become a major risk.
    I say "possibly" as, along with Minder, I can see no isolation on what you have shown.

    There are other low voltage isolated transformer style of installation that will get your job done and in safe conditions.
    A standard plug pack for example.

    I'm still curious as to why you believe it is necessary to shift the pressure tank/ switch in the first place.
    Is it a national secret?
     
  17. TimF

    TimF

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    Feb 13, 2017
    In looking at the board are you able to identify all components and are you sure there is nothing or no way that it does isolate? And by unsafe do you mean that the light wires running to the pressure switch (my switch leg, probably #22) could become energized with the 240vac and melt or electrocute someone? I am not overly familiar with isolation but assume that is the risk we are discussing and I do want to clarify it with the manufacturer before installing it. The engineer in their tech department told me that the 24vac leg is designed to operate on very small wire, basically the same as doorbell wiring. I would have to assume if they are selling large numbers of this product they are not inherently unsafe. But then again, maybe they are and they require something special in the installation phase that makes them safe.

    On the national secret front, I have to move the tank so it's inline before my filter and softener or it will be pushing water back through them when water for outdoors is called for. By "shift" the pressure tank/switch I gather you mean why I think I need to move the switch with the tank rather than just the tank and leaving the switch where it is. I think I have said it and am not trying to be cryptic. I don't know that I need to. After doing an internet search and reading posts on a number of plumbing/water well forums it looks to me that many well/water system professionals think it leads to problems (mostly with inconsistent and frequent cycling) if the switch is not near or at the tank. That is the only reason I think I may need to move it, because a number of people in the industry have said it causes an issue. I don't know that it will or does or it won't or doesn't. My inclination is that is doesn't usually, won't in my case but in some special situations it does and probably those are the ones I am reading about and the people that are making mention don't realize it's a special situation and think it's the norm. But I don't know for sure why I see quite a few posts that saying your pressure switch needs to be near or at your pressure tank.
     
  18. Bluejets

    Bluejets

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    Oct 5, 2014
    IF the unit is a non-isolated supply and IF the unit is not installed in an appropriate manner then there is a possibility of a dangerous situation.

    Suffice to say a woman in Aus was killed by a non-isolated supply type Iphone charger (after-market from who knows where) It blew up while she was talking on the phone with the charger plugged in. Basic layout is, mains power in, non-isolated supply with the output coming out into the real world on the end of a charge plug. Get the idea?

    Not trying to be cocky here , just trying to show the differences in a basic way so perhaps you will start to understand.

    You don't know the difference, but those of us with the qualifications do.

    If you start running back to the manufacturer with wild accusations about their product you can be certain you will end up with a lawsuite on your tail.

    Best advice would be get a qualified electrician.


    I'm still baffled by your reason to shift the pressure tank/switch.

    You are correct in saying the pressure switch should be adjacent to the tank but in your reasoning you say the pressure tank and pressure switch must be installed before the filter unit.

    Surely if the tank and switch are adjacent to the existing pump location they would already be before any filter arrangement.
     
  19. TimF

    TimF

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    Feb 13, 2017
    I did an addition to the main house including a shop and guest area which moved the location where the water from the pump comes into the structure. The plan was to move the tank later to a prepared spot near where the supply comes in and install the softener and filter there. My outdoor bibs and water supply T off before the supply reaches the house. I had the plumber put in a drain and plumb the incoming supply to easily allow for adding the tank the filter and softener at that spot just inside the new structure. It's about 40' from the existing location. If I leave the tank where it is then the water will run through the filter and softener before entering the pressure tank. This would be fine except for any water that is called for (a bib, sprinklers, drip water system, etc.) for the outdoor system will come from the pressure tank (or some will) and that will have to go back through the filter and the softener (since the pressure tank is "in front" of them). So I need to get the tank behind them and then I don't have that issue. It was in my design plan but moving the pressure switch (which, as we have discussed, I may or may not have to do) had not been factored in by the plumber or myself. I will attach a drawing that represents what I am talking about.

    Of more interest to me, and what I had hoped for when I started this thread was someone with much more knowledge on the subject to make a specific suggestion of components and an explanation of how and why. Something like, "this relay or connector (and a link or part number) with the primary powered by this transformer (and a link or part number)plugged into a 120vac would work well." That is what I anticipated having in the end. Me getting a relay (or connector) that was rated high enough for my need (240vac, single phase, 10amp draw) and a transformer and putting them in a enclosure and wiring it up. I still would like to do that if you (or anyone) cares to make specific component suggestions. It sounds like if I use a separate 24vac transformer and power the relay I have absolute isolation and eliminate that concern. The rest actually sounds pretty simple to me.

    And no, you did not come off as cocky, just giving me the info I am asking for. I hear what you say about a qualified electrician but in my experience, whether is plumbing, electrical work, auto repair, framing painting, pool automation, etc, ... figuring it out and doing it myself almost always nets a much better and more safe end result.

    Thanks
     

    Attached Files:

  20. TimF

    TimF

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    Feb 13, 2017
    After doing quite a bit of reading on the subject I think this document states that indeed the input is isolated. It's an information sheet on "Functional Devices" RIG line of relays, one of which is the relay we are discussing (RIBM02ZNDC). I believe the DC at the end of the part number stands for "Dry Contact" which, I now understand, would mean the input is galvanically isolated. It is also UL Class 2 tested which means UL has tested the device to make sure that is the case. I am also now quite confident that the switching method I am planning to use will work and be safe. Thanks for the input and prodding me to delve deeper into it.

    http://www.victordistcontrols.com/wp-content/uploads/2014/03/FD_Dry_Contact_Input_Relays.pdf



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