circulating pump timed relay latching

Discussion in 'General Electronics Chat' started by Danrower, Oct 12, 2013.

  1. Danrower

    Thread Starter New Member

    Oct 12, 2013
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    I would greatly appreciate design advice.

    I have installed pipe and a circulating pump for a 100’ long house with the water heater and pump located at one end. 2 Bathrooms located 50’, and 2 bathrooms 90’ from tank and pump. I have installed a 4 conductor 22 gage wire from the baths to the pump in anticipation of remote pump control. Pump and circulating function work well, controlled by a manual 120 v. switch. Originally thought I would circulate the water continuously in the insulated lines, but I believe that will cause significant energy consumption (additional heat loss), so have decided to install a “demand” system where the pump would be remotely actuated at the baths in order to eliminate the cold water run out. Takes about 8 minutes for pump to supply to far end of house.

    Pump specs:115v., .37A, 1/100 hp

    I want to install 5 low voltage remote momentary push button switches( with led to indicate pump operation), which would activate a timed (latched?) relay for approximately 10 minutes, then auto turn off, using the preinstalled 4 conductor 22 gage wire.

    The relay I think I need:

    http://www.ebay.com/itm/271085004219?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649


    The switches I think I need:

    http://www.ebay.com/itm/251320034864?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

    The Power supply I think I need:

    http://www.ebay.com/itm/121191034179?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649


    I am confused about the exact wiring in order to make this a latching relay.

    I suppose it’s ok to mix 120v. ac with 12 v dc through the relay?

    In the spec sheet for the relay they suggest the installation of a second relay, as found on page 10 of the spec sheet:

    http://www.ia.omron.com/data_pdf/data_sheet/h3y_ds_e_4_2_csm92.pdf

    “Do not connect the H3Y as shown in the following circuit diagram on
    the right hand side, otherwise the H3Y’s internal contacts different
    from each other in polarity may become short-circuited.”

    “Use the following safety circuit when building a self-holding or selfresetting
    circuit with the H3Y and an auxiliary relay, such as an MY
    Relay, in combination.”

    Am I on the right track? Right equipment?

    Will the timer open the relay, breaking the 12 v jump across the switches, at the end of the set time (approx 10 min)

    Do I need to install a second relay, and why?

    Thanks in advance for wading through this, I will much appreciate your advice.
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    It looks like the precaution is to prevent opposite polarity appearing across any internal contacts.
    What is the purpose of the flow being timed, upon anyone opening a tap, could not a simple P.B. start the pump and latch in as long as the demand was there. When the user turns the tap off at the end of the required use, the pressure build up trips a P.S. and unlatches the pump supply?
    Max.
     
  3. Danrower

    Thread Starter New Member

    Oct 12, 2013
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  4. Danrower

    Thread Starter New Member

    Oct 12, 2013
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    Actually, the purpose of the timer is to turn the pump off, after the hot reached farthest point, otherwise, run forever, and I'll be keeping the water in the pipes hot 24/7.
     
  5. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    So whats the point? a 2 minute shower only?

    person presses button.. pump turns on pumping water.. water is cold out of shower head for 4-8 minutes then 2 minutes of hot water before the timer turns off the pump?... I don't get it..
     
  6. Danrower

    Thread Starter New Member

    Oct 12, 2013
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    After the pump circulates the water to the far end of the house, with no tap being opened, there is hot water in the line. so long as hot water is used, hot is in the insulated line and hot comes out from the heater. When the use stops, the water cools in the line. pump circulates water in a 60 psi line. Normal city water pressure.
     
  7. Danrower

    Thread Starter New Member

    Oct 12, 2013
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    This is not a pressure pump. this is a circulating pump. Sorry I was not clear.
     
  8. MaxHeadRoom

    Expert

    Jul 18, 2013
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  9. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    sorry..thought this was some weird "no city water" /pump is your only pressure source setup for some reason..

    so yeah just run the 12V through the switches to the "coil" side of the relay.. Switch one leg of the 120V pump voltage with the other "contact" side.. Keep each side isolated and voila.. 12V applied to relay and contacts close turning on pump.. after set time relay contacts ope and pump turns off.
     
  10. Danrower

    Thread Starter New Member

    Oct 12, 2013
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    Thanks Max, NO pressure tank. this is a circulating, or recirculating pump in a 60 psi city water supply system. The purpose of the pump is to circulate hot water from the water heater to the far end of the house, and there is a return line to the bottom of the water heater (conventional 50 gal) .
     
  11. Danrower

    Thread Starter New Member

    Oct 12, 2013
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    Thanks Mcgyvr,

    when you say isolated, do you mean "be careful not to cross connect the 12vdc with the 120 v ac?"
     
  12. Danrower

    Thread Starter New Member

    Oct 12, 2013
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    Thanks Mcgyvr,

    When you say to keep isolated, do you mean "don't cross connect the 12vdc with 120 v ac in the wiring of the relay?"
     
  13. MaxHeadRoom

    Expert

    Jul 18, 2013
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    The app sheet recommends using an Aux relay (MY) in order to save on breaking a higher inductive load shortening the life of the timer contacts, the second diag. shows a contact to latch in an aux relay which is reset by the Timer time-out, the local push buttons would be OR'd together or in parallel with each other.
    Max.
     
  14. Danrower

    Thread Starter New Member

    Oct 12, 2013
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  15. MaxHeadRoom

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    Jul 18, 2013
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    That should work, I would also pick up a spare for that price.
    I also would be inclined to use the self latching circuit in the app note and use momentary buttons, this way one does not accidentally be kept on.
    If you needed the indicator function, you may have to run 3 wires to each switch for an indicator line off of a spare contact on the relay.
    If you have four cond. to each then that would work.
    Have you considered the contingency of someone using another B.rm within a short period of the pump time out and not needing the pre pump?
    Max.
     
    Last edited: Oct 12, 2013
  16. Danrower

    Thread Starter New Member

    Oct 12, 2013
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    I will order now, thanks so much Max!
    Switches will be wired in parallel, and a secondary actuation in a different bath should have no effect on the original cycle, I think. and they run off the same water trunk line, so the original 10 min run will provide hot for all, for at least 30 minutes. Then the water in the lines will cool.
    Also, I think I'll have at least 1 open contactor on the timer relay for the led indicator.
    Is it necessary to run the neutral 120v ac through the relay, or can I treat it like a switch and bond the neutral outside the relay?
    Max, very much appreciate your taking the time to look at this. Your the man!
     
  17. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Yes a spare timer contacts could be used for the LED's.
    The 120vac live cond, will be switched by the aux relay and the neutral will go direct to the pump.
    Don't forget the earth ground cond.
    Also for safety reasons I would be tempted to connect the 12vdc common to earth ground conductor.
    Max.
     
  18. Danrower

    Thread Starter New Member

    Oct 12, 2013
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    Max,
    Mucho Mucho thanks for the guidance. Ordered 2 of the MY relays, and the timer relay.
    really good pointers.
    Theory question: Is the aux relay a sacrificial relay, or is the construction of aux relays make them better to resist the degradation across the contactors from spark? ( I'm assuming that is the prob.)
    Again: Thanks much!
     
  19. MaxHeadRoom

    Expert

    Jul 18, 2013
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    In this case the cost of the replacement timer is not that great, but where timer costs can be quite high it is normal to fit an aux relay, not only can the contact rating be improved if necessary but the cost of replacement is usually cheaper for a simple relay.
    The rating in many of these devices are given with resistive loads, so the rating drops when using inductive loads.

    In the case of your loads, there may not be a need for great concern, but I like to play it safe.
    Max.
     
  20. doug08

    Member

    Jan 30, 2011
    153
    2
    will work perfectly for you! Just make sure your 12v power supply has a sufficient amount of current for the circuit and relay coil. Make sure the relay contacts are rated for the load you intend on using. The circuit is super simple, and has worked flawlessly for me for over 2 years now. The link to the schematic is located below the video.

    https://www.youtube.com/watch?v=0hGsXCYIamk
     
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