Help request: making an endswitch on a 110V ac system

Discussion in 'The Projects Forum' started by lmtxprss, Jan 10, 2012.

  1. lmtxprss

    Thread Starter New Member

    Jan 10, 2012
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    Here is the scenario. I have 7 zone valves operated on 110V for my hydronic heating system. They are all powered individually and controlled by thermostats. What I want to do is to be able to turn on a pump when one or more of the thermostats is calling for heat. My problem(?) is that if I wire all of the zone valves through to the pump, all of the valves will open when one is energized. What I was thinking (and I could be way off here) is to put a diode in each line between the zone valve and the pump. It is my understanding that the diode will only allow current to pass one way, thereby preventing the other valves to be energized. The total load of the pump is 25W - 70W.

    Am I on the right track?
    Is there a specific type of diode I should be using?
    Is there a size of diode I need?
    Where to find such a beast?

    Any help and or suggestions would be greatly appreciated!

    Thanks
    Lano in Canada
     
  2. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    Is the thermostat/signaling done at the standard 24V, or is it all 110V?

    If it is all 110V, I'd strongly suggest having an electrician work on it, as a diode won't help. Even the 24V control is an AC control, so a diode would still pass half of the waveform.
     
  3. lmtxprss

    Thread Starter New Member

    Jan 10, 2012
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    It is all 110V.
    Thanks
     
  4. crutschow

    Expert

    Mar 14, 2008
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    A simple but somewhat kludgy way would be to have seven 110VAC relays with each relay coil controlled by one of the thermostats. Wire the contacts of each relay in parallel to control the 110V to the motor (which makes a sort of AC "OR" gate). That way the motor will be powered only if one or more of the thermostats is closed.
     
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  5. wayneh

    Expert

    Sep 9, 2010
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    Not as simple but maybe more elegant would be to detect an AC signal (ie. current) on the power line going to all the valves. I assume current is zero when they're all off. If any of them turn on, a current could be detected and a DC circuit could throw a relay to turn on the pump.
     
  6. strantor

    AAC Fanatic!

    Oct 3, 2010
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    I don't see that as being kludgy. I see it as being the simplest, most reliable way to do it. What's kludgy about it?
     
  7. lmtxprss

    Thread Starter New Member

    Jan 10, 2012
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    Sounds interesting, that being said, with what do I detect a current?? I'm in construction by trade but raised on the farm... that's where my DIY spirit comes from!
    Thanks
     
  8. lmtxprss

    Thread Starter New Member

    Jan 10, 2012
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    Thanks Carl, this indeed might be the ticket, thanks!
     
  9. BillB3857

    Senior Member

    Feb 28, 2009
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    An accumulator tank, check valve and pressure switch, similar to a deep well water system? In those, the pump only runs when water flows.
     
  10. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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  11. williamj

    Active Member

    Sep 3, 2009
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    lmtxprss,

    crutschow,s suggestion would be the way I'd go. I did a simple diagram showing how it might look (see attached). I only showed three zones but you get the idea.

    good luck and be careful,
    williamj
     
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  12. lmtxprss

    Thread Starter New Member

    Jan 10, 2012
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    So i'm looking for a (7) 110VAC SPST relay?
     
    Last edited: Jan 11, 2012
  13. lmtxprss

    Thread Starter New Member

    Jan 10, 2012
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  14. crutschow

    Expert

    Mar 14, 2008
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    Only that it's perhaps not as elegant as converting the signals to DC and using digital logic which would require just one relay. But kludgy is in the eye of the beholder.;)
     
  15. crutschow

    Expert

    Mar 14, 2008
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    Seven of those should work.

    Edit: Question -- Are the valves driven directly from the thermostat?
     
  16. lmtxprss

    Thread Starter New Member

    Jan 10, 2012
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    Yes, voltage is sent to the thermostat and then back to the valve when condition met. I have a junction box in the utility room where all the pumps are located that I can easily access the circuits. Thanks for all your help!!
     
  17. crutschow

    Expert

    Mar 14, 2008
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    The reason I ask is to determine if the thermostat is capable of providing the current to the relay. If it drives the valves directly, then there should be no problem. If it goes through some circuitry before driving the valve, then you may need to determine how much current the thermostat can deliver.
     
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  18. williamj

    Active Member

    Sep 3, 2009
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    lmtxprss,

    crutschow is again on point. Seven of those relays should work. If the zones can handle the solenoid current draw you should be able to parrallel the relays with the solenoids. And if there is physically enough room, you might consider mounting the relays along side of your solenoids. I've modified the first diagram to illustrate.

    again, good luck and be careful,
    williamj
     
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