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Wiring Relays with Flow sensors

Discussion in 'Sensors and Actuators' started by TMASCO, Jan 30, 2010.

  1. TMASCO

    TMASCO

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    Jan 30, 2010
    Hello, I am hoping someone can assist me in determine the correct way to wire a project that I am currently working on. I have totally confused myself on how to wire each control.

    My Goal:
    To install a flow switch/sensor into the main hot water line coming from the heater, this will turn on when it senses the draw for hot water. - Then the output from the sensor will activate the 10sec “delay-on” relay. Once the ten seconds has elapsed the relay will turn the pump that circulates the water throughout the system. – Once the draw for the main flow of hot water is stopped, the flow sensor will not recognize this because the pump will generate the flow over the sensor and therefore the pump will continue to run (this is ok). – On the hot water return pipe that the water continues to flow through there is an aquastat which is set to 130 degrees, once the aquastat senses that the water has reached 130 degrees it will break the current to the pump and therefore there will won’t be any flow of water over the flow sensor. Then the system will reset itself till the next time there is a demand for hot water. In theory this should work.

    SEE Attachments

    • System Design
    • My Best Guess on Wiring this Project


    Parts list: WILL FOLLOW IN NEXT POST

    Since I have 110v ac at the location I plan on operating all controls by 110v ac. Due to the large number of wires and connection I have managed to completely confuse myself and would hate to damage any of these devices. Therefore any help would be greatly appreciated.

    I should mention that all of the items are installed in the system and that the aquastat has been installed and set to cut out at 130 degrees. The problem I am having is how the flow meter and relay should be energized also where the pump leads and aquastat should be tied into the circuit. I have tried to map the connections out on paper but I get confused with the purpose of each wire on the relay and flow meter.
     

    Attached Files:

  2. TMASCO

    TMASCO

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    Jan 30, 2010
    The parts list for the project I noted in my first post is as follows

    Parts list:
    • Relay – SSAC model TRU3 (11 pin DPDT) (http://www.ssac.com/catalog/TRU01A01.pdf)

    • Flow Sensor - IFM Electronic – SI8504 (SID10ADBFKOW/LS) (http://www.ifm-electronic.com/products/us/printout/si8504.htm)

    • Pump – Taco model 005-BT4 (http://www.taco-hvac.com/uploads/FileLibrary/101-030.pdf)

    • Aquastat – White –Rodgers model 1127-2 (http://www.white-rodgers.com/wrdhom/pdfs/instruction_sheets/0037-1209.pdf)

    Thanks
     
  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    OK, the first problem is with your placement of the flow sensor. The first time that water starts to flow, the pump will turn on. The pump will keep water flowing through the sensor and thus it will never turn off.

    You need to place the flow sensor in the cold water line to the "left" of the hot water return.

    You circuit diagram is wrong too. But at present I don't have time at the moment to correct it, or check that all those components are mains rated -- which they need to be.

    edit: OK, it looks like they're all mains rated.
     
    Last edited: Jan 31, 2010
  4. TMASCO

    TMASCO

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    Jan 30, 2010
    *steve*
    Thanks for the reply, the thought process is that when the aquastat reaches 130 degrees the contacts will open and therefore the power to the pump will be cut which will cause the flow sensor and relay to reset untill the next call for hot water.

    If I place the flow sensor in the cold line it will keep the pump from running after the call for hot water has stopped (we want the system to continue to run until the 130 degree point is reached in the circulation loop then cut the circut to the flow sensor and pump).

    The pipes are all insulated and some of the heat should be retained in the system until there is a call for hot water at a later point.

    If you get a chance to edit my wiring diagram it would be greatly appreciated! ( I don't want to burn out any of my components by not wiring it correctely)

    Thanks again for the timely responce.
     
    Last edited: Jan 31, 2010
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Sorry, I didn't set this thread to alert me when you replied.

    OK, from what I understand, you want the pump running all the time there is demand for water. In addition to that, you want the pump to continue to run after there is no demand for water, until such time that the water temperature reaches 130F. Then the pump turns off and stays off until there is demand for water.

    It's getting late, so you'll have to confirm this with the specs, but I assume the relay stays pulled in as long as the initiate contacts are closed, then remains pulled in for some preset time period.

    (I checked) I'd set the relay up for delay on break, and set the time interval for 1 second. This means the pump will run for 1 second longer than necessary, but eliminates problems caused by sensors "chattering".

    What seems logical to me is that the flow sensor is in the cold water line. It will initiate the pump as soon as there is demand. Then I would connect the aquastat to the initiate contacts via one set of N.O contacts. This means that the aquastat holds the relay initiated but only once it has already pulled in (i.e. it will keep it closed after demand ceases if the water temp is low. The other set of contacts should be used to control the pump.

    With only 1 set of contacts, switch the active lead, not the neutral.

    I'm really not happy that you're doing mains wiring if you don't understand basic circuits though. Your initial design seems to indicate that you have very little training or experience. Is that right?

    I'm pretty sure that the "input voltage" (pins 2 and 11 of the relay) need to be connected to the mains, as do the L1 and N connections of the flow sensor (you did the latter, not the former).
     
  6. TMASCO

    TMASCO

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    Jan 30, 2010
    I am not sure what you mean by this, I thought I did in the diagram I posted

    Thanks for all of you help and please bear with me as I try and figure this whole thing out!
     
  7. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    The flow meter needs to be in the cold water line.

    the aquastat is in series with the flow meter so that the relay is only initiated when there is both flow *and* the water temperature is < 130F.

    Once the relay pulls in, it shorts out the flow meter so that control is passed entirely to the aquastat. When that senses 130F the relay will drop out turning off the pump.

    The pump will therefore turn on and off if there is prolonged low demand for water where the heater's capacity exceeds the requirement to heat the water. However it will continue to run after demand ceases to bring the water temperature up to 130F should that be required.

    Sorry for the poor quality of my drafting in the attached circuit.

    The relay should be set as I suggested in a previous post.
     

    Attached Files:

  8. TMASCO

    TMASCO

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    Jan 30, 2010
    By RLY set you mean the 1 sec delay on break.

    Thanks again for all of your valuable input. I am looking forward to beginning the wiring process!
     
    Last edited: Feb 3, 2010
  9. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Well, here's my dilemma. As everything is placed right now I see several possible problems:

    1) as you turn on the hot water tap, water flows from the cold water source, through the pump (backwards) and out, leading to cold water.
    2) you turn on the tap and water flows through the hot water reservoir and the flow sensor to the outlet, but the water trapped in the section of pipe near the pump is >130F and thus the pump doesn't turn on even though cold water is flowing to the tap once the reservoir of hot water is used up.

    To eliminate all these problems, I would ensure that:

    a) water cannot easily pass backwards through the pump
    b) water flow is sensed in the cold water line before the return
    c) water temperature is sensed at the outlet of the reservoir where it will receive flow if either a tap is open or the pump is running.

    This is all *way* outside my area of experience, so you may want to pass all of this by a plumber and an electrician. In Australia, I'm pretty sure we'd be using low voltage sensors (but maybe not low voltage pumps). As a do-it-myselfer, I'd not want mains to come within cooee (http://en.wikipedia.org/wiki/Cooee) of my water supply.

    Yeah, they're just a set of contacts. shorting them out is fine (that's what they do to themselves in any case)

    Rate it at a suitable value for the pump. Everything else will draw way less current. Motors can draw large amounts of current at startup, so get a recommendation from your supplier.

    I'd actually be inclined to power the circuit from a source that has an ELCB on it as well. If something does go wrong, it will break before you electrocute someone in the shower.

    Should be #5 on the flow sensor.

    In this case you don't need to bother. There are several reasons:

    1) it's all powered from AC -- a diode across a relay powered by AC will not suppress voltage spikes, but it will short out the power to the relay every other half cycle (blowing the diode or a fuse)
    2) your relay is not just a relay but a fairly complex electronic circuit incorporating timers, a power supply, logic, and also a relay. There is almost certainly a diode across the relay's coil internally (where it is powered from a DC source)
    3) this circuit is all switches and motors -- there is nothing to be damaged. (Even though the "relay" is electronic, you have to assume that it is protected from itself)

    Let me suggest that it's a good first try. It's possible that some of the required connections are not shown clearly and that may have mislead me.

    There are alternative ways of wiring the circuit.

    One alternative (in retrospect, what you may have been getting at) is to place the water flow sensor inside the pump loop so that the pump maintains the water flow even without demand, and place the aquastat in series with the pump to turn the pump off (and shortly thereafter the relay) once the water reaches 130F. It still suffers from potential problems of water running the wrong way through the pump.

    The attached scan is what I think you meant. I still think the aquastat should be where you show the flow sensor, but the flow sensor is placed correctly for this design (just make sure that water cannot easily flow backwards through the pump).

    Yes, that's right.
     

    Attached Files:

  10. TMASCO

    TMASCO

    12
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    Jan 30, 2010
    As mentioned above a will draft a new flow diagram moving the sensor to the cold in line so we can make sure we are on the same page.
     
  11. TMASCO

    TMASCO

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    Jan 30, 2010
    *steve*
    Attached is the revised water flow chart - moving the "Flow Sensor" to cold water in line.

    Is this what you were picturing?
     

    Attached Files:

  12. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    I think the aquastat should be between the heater and the taps (and inside the recirculation loop). or hot water trapped in the recirculation loop will prevent the pump from turning on.

    I have another question or two though...

    1) Why have the recirculation loop if the heater has no tank?
    2) What turns the heater on and off? water flow from its own internal sensor?
    3) Does the heater work correctly when fed with already hot water
     

    Attached Files:

  13. TMASCO

    TMASCO

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    Jan 30, 2010
    Thanks again!
     
  14. TMASCO

    TMASCO

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    Jan 30, 2010
    *steve* - I have taken another shot at the wiring diagram, but this time I included the water flow diagram. Can you follow what I did and is it correct?
     

    Attached Files:

  15. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Ah!, now that makes perfect sense! From your original drawing it looked sort of like the plumbing for a solar booster on a HWS. (can you tell I'm from a hot climate?)

    It's probably not wonderful for energy efficiency, but I imagine it works a treat in cold climates.

    Are you in an area that has the potential for frozen water pipes? We have (almost) the opposite problem here. In summer our cold water can be almost as warm as our hot water.

    But also please remember that "On the internet nobody knows that you're a dog"

    My arguments may appear sound, but I have admitted that this is not even close to my area of expertise. My profession requires me to pick up information and to solve problems on the outskirts of my knowledge. I end up sounding authoritative at times, but in my professional work all of my conclusions are passed by a *real* expert.

    Considering the possible negative impact of this going wrong, I suggest you do the same.

    That appears to be close to your original drawing, and very similar to my "alternative" circuit.

    I presume the aquastat is rated for turning the pump on and off -- if so, it's probably better operated with a load than simply as a set of contacts (it keeps the contacts clean).

    Again, my caveat that the pump will not start if the water near the aquastat is >= 130F, but your explanation and observations make that moot. I presume that the lagging on the pipes will not cover the aquastat, so it will probably cool fairly quickly once the pump stops.

    Note that with the aquastat in series with the pump, whilst it will turn off the pump when the water reaches 130F, it cannot maintain power to the pump after demand for water has ceased.

    Personally, I think that's a feature, as someone briefly turning on a hot water tap (by mistake perhaps) will not command the system to heat the entire loop to 130F. However, if you want that behaviour, the flow sensor needs to be placed back where you originally had it.

    Yes, I realise we've come back to where you started (wipes egg off face), but in my defence, I think you've shown the position of some non-return valves and corrected the wiring to the relay.
     
  16. TMASCO

    TMASCO

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    Jan 30, 2010
    Yes the winter can get relatively cold here, currently it is 15 deg F outside, our monthly heating bills run about $1,000 in the winter time. I am located in the state of Connecticut here in the USA.


    [/QUOTE]But also please remember that "On the internet nobody knows that you're a dog"

    My arguments may appear sound, but I have admitted that this is not even close to my area of expertise. My profession requires me to pick up information and to solve problems on the outskirts of my knowledge. I end up sounding authoritative at times, but in my professional work all of my conclusions are passed by a *real* expert.

    Considering the possible negative impact of this going wrong, I suggest you do the same.[/QUOTE]

    I will try and do a model set-up of what we discussed, on paper it looks great, I believe the model set-up will be the same.


    [/QUOTE]That appears to be close to your original drawing, and very similar to my "alternative" circuit.[/QUOTE]

    I thought I copied your last diagram exactly as you posted. What did I do wrong? Please correct me, I know I have wires all over the place but this is for reference purposes only.

    [/QUOTE]I presume the aquastat is rated for turning the pump on and off -- if so, it's probably better operated with a load than simply as a set of contacts (it keeps the contacts clean).[/QUOTE]

    Again, I thought I copied your diagram exactly

    [/QUOTE]Again, my caveat that the pump will not start if the water near the aquastat is >= 130F[/QUOTE]

    That is true, if the water at the aquastat is => 130F the pump will not operate that is why the aquastat is at the end of the circulation loop - when the temperature is => 130F at the aquastat the water should be => 130F at the beginning of the circulation loop - also there is a check valve after the aquastat to prevent any water back flow.

    [/QUOTE]but your explanation and observations make that moot. I presume that the lagging on the pipes will not cover the aquastat, so it will probably cool fairly quickly once the pump stops.

    Note that with the aquastat in series with the pump, whilst it will turn off the pump when the water reaches 130F, it cannot maintain power to the pump after demand for water has ceased.[/QUOTE]

    Isn't that whats supposed to happen - please make any corrections

    [/QUOTE]Personally, I think that's a feature, as someone briefly turning on a hot water tap (by mistake perhaps) will not command the system to heat the entire loop to 130F. However, if you want that behavior, the flow sensor needs to be placed back where you originally had it.[/QUOTE]

    That is why I originally had the 10sec(adjustable +/-) delay-on for the purpose of someone turning on the hot water tap briefly - I will move the flow sensor to where ever you think it belongs

    Yes, I realize we've come back to where you started (wipes egg off face), but in my defense, I think you've shown the position of some non-return valves and corrected the wiring to the relay.[/QUOTE]

    It's clearly my inability to explain what I am thinking - I just want to get it correct, that is why I am always looking for feedback - Keep it coming!
    I still can't figure out how to do the individual quotes - OH WELL
     
    Last edited: Feb 4, 2010
  17. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Perhaps you had better explain what the desired behaviour is in the circumstance where the water in the loop is cold and a person turns on the hot tap for a very brief period.

    *WOW* $1000 per month for heating. And I thought that $650 for 2 months over summer for cooling was a lot.
     
  18. TMASCO

    TMASCO

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    Jan 30, 2010
    You have a point - my thinking was that the system would be delayed in starting the circulating system due to a mistake- a false start-
     
  19. TMASCO

    TMASCO

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    Jan 30, 2010
    *steve*
    - I was wondering if you got a chance to correct my wiring diagram - I am anxious to start a prototype and would like to have everything correct so I don't blow-out any of the components.

    You have been a great asset to this project!
     
  20. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    As far as I can tell, the wiring diagram looks good.
     
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