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Thread: Alternating relay wire confirmation help

  1. #1
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    Alternating relay wire confirmation help

    So based on the wire diagram it looks very basic to understand. I think my problem is I am misunderstanding the relay operation. I thought yhe way this particular relay worked is it will alternate each time the control switch was to open. It states that in the description. I have 2 air compressors that share a common pressure tank. I want to alternate between the 2 air compressors each time there is a demand. I wired it up as per my little drawing/diagram. So I applied power. My pressure switch is closed because the tank is empty of air. So cc1 energizes. Looks good. Well once my tank pressure reached it’s set pressure. The pressure switch opened. The relay switched states and energized cc2 even though my tank pressure switch is still open. It seems like the both sets of contact can’t be open at the same time on the alternating relay. Thinking about it. I think if I wire a 2nd pressure switch set at same pressure in series with cc2.
    It will keep cc2 de energized. When there is a demand the pressure switch closes energizing cc2. Once the pressure switch/control switch is satisfied and opens its contacts. It will cause the alternating relay to switch to cc1 again. Looks like I need a pressure switch in series with both cc1 & cc2. And one pressure switch as the control switch. I will redraw my theory and post it. As of now this is the manufactures info.
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    So I couldn’t wrap my head around how to make it work until I starting writing my post. See my wire diagram. This should work. Looks like I only need 2 sets of contacts on the pressure switch to make it work. Name:  EB0D3A23-42A5-4828-894D-D35ED885EB71.jpeg
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  3. #3
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    Quote Originally Posted by anthonyac1 View Post
    So I couldn’t wrap my head around how to make it work until I starting writing my post. See my wire diagram. This should work. Looks like I only need 2 sets of contacts on the pressure switch to make it work.
    Should be able to use the pressure switch between 3 and the commons on the contractors. Is the second pressure switch a safety?
    Propagating the formula. http://www.noagendashow.com/

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    Quote Originally Posted by orion242 View Post
    Should be able to use the pressure switch between 3 and the commons on the contractors. Is the second pressure switch a safety?
    No the pressure switch is not a safety switch. The pressure switch serves 2 purposes. One it triggers the alternating relay to swap between loads. Also the pressure switch opens shutting down the air compressor once the pressure tank reaches the set cut out pressure.
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  5. #5
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    Roger, so its a single pressure switch with dual contacts.
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  6. #6
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    Quote Originally Posted by orion242 View Post
    Roger, so its a single pressure switch with dual contacts.
    Yep. But I can do as you mentioned if I break the common of both contactors through one set of contacts. Then I use the 2nd set of contacts to trigger the alternating relay. That will work atleast in my head it works.
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  7. #7
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    Should do the same with the switch between 4 & 1. Then all the switching is done on the hot side.

    Either way should get'r'done.
    Propagating the formula. http://www.noagendashow.com/

  8. #8
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    Here you go.
    First take pressure switch 1 & 2 out of the picture. Connect terminal 2 to compressor 1 contactor and terminal 8 to compressor 2 contactor.
    Now change the jumper 1 to 4 so it connects 1 to 5.
    The compressors should now run 1 at a time and alternate on each run.

    Now lower the cut in of pressure switch 1 & 2 to a setting lower than the control pressure switch.
    Connect pressure switch 1 from 4 to 2. (leave all other wires in place from above)
    Connect pressure switch 2 from 4 to 8.
    Pressure switch 1&2 will now run both compressors whenever the pressure is below its setting. (This functions like a backup if lead pump fails or control pressure switch fails or the relay fails.)

  9. #9
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    You can use it with one pressure switch with one set of contacts. On the first hand drawn schematic you need to move the jumper from 1 and 4 to 1 and 5. This enables power to the compressor control only when the pressure switch is calling.

  10. #10
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    Quote Originally Posted by billcontrols View Post
    Here you go.
    First take pressure switch 1 & 2 out of the picture. Connect terminal 2 to compressor 1 contactor and terminal 8 to compressor 2 contactor.
    Now change the jumper 1 to 4 so it connects 1 to 5.
    The compressors should now run 1 at a time and alternate on each run.

    Now lower the cut in of pressure switch 1 & 2 to a setting lower than the control pressure switch.
    Connect pressure switch 1 from 4 to 2. (leave all other wires in place from above)
    Connect pressure switch 2 from 4 to 8.
    Pressure switch 1&2 will now run both compressors whenever the pressure is below its setting. (This functions like a backup if lead pump fails or control pressure switch fails or the relay fails.)
    Thank you for the info. Sorry for the late reply. I rewired the unit about 2 weeks ago. I switched it from 1-4 to 1-5. Not sure how I could not see that. Lol glad you pointed that out. My 2 pressure switches are in series. One is the main control switch. The other pressure switch is to open at a higher pressure in case the control switch fails closed. Works like a charm.
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