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Discuss Does such a relay exist? Or be built? in the DIY Electrical Forum area at ElectrciansForums.co.uk.

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  1. fezster
    Offline

    fezster EF Member

    Location:
    Uk
    I was wondering if anyone could tell me if the following relay exists, or can be easily built using off the shelf parts?

    I need to monitor 3 x 240V inputs and switch 1 x 240V output. However, every time one of the inputs is activated, I need the output to disengage for a period of time before re-engaging.

    So as an example:

    1. Input 1 is 240V. Output goes to 240V.
    2. Input 1 is off. Output goes to off.
    3. Input 2 is 240V. Output goes to 240V.
    4. Input 1 goes to 240V. Output goes to off for 'x' seconds, then goes to 240V.
    5. Input 2 is off. Output stays on.
    6. Input 1 is off. Output goes to off.

    I've looked into building a custom relay using an arduino for the control logic, but was hoping there was a solution I could just buy.

    I've taken a look at the DMB51CM24 Carlo Gavazzi and this seems to do what I want, but only for a single input. Whereas, I require 3 inputs.
     
  2. Vortigern
    Offline

    Vortigern Electrician's Arms

    Location:
    England
    Business Name:
    F.H. Electrical
    Why not get three DMB51CM24 Carlo Gavazzi
     
  3. Andy-1960
    Offline

    Andy-1960 Electrician's Arms

    Location:
    Wolverhampton
    Schneider Zelio or Siemens Logo May be the solution.
    They are basically a programmable relay that will do what you need.
    You will need to write a little programme and download it to the unit but it’s simple enough to do.
     
    • Informative Informative x 1
  4. PEG
    Offline

    PEG Trusted Advisor

    Location:
    Manchester
    What loads are you switching?

    The magnitude of these,will determine what is available.
     
  5. davesparks
    Offline

    davesparks Trusted Advisor

    Location:
    guildford
    off the top of my head three timing relays with a delay-on function should do the job, I don’t think this would warrant the cost of a programmable relay.
     
  6. Rob
    Offline

    Rob Trusted Advisor

    Location:
    North west
    Can get a Siemens Logo or Rockwell Micro 810 for around £50 nowadays.

    Software is free, a little more expensive than 3 timing relays but not much. However, less wiring time, easier to modify and a cleaner solution overall.

    Any design I make now with over 6 control relays to do a function gets one of those thrown in.
     
    • Agree Agree x 2
  7. fezster
    Offline

    fezster EF Member

    Location:
    Uk
    Thanks for all of the suggestions.

    The application is for boiler control. I believe the loads are negligible as the inputs to the relay will be the Switched Live from the Motorised Valves, and the output is a 240V control signal to the boiler to fire it.

    I'll do some research into the Siemens Logo and Rockwell Micro 810, not having used anything like this before.
     
    • Like Like x 1
  8. fezster
    Offline

    fezster EF Member

    Location:
    Uk
    I could do with some more guidance actually. These programmable smart relays are a vast topic.

    I believe the Allen Bradley 2080-LC10-12AWA is suitable for my 240V switching. It has 8 inputs and 4 outputs. To expand on what I specified earlier, I actually want 2 outputs:

    The second output is also 240V AC and will be enabled continuously as long as one input is live. This will be powering a secondary pump and has a max current draw of 0.5A. So the end result is that the pump runs continuously when any zone valve is open, but the boiler restarts it's sequence when any zone valve opens (regardless of if any other is already open).

    I'm reading the manual for the controller here:

    http://literature.rockwellautomation.com/idc/groups/literature/documents/um/2080-um001_-en-e.pdf

    But any pointers on achieving what I require? And do I require any other devices other than the controller itself (I'm thinking electrical suppression devices, to maintain the life of the controller)? Thanks!
     
  9. Rob
    Offline

    Rob Trusted Advisor

    Location:
    North west
    That controller will do what you need it to.

    Having 4 outputs will not be an issue. Just means you have 2 spare.

    They are relay outputs, so will be volt free.

    Wont need any suppressors, just an MCB or fuse to protect the controller and it's outputs. I think you also need a USB adaptor that's a couple of quid to program. The 820 and 830 versions don't need it as they are bigger and usually come with a built in Ethernet port.
     
    • Like Like x 1
    • Agree Agree x 1
  10. snowhead
    Offline

    snowhead Trusted Advisor

    Location:
    Mildlands
  11. Devonchris
    Offline

    Devonchris Regular EF Member

    Location:
    Devon
    Business Name:
    O
    Just out of curiosity, why does the boiler need to restart its sequence when it's already running?
     
  12. fezster
    Offline

    fezster EF Member

    Location:
    Uk
    How would this work with multiple inputs, though? And being able to control the output depending on the sequence of those inputs?
     
  13. fezster
    Offline

    fezster EF Member

    Location:
    Uk
    I have multiple heating zones and the boiler (a Vaillant 438) is very sensitive to the flow/return temperature differential being too high. When any zone is hot, the opening of a cold zone inevitably leads to this high differential. The boiler then goes into a waiting period (called S53). It does recover from it, but it's extremely annoying, as everything runs lukewarm until it starts up again.

    If the boiler is allowed to switch off when this event occurs (with the pump still running), the hot and cold water can be allowed to mix before the boiler fires up again - it will then perform as per normal. I've tried this sequence of events manually and it works, so it would be nice to automate it.
     
  14. Devonchris
    Offline

    Devonchris Regular EF Member

    Location:
    Devon
    Business Name:
    O
    I see. Thanks for that.
     
  15. darkwood
    Offline

    darkwood Super Moderator Staff Member Trusted Advisor

    Location:
    West Yorkshire
    PLC function block mode is the best way and not too hard to pick up on, you have special featured blocks that handle decision making for you and you just put in and tick what you want in the block settings, timer functions can also be added where and when and triggered how you like, the programming options here are endless and a simple program could sort all this out.. don't be scared to download the free software for the Zelio Soft2 or the millenium 3 depending on what PLC brand you want to favour.

    PS - before altering any normal functioning sequence of the boiler though I would contact their tech' and just ensure what you want to do will not compromise how the boiler runs safely and efficiently.
     
    • Like Like x 1
    • Informative Informative x 1
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