Relay wiring

Discussion in 'General Electronics Chat' started by garyswan, Mar 26, 2006.

  1. garyswan

    Thread Starter New Member

    Mar 26, 2006
    1
    0
    Hey guys, I am needing some help with a simple problem. I need a relay wired into a control circuit to allow operation of 3 fans totalling about 12 amps (240v) to be operated by a CPU. The CPU can not handle more than 10 amps thus the need for the relay. The problem is I don't know where to hook my power line, control wires for input and output, and load lines on the relay. I have an omron general purpose relay with terminals desginated as L1, L2, T1, T2, 0, & 1. I am embarrased to even ask this question cause I have been doing residential wiring for years but never had to wire up a 240v relay into a CPU. Any help would be greatly appreciated. TIA, Gary
     
  2. Gadget

    Distinguished Member

    Jan 10, 2006
    613
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    Need some clarification, and perhaps a diagram. The way it reads at the moment, you have One MOTHER of a CPU, and some pretty extreme cooling requirements. Perhaps you could just hire a chopper to hover above it..?

    Perhaps it is a PLC controlling a refrigeration plant or something..?

    On a more serious note,
    If you are not a Licenced Electrician, or suitably qualified/trained person, then GET ONE to do this... I am assuming this is the case, as I wouldn't expect someone qualified to do this work having to ask about something this basic..?
    Playing around with 240v when you don't know what your up to can be Lethal, and I feel morally obliged not to offer any more advise than this.
     
  3. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    Gary: Do you have a part number on that Omron relay?

    Gadget: He said "CPU," not "personal computer." My siter-in-law's espresso machine has a CPU. So do most of the fire alarm panels that are used to shut down air handlers. ;)
     
  4. Gadget

    Distinguished Member

    Jan 10, 2006
    613
    0
    Sorry, When Did I mention Personal Computer..????

    CPU translates to Central Processing Unit, and not a single one I know of can supply much more than 10 milliamps, let alone 10 amps without some kinda interfacing. Hence the reference to my guess about the poster's term "CPU" perhaps in reality being a PLC... (Programmable Logic Controller), which..... surprise surprise, also has a CPU at it's heart and most PLC's have outputs quite capable of switching 10 amps.

    As this is a Guess, Perhaps the poster can clarify this and also let us know if he has the qualifications that will allow him to stuff around with 230 - 240v MEN wiring, without endangering other people. The nature of his first post doesn't fill me with the confidence that allows my conscience to encourage him to get deeper into the wiring nest.
     
  5. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    No offense was intended, Gadget. We often use "CPU" to refer to the board in an FACP. Same board contains PS capable of several amps. Sorry for the miscommunication.

    Gary says in his post that he's been wiring for years.
     
  6. Erin G.

    Senior Member

    Mar 3, 2005
    167
    1

    L1 and L2 are for the 240volts from your power supply, such as a circuit breaker. T1 and T2 go to the motor. 0 an 1 are for the contactor that closes L1 to T1 and L2 to T2 to make the motor run. Look on the relay to see what the control power (coil) voltage rating is: Usually it's 110 to 120VAC. If so, hook up 0 to your neutral. 1 would be hooked up to the hot 110VAC through an on/off switch. In this case the on/off switch is the CPU, so hook it up to the correct output on the CPU. Then, you're done!

    If you need me to I can post a drawing later: Just lemme know :)

    Good luck!
     
  7. Erin G.

    Senior Member

    Mar 3, 2005
    167
    1

    Hey Gadget, not to play devil's advocate or anything: In the power and controls industry, CPU is a common mis-nomer that we apply to anything that actually does use a CPU to control things. A perfect example of this is the PLC you mentioned. The CPU does the thinking, but the contacts handle the load. Just a matter of jargon, really.

    I do understand and appreciate your concerns, though.

    erin
     
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