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induced noise

Discussion in 'Electronic Basics' started by Mike Riddell, Nov 23, 2003.

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  1. Mike Riddell

    Mike Riddell Guest

    Hello, I'm in the process of building a lab for my electronics and
    computers. I plan on running three separate circuits: one for the
    computers, one for my test equipment and one for general usage. I would
    like to use 14/3 cable to run from the panel to the workbench areas but I am
    concerned that there is the possibility of noise being induced into one of
    the other circuits. The 14/3 would be the cleanest way of routing the wire
    but running three separate wires would not be a problem either. Am I being
    overly cautious or is this a valid concern? Your input would be greatly
    appreciated.
     
  2. You'll be fine, go ahead. Use 12/3 if you going to load to 20 amps.
    hank wd5jfr
     
  3. Dbowey

    Dbowey Guest

    Mike posted:
    You will be less likely to have noise if you use separate wires to bring in the
    power.

    You should use 14/3 "with ground." 12/3 with ground would be only a little
    more expensive, and you would then have 20 Amp capability if you also use 20
    Amp breakers. The ground wire provides a safety ground.

    Also, if you want to have 220 (240) Volts available at the lab, be sure each of
    the 110 connections at the breaker box ( Red & Black) is tied to a different
    side of the incoming line. You will have 110V from Red to neutral (white), and
    110V from Black to neutral, and 220V between Red and Black. A "220V" breaker,
    due to how it is built, connects to the two different sides when it is seated
    in the box.

    Also, a GFCI would be a good idea for a lab. Mine operate on just a few
    hundred millivolts. I've popped them off without feeling anything, so I know
    they are a good thing to have.

    Don

    Don
     
  4. As I read this, I suspect you are planning to run a _single_ 14/3
    cable which will carry all three circuits - this is neither legal or
    possible, as you need hot, neutral, and safety ground wires for _each_
    circuit.

    According to my knowledge of the Canadian Electrical Code, you must
    use three separate 14/2 cables, if the circuits are fed by 15 amp
    breakers, or 12/2 if you have 20 amp breakers. A 14/2 or 12/2 cable
    will actually have three conductors: black (hot), white (neutral) and
    uninsulated (safety ground).

    If two of the circuits are on opposite 120V phases, you could combine
    them into one 14/3 or 12/3 cable, sharing the neutral.
     
  5. Mike,

    You ARE aware that there are filtered power feeds, right?
    Corcom comes to mind....but there are others.
    If you properly install a good filter on all three drops,
    you should not couple any noise from one circuit to another.


    --
    *
    | __O Thomas C. Sefranek
    |_-\<,_ Amateur Radio Operator: WA1RHP
    (*)/ (*) Bicycle mobile on 145.41, 448.625 MHz

    http://hamradio.cmcorp.com/inventory/Inventory.html
    http://www.harvardrepeater.org
     
  6. Dbowey

    Dbowey Guest

    dbowey's post included:
    "You will be less likely to have noise if you use separate wires to bring in
    the
    power."

    --

    That IS NOT what I intened to say. You will be less likely to have noise if
    you use cable (14/3 or 12/3 with ground) to bring in the power.

    Sorry about that..

    Don
     
  7. John Larkin

    John Larkin Guest

    Ac power is noisy; there's no point in separating circuits.

    John
     
  8. Ross Mac

    Ross Mac Guest

    If you are worried about electrical noise, just install a good UPS...No
    matter how you wire it....what comes off the pole is not always
    clean.....Ross
     
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