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240v vs 120v Silvias

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  • #16
    Re: 240v vs 120v Silvias

    When looking for how much "grunt" an appliance has, you have to look at watts. Thats irrespective of whether youre in the USA, Melbourne or in your 12-volt car.


    The current in the USA is approx twice that of Australia, but when working out what power the appliance has, you look at Watts.

    watts = amps x volts

    A 4 amp appliance in the US would produce 440 Watts (w= 4 amps x 110 volts)

    But a 4 amp appliance in Australia would produce 960 watts ( 4 amps x 240 volts).

    A 50 watt TV which can run on 12 volts takes a hefty 4 amps of current, (which can cause heating along the power circuit).

    The same 50 watt tv on 240 v draws a trifling --and safer-- 0.2 amps.

    These are approximations only, as mains power is probably closer to 230 V and 12v power can range from about 13.8 volts down to 11 for a flat battery.

    --Robusto

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    • #17
      Re: 240v vs 120v Silvias

      One other thing to remember when talking about American appliances...

      Because the voltage is half and the current must therefore be double for the same power output (very approximate for ease of explanation):

      The voltage at any appliance is lower than the supply because current flowing through the power cables causes voltage to drop due to the "resistance" to current flow - so American power cables are thicker to (hopefully) reduce this drop.... but a 1 volt drop in America is 1% where in Australia it is only 0.5% of the voltage.

      The effect of that voltage drop is compounded as 1% less voltage causes 1% less current to flow in the appliance- so the power becomes 0.99 X 0.99 or 98% of what it should be - in Australia it is 99% of what it should be..... and longer cables make this even worse in both cases! (like extension cords on heat guns)

      This is also significant with PIDs where the solid state switch drops about a volt (often a bit less)..... this also reduces heater output far more in America than in Australia......

      Thus endeth the "Circuit theory 101 lecture"

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      • #18
        Re: 240v vs 120v Silvias

        Originally posted by JavaB link=1171793225/15#16 date=1172722828
        The effect of that voltage drop is compounded  as 1% less voltage causes 1% less current to flow in the appliance- so the power becomes 0.99 X 0.99 or 98% of what it should be - in Australia it is 99% of what it should be..... and longer cables make this even worse in both cases! (like extension cords on heat guns)

        This is also significant with PIDs where the solid state switch drops about a volt (often a bit less)..... this also reduces heater output far more in America than in Australia......

        Thus endeth the  "Circuit theory 101 lecture"
        Yes, the SSR does sap a little power, but I wont be standing impatiently next to the Silvia cursing that its taken an extra 1/500th of a second to reach steady state!

        --Robusto

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        • #19
          Re: 240v vs 120v Silvias

          Originally posted by robusto link=1171793225/15#17 date=1172725765

          Yes, the SSR does sap a little power, but I wont be standing impatiently next to the Silvia cursing that its taken an extra 1/500th of a second to reach steady state!
          --Robusto
          Well according to PID kits site - a Watlow SD3C on a Silvia takes 120 seconds to recover to steady state .... so without the SSR it would recover all of 1 second faster!!!! (That would require the use of an unreliable mechanical relay) or without the PID altogether recovery time is about 90 seconds - with massive overshoot - taking an additional 100 seconds or so to coast back to ideal temperature.

          I know what Id prefer .

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          • #20
            Re: 240v vs 120v Silvias

            You get no arguments there. Without a PID, small boiler non-hx machines such as the Silvia, Gaggia, are like a playground swing in the dark, going from one side to the other. When it finaly settles down, someone (the thermostat) gives it an almighty push once again and off it goes.

            --Robusto

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