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Solo to control and drive 60V Quartz Elements

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  • Solo to control and drive 60V Quartz Elements

    I have been using the relay outputs of two sepperate SOLO units for a few years now to control 120Volt elements, directly in circuit, to heat from two sides.

    Now we have to use 60V elements and still heat from two sides.

    Can we simply series two 60V elements with the relay output and use a thermocouple in space between the elements with a single SOLO controller?

    Can we simply parallel two 60V elements with the relay output, use a stepdown transformer, and use a thermocouple in space between the elements with a single SOLO controller?

    Will we have to continue to use two sepperate SOLO units and step down the voltage?


  • #2
    You can Series the elements.. Been There Done That..

    I'd do the One Controller..

    The only 'Problem' is USUALLY when you have to replace elements, replace both.. because as things age, the resistance will GENERALLY change together.. IF you pop in a New Heater with an old one, they are no longer ballanced in Resistance, and one will get more voltage than the other..


    I did a 120Volt 3 Phase Delta heater configuration, in a rotating heater assembly ( Production Line ).. that was a little Odd to work on.. As long as each heater bank is getting it voltage SOMEHOW, it will work..

    Cap

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    • #3
      Originally posted by Cap View Post
      You can Series the elements.. Been There Done That..

      I'd do the One Controller..

      Cap

      Thank you.

      But now they want me to use 85V elements. Perhaps series mount with 110V will yield a 33% drop in power, but still work? Spec is 300W for the elements and so 200W will be realized?

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      • #4
        Yes.. 85 Volt elements running on Series 120 Volt Circuit will be 120/170 or 70% Voltage.. and with a 'Normal' of 3Kw *70% will now be 2.1Kw.. if that is enough heat to start with.. might have to increase the 'Start Up' time for the unit..

        You could use a 'Boost Transformer' to add 48 Volt to the 120 Line to get 168 Volt for your series Heaters.. BUT depending on the Temp Controller Out put, you'd have to 'Remote' the output of the Controller to some Solid State Relay Unit.. as your controller is ( Likely ) running on 120 Volt, but the Heaters are at 168.. I'd have to see the EXACT way the controller is wired into your circuit, and what controller it is..

        You should still be able to run the Output from the Controller to the series bank, and keep the entire thing on 120 Volt.. rather than having to use some sort of relay, as they get very cumbersom.. and you'd have to use a Solid State relay, as when the controller aproaches temp it will duity cycle the Heaters, and likely KIL any normal 'Dry Contact' relay..

        The other way would be to drop down the 120 to 85 Volt.. that is not so simple.. as you need to loose 35 Volt.. not many 35 volt transformers out there.. so you'd be 24 + 12 to get 36 volt drop.. NOW you have TWO Buck Transformers hooked up as well as the relay drivers.. I think this one does not pass the KISS test..

        I'd series the 85Volts and see how it runs..

        Cap

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        • #5
          +1 on the 85v in series.
          I guess the positive side is the elements should last longer (as long as they will supply the required heat).
          Circumstances don't determine who we are, they only reveal it.
          Jason Wolthuis

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          • #6
            Originally posted by CMDR MOORE View Post
            But now they want me to use 85V elements. Perhaps series mount with 110V will yield a 33% drop in power, but still work? Spec is 300W for the elements and so 200W will be realized?
            (110/(85 * 2))^2 = 0.42
            about 65% of the rated voltage means about 65% of the rated current, 65% * 65% = 42% of the rated power
            300 * 0,42 = 126W
            the question is, is 126W enough?

            One might use a 24V buck transformer to take your 110V down to 86V and put the elements in parallel, or if your line voltage is closer to 120V, a 32V buck.

            300W @ 85V = 3.5A, I think I'd use am external contactor or SSR instead of the SOLO internal relay directly.

            Another question, where does one get 85V heating elements (and why)?

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            • #7
              300 watts divided by 85 (rated volts) = 3.53 (ohms of resistance).
              3.53 * 60 volts (120 volts in series) = ~ 211 watts.
              Circumstances don't determine who we are, they only reveal it.
              Jason Wolthuis

              Comment



              • #8
                Originally posted by Cap View Post
                'Normal' of 3Kw *70% will now be 2.1Kw..
                Woops.. I added a Zero.. did not see the 300 watt.. I saw 3000 Watt!!.. I usually run big heaters..

                Still the same Idea..

                Cap

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                • #9
                  Originally posted by plcnut View Post
                  300 watts divided by 85 (rated volts) = 3.53 (ohms of resistance).
                  3.53 * 60 volts (120 volts in series) = ~ 211 watts.
                  Um, actualy, 300W / 85V = 3.53 Amperes
                  85V / 3.53A = 24 ohms
                  or 85V^2 / 300W = 24 ohms

                  see: Joule's first law

                  O.P. mentioned 110V, 110/2 = 55
                  55V ^2 / 24ohm = 126W

                  at 120V / 2 it would be 150W

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                  • #10
                    Originally posted by Tinker View Post
                    Originally posted by plcnut;
                    300 watts divided by 85 (rated volts) = 3.53 (ohms of resistance).
                    3.53 * 60 volts (120 volts in series) = ~ 211 watts.
                    Um, actualy, 300W / 85V = 3.53 Amperes
                    85V / 3.53A = 24 ohms
                    or 85V^2 / 300W = 24 ohms

                    see: Joule's first law

                    O.P. mentioned 110V, 110/2 = 55
                    55V ^2 / 24ohm = 126W

                    at 120V / 2 it would be 150W
                    Ouch! I cant believe I said that!

                    Thanks Tinker I was looking at your numbers and thought "He sure is making this more complicated than it needs to be"... but I was making it to simple... by leaving out half of the equation.
                    I stand corrected. Thanks for pointing it out!
                    Circumstances don't determine who we are, they only reveal it.
                    Jason Wolthuis

                    Comment



                    • #11
                      Thanks.

                      Thank you for the help. I will be trying out a Variac at first and then select a fixed voltage solution.

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