Do I misunderstand dielectric breaks Ohmic values?

Discussion in 'Water Heater Forum, Tanks' started by Toukow, Mar 29, 2021.

  1. Toukow

    Toukow New Member

    Joined:
    Jul 8, 2019
    Location:
    Seattle, WA
    Can one of you please straighten me out on the following? I'm replacing my water heater and currently have the copper corrugated lines with the plastic sleeves at the threaded connector as shown in photo. The water heater has lasted 17 years, so things have been good.

    I went and purchased new water line connectors which look exactly like the ones I currently have. I'm a bit confused on the following: I inferred that a dielectric break should have zero conductivity (or infinite ohmic value) between the brass threaded connectors and the copper corrugated tube. I expected at least a large ohm reading of some sort. I'm getting 3.3 ohms. Both new corrugated connectors test similarly at both ends. I wondered if it would change position when tightened, so installed it on a nipple and measured as shown.

    Is this ohmic value normal, or are the parts defective? Or given the low voltages generated with electrolysis, is such a low ohm value is adequate?

    Thanks, Toukow

    Measuring Ohms-001.JPG
     
  2. Reach4

    Reach4 Well-Known Member

    Joined:
    Sep 25, 2013
    Location:
    IL
    Are you are measuring between two metal pipes that each probably touch stuff that be sorta grounded? Plus, if there is water in that pipe, it can carry current too. I don't know how much that might contribute.
     
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  4. phog

    phog Active Member

    Joined:
    Jul 29, 2017
    Location:
    Rochester NY
    The dielectric coupling is only intended to make a protective sleeved section in the interior (wetted) surfaces. It is not intended to completely break electrical continuity between pipe sections. I think that the plastic sleeve basically just adds extra physical distance that ions must travel through the water during the corrosion reaction. Which in turn slows down the reaction rate. I don't claim to be an expert though, and could be wrong.
     
  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Joined:
    Sep 2, 2004
    Occupation:
    Retired Systems engineer for defense industry.
    Location:
    New England
    Take two different metals, connect them together, add some heat (especially if there's an even slightly conductive liquid involved - water, unless extremely pure, is a conductor, not a great one, but enough), and they can produce a voltage as in a battery. That can lead to ions moving that can eat away the metal on one of them. You can look up the chart of how reactive various metals are, and when trying to minimize the effect, you want to choose two that are as close together as possible. But, a dielectric insulator can help minimize that effect as it can help minimize the field strength. You're trying to minimize the galvanic reaction caused by different metals Galvanic Corrosion Chart – Thelen Tree Farm Many WH have a glass lined tank made out of steel, so trying to minimize corrosion on the parts where dissimilar metals can touch helps, as does using a sacrificial anode.

    From Wikipedia:
    "A dielectric (or dielectric material) is an electrical insulator that can be polarized by an applied electric field. When a dielectric material is placed in an electric field, electric charges do not flow through the material as they do in an electrical conductor but only slightly shift from their average equilibrium positions causing dielectric polarization. Because of dielectric polarization, positive charges are displaced in the direction of the field and negative charges shift in the direction opposite to the field (for example, if the field is moving in the positive x-axis, the negative charges will shift in the negative x-axis). This creates an internal electric field that reduces the overall field within the dielectric itself. If a dielectric is composed of weakly bonded molecules, those molecules not only become polarized, but also reorient so that their symmetry axes align to the field. The study of dielectric properties concerns storage and dissipation of electric and magnetic energy in materials. Dielectrics are important for explaining various phenomena in electronics, optics, solid-state physics, and cell biophysics.

    Although the term insulator implies low electrical conduction, dielectric typically means materials with a high polarizability. The latter is expressed by a number called the relative permittivity. The term insulator is generally used to indicate electrical obstruction while the term dielectric is used to indicate the energy storing capacity of the material (by means of polarization). A common example of a dielectric is the electrically insulating material between the metallic plates of a capacitor. The polarization of the dielectric by the applied electric field increases the capacitor's surface charge for the given electric field strength."
     
  6. fitter30

    fitter30 Well-Known Member

    Joined:
    Feb 2, 2020
    Occupation:
    Retired service tech
    Location:
    Peace valley missouri
    Ohm reading can only be taken with one side disconnected from the system. With both sides connected reading can run through the piping and faucets to get to both sides of the fitting.
     
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