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Re: Ferrite ID

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On 26/09/2026 1:58 am, David Lesher wrote:
> Rheem tankless water heaters, fed with dual 40A 240V circuits,
> are driving all the Leviton and other brand dimmers berserk.
> The lighting all dims and flickers beserkly. The Rheem has a
> sharp spike at the peaks of the positive and negative cycles;
> that is the cause.
> 
> The cure is some ferrite chokes on the power feeds. But fields
> class was Many Decades ago. I'm trying to decide if I want ones
> with an ID that just accepts the #8 stranded, or it doesn't
> matter that much if it's a loose fit.
> 
> Thoughts?

RM ferrite cores are available in a fair range of sizes.

https://www.tdk-electronics.tdk.com/en/529410/products/product-catalog/ferrites-and-accessories/rm-cores-and-accessories

Here the data sheet for the TDK RM10 core taken from that site.

https://www.tdk-electronics.tdk.com/inf/80/db/fer/rm_10.pdf

You'd buy two RM10 (or whatever) core pairs, wrap the power lead around 
the central pole of one half of the pair, clamp the other half on top 
and use a pair of spring clips (B65814B2203X000) to hold them together.

Broad-line distributors tend to stock them, but they rarely have the 
whole range.

Bigger cores go up to RM14 and you might be able to pack in a couple of 
turns of power lead. RM4 is the smallest, and probably too small for the 
application.

A single turn around an RM10 core is worth about 5uH (from 1.6uhH to 
16uH) depending on the ferrite. It goes up as square of the number of turns.

If you dig into the application notes you can find out about magnetic 
saturation.

You were probably thinking about ferrite beads/ferrite tubes, but they 
tend to be a bit idiosyncratic.

-- 
Bill Sloman, Sydney

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Ferrite ID David Lesher <wb8foz@panix.com> - 2026-09-25 15:58 +0000
  Re: Ferrite ID John R Walliker <jrwalliker@gmail.com> - 2026-09-25 17:02 +0100
  Re: Ferrite ID Bill Sloman <bill.sloman@ieee.org> - 2026-09-26 02:55 +1000
  Re: Ferrite ID john larkin <jl@htigct.com> - 2026-09-25 17:13 -0700
    Re: Ferrite ID Bill Sloman <bill.sloman@ieee.org> - 2026-09-26 16:39 +1000
      Re: Ferrite ID john larkin <jl@glen--canyon.com> - 2026-09-26 09:10 -0700
        Re: Ferrite ID Bill Sloman <bill.sloman@ieee.org> - 2026-09-27 16:32 +1000
          Re: Ferrite ID Brian Gregory <void-invalid-dead-dontuse@email.invalid> - 2026-09-28 23:30 +0100
            Re: Ferrite ID someone <2a59d59e3809f827ce709d3815e3950eef4a6a93af5557a93a7fdfba71460843@example.com> - 2026-09-29 19:15 +0000
              Re: Ferrite ID Bill Sloman <bill.sloman@ieee.org> - 2026-09-30 17:24 +1000
                Re: Ferrite ID john larkin <jl@glen--canyon.com> - 2026-09-30 07:50 -0700
                Re: Ferrite ID someone <2a59d59e3809f827ce709d3815e3950eef4a6a93af5557a93a7fdfba71460843@example.com> - 2026-09-30 20:00 +0000
        Re: Ferrite ID Bill Sloman <bill.sloman@ieee.org> - 2026-09-27 16:34 +1000
        Re: Ferrite ID someone <2a59d59e3809f827ce709d3815e3950eef4a6a93af5557a93a7fdfba71460843@example.com> - 2026-09-28 16:30 +0000
      Re: Ferrite ID someone <2a59d59e3809f827ce709d3815e3950eef4a6a93af5557a93a7fdfba71460843@example.com> - 2026-09-28 16:30 +0000
    Re: Ferrite ID someone <2a59d59e3809f827ce709d3815e3950eef4a6a93af5557a93a7fdfba71460843@example.com> - 2026-09-28 16:30 +0000
  Re: Ferrite ID Ian <devnul@blackhole.com> - 2026-09-26 11:57 +0100
    Re: Ferrite ID Bill Sloman <bill.sloman@ieee.org> - 2026-09-29 00:42 +1000
      Re: Ferrite ID Martin Rid <martin_riddle@verison.net> - 2026-09-28 11:04 -0400
        Re: Ferrite ID someone <2a59d59e3809f827ce709d3815e3950eef4a6a93af5557a93a7fdfba71460843@example.com> - 2026-10-01 04:15 +0000
      Re: Ferrite ID Ian <devnul@blackhole.com> - 2026-09-30 17:47 +0100

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