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Ferrite ID

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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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#748195 — Ferrite ID

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?



-- 
A host is a host from coast to coast...............wb8foz@panix.com
& no one will talk to a host that's close..........................
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

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#748197

On 25/09/2026 16:58, 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?

A reasonably tight fit gives better results, as does using
a ferrite tube rather than a short bead.
However, if its a loose fit you may be able to feed multiple turns 
through it which works well at lower freequencies.
The material does make a difference too, according to the
frequency range you are trying to absorb.
John

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#748200

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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#748210

On Fri, 25 Sep 2026 15:58:05 -0000 (UTC), David Lesher
<wb8foz@panix.com> 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.

Probably diode reverse recovery, although I don't see why they would
care to rectify.

Is this a resistive water heater? That's very inefficient.

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#748217

On 26/09/2026 10:13 am, john larkin wrote:
> On Fri, 25 Sep 2026 15:58:05 -0000 (UTC), David Lesher
> <wb8foz@panix.com> 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.
> 
> Probably diode reverse recovery, although I don't see why they would
> care to rectify.
> 
> Is this a resistive water heater? That's very inefficient.

Tankless implies instant heating, which uses a lot of power. It is 
remarkably efficient, in that you don't waste any of the energy keeping 
the environment around storage tank warm. You'd get more heat per watt 
if you used a heat-pump, but you have to collect most of that heat from 
the environment, which is slow and call for bulky heat-exchangers.

Sharp spikes at the peaks of the positive and negative cycles doesn't 
necessarily imply diode rectifiers - if they just connected to the main 
only at the peaks of the cycles you'd get the same kind of brief current 
spike.

It's totally incompetent design - everybody should know how to do power 
factor correction - but the extra components cost money, and tankless 
water heaters are strictly from hunger.
-- 
Bill Sloman, Sydney

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#748243

On Sat, 26 Sep 2026 16:39:22 +1000, Bill Sloman <bill.sloman@ieee.org>
wrote:

>On 26/09/2026 10:13 am, john larkin wrote:
>> On Fri, 25 Sep 2026 15:58:05 -0000 (UTC), David Lesher
>> <wb8foz@panix.com> 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.
>> 
>> Probably diode reverse recovery, although I don't see why they would
>> care to rectify.
>> 
>> Is this a resistive water heater? That's very inefficient.
>
>Tankless implies instant heating, which uses a lot of power. It is 
>remarkably efficient, in that you don't waste any of the energy keeping 
>the environment around storage tank warm. 

We leave the heat on here all year. I just heard it kick on.  So heat
leakage from our gas water heater, and heat leaking into the house
from hot-water pipes, or heat from gas cooking, are all good.

San Francisco is planning to require all new water heaters to be heat
pumps, so I just had our gas heater replaced with a really good one.
And I plan to replace the sacrficial anodes every few years.

I've never talked to a plumber who had heard of sacrificial anodes!


You'd get more heat per watt 
>if you used a heat-pump, but you have to collect most of that heat from 
>the environment, which is slow and call for bulky heat-exchangers.
>
>Sharp spikes at the peaks of the positive and negative cycles doesn't 
>necessarily imply diode rectifiers - if they just connected to the main 
>only at the peaks of the cycles you'd get the same kind of brief current 
>spike.
>
>It's totally incompetent design - everybody should know how to do power 
>factor correction - but the extra components cost money, and tankless 
>water heaters are strictly from hunger.

A resistive heater has unity power factor.


John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics

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#748260

On 27/09/2026 2:10 am, john larkin wrote:
> On Sat, 26 Sep 2026 16:39:22 +1000, Bill Sloman <bill.sloman@ieee.org>
> wrote:
> 
>> On 26/09/2026 10:13 am, john larkin wrote:
>>> On Fri, 25 Sep 2026 15:58:05 -0000 (UTC), David Lesher
>>> <wb8foz@panix.com> 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.
>>>
>>> Probably diode reverse recovery, although I don't see why they would
>>> care to rectify.
>>>
>>> Is this a resistive water heater? That's very inefficient.
>>
>> Tankless implies instant heating, which uses a lot of power. It is
>> remarkably efficient, in that you don't waste any of the energy keeping
>> the environment around storage tank warm.
> 
> We leave the heat on here all year. I just heard it kick on.  So heat
> leakage from our gas water heater, and heat leaking into the house
> from hot-water pipes, or heat from gas cooking, are all good.
> 
> San Francisco is planning to require all new water heaters to be heat
> pumps, so I just had our gas heater replaced with a really good one.
> And I plan to replace the sacrficial anodes every few years.
> 
> I've never talked to a plumber who had heard of sacrificial anodes!
> 
> 
> You'd get more heat per watt
>> if you used a heat-pump, but you have to collect most of that heat from
>> the environment, which is slow and call for bulky heat-exchangers.
>>
>> Sharp spikes at the peaks of the positive and negative cycles doesn't
>> necessarily imply diode rectifiers - if they just connected to the main
>> only at the peaks of the cycles you'd get the same kind of brief current
>> spike.
>>
>> It's totally incompetent design - everybody should know how to do power
>> factor correction - but the extra components cost money, and tankless
>> water heaters are strictly from hunger.
> 
> A resistive heater has unity power factor.

But we haven't been told how Rheem went from mains AC to to the current 
that they put through their resistive heaters. It won't have been 
through a 50Hz mains transformer - higher frequency transformers are 
much cheaper and more compact.

The power factor of the resistive heater isn't going to be all that 
relevant.

-- 
Bill Sloman, Sydney

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#748317

On 27/09/2026 07:32, Bill Sloman wrote:
> But we haven't been told how Rheem went from mains AC to to the current 
> that they put through their resistive heaters. It won't have been 
> through a 50Hz mains transformer - higher frequency transformers are 
> much cheaper and more compact.

Apparently they use a Triac so that they have full control over the 
power fed into the heaters. The control system seems to attempt to make 
a kind of PID control loop to keep a constant temperature no matter what 
the flow rate is.

That does explain the large spikes, potentially one every mains half cycle.
That kind of control system really needs a lot more than a ferrite to 
reduce spurious emissions.

-- 
Brian Gregory (in England).

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#748332

Good points! But for tankless heating, the conventional PID is too sluggish to regulate temperature against potential inlet flow rate and temperature changes that can occur abruptly.

Feed-Forward Calculation (The Bulk Adjustment): Internal flow-rate sensors and inlet temperature thermistors instantly measure real-time changes. Before the water even reaches the heating elements or heat exchanger, the board uses a feed-forward equation (Power = Flow × Δ T × Constant) to calculate roughly 90–95% of the raw energy required to meet the set point.

 Once the feed-forward mechanism gets the temperature close to the target, the PID feedback loop steps in. It continuously samples the output temperature sensor and dynamically adjusts or "trims" the remaining percentage of power to account for residual errors or system inefficiencies, holding the target output precisely.

It's all digital.

-- 
For full context, visit https://www.electrondepot.com/electrodesign/ferrite-id-4411649-.htm

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#748342

On 30/09/2026 5:15 am, someone wrote:
> Good points! But for tankless heating, the conventional PID is too 
> sluggish to regulate temperature against potential inlet flow rate and 
> temperature changes that can occur abruptly.
> 
> Feed-Forward Calculation (The Bulk Adjustment): Internal flow-rate 
> sensors and inlet temperature thermistors instantly measure real-time 
> changes. Before the water even reaches the heating elements or heat 
> exchanger, the board uses a feed-forward equation (Power = Flow × Δ T 
> × Constant) to calculate roughly 90–95% of the raw energy required to 
> meet the set point.
> 
> Once the feed-forward mechanism gets the temperature close to the 
> target, the PID feedback loop steps in. It continuously samples the 
> output temperature sensor and dynamically adjusts or "trims" the 
> remaining percentage of power to account for residual errors or system 
> inefficiencies, holding the target output precisely.
> 
> It's all digital.

It can be. That used to be an expensive option. Sampling takes time and 
imposes a delay, and doing it quickly enough used to be even more expensive.

-- 
Bill Sloman, Sydney

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#748348

On Wed, 30 Sep 2026 17:24:47 +1000, Bill Sloman <bill.sloman@ieee.org>
wrote:

>On 30/09/2026 5:15 am, someone wrote:
>> Good points! But for tankless heating, the conventional PID is too 
>> sluggish to regulate temperature against potential inlet flow rate and 
>> temperature changes that can occur abruptly.
>> 
>> Feed-Forward Calculation (The Bulk Adjustment): Internal flow-rate 
>> sensors and inlet temperature thermistors instantly measure real-time 
>> changes. Before the water even reaches the heating elements or heat 
>> exchanger, the board uses a feed-forward equation (Power = Flow × Δ T 
>> × Constant) to calculate roughly 90–95% of the raw energy required to 
>> meet the set point.
>> 
>> Once the feed-forward mechanism gets the temperature close to the 
>> target, the PID feedback loop steps in. It continuously samples the 
>> output temperature sensor and dynamically adjusts or "trims" the 
>> remaining percentage of power to account for residual errors or system 
>> inefficiencies, holding the target output precisely.
>> 
>> It's all digital.
>
>It can be. That used to be an expensive option. Sampling takes time and 
>imposes a delay, and doing it quickly enough used to be even more expensive.

I think the cheapest ARM microcontroller is about 8 cents. It can
probably compute fast enough to handle running water.


John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics

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#748359

All tankless heaters have minimum flow rates that must be detected before they activate the heater. The most common limit is around 1.5 GPM, although some are higher, some are a bit lower at 1 GPM. So flow rate measurement is a fundamental capability they all have anyway.

If you hang an inductive reactance at the input to limit the interference, you will almost certainly have to rework the thyristor snubber network, or face serious consequences ranging anywhere from component failure to loss of turn-off commutation (not good at all).

Since it's a 40-Amp circuit, the filter solution will be pricey. But a $150 self-contained and NEC compliant device wired between the line and heater is cheap compared to what a false-economy alternative solution ends up turning into, and the performance is much better.

-- 
For full context, visit https://www.electrondepot.com/electrodesign/ferrite-id-4411649-.htm

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#748261

On 27/09/2026 2:10 am, john larkin wrote:
> On Sat, 26 Sep 2026 16:39:22 +1000, Bill Sloman <bill.sloman@ieee.org>
> wrote:
> 
>> On 26/09/2026 10:13 am, john larkin wrote:
>>> On Fri, 25 Sep 2026 15:58:05 -0000 (UTC), David Lesher
>>> <wb8foz@panix.com> 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.
>>>
>>> Probably diode reverse recovery, although I don't see why they would
>>> care to rectify.
>>>
>>> Is this a resistive water heater? That's very inefficient.
>>
>> Tankless implies instant heating, which uses a lot of power. It is
>> remarkably efficient, in that you don't waste any of the energy keeping
>> the environment around storage tank warm.
> 
> We leave the heat on here all year. I just heard it kick on.  So heat
> leakage from our gas water heater, and heat leaking into the house
> from hot-water pipes, or heat from gas cooking, are all good.
> 
> San Francisco is planning to require all new water heaters to be heat
> pumps, so I just had our gas heater replaced with a really good one.
> And I plan to replace the sacrficial anodes every few years.
> 
> I've never talked to a plumber who had heard of sacrificial anodes!

Intelligent plumbers have been warned off?

> You'd get more heat per watt
>> if you used a heat-pump, but you have to collect most of that heat from
>> the environment, which is slow and call for bulky heat-exchangers.
>>
>> Sharp spikes at the peaks of the positive and negative cycles doesn't
>> necessarily imply diode rectifiers - if they just connected to the main
>> only at the peaks of the cycles you'd get the same kind of brief current
>> spike.
>>
>> It's totally incompetent design - everybody should know how to do power
>> factor correction - but the extra components cost money, and tankless
>> water heaters are strictly from hunger.
> 
> A resistive heater has unity power factor.
> 
> 
> John Larkin
> Highland Tech Glen Canyon Design Center
> Lunatic Fringe Electronics

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#748300

If you go heat pump, get the dual with electric resistance heater backup.

NIST just patented a design for a heater that maintains water in the tank at 160F so as to kill Legionella, and then cools it by about 40F as it enters the external pipes by exchanging outgoing water with incoming cold water.

-- 
For full context, visit https://www.electrondepot.com/electrodesign/ferrite-id-4411649-.htm

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#748303

Rheem is one of the better manufacturers. They use a sophisticated heat exchanger to maximize the heat transfer and response time. There are many more considerations you're not aware of ranging from engineering, science, available technology, lifetime of components under myriad operating conditions ( not least of which is water chemistry), market acceptance, profits, etc., etc. In the U.S. right now, you have electric resistance, gas flame, heat pump, solar, and that's about it.

-- 
For full context, visit https://www.electrondepot.com/electrodesign/ferrite-id-4411649-.htm

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#748302

As far as I can determine, Rheem uses TRIAC cycle-by-cycle phase angle control to modulate the power level delivered to the heater using temperature sensor feedback. They justify this based on the belief that all the other devices in the system should be filtered from the conducted interference they produce by design. Their phase angle control puts the interference spectrum in the high-frequency bands, so that reasoning makes sense. Another consideration is that for fast response the heater doesn't have a huge amount of thermal mass/ capacity, thereby requiring a higher frequency phase angle approach to power modulation so as to make the temperature fluctuations imperceptible to the user.

AI links to this Schaffner EMI filter as a possible solution, 45A and 250V :
https://www.digikey.com/en/products/detail/te-connectivity-schaffner/FN2410-45-33/1928935

There are others, but more people sell and use this manufacturer.

It should be available on eBay for about the same price $150.00.
Datasheet is here:
https://www.te.com/commerce/DocumentDelivery/DDEController?Action=srchrtrv&DocNm=FN2410_and_FN2412&DocType=Data%20Sheet&DocLang=English&DocFormat=pdf&PartCntxt=CAT-P97-F2410

The hard part is the CISPR 17 Filter Attenuation curves. Schaffner has a write-up here:
https://docs.rs-online.com/2ede/0900766b815239a0.pdf

The water heater is a non-linear 6-ohm, and suprisingly the typical line feed is asymptotic to 50-ohm at high frequency ( so say the LISN practitioners). My guess is the CISPR 17 50/50 asymmetric curve applies, Curve B. And then, based on their write-up of the CISPR 17, the actual application should do no worse than 20dB, making the attenuation at the troublemaking frequencies nearly 60 dB.

-- 
For full context, visit https://www.electrondepot.com/electrodesign/ferrite-id-4411649-.htm

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#748226

On 9/25/26 16:58, 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?
> 
> 
> 

First, need to define the rise time and shape of the spike,
to work out how much inductance is needed to filter it, along
with any caps at the supply side, for low pass filtering. You
could also try separating the feed to the heater, from
everything else, to reduce voltage drop effects. 40 amps is
pretty high current for a domestic setup, though electric
showers often match that, or more.

Sounds like a poor quality emc side of the design though.

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#748297

On 26/09/2026 8:57 pm, Ian wrote:
> On 9/25/26 16:58, 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?
> 
> First, need to define the rise time and shape of the spike,
> to work out how much inductance is needed to filter it, along
> with any caps at the supply side, for low pass filtering. You
> could also try separating the feed to the heater, from
> everything else, to reduce voltage drop effects. 40 amps is
> pretty high current for a domestic setup, though electric
> showers often match that, or more.
> 
> Sounds like a poor quality emc side of the design though.

Absolutely. Screwing up light dimmers is vandalism. Sticking on 
arbitrary inductance and seeing if it makes a difference is a perfectly 
respectable way of starting to get to a better engineered solution, and 
if it does stop the light dimmers from going beserk without needing all 
the work a a well-engineered solution would take, it is a cheap way to 
get there.

There's a lot to be said for a bit of quick and dirty tinkering to get a 
clearer idea of what's going on. It works a lot better if you know what 
you are doing and have the kind of diagnostic tools that let you see how 
much difference your tinkering has made, but you can get lucky.

-- 
Bill Sloman, Sydney

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#748298

Bill Sloman <bill.sloman@ieee.org> Wrote in message:r
> On 26/09/2026 8:57 pm, Ian wrote:> On 9/25/26 16:58, 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?> > First, need to define the rise time and shape of the spike,> to work out how much inductance is needed to filter it, along> with any caps at the supply side, for low pass filtering. You> could also try separating the feed to the heater, from> everything else, to reduce voltage drop effects. 40 amps is> pretty high current for a domestic setup, though electric> showers often match that, or more.> > Sounds like a poor quality emc side of the design though.Absolutely. Screwing up light dimmers is vandalism. Sticking on arbitrary inductance and seeing if it makes a difference is a perfectly respectable way of starting to get to a better engineered solution, and if it does stop the light dimmers from going beserk without needing all the work a a well-engineered solution would take, it is a cheap way to get there.There's a lot to be said for a bit of quick and dirty tinkering to get a clearer idea of what's going on. It works a lot better if you know what you are doing and have the kind of diagnostic tools that let you see how much difference your tinkering has made, but you can get lucky.-- Bill Sloman, Sydney

I have an isobar power tap that I use for such occasions.  Have
 been told in the past,  that's not going to work.
 
But it works like s charm every time.

Cheers
-- 


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#748367

Those things are using cheap MOVs. I know from personal experience that they work, but you're subjecting those components to continuous conduction clamps of unknown intensity, which disqualifies them as a permanent solution. MOVs have super-sounding peak energy ratings, but their steady-state RMS ratings are pathetic. They're intended for infrequent transient pulse clamping, not a cycle-by-cycle load.

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