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Re: [RFI] Question Regarding Variations In Solar Panel RFI?

To: Rfi List <rfi@contesting.com>
Subject: Re: [RFI] Question Regarding Variations In Solar Panel RFI?
From: Tony <73guddx@gmail.com>
Date: Fri, 25 Sep 2020 20:03:23 -0400
List-post: <mailto:rfi@contesting.com>
Jim:

Tom Simpson (Solar Edge Engineer) will be visiting the site sometime in the near future so I'm hoping he'll address the potential problems you mentioned.

The issues you describe may also explain why the suppression hasn't been very effective. The noise was 15db over S-9 prior to the suppression being installed and it's now S-9 plus a tad for a reduction of roughly 10db.

This installation may require the methods used by Tony Brock-Fisher which includes chokes between the inverter and mains which is something Solar Edge frowns upon. Not sure if it's a cost or a code issue.

Thanks Jim.

Tony -K2MO





On 9/25/2020 6:49 PM, Jim Brown wrote:
Tony,

There are MANY variables and wiring errors and system layout errors that can contribute to how much RFI is radiated. One issue that Teff communicated to me was that the framing holding the panels was bonded to ground on the other side of the building from the power entry. If this is true, it creates a current loop that could be causing or contributing to your problem.

Wiring can be prevented from radiating by shielding, IF, AND ONLY IF, the shielding is continuous. In the real world that I'm aware of, the only shielded AC wiring is that which is enclosed in steel conduit, that is continuously bonded together. That's quite rare in residences, except in cities like Chicago, where the Electricians Union has it written into the city's Electrical Code as a means of providing more work to Electricians.

Running twisted pair for power can prevent radiation from the current-carrying conductors (phase and neutral), but won't help with common mode RF current, which is nearly always on the green wire. And the common mode current is there because of bonding failures, either in the construction of the equipment itself, or in the installation, or both.

The wiring inside the home could be hot with RF as a result of wiring errors at outlets, at panels (double-bonded neutral), even bonding at equipment. At the home I bought in California, I found an outlet wired with neutral and ground reversed, and I found outlets in the kitchen of a "mother-in-law" garage apartment fed between phase and green rather than phase and neutral. I also found no ground at all at the service entrance -- it was bonded to a hose outlet that was fed by PVC pipe!

73, Jim K9YC

On 9/25/2020 3:22 PM, Tony wrote:
All:

The reports I've read suggest that the strength of interference caused by solar panel systems can vary from one installation to the next EVEN when the distance to the source is similar. That variation could be attributed to radiating conductors tied to the system such as the house wiring.

We found high levels of RFI on the A/C lines throughout my neighbors home and that's likely the case with all Solar Edge installations since there are no chokes between the mains and inverter.

Given those facts, would a large home with long runs of un-shielded Romex produce higher levels of interference compared to a smaller home with shorter runs? Or does the resonance of the wiring play more of a role than length and number of runs?

It's an oversimplification, but it seems logical to consider what's connected to system and not just the system itself.

Tony -K2MO

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