Heater and Water Heater RFI Proofing

07 Oct

The other day I mentioned having RF Hot plumbing. I thought I would post a picture of some of my RFI prevention ideas. It is important to remember that I worked on both ends of this natural gas and copper run. When I sniffed the closet on the first day it had Hot RF on both Natty gas and AC copper tubing to the AC air handler mounted above the Trane Heating unit. It was also hot outdoors where the copper entered the AC Condenser unit as well as the Natural Gas entry into the house. I first clamped ferrites all along the copper AC plumbing and also the NG flexi tubing in this closet. Then I went outdoors to the AC unit and it was quiet-a lot quieter than on the previous day, however the Gas Meter end of things was still very RF Hot. Lastly I reattached the loose ground at the Gas Meter end outdoors. I am not sure which element fixed the noise but it has been gone for 2 full days now. I should pull my snap its and see if the noise comes back and may yet do that, but for now I will leave them in place. The RFI problem could have been caused by a rusty bolt or some rusty hardware that I disturbed when putting the ground wire in place. We have a commercial radio broadcast station within a thousand feet of my house and the Gas Meter hardware is rusty. Rusty hardware in the presence of a strong RF Field is essentially a back biased diode and gens up severe RFI broad banded. Strength depends on multiple factors but field strength is pretty important. My sense is that the rusty hardware was not the primary cause as the nature of the RFI was modulated by 60 Hz and had the normal buzzy character. The noise could have been a composite of all of these things as well. The point again is that just because it runs to ground or through ground does not mean it is incapable of carrying RFI. Test everything.

I test for RFI (sniffing) with a cheap shortwave (Yachtboy) and a homemade B Field RF Sniffing loop that has been detailed on this blog several times. Here then is a photo:


Snap its applied to metal plumbing.


Thanks for reading my Blog. Best, Chas W5PG

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Posted by on October 7, 2010 in Radio, RFI


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