[RFI] Grounding of A Rinnai RC80HPI Tank Less Water Heater

Jim Brown jim at audiosystemsgroup.com
Fri May 8 21:11:04 EDT 2015

The short answer to your question is that all of that equipment MUST, by 
Code (which carries the force of Law) be grounded by the "Green Wire" of 
the circuit that feeds power to it. In addition, that connection must be 
bonded to all exposed metal parts on the equipment.

But there's a lot more to it than that. First, a connection to earth is 
NOT part of a solution to RF noise problems, but that bonding IS 
important. That's something I would check.

Given the poor condition and/or sloppiness of the power wiring, I would 
look into that, and consider replacing it. It's also possible that 
something is mis-wired there. If you do replace it, buy twisted triplet 
or twisted quad cable from the electrical supply store or the big box 
store. Twisting is great at reducing RFI. 240 volt power must be fed by 
the two "hot" conductors, plus the Green for Ground. Make sure that 
Green is used for GROUND, and NOT for power.  Make sure that Neutral is 
NOT used for Ground. Make sure that Green is not used to carry power.

And from your description, I would mistrust the capabilities of the 
contractor for that tankless heater and find a smart electrician to do 
this work if you are not qualified to do it yourself. I suspect that the 
source of the noise is control circuitry for that unit, but you might be 
hearing it because of bad/wrong wiring.

73, Jim K9YC

On Fri,5/8/2015 4:59 PM, Wm.Glenn Pearson wrote:
> Hi,
> I have a major rfi problem to which I have devoted enormous time
> investigating. I will shortly prepare a query to ask the group once I can
> get my thoughts organized. But I have made several discoveries which may or
> may not be important. I have a Rinnai RC80HPI Tank Less Water Heater which
> was installed several years ago. I discovered that it is not grounded except
> through its outlet ground. The product manual indicates that NEC, ANSI/NFPA
> 70 be referred to for grounding (separate ground)  it or not.
> Even more interesting is that my plumber used long drop cord (sold by Home
> Depot) to its final destination at an outlet box wired to my breaker panel.
> The actual 3 conductor AC cable from the unit is rather poor looking now.
> Furthermore, he had wrapped excess drop cord cable around a nearby natural
> gas conduit and an electrical feeder line. When I move the wrapped bundle
> the water heater started making "squawking noises." I rerouted the drop
> cord.
> This led me outside to investigate our 3 gas Heat and Air Systems to see
> whether or not they were grounded. There is an outside sub breaker box for
> the system with a single fed back to my breaker panel. Today a service man
> was by for the seasonal inspection and so I asked him whether or not the
> units should be tied to a earth ground. He indicated they were depending on
> the ground in the wire back to the panel box.
> The next item along this same line is that we have a commercial
> de-humidifier under our house as well. It too is fed by a long drop cord and
> plugged into the same circuit as the water heater. Its distance from the
> panel box is about 20 feet. The same is true for the water heater as well.
> Over all I have been going thru the process of cutting house power and
> monitoring for problem circuits and devices as I turned each back on. I must
> note that unplugging the heater and de-humidifier has no effect on resolving
> my problem.
> I am of the mind for each device, a separate circuit should have been run
> with its own outlet box. I am unclear with regards to separate grounding of
> the HVAC units. Your thoughts and advice is most appreciated. Hopefully
> shortly I will be able to fill in more of the details of my killer rfi
> problem.
> Thanks,
> Glenn Pearson, WU2G
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