On 11/13/2010 8:12 AM, Chuck Shinn wrote:
> I recently found a VERY noisy gas line and connector to my
> tankless water heater which produced as much QRN as any other closely
> coupled wiring or guttering etc. I used large ferrites on my flexible
> conduits and gas line and also snapits on my AC condenser copper
> plumbing to reduce/eliminate the QRN.
Interesting. This means that the gas line is carrying RF current, which
in turn suggests that something is not properly bonded in that
installation. I would carefully study how the power to that heater is
wired. If it's a 220V circult, there should be two hots and a green wire
(ground). If the heater also uses 120V, there should be two hots, a
neutral, and a green wire. The green wire must be connected to the frame
of the water heater. If that wire is missing or not connected properly,
noise will flow on any other conductive path between the heater and ground.
I would suspect similar installation problems when one furnace of a
given make/model is noisy and another is not. Like the Lennox noted in
several posts.
Think about this when chasing noisy appliances like this. All current
flows in some sort of loop that includes its source. If the AREA of the
enclosed loop is small, the magnetic field will be small, so little
noise will be heard. Likewise, when current flows out on one conductor
and back on another that is very close to the first, their EM fields
cancel and there is little radiated noise. Thus, the key is to make
that current loop small by providing a TRANSMISSION LINE to carry that
current. THAT'S why it's so critical to provide a green wire path that
parallels the hot conductors.
Another point. It is not enough to say that Brand A is noisy and Brand
B is not without keeping track of the TYPE of unit. Any unit with a
variable speed motor controller is FAR more likely to be noisy than an
older unit with a conventional motor. It's great that Mel has cited
products by make/model, which makes his info much more useful. Many
thanks, Mel.
73, Jim K9YC
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