VE3WO and I went through a similar situation with
Kidde CO detectors last year, where very low levels of
RF on the low bands were triggering them. We resolved
it in conjunction with two very cooperative neighbours
by replacing the units with battery powered devices.
Kidde were completely unhelpful - they hid behind
their UL approval which included RF susceptibility
tests at a few spot frequencies (with the lowest being
27MHz), and claimed that that was all that was
necessary - even though it was clearly printed on each
unit that they were incorrect. They attempted to blame
Travis' transmitter, and so on. After a while they
just ignored our messages.
My first attempt at correcting the problem had been to
pass the power wires through a toroid - this was
marginally effective but not sufficient - and had no
galvanic connection to the power line.
I am sure that a parallel capacitor and the toroid, or
a filter in line with the unit would have cured the
problem as there is no question that the AC wiring was
acting as an antenna. However, neither Travis nor I
were happy with the idea of fitting even properly
rated capacitors across an AC line on somebody else's
property. That is changing the design of the system,
requires regulatory approval, and cannot possibly
comply with code. I shudder to think of the liability
issues if there were to be an electrically related
fire in that house.
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