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Tom made me look at this circuit again. I realized that the series diode is
not going to isolate noise all that much. The primary noise will be a
negative 14V spike.  At very high frequencies, when the switch is turned
off, stray capacitance around the wire will tend to hold the wire at +14V
for a very short time. The diode will be forward biased by the -14 volts
from the flyback circuit, so the major noise from the flyback circuit still
gets through to the wire. The diode will isolate any secondary ringing
noise, but that is very minor and probably not very significant. MOV's do
have a little capacitance, not enough to overload the switch contacts, but
enough to dampen the high frequency noise a little. As a result, the -14V
spike that the MOV allows is not going to have a very fast rise time (a
high frequency component), so, I don't think the MOV circuit is going to
need any extra components to help filter out the -14V spike. In other
words, drop the series diode idea, it is not going to help significantly.
Every extra component increases the probability of failure. Diodes usually
fail shorted, but they can on occasion fail open. Keep it simple, the
little noise this series diode will get rid of is not worth the added
complexity. We are stuck with either a low noise parallel diode, or a more
noisy but safer MOV. There is no way that I can think of to really help the
MOV, but it will not be that much more noisy than the diode. Tom suggests
putting all three, the diode MOV and Solenoid in parallel. The diode would
take the full flyback current, and limit the noise to the low 0.7 Volts.
The MOV would limit secondary ringing voltages to 14V. Secondary ringing
voltages would quickly short out the diode if they exceeded 50Volts. This
is a safer way to use the lower noise diode circuit. I think I will use
Tom's idea on my high current inductive loads.

Thanks Tom,
Regards,
Ed.