Pop` wrote:

Pete C. wrote:
w_tom wrote:

Common mode surges are a most typical source of electronics damage.

useless bogus blather deleted

There you go again with your nonsense.

Care to explain how a common mode surge can damage a device that has
no ground connection?

A device with only two electrical connections, hot and neutral, does
not care in the least what the voltage on these lines is relative to
ground. 0 Volts and 120 Volts or 12,000 Volts and 12,120V look
*exactly* the same to the device. Unless the surge is high enough to
blow through the insulation of the devices enclosure and arc to
ground it is absolutely irrelevant to the health of the device.

Pete C.

I'm not agreeing with the previous post, but ... common mode surges are
rarely only common mode. With all the "stuff" connected to the wires there
is, IME, often an associated longitudinal imbalance in the wires that causes
the 120V relationship to shift, usually not in a 60 cycle pattern (harmonics
and sub-harmonics). If it last for long, the protection elements usually
burn out within a short time and then the voltages make it to the equipment
itself.
The old 600V tubes used on phone wires could withstand it pretty well,
but the electronic and solid state components cannot. That's also why surge
suppressors have lights on them to indicate their operational status:
Although a protector works by shorting surges away from the equipment,
eventually they will "burn out" and become an open ckt to surges. In turn,
that's why the joule ratings on a suppressor are the most important spec.
The more joules it can handle, the longer it can last through a long or a
series of surge/s.
The 600V protection afforded by phone lines, by the way, is why any
decent surge suppressor also includes connections for the phone lines to run
thru. After any serious surge conditions, there are always a plethora of
fax machines, answering machines, modems, etc. etc. being either repaired or
replaced.

Pop`

Clearly a big enough and long enough duration surge i.e. nearby
lightning hit has a good chance of exceeding the capabilities of any
reasonably affordable protection device. My point though was that the
inexpensive suppressers do still provide some protection even if they
don't have a ground and that a true common mode surge of modest
amplitude will have no effect on a device that has no ground connection.

Pete C.