| Sounds reasonable. But Francois Martzloff, who was the US-NIST guru on
| surges, wrote in one of his technical papers
| "The fact of the matter is that nowadays, most electronic appliances
| have an inherent immunity level of at least 600 V to 800 V, so that the
| clamping voltages of 330 V widely offered by TVSS manufacturers are
| really not necessary. Objective assessment of the situation leads to the
| conclusion that the 330 V clamping level, promoted by a few
| manufacturers, was encouraged by the promulgation of UL Std 1449,
| showing that voltage as the lowest in a series of possible clamping
| voltages for 120 V circuits. Thus was created the downward auction of
| "lower is better" notwithstanding the objections raised by several
| researchers and well-informed manufacturers. One of the consequences of
| this downward auction can be premature ageing of TVSS that are called
| upon to carry surge currents as the result of relatively low transient
| voltages that would not put equipment in jeopardy."
I assume the 330 volt level mentioned it pair to 120 RMS volt circuits,
and 660 volts would be the level for a 240 RMS volt circuit. Would his
discussion of 600 to 800 volts them be doubled to 1200 to 1600 volts?
Or maybe his 600 to 800 volt experience is actually _because_
a lot of
electronics are made to work OK on 240 volts international power per
the CE standards he mentions.
If I am running my computer with an autoranging (100-240 volt) PSU on the
120 volt L-N circuit, and some power distribution event (such as a line to
ground fault on a different MV phase) raises it to 150 volts or more, I
won't be worried about that. But if I am running it at 240 volts L-L, the
same event could deliver 300 volts. Tell me just how long a typical PSU
(of the autoranging type) can handle that 300 RMS volts (424 volts peak).
Try running one on 277 volts for a year and let me know if it keeps on
Sure, a single narrow spike at 800 volts is not going to affect a PSU very
much if at all. But some sustained overvoltage might. Big wide spikes
might. Repeated spikes might.
If that voltage is what the UL says is right, and tests for (I presume
they have surge simulation tests under power to verify that MOV devices
don't just open back up under a surge event, etc), then that is what
is needed to get UL listing, which is what is needed to get insurance
coverage in case some distribution overvoltage event I can't prove is
caused by the utility causes my house to burn down. Having my own home
made surge protectors, even if they are supplementary to 240 volt ones
listed by TUV, is not likely to impress the insurance adjuster. It would
be hard enough explaining that the computer is made for 240 volts. All
the rest of it would have to be shown to be made for 240 volts as well.
Now I wonder if UL tests computer PSUs for operation at 240 volts, too,
or just at 120 volts even though specified to be usable at 100-240 volts.
|> or that 240 volts USA-style really has 120 volts between
|> both line wires and ground.
| Certainly true that the operation of the suppressor is not what the
| manufacturer intended.
The only UL-listed 240 volt ones I have seen are the "whole house" type
you plug into a breaker panel. I am considering that as an option to
run my computers on 240 volts, in a subpanel just for the one computer