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Battery Backup - Get One
4wd:
Almost all 'cheap-o' surge suppressors I've seen, (or have), use MOVs because they're cheaper than circuit-breakers. A typical cheap surge suppressor circuit is, (taken straight off one I just pulled apart): -4wd (June 07, 2009, 10:20 PM)
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That circuit is incorrect. View MOV datasheets. Leakage currents are well below 1 ma. An LED requires at least 10 ma. Furthermore, 1 milliamp through an MOV is a test current for its threshold voltage - a voltage well above what should be on AC mains.-westom (June 07, 2009, 10:44 PM)
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Aaargh! You're right, next time I'll grab some glasses - corrected circuit:
Battery Backup - Get One
Circuit breaker does nothing for surge protection for so many reasons. CB is a device required for every power strip – with or without protector circuits. Installed only for human safety.
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ummm, yes - as I stated.
Your assumption is that the MOV can fail catastrophically. As repeatedly noted, that is not an acceptable failure mode.
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No offence but while it may not be an acceptable failure mode, it is a fact of life. Everything is subject to catastrophic failure no matter how well engineered or designed it is. The fact that something hasn't failed catastrophically is simply due to not having the right circumstances in place for it to occur.
EDIT: And as a side note, it shows you how cheap they make these things because that really isn't a good way to power an LED from 240V - the resistor dissipates for more power than is necessary all because they don't want the added expense of a mains-rated capacitor.
westom:
No offence but while it may not be an acceptable failure mode, it is a fact of life. Everything is subject to catastrophic failure no matter how well engineered or designed it is. -4wd (June 08, 2009, 01:05 AM)
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And airplanes don't crash. Why is an airliner crash international news? Because the event is so close to zero as to be virtually zero.
Catastrophic failure is unacceptable because house fires are unacceptable. Still, they happen. So we installed things that 'virtually' do not suffer catastrophic failure - ie 'whole house' protectors. And locate them where failure is less likely to create fire - ie service entrance. Plug-in protectors have a (relatively) high failure rate (which is why another international standard is forthcoming) and get located where fire risk is higher.
Why is that failure rate so high? Failures promotes sales. "My protector sacrificed itself to save my computer." Some protectors are designed to maximize profits - not protection. Take a $3 power strip. Add some $0.10 parts. Sell it for $25 or $150.
Anything they can do to make that fuse trip faster means less fire threat - and even more promoting the protector. But limits exist. If the fuse blows too easily, then it does not even quality as a protector in UL or equivalent 'human safety' testing.
Meanwhile, your fuse must be in the wrong spot. That thermal fuse must extinguish a light when it blows. More often, that light is a Neon glow lamp. Easier to power on 240 volts.
OldElmerFudd:
Truly interesting discussion. Thanks, everyone!
I've been using a Cyberpower CP1500 with the LCD screen for the home office machines, and an APC BR1500 for the server. Both have been running without problems for the last couple of years. I keep an older APC 850 to use with a machine dedicated to audio work; there's seldom any load on it. I've had battery backups since I built my first 486 machine, and yes, surge protectors as well.
Lightning isn't the issue here in Los Angeles; I'm more concerned with having equipment bolted down when the ground shakes!
Tinman57:
Let's see, my electric goes through three fuse boxes, my computer system is on a battery backup plugged into a voltage regulator to prevent the battery backup from constantly switching from online to offline while on generator power. I think I'm pretty well protected... ;)
westom:
Let's see, my electric goes through three fuse boxes, my computer system is on a battery backup plugged into a voltage regulator to prevent the battery backup from constantly switching from online to offline while on generator power. I think I'm pretty well protected... ;)-Tinman57 (July 01, 2009, 08:28 PM)
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You may be protected. But your electronics are not. Fuses do not protect electronics or appliances. Fuses only stop fires from happening after the damage has been done. Fuses, circuit breakers, etc are only for protecting human. Even the UPS does not provide and does not claim to provide appliance protection.
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