UPS vs. Surge protection? Can we not have both?
I looked at a manual for an old Back-UPS ES-350, and it didn't say anything about using an external surge protector or not.
Then I looked at a manual for an old Back-UPS ES-750, and it says, "Plug the Back-UPS ES power cord directly into a wall outlet; not a surge protector or power strip."
No explanation. The best explanation so far is from Bill Bright who said "This is because surge protectors often reshape the sine wave which can confuse the UPS."
I can't relate to that. If the voltage doesn't get high enough to cause the surge-protecting components (MOVs -- metal oxide varistors) to conduct, then they are essentially out of the circuit and can't effect the sine wave.
I wonder if Bill might be thinking of UPSs. If the AC goes out and the UPS is supplying AC from its battery storage, they don't deliver a smooth sine wave. Instead, they "build" a quasi-sine wave out of tiny steps, which is like a sine wave with a high-pitched squeal superimposed on it. Things like old CRT TVs and I think some motors didn't like the stepped square wave. I think most things today with switching power supplies, like computers, peripherals, and things that are powered by wall transformers don't care if the sine wave is a total mess. Someone correct me if I'm wrong, but the stepped sine wave seems like less and less of a problem as we get more and more modern, except for some motors, and maybe compressors like in air conditioners.
And I also have a theory about the statement about "no surge protectors or extension cords." I think the UPS manufacturers have the same concern as air-conditioner manufacturers. They just want to avoid voltage drops in skinny extension cords and another set of problematic AC plugs and sockets. But both manufacturing industries could do us a favor and except that if we add a surge protector or extension cord that's rated 15 amps / 1875 watts, then it's not going to do anything to make the UPS or the air conditioner look bad.
Check your newegg.com for surge protectors -- highfalutin extension cords? I don't think so. You can get surge protection on these consumer products at least up to 4000 joules. The few-hundred joules of protection in UPSs are a joke, nothing more than something they can put on the pretty carton to give it more marketing appeal so you'll take it off the shelf. After all, if the other manufacturers are adding surge protection, then they better do it to, or it won't look good. But that's not really the business they're in, so they only give you a token few-hundred joules.
Getting down to brass tacks, my method has been to plug the surge protecting highfalutin extension cord into the wall first, and then plug the UPS into it.
Then, when the lightning bolt causes the MOVs to conduct, and the MOVs short the megawattage to ground, the surge of current for those few milliseconds will come out of the wall, go through the surge protector, and go back into the wall.
But if you plug the UPS into the wall first, and then plug the surge protector into the UPS, then when the lightning strikes and the MOVs conduct, the surge current will have to flow through the UPS -- which has some delicate electronics -- before it can get to the surge protector and be shorted back into the wall, and of course it will have to go through the UPS a 2nd time in the process.
You might ask, in the arrangement where the UPS is plugged into the wall first, what happens to the MOVs in the UPS if there's a surge? Since they are low-joule devices compared to what's inside the surge protector, they would smoke, depending on how harsh the surge is. And then if there is still surge-voltage after the UPS's MOVs have given up their ghosts, then the MOVs in the surge protector would take over. The burnt MOVs in the UPS would smell like fire, but their MOVs burning up would not affect their operation, since MOVs fail "open." Unless they really catch fire...
I've been plugging surge protectors into wall sockets and UPSs into surge protectors for 15 years, and the hardware has never complained. But that doesn't mean I haven't been lucky and that I truly am doing it wrong, so I'll brace myself if anyone cares to tell me where I went astray.
On a tangent, other advantages of the Belkin surge protecting highfalutin extension cords is that they include an integrated AC-wiring test, with an LED to alert you if the wiring is wrong. And they include another LED that alerts you if the MOVs have absorbed too many surges and are no longer firing at their specified voltage, and therefore the highfalutin needs to be replaced. In my barebone-basic UPSs that are almost (half) as old as I am, they don't have either LED function. So, if you're relying on the UPS for surge protection, how do you know that function is still good or not?
In summary, no matter how much lightning protection you build in, there are some lightning bolts that are bigger than any of us, and it won't matter what protection you've instituted -- everything will be vaporized. But lightning isn't the only source of surges, and not all lightning hits you directly in the head, so having as much Joule-protection as possible is obviously the best strategy, and you're not going to get that from the little MOVs they put in UPSs.
It occurs to me that there's another method that will make both sides of the argument happy. Consider that when the surge voltage hits and the MOVs short out momentarily, by definition of "short," the voltage across the MOV is zero, and therefore the voltage between those two wires is zero. If you have a short between two wires so their voltage is zero, then the voltage at the next AC wall-socket a few feet away is going to be really small. The point is that by plugging a surge protector into the wall, there's a whole sphere of house wiring around the highfalutin that is protected from surges.
So my strategy is that I put a 4000 joule surge protector on my computer station. And I put one on each television setup with all their associated delicate electronics. And I found an AC wall socket wired directly to the circuit breaker box in the basement -- I plugged a surge protector into it, even though I don't have anything down there to plug into the surge protector. But the intention is that any surges coming from outside or from any circuit will get stopped by that surge protector and won't be able to find their way to any other circuits. And I check the LED a few times a year to see if it needs to be changed yet. After a couple of years, it's still good. About four 4000 joule surge protectors scattered around the house, preferably on different circuits, should really keep the whole house protected, unless a lightning hits you in the head.
I finally had one surge protector out of a dozen go bad, according to its LED, after about 5 years. Maybe it was a manufacturing defect. Your mileage may vary if you're in a lightning capital like Florida or Kansas, where you might have them fail more frequently.
Oh yeh, my strategy for making everyone happy... Plug the surge protector into the top AC wall socket. Then, plug the UPS into the bottom AC wall socket. That way, you're following the letter of the law by "not using a highfalutin extension cord" on your UPS, and the UPS will enjoy true surge protection when the MOVs two feet away short out the surges.