Do UPSes protect from surges under this scenario?

OK, under a typical scenario, you may have some equipment plugged into a UPS, and when there is an electrical surge, it goes through the UPS's power cord to the UPS and then gets stopped there. So it basically protects everything "behind" the UPS from "outside" surges.

But do UPSes prevent surges that occur "behind" it from damaging other connected equipment? Here's a scenario:

- some equipment is plugged into a UPS

- one of those components is a cable modem. (this is so that the cable modem can still function during a power outage, as the cable line would still be functional.) Let's say that the UPS does not have coax protection, so the coax on the cable modem goes directly into the wall.

If a surge were to occur on the cable line (and this must be possible since some surge protectors and UPSes offer coax protection), then it might go through the cable modem, the cable modem's power cord, and then hit the UPS. Would the UPS stop this surge from harming the other connected equipment?

Reply to
void
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You are making so assumptions that even the UPS manufacturer does not make. However he 'shorts' you enough facts so that you will 'assume' as you have.

Will the UPS stop, block, or absorb what even 3 miles of sky could not? Is that silly little one inch component going to stop all that? Of course not. Effective surge protectors do not stop, block, or absorb surges. They do as Ben Franklin demonstrated in 1752. This is all explained in greater detail in: "Opinions on Surge Protectors?" on 7 Jul 2003 in the newsgroup alt.certification.a-plus at

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or "Power Surge" on 29 Sept 2003 in the newsgroup alt.comp.hardware at
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(changes to Google for worse means technical discussion only starts at second group of posts starting with post 11). For many other technical sources: "strange problem after power surge/thunderstorm" in comp.dcom.modems on 31 Mar 2003 at
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(changes to Google for worse means technical discussion only starts at second group of posts starting with post 6).

Even many cable companies are now teaching their installers these installation requirements. A surge protector is not protection. Furthermore cable requires no surge protector. The cable must connect to surge protection before cable even enter the house. No surge protector required because connection is made using a copper wire. Same applies to every incoming utility including telephone line (telco provides the protector that is connected to protection) and AC electric.

The most common source of modem destructive surges seek earth ground by striking wires on telephone pole, entering building, passing through computer and/ or modem, and then obtaining earth ground on cable. Even worse, the naive say the modem was damaged; therefore the surge must have entered on cable, damaged modem, then stopped.

If surge enters on modem and has no path to earth ground via some other wire, then no complete electrical circuit exists. No incoming AND outgoing path through a modem or computer means no surge damage. Even worse, the plug-in UPS can make surge damage to an adjacent computer even easier. Notice a wire they would have you forget. That green wire bypasses UPS protector to make a direct connection to motherboard and chassis plate. Where is the protection to stop or block that path?

Just another example of what the UPS manufacturer forgot to mention to get you 'to assume' mythical protection. Protection is about earthing every utility wire to a single point ground - either by direct wire of via a surge protector

- before that wire can enter the building.

In the meantime, if anything in your building is creating destructive surges, then the first thing destroyed would be the surge generator. Also destroyed are smoke detectors, dishwasher, dimmer switches, clock radio, etc. Where are these destructive transients from household appliances? Why are we not trooping to the hardware store every week to replace these damaged appliances? The internal generated surge is a myth. One way to suspect a myth: they don't even provide numbers. Notice the so many numbers also provided in those previous discussions.

Surge protecti> OK, under a typical scenario, you may have some equipment plugged

Reply to
w_tom

Why do so many people think that you are wrong?

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Reply to
void

Because they are not well grounded in basic electrical theory.

Reply to
Boris Mohar

You could always place a surge suppresser such as this at your groundblock, which would help. But nothing will give you 100% protection. Went to a house once where the TV set in a detached building (workshop) fried. The surge created during that event fried the surge protector, which had a CATV drop connected to it. The surge traveled up the drop to the house, where it proceeded to fry the drop amp and melt the coax inside the wall and ceiling 'til it got to the groundblock, where it went to ground.

True, that was just a surge strip, but I don't see why there isn't the same potential with a UPS.

CIAO!

Ed

snipped-for-privacy@no.spam.com wrote:

Reply to
Ed Nielsen

No, it does not protect the protected from one another.

There are a few high end systems that have 'three way protection' that may protect the equipment from one another. - RM

Reply to
Rick Merrill

Not all UPS devices do this. Check the specs for the equipment you have (or will purchase). Look for over-voltage protection and noise filtering. The only thing that some simple UPSs will do is to switch to backup battery power when the line voltage drops below some threshold.

It might be less expensive to put each piece of suspect equipment on its own UPS.

What kind of equipment are you worried about creating a voltage surge. I would only expect that from a large inductive load, like a motor.

Reply to
Bob Haar

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