i cannot understand how most surge strips can be safe. p

[hurk27]

Re: i cannot understand how most surge strips can be safe. p

Awwt most microwave ovens some TV's and even a few stereo receivers have a mov in them but the manufacture places them before the fuse this way they will know if the damage to the appliance was done by ether a lost neutral or someone miss-wiring it to 220v when it called for 120 volts. this way they can refuse a warranty claim.

[ September 17, 2003, 01:26 AM: Message edited by: hurk27 ]

 

[rong111]

Re: i cannot understand how most surge strips can be safe. p

dereck, sorry i used the wrong terminology again.

i meant that there is voltage present on some of the older surge strips between the green wire and the white wire. the radio shack outlet tester finds an open ground or a floating ground on these units also. my homes electric service is fine(no voltage present on conduit to white here).
don't worry though, these units are now in the garbage and have been replaced by isobar's today! thanks for the information about them.

also, i have seen ups's for about $450 that are "line interactive" and use an "advanced" "synthetic" sine wave. they have "avr" auto-voltage-regulation. and do not go to battery in the 75v.-145v. range. aps makes one of these called back-ups pro. is this alright for a (expensive) home computer? how can i know beforehand if a unit that does not have true sine-wave will ruin my machine? i know a motor can only run on true sine-wave. but computer switching power supplys should usually be ok? or will it kill it early? the only problem is that the true sine-wave units are over $600. that seems like a steep price for a home computer.

ron g.

 

[rong111]

Re: i cannot understand how most surge strips can be safe. p

i just noticed something pretty bad about ups's under $600! even though my computer is in my house, it is my cad workstation. the replacement cost of the machine and two monitors is real high. now, these (inexpensive) ups's even though they are line interactive have a total harmonic distortion of anywhere from 20% to over 30%! also, they have a single harmonic of more than 20%. i take it that it is a pretty poor idea to hook up equipment valued in the thousands to one of these devices?
i realize it will (probably) run on this load, but it can't be good to provide power that dirty. can it? if i have to spend $600+ on the ups i will(reluctantly).

ron g.

 

[brian john]

Re: i cannot understand how most surge strips can be safe. p

RONG:

Harmonics in access of 20%? Current, Voltage input, output?

What is your concern?

 

[rong111]

Re: i cannot understand how most surge strips can be safe. p

well, one i was looking at had a thd of 30% output on battery. that means that it is no were near sinusoidal output. i realize that a lot of computer equipment can run on a square wave output. but there has got to be a reason all the good ups's feature a true sinewave output. i.e. thd less than 2%. the loads that are on residential current tend to create an output at any given time that is not sinusoidal. from motors compressors etc. still if i measured the harmonics at an outlet i doubt that the ac in my house has 30% thd. these things do not have a very good dc/ac converter. i know that a modern computer can deal with a square wave(usually) but the whole idea was to feed it better current than the poco provides not worse! plus i would think that the cheap ups can ruin the mov that is present in the computers psu. not to mention the capacitors. then their is the monitor, i have heard a unit that provides power that noisy can ruin the crt guns. as usual if i am totally misinofrmed about this, feal free to correct me!


ron g.

 

[brian john]

Re: i cannot understand how most surge strips can be safe. p

Rong:

30% voltage THD or 30% Current THD?

Big difference between the two.

As for your question regarding, damage to the PC, monitors etc. NO CLUE. But many smaller data centers are now utilize multiple small "cheap" UPS's in lieu of one large UPS. I don't necessarily agree with this philosophy for a variety of reasons. But I know of no facility experiencing PC/monitor failure's that are utilizing this multiple small UPS installation.

 

[rong111]

Re: i cannot understand how most surge strips can be safe. p

i honestly do not know if they meant 30% thd for current or voltage. it just says 30% thd and 20% thd single harmonic. now i do know if you step up several models it goes to less than 5% thd. so as usual you get what you pay for. i would imagine the data centers are not using the cheapest ones(hopefully). $600 and over for a 700+va unit will buy a real good one with "pure sine wave output". as far as dual conversion, those are over $1000. i would bet most single machine users do not opt for a dual conversion unit. i am sure the units they do get still work. it is just that under $200 i think people are better off without one. the sub $200 ups's look like they can wreck equipment judging by their specs. i think i will go get a pure sine online unit. the dual conversion seems like overkill. the $200 unit with step wave and 30% distortion(whatever they mean) does not seem like a great idea.

ron g.