View Full Version : Surge Protectors

25-12-2001, 10:00 AM
How do I find out about power surge protectors, balancing cost against performance.
ie, What's the guff!!!

25-12-2001, 11:11 AM
unforunatly there is very little testing done on them. consumer mag did some testing ages ago but most manafactures have changed their products since then.

i would recommend panamax. $150 for the power surge protector and $50 for the telephone protector (roughly). has life time warranty. powercor also make a good one but its $300-$400(last time i looked) the cheaper models are useless.
pdl are known to be ok for a cheap one ($45) but you get what u pay for. hpm...not to sure, earlier ones where shockingly bad.

the panamax telephone protector is far better than the usual middle of the road type. i've seen more dead pc's and house alarms caused by telphone spikes than power spikes.

if you are in a high risk area then a surge/lightning diverter would be advisable. these connect to the incomming mains into the house and divert any voltage above 1000v. note they are not those plug in fuseboard mov type ones.

the only other word of advise is don't beleive the makers specs.

25-12-2001, 10:08 PM
I wouldnt place too much reliance even in the Panamax. I bought one AFTER I had a lightning strike and looked at the innards. There is little common mode surge protection built in, and it could be too slow. Common mode surge is when you get high voltage on both lines relative to earth, thus devices from each line to earth are required to short out high voltage in as little a time as possible before the surge can reach the modem. There are gas arrestors in the unit which will do this but they are too slow for full protection, the other devices are 2 positive temperature coefficient varistors and a high voltage transistor connected as a diode across the lines. To improve on this I added 2 bi-directional transzorb 300 volt transient voltage suppressor diodes with response times of nanoseconds from each line to earth.

The best protection if you are around, is to unplug the modem from the phone lines if a storm threatens, and NEVER have your computer on during a lightning storm. This is from bitter experience.

26-12-2001, 11:11 AM
Unless you live in the boondocks a metal oxide varistor will clip blips of overvoltage, such as we occasionally get here in Wellington with the Cook Strait cable A C converter gear.

If you build your own unit, be sure to fuse the phase leg because MOVs can short out and get very hot.

There is not much you can do for a lightening strike, I see a few modems with shorted input circuits from induced charges and do not believe that line protectors are all that useful.

Dick Smiths presently have an assortment of Zap boxes 'on special' and they are probably sufficient for domestic use.

27-12-2001, 03:20 PM
There are number of problems with protection devices. MOV resistors fail internally -- after a number of hits they go open and there is no protection. There is often no visible sign that the MOV has failed.

These days, with earth leakage circuit breakers used instead of isolating transfomers for outside work the isolating transformers can be picked up cheaply, and will give quite good protection from common-mode surges (lightning etc). They will also give some protection from spike surges because a transformer is a lowpass filter.

A UPS will give you quite a lot of protection.

You should use a gas discharge protector on telephone lines -- you used to get one in the 'master block', but not in the 2 wire system. There is probbaly less zapping on the telephone lines with underground cables, but anywhere with overhead lines is at risk.

29-12-2001, 06:09 PM
In my experience, you can get a decent 400VA UPS, like the Weli or Informate ones, which have modem protection for around $199. thats the same as a decient power board, but with additional features.

Not only do you get surge protection, but also Voltage regulation - which is more important in some areas. Plus shut down software, etc.

Over 60% of PC damage is from incorrect voltages (APC Brochure).

I had a power board, and it fried - now I use a UPS.