Surge protection help needed

If your really worried about protecting them then your going to need 2 areas of protection. One at the panel and one at the unit itself. That is what the IEEE recommends for protection. I realize that you have slightly different standards but not that much different. OR Bite the bullet and put in a big UPS that has voltage regulation and surge protection.

Remember if you have Ethernet going out from where these machines are and going to a machine fed from another panel/source, you can get a difference in ground voltages. If you have this condition please consult a professional. It will be worth the money and time.

Sorry I do not know of a simple/cheap solution

Plug-in UPS does not even claim to protect from the type of transient that damages computers. Any protection provided by that UPS is already inside a computer power supply. Furthermore, the plug-in UPS connects computer directly to AC mains when not in battery backup mode.

Do not assume a surge protector is going to stop, block, filter, or absorb a surge. Simply the urban myth used to promote ineffective protection such as the plug-in UPS. Concepts that will become obvious in newsgroup discussions cited below.

Computer already > We have an office with a spur, single-phase 240v 30A that feeds

What I believe you are talking about is a spark gap device I believe. But let me clue people to one thing. We hear about using a common ground. But that is really wrong when designing electronic equipment. First each circuit, particularly input and output circuits should have their own wire to the common ground. Second in swithching power supplies and other devices that switch. the return wire should be to the switching device and then that loop should be returned to the common ground point with out carrying any other ground currents, so switching current generated voltages are not impressed on other circuitry. This is often a source of ripple and oscillations. I went through this when I had to teach a class at Kennedy space center on how to make measurements between points above ground.

In fact I suggested the use of Battery operated scopes as differntial scopes often did not have enough common mode rejection.

Thanks for that w_toml. Very interesting.

Around where we are lightning strikes are pretty rare, but we can count on a blackout 1 or 2 x per year. I've always unlpugged anything like a PC in these circumstances to avoid the surge when power is reconnected. How much of a concern is the reconnection surge? Does the same rule about effective earthing apply?

Power restoration is a surge of current; not a voltage surge. With so many things taking full power simultaneously, load is just too large to create excessive voltage. Furthermore, appliances must withstand in excess of 600 volts transients. Computer power supplies typically withstand on the order of 1000 volts differential and 2000 volts common mode transients; without damage. If suffering voltages that large when power is restored, then every GFCI, electronic timer switch, clock radio, etc also requires replacement.

Have not observed it, but another possible source of serious comm> Thanks for that w_toml. Very interesting.