I have a surge protector that my computer is plugged into. The wiring fault light is on. Is this equipment grounded? Does the surge protector do it's job if it is not? I also have 2 prong outlets in half the house ( I rent ) can a powerstrip or a surge protector protect me in a case of a lighting strike. I thought they only come in 3 prong. A little dispute with my Landlord over this, he is saying that a 2 prong outlet is grounded and that I should buy a powerstrip or surge protector to protect all of my electrical equipment. I will if you can tell me that I could get one that will go in a 2 prong outlet.
Thank you.

labman

Older buildings were wired up with metallic boxes and conduit or flex which was grounded. Newer houses usually use 2 conductor with ground, non metallic cable. The frame of outlets and switches are connected to the ground wire, grounding the third prong. In standard 120 volt circuits, the black is hot, and the white is grounded. In older work, the metal boxes are grounded, and you can install 3 prong outlets which will be grounded. You can also instal 3 prong adapters and have a grounded third prong if you use the cover plate screw to ground the little metal tab on the adapter as it is designed to. Yeah, maybe you never saw one that way, but that is how they are supposed to be used.

For a time, maybe the 60's, houses were wired up with non metallic cable that did not have the ground wire. I know no easy fix for that. You can install 3 prong outlets that accommodate 3 prong plugs, but they are not grounded. You might even find outlets in a plastic box fed by a grounded cable where the ground wire wasn't connected to the outlet. May not be connected anywhere else either.

They make nifty little testers that you just plug into a 3 prong socket and LED's tell if it is wired correctly. You can also check it with a voltmeter or test light. With the third prong on the bottom, you should have about 120 volts between both it and the slot on the left, and the slot on the right. The left slot and the third prong should have no more than a volt or 2 if any voltage. Same for a 2 prong outlet and the cover screw. It is also possible for the ground and hot wires to be reversed.

If your outlets are not grounded, you can remove them, and look for an unconnected ground wire. You can do that with the power on as long as you are very careful not to touch the screws on the side. That could kill you. Newer outlets have a green screw in the metal frame. If not, you can still make do by putting the ground wire under where the frame screws to the box. If you have non metallic cable without a ground, about all you could do is attach a ground wire to a metal water pipe.

Getting back to surge protectors. Most are varistors based, a device that acts as an open up to a certain voltage and then acts as a conductor. Good ones have 3 varistors, one between the 2 conductors and one from each to a ground. If yours is a cheap one with a single varistor between the conductors, it doesn't matter if the third prong isn't grounded.

Some of the above doesn't meet current code. The code allows anything that met the code at the time it was installed. The national electric code may not require your landlord to upgrade to modern standards. I am not sure what you can do if the electric system is not properly grounded. Safest thing is to move. In the mean time, avoid touching anything with a metal housing and something grounded such as the sink, at the same time.

Press2Esc

Yes, the equipment is "grounded". 2-prong plug do not have a non-current carrying path to ground. Thus electrical shorts & spikes (storms) have no dedicated, low resistance path to ground. Therefore, equipment damage and electrical shock are a result.

Concerning your common 3-prong surge protectors. Cheapies are better than nothing & they do work well with 2 prong plug outlets. The technology used in the cheap protectors inherently are subject to destruction. Check them often for damage/replacement.

P2E

labman

''The technology used in the cheap protectors inherently are subject to destruction. Check them often for damage/replacement.'' Any simple way to do that without a failure risking stress? I have several I built that may be 20 years old I wonder if I should trust?. Byte printed a article telling how. Back then, you could go to Radio Shack and buy varistors for less then $2. After loosing a $300 board in my furnace a few year ago, I had to order them from Mouser. Cheap things came with a notice saying they were not suitable for use in atomic power installations. Fortunately my furnace is gas.

Maybe the cheapest thing is to just order more from Mouser and replace them.

Press2Esc

By design, MOVs operate under extremely stressful conditions whereby they obsorb high voltage transients (ESD) that can occur as fast as 500ps (1/500000000000000 of a second). Under normal opearation, they act as open circuit, when they see a surge (e.g., lightening), they change to a very low impedance (short) to obsorb the damaging transient currents and voltages. Essentially MOVs act as an electronic, auto reseting circuit breaker of sorts. To increase their current (heat) handling capabilities, several MOVs are usually connected in parallel. (Additionally, they can also be connected in series to increase voltage range). For the techies, they act as back-2-back zenors.

Test/Replacement: Without AC test equpment, replacement/failure of surge protectors is virtually impossible. Also, because of the are designed to work under random & extreme conditions, vendors typically do not publish anything concerning a recommended replacement schedule... Howerver, I know of one MOV mfg'r who publishes a recommended period for Grade A (best) MOVs of 10 years. As of 1996, Grade A MOVs are spec'd and tested to meet/exceed 1000 surges of 3000amps @ 300volts. To put some of these values in perspective, a typical house in the US is supplied with 240V @ 100-200A TOTAL service capacity.

Recommendations: For reasons mentioned above ALWAYS buy protectors that have a power indicator light that display the "health" of the protector. Also, in the US, make sure your surge protector has a UL Listing (UL1449, Feb98). This "seal" ensures the product meets the UL's quality & reliabilty test standards.

P2E

m3rdpower

Thank you all for the info. I will look into what kind of boxes I have and see what I can do. Will buy more surge protectors ASAP.
Thanks Again.
M3