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Discussion Starter · #1 ·
I need advice on the best surge protectors and grounding adapters for 2 prong low voltage transformers (ranging from 12-24 VAC output) as well as my LAN data lines (RG45). I am told I need to ensure the transformers themselves are grounded in spite of their 2 prong plugs. I have been plagued by surge destruction of numerous circuit boards on all of my systems. I just had the entire house encased in a sophisitcated grounding system and am now trying to isolate individual weak spots.
 

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Transformers don't have "prongs". Male power connectors have prongs. So how about describing the whole application? You're leaving a LOT unsaid.


I'll take a flyer on it, though. Your problem likely has nothing to do with the individual equipment and everything to do with your house wiring. Bad or missing circuit ground, more than one earth ground, etc. Grounding and bonding are simple in principle, so what is this "sophisitcated grounding system" you mention? Sounds like a disaster waiting to happen.
 

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Discussion Starter · #3 ·
I appreciate your reply but I am aware of all you say. I realize transformers have but 2 prongs--that is my point--the transformer itself needs to be grounded according to the consultant who installed the grounding system (he is UL trained, has certifcations from all relevant national and international organizations, has a list of about 200 references around world, including US Dod, DOE, all major oil companies for their offshore rigs etc. with 50 years' experience in Germany and in US for last 20 years).
 

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You should look into whole house surge protectors. These are huge MOV's that install in your breaker box and provide surge protection at the first point a surge would be entering your house.


As for your "wall wart" transformers. The neutral side of standard 120V house wiring is connected to ground in your breaker box, so they are already grounded.
 

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So if you have this hotshot doing your system, why are you asking here?
 

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We really need a more information to help. Just what equipment are you having the failures in? Under what circumstances? Do you get a lot of lightning strikes near you?


I'll assume you have a good grounding system to start with and a surge suppressor at the service entrace. You also need a surge suppressor at sensitive devices because surges can be generated within the structure and can enter the structured other than via the service entrance, and because the service entrance devices usually don't limit surge voltage to as low a level as the local devices. You can achieve reasonable surge suppression for your wall wart transformers by plugging them into a local surge suppressor, either the power strip kind, or the kind that replace the receptacle in the wall.


You also need to protect all other possible entrances to the structure that a surge can take. The most obvious are TV antenna downlead, cable TV cable, satellite TV cable, phone cable. Often overlooked are things like wiring between sprinkler actuators and control, and underground wiring from structure to decorative lighting, spa, etc. A nearby lightning strike can induce a damaging current in underground wiring that can travel back to the control possibly damaging it, and even travel back into the structure damaging other equipment.


You cannot ground a typical plastic encapsultated two prong wall wart transformer. Their encapsulated design means they don't need a ground pin. There are three prong wall wart transformers. All the third prong does is prevent electrocution in case the internal wiring comes in contact with the case and in some cases shunt electrical noise onto the equipment grounding conductor. In any case, grounding the transformer won't do a thing to prevent a surge from destroying whatever it is powering. Actually, transformers are pretty good about protecting whatever is downstream of them. Surges are very short events with short rise time. Transformers designed for powerline frequencies (50 Hz, 60 Hz) don't pass these on very well. Also, you could put a metal oxide varistor (MOV) of appropriately chosen voltage across the output of your transformers.


Just curious... How the heck did you encase your house in a grounding system? Did you build a steel cage around?
 

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If I had to guess, the "expert" is confusing the surge protection device needing a proper ground, and the devices connected to it needing a ground. There is no need for the latter, but absent the former, a surge protector will not function.
 

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Discussion Starter · #9 ·
I appreciate those who offered constructive ideas. The others make it apparent that I should look elsewhere for help. Sorry for the bother to you but I am reminded of sage advice from my grandmother--"if you cannot say something nice (in this case constructive) it may be better to say nothing." Cheers.
 

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Well, you've certainly got the "say nothing at all" part down pat.
 
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