Mains input surge protection - Page 1
Forum section: electronics / projects

author: trevwhite
author_rank: Frequent Contributor
timestamp: August 06, 2012, 02:51:47 pm
content: Hi AllI have a project that has mains in. This mains will be either 115VAC or 230VAC. I need to add some input surge protection. Whenever I try to find out what to add I get a response. Add the biggest you can afford.I dont really know what is any good. Anyone have any practical hints and tips. I was just thinking of a TVS of some sort across the inputs?ThanksTrev

author: saturation
author_rank: Super Contributor
timestamp: August 06, 2012, 04:03:13 pm
content: https://www.eevblog.com/forum/suggestions/surge-protectors-scams-and-saints/15/For a single branch circuit the simplest method is a plug in SPD. The problem is getting one that is reliable and well made, see the link above. This is preferred in case of failure or it blows, its fairly easy to diagnose and replace. In-wall and other hidden installations become harder to diagnose if it fails unless it has external annunciators, and if the MOV burn there is a fire risk if mounted behind dry wall or similar.If you need junction box protection, most require professional installation but you'll still need branch circuit protection. I think there are discussions of these in the archives and in this NIST brochure:http://publications.usa.gov/USAFileDnld.php?PubType=P&PubID=1329&httpGetPubID=0

author: jahonen
author_rank: Super Contributor
timestamp: August 06, 2012, 04:56:30 pm
content: If you are looking a solution for EMC surge tests, some thermofused VDRs might do the trick, TDK-Epcos typeSIOV-ETFV25K275E4, for example. Thermal fuse is good to have, so the VDR doesn't cause fire in case it starts to overheat due to leakage after getting enough shots of surge pulses. That should do for level 3 protection.Regards,Janne

author: trevwhite
author_rank: Frequent Contributor
timestamp: August 07, 2012, 08:19:49 am
content: Thanks for the replies.The EFTV25 looks a possible. Thanks.

author: saturation
author_rank: Super Contributor
timestamp: August 08, 2012, 02:26:09 pm
content: A very nice part, I like the integrated fuse and sensor pin all in one package. More data here:http://www.element14.com/community/docs/DOC-1445/l/overvoltage-protection-with-new-epcos-thermofuse-varistors

author: trevwhite
author_rank: Frequent Contributor
timestamp: August 11, 2012, 11:53:16 am
content: It does seem really difficult to gauge what surge protection to use and how much to spend on it. What do companies like Belkin put in there 4 way extension leads? They offer 25 years guaranteed protection. They must have it sorted.Trev

author: SeanB
author_rank: Super Contributor
timestamp: August 11, 2012, 12:08:44 pm
content: What Belkin and the others rely on is user apathy, as they place VDR's across the power line, and then hope that they sell enough so that the return or warranty rate is well below the cost of the replacement units. Using a fused VDR disconnects and then most throw it away and do not claim, as they either have lost the warranty slip or have forgotten it has a warranty.

author: saturation
author_rank: Super Contributor
timestamp: August 11, 2012, 03:07:51 pm
content: Yes, if you read the link I placed in the thread that is a common ploy; the likelihood of a surge protector blowing is fairly small, I've had only one blow in 20 years, and it wasn't in my home. By the time it does work or worse, not work and the owner attempt to claim the warranty, the owner probably cannot provide the original receipt, and the new models are probably cheaper than dealing with the claim paperwork.I called APC several years ago to claim a 10+ year old damaged PER7 to see what happens, you can find photos in eevblog archives, and without asking twice, sent me a new one in the mail, before I could even mail the old one back. They tell me they post mortem the damage to see what happened. I had to pay $6 to ship the unit back.The equipment warranty is another item, and if you claim the unit failed to protect your gear from damage, the paperwork is a lot, and you have to ship the damaged item to them for inspection: that alone can cost a lot depending on the weight of the item.You can think of surge protectors like fuses, how do you know it works or doesn't until it fails to work, or does works? Unfortunately, testing is destructive. So you go only by reputation, or by tear down and examining the construction, or do a destructive test.I would recommend you buy industrial brands or for consumers, only APC, which is the consumer arm of the industrial brands of Schneider Electric. You can find similar equivalents in your country. The reason is, power devices is their core business, and they know it well.If you know your electronics, whatever you buy I would tear down and examine the construction. If the units are glued or heat welded shut, I would not buy that brand, which is typically Belkin or Philips and other no names. There are reasons you don't what them that way for surge protection, suffice to say you cannot open them, examine them, and return them to the store if found dubious.Tripp Lite is a reputable name in surge protectors, but I tore down one unit many years ago and was appalled by the quality. So, although they continue to sell their reputable isobar at a premium price, I would prefer APC, as I've torn down about 8 of their models, and all are consistently high quality, and well designed.Quote from: SeanB on August 11, 2012, 12:08:44 pm