Most large transfer switches have a limited lifetime of forced failovers. The relays arc during the failover, causing pitting of the contacts, and eventually are considered unusable.
For large current failovers, the failover can also generate SIGNIFICANT heat. This can cause additional pitting and even metallic erosion. I've seen it. I believe it. :-) I now always recommend power that is "always on". -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Joseph L. Casale Sent: Thursday, September 29, 2016 3:31 PM To: [email protected] Subject: Re: [NTSysADM] RE: Transfer switches All I can say is if the switch is not being used for a load exceeding its rating, I am hard pressed to believe the contacts would deteriorate like that. I admit I could be wrong, but I'd have to see it with my own eyes to acknowledge it:) jlc ________________________________________ From: [email protected] <[email protected]> on behalf of NP <[email protected]> Sent: September 29, 2016 1:07 PM To: [email protected] Subject: RE: [NTSysADM] RE: Transfer switches I've have used various models of these for years and never had an issue, put 5 of them in production this year. They are networkable and alert if there is an issue. Use them for the same concept, all single power supply devices in a rack to in to this and this plugs in to two backups. https://www.amazon.com/gp/product/B00AP9EDZE/ref=oh_aui_search_detailpage?ie=UTF8&psc=1 From: [email protected] [mailto:[email protected]] On Behalf Of Ken Cornetet Sent: Friday, September 16, 2016 1:01 PM To: [email protected] Subject: [NTSysADM] RE: Transfer switches What's bad about them is that they (at least the non-industrial sized ones ) are based on mechanical relays. After some number of switches under load, the relay contacts will eventually weld themselves shut. Unfortunately, there is no way to detect this condition until the next power fail wherein the relay doesn't switch to the alternate power and your critical device goes down. Raritan makes an interesting unit that is a hybrid. It uses SCRs (like the big industrial units) but only to do the initial load transfer. It then closes the relays for the long term current carrying. This way there is no arcing of the relay contacts. It's a bit more expensive than the other brands, but not onerously so. From: [email protected]<mailto:[email protected]> [mailto:[email protected]] On Behalf Of Joseph L. Casale Sent: Friday, September 16, 2016 1:09 PM To: '[email protected]' <[email protected]<mailto:[email protected]>> Subject: [NTSysADM] RE: Transfer switches APC sells them, not sure what is bad about them? Pretty common device in all but the simplest setups I would think? jlc From: [email protected]<mailto:[email protected]> [mailto:[email protected]] On Behalf Of Ken Cornetet Sent: Friday, September 16, 2016 10:48 AM To: [email protected]<mailto:[email protected]> Subject: [NTSysADM] Transfer switches Does anyone here have experience with AC transfer switches? I find myself in the unenviable position of needing some, and pretty much all I hear about them is bad. I have some equipment that only has one power supply (no option to add a redundant supply) that will be powered by two different mains. Each main will go down periodically, but never both at once. Suggestions?
