This was originally posted on APC forums on 8/4/2012
I'm looking to buy my first UPS, probably [Back-UPS CS 350|http://www.apc.com/resource/include/techspec_index.cfm?base_sku=bk350ei&ISOCountryCode=US] or [650|http://www.apc.com/resource/include/techspec_index.cfm?base_sku=bk650ei&ISOCountryCode=US] model. I understand those UPS don't have a fan, so normally it should be totally quiet, but some googling shows that it may have noise problems like clicking or buzzing. Is it always like that or is it usually quiet?
Otherwise, which UPS is the most silent one?
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