This topic is very personal, and depends on how sensitive you are.
You can always thanks in advance in your request email and therefore avoid a new response just to be grateful. The ackowledge of receipt can be automatically sent by the machine, outlook or whatever you use.
From my point of view, the point here is not the 20 seconds email, but expressing to many "thank you" for regular day to day work. I don't feel better if someone shows its gratitude for something i am supposed to do. I think that we all should do things that are not our main task, moreover when it comes to help other people in their jobs, because they are new or simply they do not have the time. In that cases, i would like that the other person shows his gratitude in a more personal way than an email.