How to configure SharePoint SearchCenter URL?

What’s a SearchCenter?

A Search Center site, or Search Center, provides an interface for users to submit search queries and view search results. A Search Center site is the top-level site of a site collection that a farm administrator creates by using the Enterprise Search Center template or Basic Search Center template. Sample search center screenshot…

How to Create a Search Center Site…

I assumed that SharePoint is inteligent enouth to differ betweent their Keywords. 

Usually in a Search Center you can define your own query to get you sepcific results. I used a Query to filter especially for a contenttype and a given value from the Request parameter URL (”k”) like this:

{searchboyquery} {RequestParameter.k} contenttype:test

Problem

That looked great but for some reason after using sometimes the frefiner I got an empty result.

So there are no error in the ULS, no error in the Frontend, no error at all. After a small research I figured out that the extra paramter [RequestParameter.K} causes the problem.

Solution

So I removed it, after this it works very well, and the K Parameter in the request will be used in the [searchboxquery} placeholder. 

So there is a problem when I use the k Parameter directly, or I must remove the {Searchboxquery}, but I wanted the flexibility to add a searchbox later by hand.