According to the Swaminarayan Hindu philosophy, a Dev Mandir (or Hari Mandir) is one where Pictorial deities are installed. The daily rituals differ to those performed in a Shikarbhandh Mandir.
In such a mandir, the Aarti is performed only twice a day, once in the morning and once in the evening.
References
Dev Mandir Wikipedia(Text) CC BY-SA