Not sure how to change your filters and looking for a manual for your unit?

If so, here are 2 tips

The first solution is searching on your favourite search engine like Google, Bing, Ecosia

• Enter the following search query: brand name of your unit + type + manual + pdf: (e.g. Thermelec GLL400 manual pdf)
• In the search results, you'll find quickly your manual

The second smart option is searching for a how-to video on YouTube:

• On YouTube are loads of videos about every brand and unit.
• Search for instance: "how to replace filters Thermelec GL400".
• The chance someone has uploaded a video about your unit is large..