Canon FAX-L800 User Manual page 64

The fax does not enter the energy save mode in the following cases:
You can not press the ENERGY SAVER button to put the fax in the energy save
mode. The fax enters the energy save mode only after the specified time has
elapsed.
3-22 Getting Started
When documents are stored in the memory.
When a paper or document jam has occurred, when the paper cassettes have
run out of paper, or when the toner cartridge has run out of toner.
When a document has been fed into the automatic document feeder (ADF).
Chapter 3