Economy 7 Quartz User Guide
http://www.horstmann.co.uk/downloads/ElectronicDocuments/Electric-Water-Heating/E7Q-UserGuide.PDF
Datasheet
http://www.horstmann.co.uk/downloads/ElectronicDocuments/Electric-Water-Heating/E7Q-Datasheet.pdf
Hope this helps as a starting point
U.O.
April 2008