This Technical Specification applies to small and large custom built solar heating systems with liquid heat transfer medium for residential buildings and similar applications, and gives test methods for verification of the requirements specified in CEN/TS 12977-1. This document also includes a method for thermal performance characterization and system performance prediction of small custom built systems by means of component testing and system simulation. Furthermore, this document contains methods for thermal performance characterization and system performance prediction of large custom built systems. This document applies to the following types of small custom built solar heating systems: systems for domestic hot water preparation only; systems for space heating only; systems for domestic hot water preparation and space heating; others (e. g. including cooling). This document applies to large custom built solar heating systems, primarily to solar preheat systems, with one or more storage vessels, heat exchangers, piping and automatic controls and with collector array(s) with forced circulation of fluid in the collector loop. This document does not apply to: systems with a store medium other than water (e. g. phase-change materials); thermosiphon systems; integral collector-storage (ICS) systems.