This part of EN 255 specifies methods for testing and reporting of the rating and it specifies requirements for marking of air/water and water/water heat pumps with electrically driven compressors when used for sanitary hot water. When these units are used for space heating, then prEN 255-2 applies. This standard applies to factory-made units which can be ducted. In the case of unitsconsisting of several parts, the standard applies only to those designed and supplied as a complete package.