The SVCs diameter used were 14.5, 17.5 and 20.0mm ID. The effect of SVCs size on the heat flux at varying inclined angle, it found that the heat flux of 17.5 mm of SVCs ID was obtained higher than 14.5 and 20.0 mm. The low heat flux that achieved on 20.0mm ID is caused by a few space for supplied hot water, while on a 14.5 mm ID is due to smallest heat transfer area