1.TUV efficiency certification 2.Factory audit 3.Adopt world famous parts 4.Victaulic grooved connection Products efficiency Certified by TUV, Factory audited by Bureau Veritas.Modular ground source electric heat pump efficiencyGSWW60-DNNNE, HISEER modular geothermal ground source heat pump, can be easily connected together for any size heating &cooling system at the project spot. Maximum 64 ...