Last May we installed a Hydron HYT072A11MTINSS-6 water-to-air geothermal 6 ton heat pump to replace a 20-year-old ClimateMaster. We chose the Hydron over a ClimateMaster since it had a faster delivery time, and both brands are manufactured by EnerTech. The system was installed by a local plumbing and heating company recommended by the NH distributor, NorthEastGeo.com. Ever since it was installed, the system has been plagued by a low-frequency resonant vibration from the lower part of the unit. I presume this is where the compressor and motor are located. The frequency of the vibration is about 2 Hz, and is audible through most of the house. So far, I have not been able to receive support from either NorthEastGeo, or EnerTech. Neither company is honoring the warranty. One question raised by NorthEastGeo (over the phone --- they have yet to send out a rep) is whether the installation was done correctly. The original unit mounted on the floor, but the hydron is mounted on a hollow plastic base that is raised on concrete blocks. Two pictures attached show the region from which the vibration emanates and the mounting base. Do the forum experts have any comment on this. Is this likely to be an installation issue or a fault with the unit? Any advice on how to proceed in order to get the required warranty support?