I have a WF Envision NDV026 It was installed in Jan of this year. House was built in 1994, ducts are in the attic, house has a basement which has duct work for it downstairs. Main level and basement are heated and cooled with this unit. I was supposed to heat and cool main level and basement for less money than it took to do with the traditional heat pump which only did the main level (and have more comfort). Returns upstairs and downstairs. unit is located in the basement at one end of the house. House is 1500 square feet main level and 1500 square feet basement, 3000 total Ground source loop. The unit will not keep up when the temperature hits high 80's or above outside. Currently it is 78 degrees in the house;it is 94 degrees outside. Contractor has been back several times to adjust fan speed, and has covered/uncovered the return for the basement area. I asked the contractor to get the factory technician involved and he did. The factory tech found the water temp coming in was too high and his recommendation was to add more length to the loop. Contractor added an additional loop. Loop was dug with a ditch witch and he said the average depth was 4 feet. The original loop was dug with a track hoe, all of the loops were in one trench (4-5 feet deep). Soil is red clay with a lot of stone (sandstone mainly). After that we still have the same problem. this is a two stage unit, it hits stage 2 mid morning and runs all day, it will be after midnight before it stops running (gets down to 74 degree setting). Contractor was back today and changed out the water in the loop. I feel the unit is not working properly or is undersized. Other contractors quoted the 26 for the upstairs only. Any thoughts on this would help me a lot. I feel the contractor may be inexperienced in these units even though he told me he was a factory trained rep. More info: When we turned the unit on in the winter after the install the heat was just not comfortable. This is in comparison to my original 17 year old outside unit heat pump. Power bill is almost identical to last year. Thanks!