Hi guys. I am new to the forum. I am in the process of building a new home. It is coming time to make a final decision on my geothermal unit and I need a little help. I live in Tennessee. My home will be 3100 sf with all the living space on one floor with basement garage. House faces to the south. Design heating load 49,872 btu. Design cooling load 35,816 btu. My 1st decision is 4 ton or 5 ton. I have gotten 4 quotes. Only one has recommended 4 ton, the rest were all 5 ton. I am leaning 5 ton for that reason, my builder is also recommending 5 ton, would rather have more than enough than to build and find I don't have enough. Unless someone can convince me otherwise. More than likely going to do cellulose bib insulation on the walls with blown in in attic space. The other choice I have is WaterFurnace series 5 or series 7? $4500 difference in the two with the 5 ton. One company gave me an estimated breakdown of my estimated heating and air expense. There was only $11 difference a month between the two. I know series 7 is more efficient but if they are correct on the utility expense difference, it takes a long long time to make up the $4500 when it is $11 at a time? So it is hard to see spending the extra money for a series 7. Any thoughts or advice? Thanks in advance.
The annual heating load calculated was 52,800,000 btu and annual cooling load was 34,800,000 btu. Annual hot water load 18,600,000 btu.
Okay, you mentioned 2 different loads so I picked the second. Not knowing where you are in TN I picked Nashville and ran 3 operating cost models. 3, 4 and 5 ton Climatemaster TE 30's. The most expensive to operate was the 5 ton and the least expensive was the (drum roll please......) 3 ton. Least expensive to buy, least expensive to run....win-win. Now manual J if that is how they are establishing the load, tends to have a little fat in it so I would say that the 5 ton is grossly oversized (at least in Nashville) and the worst part is no one in your area seems to get it. FWIW I wouldn't use a 5 ton for that load in MI. I would have the companies show you how they arrived at sizing and challange them to build operating cost models and try different sizes. YMMV
Thanks for the reply. My builder is pushing me to make a decision so we can get rolling on the hvac. Really need to decide today, so thanks, been waiting on some help. I wasn't sure which load numbers were needed. The 2nd set of load numbers were listed under annual load on the geo design report. The 1st set were from design data column as btuh. If I can save the money and install a smaller unit, I might be able to use that money and spend towards foaming the attic space, which would help my cause on smaller unit. Any other thoughts?
Your builder is amongst the people suggesting an oversized unit. I would make him wait til you are comfortable with your choice.
The load seems high for a new 3100 sqft build in TN. If is right, 4 ton would be good. 5 would be too much. I would be looking to upgrade insulation values and air sealing techniques. 2 or 3 ton would probably be best for a well built 3100sqft home in TN
I have decided to go with 4 ton and upgrade my insulation. My decision now is series 5 or series 7? I am putting the unit in a basement garage which I am afraid will void the warranty on the series 7 since it is supposed to be installed in conditioned area and could cause it to overheat. My installer says "he THINKS he can make it work with warranty still intact by enclosing it in a closet with a vent". I am a little uneasy with him being non committal about the warranty. I don't want to spend this much money and risk not having a warranty on the unit. Any opinions?
If you are going to oversize then I definately hope you use a 7. Build a room around the unit, insulate and condition it and then it won't be in "unconditioned" space by definitition. It is no different than somebody who carves a mud room out of their garage and brings it into the conditioned envelope vs out in the garage. If the installer (as in the same guy that wants to oversize system) does not know the definition of conditioned or unconditioned space, get somebody who does.
