New Home HVAC Advice
Hello all! I'm looking for some advice on the HVAC system for our new home. We are building our new home and are going with a WaterFurnace geothermal system. My question has to do with sizing. First, the details!
We live in central MO. Our home will be a rancher with about 2300 square feet on the main level. We will have quite a few windows, but excellent insulation (very tight house). We will have a 168 square foot sun room on the back of our house that will be almost all windows. Below that will be my office. I work from home and it gets warm in there in the summer. We will also have a fully finished basement. We want to zone the basement, the office, and the sun room separately from the main level.
The coop electric service that we are on recommends a 6 ton unit and will only give us our rebate ($750/ton) if we go with that size. However, the issue is that the Water Furnace 7 Series is the only unit that we can have separate zones in the office and sun room due to the size of those two rooms. Since it is variable and can 'kick in' at 20% of rated capacity, it will work. The 7 Series does not come in a 6 ton unit.
When our HVAC contractor originally performed the calculations, he came up with a 5 ton unit, so I thought we were all set. However, after he spoke with the coop, they recommend a 6 ton unit, so that leaves us with a 5 Series. With a 6 ton 5 Series, we can only have 2 zones: 1 for the basement and 1 for the main level.
As far as cost, without the rebates, our total out of pocket after tax credits and rebates (rebate only on the 6 ton) will be $5700 more for the 7 Series unit with 5 zones (an extra zone for the master bath is available for just the cost of a thermostat due to the layout).
Now, the question. Which would you recommend? I prefer the 7 Series for the extra zoning ability and the extra efficiency, but I don't want an under-powered unit that will hurt efficiency or longevity of the equipment. I also thought about drilling an extra well to go with the 7 Series to get just a bit more efficiency. Thoughts?
Also, would going with an open loop system be more beneficial? We will have a well, so if it is more beneficial, we could size the well properly and go that route.
Thanks for your help! I greatly appreciate it!
Hands down I would go plead my case to the co-op that a Waterfurnace 7 series is a 6 ton unit. Look at the specification data and tell me differently.
The 5 series NDV072 shows at a 30 degree entering water temperature a 52K-55K BTU capacity depending on water flow and CFM, at 40 degrees it is 61K-64K BTU's of heating capacity.
The 7 series NVV060 shows at a 30 degree entering water 56K-60K BTU of capacity depending on water flow and CFM and at 40 degrees shows 64K-68K BTU's.... So yes the 7 series is "rated" as a 5 ton, but realistically it provides MORE capacity than a 6 ton dual stage! I would take the specification manuals to the co-op and say, so why does the NVV060 not qualify when it provides more BTUS?
Oh and Cooling just because :-)
5 Series at 90 degrees 65K-68K
7 series at 90 degrees 54K-55K BUT it has superboost mode which will give you 24 hour spurts of cooling with 30 percent higher capacity, so really its more like 70K-72K
Hands down I recommend the 7 Series, it is so much quieter, more comfortable, you wont' regret it at all. Just make sure they install the FCV flow center with the grundfos magna variable speed pump. If the installer trys to tell you all they install is the single speed pumps walk away and find another dealer. There are some great companies that sell Waterfurnace in MO, but a few of them do not have much 7 series experience.
For the record, the 5 series will actually allow up to 4 zones, but I would not install more than 2 because you will have noise issues and comfort issues and I have found that no matter how well the ductwork is designed if you want more than 2 zones you need a 7 series.
Thanks for the info SkyHeating! We will definitely be getting the variable speed pump. I feel really comfortable with out contractor. They are actually the #1 Independent WF dealer world wide for the last 3 years (according to their web site ). They put a GSHP in our current home for us about 3 years ago and we were very impressed with them.
On the 4 zones for the 5 series, our contractor said the same thing. They could do 4 zones since the 5 series supports it, but they won't. They refuse because we wouldn't be happen and it would shorten the life of the unit, and many other problems. His response: "if you find something that will zone a 6 ton unit for that small of a space, run away as quick as you can!"
Another question I have is does creating 4 zones shorten the life span or decrease the efficiency of the 7 Series? My thoughts are that it wouldn't since it would be running at such a low level for each zone that it would actually be better for it, but that may not be correct.
I will be speaking with the coop to try to convince them. I just wanted to get more opinions before I do that. From what I understand, the representative at the coop is nearly impossible to sway, but I will try to go in armed with some good info and see what I can do. At this point, it looks like we will be going with the 7 Series, since it sounds like we will be much happier. You don't see any issues in heating and cooling our entire home with a 5 ton unit? I could attach a copy of our house plans if that would help.