We have decided to go with geo on our whole-house renovation in the DC metro area, and are rookies to geo. Even though I've been trying to read up on this area (via this forum and other places), there are a lot of nuances and technical information that I don't understand. I'm hoping that you experts will raise my comfort level so we can make an educated decision. And unfortunately, we need to make a decision ASAP. Like another recent poster (newtogeo), I can shop for quotes, but what I'm most interested in is the following: 1. What looks to be the correct load calculation? (one quote is for 6 tons vs. another for 7 tons) 2. Should we do the zoning? 3. Does these quotes look thorough? What's missing, needs to be clarified? 4. Does the price seem reasonable (again, not asking to shop quotes, but is it reasonable for the proposed work and loop configuration)? Background information: This is for a 5,700 square foot brick home in the DC metro area. Basement is about 1,400 sq. ft. First floor is about 1,950 sq. ft. Second floor is about 1,400 sq. ft. Third floor is about 700 sq. ft. (with an additional 200 sq. ft. of attic space). New Marvin windows have been installed with the exception of a few rooms. We also are spraying foam insulation in several rooms, including under all roofs (Icynene LD-C-50). We plan to install two systems (one covering basement and first floor; second for the upper two bedroom floors). Re: the load calculations -- Installer #1 is recommending a 4 ton and a 3 ton system, ClimateMaster Tranquility 27 (originally this installer recommended two 4 ton systems). No zoning (i.e., one zone per system). Installer #2 is recommending two 3 ton systems, Water Furnance Envision. Zoning on each floor using IntelliZone and we also may sub-zone on the second and third floors. What looks like the right load calc??? 15KW auxiliary heat on both heat pumps is included. Duct work is all new. Hot water generator on both heat pumps and storage tank is included (is this the same as a desuperheater?), which will be connected to our current AO Smith NG hot water heater. Kitchen (including make-up air) and bathroom exhaust (4 full and 1 half bath) is included. Two humidifiers are included (Aprilaire by-pass, model 600 or 700). Re: the zoning -- I heard that ClimateMaster does not recommend zoning on their systems. Has anyone had problems with this? Estimate 1 which uses ClimateMaster equipment has no zoning. Estimate 2 has two zones per system (so 4 zones total). What makes sense here? We've been told that 3 wells are needed for the 7 ton total systems, and 2 wells for the 6 ton total systems. These are vertical loops and will be joined in parallel. Both heat pumps will be running off this combined loop field. (Sorry, I hope I'm using the correct technical terms here.) Based on the quotes, we're estimating that the cost difference between a 3 and 4 ton system is about $5K ($3K in well drilling, $1K in casements, $1K in equipment price). We estimate that zoning within the two systems is an additional $6-7K. Do these quotes make sense? Anything we should specifically ask about, or is concerning? Do the prices seem reasonable for the amount of work? Thanks for your advice and insight. This is a lot of money, and our dream house that we'll be living in for 20-30 years, so we want to make the right decision.
As a consultant After a quick look. In my first career, I didn't realize how much this would mean to me in the future - "you don't need to know the recipe, to know if it tastes good." You've been provided with a lot of information, and even us as professionals, glaze over when looking at another's work. Of course, being paid helps clear the eyes. Really by providing a lot of information like this, one ends up coming up with a lot of questions. Your contractors should be the ones putting this in to context. So, firstly, I wouldn't get to hung up on details - like the one's being provided. Step back and just ask for some sort of performance guarantee if you want - ie, will this keep our home at 72F in the winter and 68F in the summer (something like that). But some notes. - the right load calc. is a difficult question to ask us on the internet without the details the contractors had. And even then, it takes some work to do correctly (or verify). -zoning is relevant if you want different temperatures in different locations or they plan on staging units on common ducting. -look at a preheat tank for the desuperheater. Don't have hot water plumbed directly in to a NG tank. -vertical loops headered in parallel is appropriate. Sizing, not sure. - if it helps, compare this pricing against a high-efficiency "anything else" system and see what the cost difference is.
Aux heat seems to be over kill. 15Kw equals 51,195 Btu's/Hr multiplied by two equals 102,239 Btu's/Hr. (8.5 Tons) That's a lot of Btu's and a lot of extra electric power needed to run it. We have no systems with more than a 10Kw strip heater installed. 10Kw will provide all the heat needed, at design temperature (-5), for MOST of our installs (In eastern Iowa), the rest fall a bit shy but our customers understand the limitation and know EMERGENCY heat is very temporary. Besides, many of our customers have gas log fireplaces that will heat most of the home on it's own. Begry
Phew! That was a lot of work to try to answer your questions. Give us the Cliff's notes next time. 1st, 6 tons is a lot. Both are loading heavy. Should not need much auxiliary. 2nd, second bidders op cost calc is for 9 tons. 6 are quoted YMMV. 3rd, zoning geo is more sophisticated than 90% of the guys installing it. If this is a gut and remod. Why not take the opportunity to bring the load down farther and reducing heating requirements. If you emphasize quality of the installer credentials and references, the rest will take care of itself.
Work hard on the envelope rather than buying more tonnage. Be sure via testing that the foam insulation actually air seals wherever applied...thickness is necessary but not sufficient to actually derive the expected performance from foam. Anyone performing a load calc without blower door infiltration data, especially on a big multistory house is asking for trouble. Many HVAC companies recommend against zoning...because they lack the ability to properly execute it. I do a lot of zoning...is it the right answer every time? Of course not, but be sure the reasons to avoid it are valid. Having a single system serve more than one floor is tricky without zoning; at minimum will require manual damper adjustments between heating and cooling seasons...why not let automation handle such a mundane task?
The short answer is automatic things cost more and break Among the other benefits of automatic zoning however is it is an application where I do endorse setback (even on geo).
Wait, I'll check on number one child's dental schedule. She is inside the beltway and we will be there when they yank her wisdom teeth. Why are the called that? Mark
Wisdom teeth, or third molars, are the last teeth to develop and appear in your mouth. They come in between the ages of 17 and 25, a time of life that has been called the "Age of Wisdom."
