Opinions wanted: solar, geothermal, 14 SEER, 16 SEER???

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Comments

  • CatscratchCatscratch Solar Expert Posts: 30
    So the 14 seer is good up to 1500sq/ft. What about a 3000sq/ft house? We are building 1490sq/ft ground level with a full basement adding up to just shy of 3000sq/ft. We honestly will probably block off vents and doors most of the time so that we are doing minimal heat/air in the basement. BUT, the system will be for both levels... is the 16 seer the best choice in these conditions?

    Also, air conditioning is our biggest concern as we will have a wood burning stove that we've proven to use a lot. It should be a while before my health keeps me from cutting and burning wood so heat should be supplemented (knock of wood).
  • SolarPoweredSolarPowered Solar Expert Posts: 626 ✭✭✭
    At 3000sq/ft take what ever budget you thought you had and tack 30% on to that.
    Home that size typically requires a seer16 minimum , or 18 and a minimum of 6.5kWh of name plate solar of some high harvesting micro inverters. That's if you don't have a swimming pool or hot tub, if you do you are looking at roughly 8kWh of solar.

    My suggestions on the cheap for hot Kansas City Heat.

    - thermostat controlled Attic Fans
    -paint your house in a neutral white
    - build as much solar on the south bound as possible
    - spend the extra money on recycled high density blown insulation
    -cross your fingers on a 16 seer, not running to long continuos cycles.
    -spend the extra money on 5/8" drywall VS the building code standard 1/2" drywall for walls. Not only does it improve fire rating it will also help with insulate properties and is cheaper per sq/ft than any other insulate material.
  • CatscratchCatscratch Solar Expert Posts: 30
    I'm getting confused (excuse my ignorance). I was thinking that seer was efficiency and tonnage had to do with the size of the house. I understand this may be a basic way of thinking of it, but at 3000sq/ft and fiberglass batts we were calculated to need a 5 ton unit. Closed cell foam increased our R values and reduced air infiltration to drop our needed tonnage to 4 tons. Honest question here: how does needed seer rating change with sq/ft? I thought tonnage changed with that variable. I need help:)
    I hadn't thought of drywall as part of this system.
    House is facing east/west. Windows mostly to the east and under an 8ft overhang. No windows to the south or west.
    ps- no pool or hot tub.
  • SolarPoweredSolarPowered Solar Expert Posts: 626 ✭✭✭
    Seer 14 units are much smaller than seer 16 and 18 units, the amount of time it takes to cool the coolant is what you need to pay attention to. You can possibly find a 4 ton seer 14, but it will take alot longer to cool 4 ton, than it would a seer 16. Seer 16 and seer 18 handle much larger capacities to cool a home per sq/ft based on less continuous cycles than a seer 14. Larger units require more load at start up, and during continuous duty cycle draw more power than the seer 14 obviously, but the larger units work loads, can work less per continuous duty cycle and from the energy demand cools the home sooner. Because the seer 14's are typically smaller there is a point in which per sq/ft of home the continuous duty cycles of a seer 14 could (per kWh) use more power than a seer 16 unit that could cycle in less time. You really have to get a energy specialist in your home that deals with this, not the HVAC guy who wants to sell you their specific product line with the vendor they deal with, or your contractor/builder who is just trying to please you on your budget so he can get off the job and get paid.



    Highest efficiency per/seer ton, for reduced continous duty cycles in kWh ( the big difference in the cooling efficiency is whether or not the unit can use R22 coolant, if its a new build I doubt you get R22)
    seer 14 2~2.5 tons 25~30 amp loads
    seer 16 2.5~3 tons 30~40 amp loads
    seer 18 3~4 tons 40~50 amp loads

    Now you can get a seer 14 that can handle 4 ton but the amp/load is higher/ cooling efficiency is less than the 16 seer, or 18 seer per ton cycled.
    seer 14 3.5~4 ton 30~35 amp loads
    seer 16 4~5 ton 35~45 amp loads
    seer 18 5~5.5 ton 45~55 amp loads


    Also for your solar system if you only have east and west facing azimuth's you will want to only look into mono crystalline, invest into some stand off's to make a tilted 3" or greater delta V to face south. I have pictures if you don't know what I am describing.
  • CoffeeAddictCoffeeAddict Registered Users Posts: 3
    Catscratch wrote: »
    I'm getting confused (excuse my ignorance). I was thinking that seer was efficiency and tonnage had to do with the size of the house. I understand this may be a basic way of thinking of it, but at 3000sq/ft and fiberglass batts we were calculated to need a 5 ton unit. Closed cell foam increased our R values and reduced air infiltration to drop our needed tonnage to 4 tons. Honest question here: how does needed seer rating change with sq/ft? I thought tonnage changed with that variable. I need help:)
    I hadn't thought of drywall as part of this system.
    House is facing east/west. Windows mostly to the east and under an 8ft overhang. No windows to the south or west.
    ps- no pool or hot tub.

    SEER is efficiency and tonnage does have to do with the cooling load of the house(in conventional houses, square footage is a decent starting point for rule of thumb calculations). If your AC guy is using nothing but square footage to calculate your cooling requirement, you need a new AC guy. He should be doing a Manual J(cooling load for your building at your site) calculation at least.

    I would love for SolarPowered to explain what he is talking about. Yes, higher efficiency coils(evaporator and condenser) are larger in size than lower efficiency units. This is for better heat transfer among other things and contributes to lower energy usage throughout the system. If you are comparing which unit to get, compare the cost of the same size unit in 14, 16, and 18 SEER. Typically it is a much better investment to upgrade insulation and go with the cheaper and lower SEER unit. If you are in a highly-insulated home, you will also need to look at an HRV or ERV as well. The scheme of changing the tonnage because of SEER makes absolutely no sense to me. Maybe I'm missing something. There is more to consider here, such as latent vs sensible heat and how your proposed equipment performs in that area, but you likely don't have to worry about this. More so if you have a multi-stage or variable-speed condenser unit.

    Personally I would upgrade the insulation and go for the cheapest two-stage condenser unit(likely at least 16 SEER) and variable speed air handler to allow for part-load operation. This will help you with humidity levels in the house, general space comfort, and energy usage. It also allows you to run the AC at a lower electrical demand in case you want to run the AC off of an inverter or generator.
  • SolarPoweredSolarPowered Solar Expert Posts: 626 ✭✭✭
    Every manufacturer rates seer efficiency differently.
    You can get a seer 13 from one manufacturer, that will state it has an efficiency of its competitor of a seer 14 (based on tons, or increased cooling factors), most importantly the load (amp draw) that the condenser/coil require do not necessarily have to do with the seer rating it has to do more with tons required and continuous duty cycles. How manufacturers determine the seer is from the compressor unit not the condenser unit. You can see the same condenser type/style/size that one manufacturer could claim as 13 seer, while another manufacturer claims as a 14 seer, but both can do the same comparable output as far as a measurement of cooling tons. Same goes for some manufacturers that call out a 14 seer, while others that claim the same ton output call out for a 15 seer.

    People should pay more attention to amp load and tons instead of seer efficiency.
    If you look at a compressor/condenser from the 1980's, and compare and contrast a compressor/condenser that is current, yet had the same seer rating you would see that the standard for seer is always changing.

    Sometimes this is just a different coil VS condensing unit, or vise versa.
    If you have a 3000 sq/ft home as a base calculation, assume that all walls are 8' high (standard) you would roughly have 24,000cu/ft, convert to a BTU (24,000 X 1027 =24648000 BTU). This is the energy required for that volume of cubic/ft.
    Now to convert to tons divide by 12,000.
    12,000/24648000=4.87 tons

    No matter how much you insulate your home tons is equal to the cubic ft, not how well you insulate the home.

    If you use a 4 ton (seer 14 or 13 depending on manufacturer) rated for 4 tons, but no matter what the home requires enough energy for heating and cooling for 24,000cubic/ft. No matter what the insulated condition, a 4 ton to equalize the cubic area will require roughly 87% more duration or power consumption than a seer 16 rated at 5 ton, because 4 ton is what we are using as our comparable data is already going to be our factor of 100% any tons required over 4 ton to 5 ton is 1% increments per every .01 ton required per cu/ft. A 5 ton at 4.87 tons is assumed to be a 13% reduction in continuous duration, (this is our assumed de-rate).


    (Seer 14) 240v X 30amp= 7.2kWh (1 hour duration)
    (Seer 16) 240v X 40amp= 9.6kWh (1 hour duration)

    Now add the derate factor for continuous duty based on cubic feet/ton/energy needed for the 5 ton since its only 4.87ton, that is actually required.

    (seer 14)7200 X 1.87 = (13.46 kWh 1hour 45 minutes continuous,to cool a home of 24000cu/ft)
    (seer 16)9600 X .13 = 1.248 kWh derate
    9600 -1248 = (8.352kWh 45 minutes continuous, to cool a home of 24000cu/ft)

    Tons, and cu/ft in a measurement of cooling or heating is a required time frame in comparison to the energy needed for consuming kWh .

    There is greater efficiency using the 16 seer VS the 14 seer hands down.

    Now don't get me wrong, there are environmental impacts. If you install a seer 14 condenser in the shade, vs installing a seer 16 condenser in the hot sun there are definitely environmental impacts that change the mechanical cooling needs of that condenser as far as optimizing duration and efficiency. So obviously keep the condenser as shaded, out of the sun as possible, to get optimal efficiency.

    Right now, my client and I are debating with a couple HVAC installers between a seer 13 and a seer 14 just because of the manufacturer differences between the specs, they both almost react equally as far as the load. Both require 30amp, continuos loads.
  • Dave AngeliniDave Angelini Solar Expert Posts: 5,085 ✭✭✭✭✭
    And this is the debate that keeps going. The numbers for size you list SolarPowered are what people who expect to cool down a hot home in less than an hour. The mini split strategy of using a much smaller unit that is on dawn to dusk, never lets the home get hot, uses less energy, avoids ducting, and uses very high SEER 25+ does the job really well. Both methods are valid but one uses much smaller peak loads and is easier with solar.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • SolarPoweredSolarPowered Solar Expert Posts: 626 ✭✭✭
    And this is the debate that keeps going. The numbers for size you list SolarPowered are what people who expect to cool down a hot home in less than an hour. The mini split strategy of using a much smaller unit that is on dawn to dusk, never lets the home get hot, uses less energy, avoids ducting, and uses very high SEER 25+ does the job really well. Both methods are valid but one uses much smaller peak loads and is easier with solar.


    The way technology is evolving eventually it is all going to be mini split, regulated on digital thermostats per room of the house.
    The only way centralized heating/cooling can keep up with mini split technology is by having a "multiple" stage condenser/compressor, and as well having thermostat controls and sensors through out the home, regulating each room individually.

  • Dave AngeliniDave Angelini Solar Expert Posts: 5,085 ✭✭✭✭✭
    I just hope the energy to power all these heat-pump devices and the devices them selves will be talk with a controller or smart grid ( or an offgrid Inverter) to automate this. The dream of having max cooling, heating, or other large loads that can respond to clouds (lower power) or best times for grid power use is still far away. They have a terrible time in Hawaii with all the grid solar and afternnoon clouds running large cooling loads. The utility has generators starting from the low voltage caused by clouds in the summer tropics. These events are often 5 minutes or so.
    Thanks for the calculator link.
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • SolarPoweredSolarPowered Solar Expert Posts: 626 ✭✭✭
    That's why Mono Crystalline-Micro inverter only, for on grid applications, that require great load demands. String inverters-poly Crystalline and cloud cover don't work at all. Mono requires less angle of incidents unlike poly and will also harvest at lower irradiance levels so overall daily yield and harvest is on average 4~6% greater than poly, then include micro inverter, looking at an additional 6~8% greater harvest VS string inverter. Thats a daily harvest yield of 10%~14% greater than poly-string inverters.

    My back ground, I am a class B restructuring title24 contractor.

    I engineer/build/design everything from car charging stations, photovioltaic, HVAC, Natural gas systems, and have patents pending for solar water heating and concentrators.

    New rapid chargers require 80amps of over current 65amps RMS loads, thats almost double the loads required for HVAC systems. Some of these home systems I restructure and design build, use both car charger and HVAC continuously (sometimes up to 130 amp RMS continuosly, which far exceeds the solar duration of insolation), so I have no option but to design/build to the 110% PUC/utility company guidelines for annualized consumption to solar production build. All that matters is true up at the end of the year.
    I only deal with clients that pay cash, I build to 110% of the PUC/utility company guidelines, following the 120% rule.

    My concerns with the O.P is that discussing using a 14seer, and having under built solar isn't going to make a dent in the utility bill, so the savings using 16 seer is critical, until the solar can expand. The O.P still has issues with west and east bound facing azimuths. This means 7" to 3" stand offs are critical for increasing delta V pitch for south azimuth, mono is the only alternative, poly is counter productive for yield.

    Its better to structure in a manner to focus more on the consumption demands, and less on solar production output which doesn't yield anything near the 100%~110% annualized build to annualized consumption.

    My average client receives about $500 cash/credit from the utility provider at annualized true up.
  • CoffeeAddictCoffeeAddict Registered Users Posts: 3
    I agree with SolarPowered on consumption being the first target for long-term conservation, along with the low-hanging fruit of better insulation. Also I understand now what you were saying about unit size, but where does humidity control come in with your planning? Let's not neglect space comfort entirely. A 5-ton unit cooling a 4-ton load may not be as comfortable, cycling far more often to maintain temperature and not removing nearly as much moisture. Maybe use the 5-ton unit with a standalone dehumidifier? I'm honestly curious as I've never heard of this approach to saving energy. I'm a BAS/Integration guy so energy consumption and space comfort are both strong interests for me. I would think EER and SHR numbers would be bigger targets here, not tonnage.

    One more thing: ducted mini-splits are a great option here, and prices are slowly getting better. You can use these like a conventional split or zoned with multiple terminal units. One main unit for the common areas with separate cassettes for the bedrooms, etc. this lets you locate the terminal units wherever you want.
  • SolarPoweredSolarPowered Solar Expert Posts: 626 ✭✭✭
    Dehumidifying filters for the return duct is the answer.

    Cost 3 times the cost of a standard filter but it is all regulated to its interior atmospheric pressure, what expells out of the system will all recycle going back in to the return system filter. You also have to have a sheet metal fabricator, fabricate the ducting as these filters come standard on dehumidifiers.

    Honeywell sells dehumidifying filters starting at $17, For a 5 ton unit, looking more at $26 maybe $30?

    Also cheapest trick in the book for dehumidifying. Fill a old sock up with cat liter, it naturally absorbs moisture, smells good and is non toxic aromatic. Find a way to hang it from the heat register/ducting unit and it will naturally absorb the moisture.

    Makes me wonder why no one has patented a an absorption filter at the heat register some one could make millions...LOL

    As for the O.P that started this thread. I hate to say it, because I am an ROI solar contractor for home owners, but the most effective route for the solar required is to probably go through sungevity, on a lease to own program. $2000 and $3000 for a pot towards the solar investment isn't even a substantial kWh of solar. Stay away from solar city, vivanti, sun run, etc, you will never see a return or savings on your money over the span of a 20 year lease they also under build the systems. Sungevity is the only lease company I know that will build you almost up to 100% of annualized consumption.

  • CatscratchCatscratch Solar Expert Posts: 30
    Wow! I'm learning a lot from you guys.

    Sorry I haven't been on here more but things have gotten BUSY. Here is a short update on the build: Budget is changing constantly. We paid the water department up front to install the lines and meter. Shortly after install we got a surprise bill for almost double the initial up front cost. I'm currently talking with an attorney about this cost and don't know how this is going to turn out yet. Fact is, this "new" cost is more than we had budgeted for the 3.5kW of solar or insulation upgrade. In response to this added expense we did a modified upgrade to the insulation. Instead of closed cell foam we added 2x4 extension to certain areas and went with thicker fiberglass insulation. I'm sure this isn't ideal but it will be better than the base system originally planned.

    So we are still considering the solar addition but aren't as eager to jump on it now that funds are shrinking. We can get 3.5kW worth of panels for $4k (after tax incentive). Our current electric rates are $.13 and will go up over time. Our house is total electric. How soon will the PV pay for itself and is it worth going out on the financial limb to get it?

    Once again thanks for all the help. I'm still re-reading ever some of your posts trying to learn some of what you guys have shared with me. Please keep it coming!
  • Dave AngeliniDave Angelini Solar Expert Posts: 5,085 ✭✭✭✭✭
    Catscratch wrote: »
    Wow! I'm learning a lot from you guys.

    Sorry I haven't been on here more but things have gotten BUSY. Here is a short update on the build: Budget is changing constantly. We paid the water department up front to install the lines and meter. Shortly after install we got a surprise bill for almost double the initial up front cost. I'm currently talking with an attorney about this cost and don't know how this is going to turn out yet. Fact is, this "new" cost is more than we had budgeted for the 3.5kW of solar or insulation upgrade. In response to this added expense we did a modified upgrade to the insulation. Instead of closed cell foam we added 2x4 extension to certain areas and went with thicker fiberglass insulation. I'm sure this isn't ideal but it will be better than the base system originally planned.

    So we are still considering the solar addition but aren't as eager to jump on it now that funds are shrinking. We can get 3.5kW worth of panels for $4k (after tax incentive). Our current electric rates are $.13 and will go up over time. Our house is total electric. How soon will the PV pay for itself and is it worth going out on the financial limb to get it?

    Once again thanks for all the help. I'm still re-reading ever some of your posts trying to learn some of what you guys have shared with me. Please keep it coming!


    If you have utility power, in my opinion it is never worth going out on any limbs financial or otherwise. Alot of what was shared really does not relate to you and was just for grins and such.
    Good Luck
    "we go where power lines don't" Sierra Mountains near Mariposa/Yosemite CA
     http://members.sti.net/offgridsolar/
    E-mail [email protected]

  • CatscratchCatscratch Solar Expert Posts: 30


    If you have utility power, in my opinion it is never worth going out on any limbs financial or otherwise. Alot of what was shared really does not relate to you and was just for grins and such.
    Good Luck

    I tend to agree. I go overboard while saving $$$, invest conservatively, and spending is like pulling teeth. Unfortunately choosing to build a house means spending lots of $$$ which conflicts with my instincts. Therefore I guess I'm trying to find ways to justify what I'm doing and trying to lessen the long term financial burden I'm putting myself into.

    I'm enjoying the general knowledge gained from this thread, even the stuff that doesn't really relate to me!
  • SolarPoweredSolarPowered Solar Expert Posts: 626 ✭✭✭
    If everything in the home is electric watch some of the heating costs.
    Converting electricity to heat is a conversion rate of 34.7%. I tend to optimize efficiencies when restructuring. Natural gas to heat(BTU, or Therms) if the appliance is energy star rated converts gas to therms at 90~97% conversion.

    1therm to 1kwh of electricity is roughly a 40% savings in energy.

    Even though cost of electricity tier 1 maybe $.13 the tier structure can escilate rapidly in a month not controlling those initial costs.
  • CoffeeAddictCoffeeAddict Registered Users Posts: 3
    Fiberglass batts? That is unfortunate if so. Blown-in cellulose is probably your best bang for the buck, then blown in fiberglass and others. Thicker exterior walls(2x6 or double 2x4, etc) with dense-pack cellulose is probably much more cost effective than foam. Depends on framing cost and other details such as window and door frames of course. At least add an inch or more of rigid insulation to the exterior to cut down on thermal bridging. Do the insulation right and you can downsize your AC unit vs a typical home. Your HVAC guy should be able to easily adjust his calcs with the new insulation numbers.

    If already framed I would do cellulose and two(minimum 1.5, more if feasible) inches of rigid insulation on the exterior. Just make sure the rigid insulation is taped/sealed at all seams.
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