Geo on both levels or one

Discussion in 'Quotes and Proposals' started by dregnier, Aug 11, 2011.

  1. dregnier

    dregnier New Member

    I have been reading alot of info on this site and others on going to geothermal. I live in Maryland and am currently on propane. I have run payback figures using conservative estimates and am happy with the projected payback. I have also chosen a contractor wisely and am going to go with a waterfurnace envision system.

    Our home is a traditional colonial that is quite large. We have had an energy audit done and the house is very well built and insulated. There is a 3 ton system ac/propane system in there now servicing the basement and the main level. The second level is the same ac/propane that is a 2.5 ton system. There is 3200 sq/ft on the main level and basement and 1900 sq/ft on the second floor. Manual J loads have been done and have confirmed 3 ton units for each floor. They are each a little oversized since the envision dual capacity's dont come in half ton increments.

    My question is has anyone gone geo on the main/basement system and a traditional air to air heat pump for the second level? What are you thoughts about a system such as that? I am thinking that since we have an open foyer, enough heat will rise from the geo unit to supplement the regular heat pump upstairs. Maryland's rebate is $500/ton capped at $2,000. I would only get this for the first system and loose it on the second system. The payback on the second floor system seems like it will take a long time to recover expenses especially since we only sleep up there.

    Your thoughts are appreciated
    Thanks in advance
  2. dregnier

    dregnier New Member

    The difference in price is about $6,000 additional for the geo unit. We plan on staying there a while but for the Additional $6,000 I could buy a newer heat pump 10 years down the road and be about the same out of pocket expense.
  3. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    What are the odds of combining the systems and coming down to 5 tons?
    What was actual heat loss/gain?

    Planning to augment second floor heat with downstairs geo suggests upsizing ground floor unit- I wouldn't be a fan of this strategy.

    We have a contributor here with geo down and ASHP up.

  4. dregnier

    dregnier New Member

    The idea to supplement the upstairs unit was mine. Before I thought about that, manual J showed a 3 ton for each geo unit. They slightly over sized to keep the unit in the first stage and very rarely need aux heat. I would have to get the actual numbers for the heat loss/ gain. I guess I could zone a 5 ton system. The second floor unit is in the attic right now so I would have to run a chase from the basement up to the attic and then tie into the existing flex ducts. My contractor however did not recomend zoning for the sole reason that by the time I had all of that work performed zoning, chase run, I would be close to the price of a second system and would have more comfort and if one system was down we could occupy another portion of the home while the broken unit is to be fixed. The main level would be a package unit while the second floor would be a split unit.

    Thanks for the response, I will update with the manual J numbers when I get them and once the Mod approves my posts they will be posted.

  5. dregnier

    dregnier New Member

    Here is My Manual J


    Having these posts reviewed everytime sure slows things down alot. Oh well this is worth waiting for.

    Attached Files:

  6. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    "They slightly over sized to keep the unit in the first stage and very rarely need aux heat"

    It kills me whenever I hear this.......
    We used to have equipment that didn't go into second stage before......It was called SINGLE STAGE.
    The reason 2 stage is more efficient is because it uses less when less is required. If equipment is oversized to prevent activation of second stage it is not a little oversized it is grossly oversized.
    Auxiliary heat is not the anti-christ either. Load requirements and cost per kwh determine the best size of equipment. Folks who design out auxiliary altogether are again grossly oversizing equipment.

    Based on info you have provided I'm gonna guess they are trying to cover they are trying to cover almost 90% of the load in first stage suggesting 5 tons might be oversized and 4 tons might be adequate.

  7. zach

    zach Member Forum Leader


    In addition to your actual heat loss number, your contractor should provide you with information about system run times and fractions in stage 1,2, and aux.

    Contractor should be able to show you what happens to these numbers with changes in equipment sizing.

    This would tell you number of hours in the year you might expect to see stage 2 and aux.

    Oversizing can also be a problem with short run times in cooling mode leading to inedaquate dehumidification not to mention more wear and tear on the compressor.

    You want right sizing.
  8. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    If ductwork will accommodate, I favor a single system with zoning.

    zone control equipment is MUCH cheaper than a second system.
  9. dregnier

    dregnier New Member

    Ok this feedback is great thanks for the replys. I have one more bit of info to provide from our home energy audit I had done back in February.

    Two story colonial with full finished basement (5,200 sq ft)
    Building leakage: 3600 CFM50
    Fan pressure: -50 Pa
    Outside temp: 53 F

    The auditor said our home was a very tight home and only had a few recommendations to add more insulation here and there.

    Before I picked my contractor out I had 4 other bids. Pricing varied a lot but once I got down to the three that were the better of the bunch all of this pricing was within $1,000 from each other. I chose my contractor because they were geo pro certified by waterfurnace had a nice list of succesfull installs on envision units, IGSHPA recommended and had a 10 year parts and labor coverage. NO labor allowance like others they must accept the recommended wages given by waterfurnace. They do sub out the looping to a local well driller that is recommended by IGSHPA. I wanted to cover my bases here after reading several places that undersized loops,systems,ducting seem to be a large problem with installs. At the same token, I don't want short cycling and humidity removal problems.

    So here is where I am and and why I am hesitating on pulling the trigger.
    The manual J (see above) shows calculated 2.5 tons for the main level and 2.5 for the second story. Waterfurnace does not make dual stage envision units in 1/2 ton increments. So is it better to have a 2 ton system go into the second stage as needed and use resistance or a 3 ton to use the single stage most of the time? I may note that the systems that we have in now are a 3 ton for the main level and a 2.5 ton for the second level. There is no humidity removal problems that I have noticed and they keep up in the hottest of days with normal cycle times.
  10. zach

    zach Member Forum Leader


    I believe you need more info to make your decision. Do understand the 1/2 ton dilema.

    When I mention run fractions and number of hours in stage 1,2, and aux, here is what I am referring to:
    Low Operating Cost

    WaterFurnace should have a similar software package which is available to your dealer/installer.

    With the software, you input your heatloss and design day along with a selected machine. You'll then get an output showing runtime and costs. Obviously, you also input fuel costs. In your case, installer likely more concerned with covering cooling load. No aux in cooling.

    In my limited experience, this is what you are looking for in order to make the most educated decison (along with installer input as he's the guy making the guarantee).

    Ask the guys who have many more installs under their belt than I ...........I'm sure they'll chime in.
    Last edited: Aug 13, 2011
  11. dregnier

    dregnier New Member


    Thanks and very interesting. I will be contacting my contractor Monday and I will update when I get more info.
  12. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    I don't see a man J load.
    When you say the manual J load suggests 2.5 tons I'm suspicious that you mean 30ish thousand btu's. If that's the case then a 2 ton is indicated.

    As I said previously, avoiding second and third stage heat often drives up installation cost without saving on operating cost.

  13. dregnier

    dregnier New Member

    The manual J load is here as an attachment.

    Attached Files:

  14. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    trouble with the download. any chance you could simply type in the heat loss/gain for each floor?
  15. dregnier

    dregnier New Member

    IT looks to be the following.

    1st floor and basement
    heating 28,337 BTU
    cooling 14,200 BTu

    2nd floor
    heating 31,495 BTU
    cooling 21,896 BTU

    Outside db (°F)

    Inside db (°F)

    Design TD (°F)

    Daily range

    Inside humidity (%)

    Moisture difference (gr/lb)
  16. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    That was my suspicion.
    Your loads are barely 5 tons between them. In my kneck of the woods that indicates two 2 tons.
    With verticle utubes 4 tons would cost about $1,000/yr to provide all heating cooling and hot water (with our electric rates) while 6 tons would cost $950. 4 Tons would cost $6000 less to install (or better if duct work is not sized for 3 tons).
    For dehumi purposes, 6 tons is not even running 50% of the hour at 92*f while it's closer to 82* for 4 tons.
    Duct work requirements are far less meaning operation will be quieter if your ducts are sized for 3 tons.
    4 tons satisfies 98% of the heating requirement without auxiliary.......and on and on.

    Again I can only speak to my kneck of the woods, but we can just as easily run the same cost comparisons for you with a cost/kwh of electricity (include tax, delivery etc.) and closest major city.

    One other thing....why is your second floor load higher than basement and ground floor put together? Does it have more square feet?....overhang the ground floor?......did you load it as though ground floor doesn't exist?

  17. dregnier

    dregnier New Member

    Cost for electricity is .095/kwh and the closest major city is Baltimore.

    One other thing....why is your second floor load higher than basement and ground floor put together? Does it have more square feet?....overhang the ground floor?......did you load it as though ground floor doesn't exist?

    I was wondering this myself as I was posting it. NO the second floor does not overhang the main level. If anything, it is the same size as all the other levels minus stairs, foyer etc. Probably around 1,600 sq/ft +,- 100 per level. I am wondering if they got these numbers switched. FYI, my contractor was the one who performed the load calc. It might be wise to hire a third party for this.

    Why would there be such a large discrepancy between what my contractor is saying and what you guys are recommending? When it comes down to hard numbers like load calcs and inputting them into software isn't that supposed to take the guess work out of it? I am begenning to think that the so called geo pro dealers from waterfurnace are more of a marketing tactic although I am sure this varies with contractor.

  18. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    There are different design philosophies.
    My AO enjoys very cheap electricity (about 71/2 cents kwh) so we can rely more heavily on auxiliary heat where on long island at 20+cents one doesn't want much aux at all.
    If your contractor is of the 100% load school (meaning he wants to handle the heat loss with just geo, a 5 ton is indicated. Since he can't get 2 stage 2.5 ton units......he uses 2 threes.

    Curiously putting Baltimore in the system and 9.5cents/kwh closes the gap considerably.

    Figuring desuperheater contributing to hot water, electric water heater and family of four, four tons of geo provides all your heating cooling and hot water for $1,020.00 while six tons provides same for $1,010/yr. Incidentally 4.5 tons costs $1/yr more than 6 tons, though that is the least likely scenario.
    Suprisingly the most expensive to operate of the choices would be 5 tons at $1,050/yr!

    Here's what I don't know....closest major city does not mean exact weather data. A city north and west of Detroit by me runs as warm as Toledo Ohio.
    Point is local contractors understand idiosynchracies in local weather.

    If you get multiple estimates you should see multiple load calcs. If they are all within 10 points of each other that's pretty reliable.

    Before discarding this contractor one could ask about design preferences. You should also compare to other contractors' designs (in your area).

    Good Luck,
  19. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader


    Joe Hardin continues to teach me about low cost fuel. His words are worth digesting, even if he is a troll.

    LOL @ Joe.

  20. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    By yooper definition everyone who lives under the bridge is a troll so that is most of us least no one called me a fudgie.

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