First 18 months with NO SAVINGS AT ALL

Discussion in 'Maintenance and Troubleshooting' started by captain, Feb 28, 2011.

  1. geome

    geome Member Forum Leader

    Cooling mode looks fantastic.

    Even though you spent a little less (electric) in 2010 than in 2008 & 2009 (May-Sept), your Cooling Degree Days (CDD) were much greater in 2010 than either of the prior two years (see below.)

    Looking at kWh (a better way to look at this since it removes the effect of electric rates), you had (May-Sept) 8% higher kWh usage (comparing 2010 to 2009), but 45% higher cooling degree days (see below) for the year. You can tweak these figures to include April and October kWh if you want and re-figure the percentages.

    Here are some figures from
    and weather station (K)NXX (Willow Grove Naval Air Station)

    Cooling Degree Days
    2010 2164
    2009 1490
    2008 1726

    I haven't looked at the Heating Degree Days (HDD) in a lot of detail. Depending on natural gas (I assume you had natural gas) prices vs electric prices, the difference may not be as great as straight electric in cooling mode.

    However - what happened with your 1870 kWh dated 1/9/2010? Comparing kWh to HDD doesn't seem consistent for this period. HDD (from a different web site) were:

    11/2010 426
    12/2010 905
    01/2011 1023
    02/2011 709

    How confident are you that the aux heat is totally disabled? Was the set point higher?
  2. Designer_Mike

    Designer_Mike Member

    Any chance you can tell us how much gas you burned during those months?
    Looks like you still have maybe a water heater drawing gas?

    We can approximate how many btu you were getting from the gas heat and compare to the COP numbers of the heat pump to come up with "theoretical" electrical usage to heat.

    Also, do you know if you loop pump is running 24/7 ...It shouldn't be and depending on the pump (s), they can suck a bit of electricity.

    Are you using the heat pump to make hot water? That control system may be doing something odd too.
  3. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    Note to self>>>>

    ......add idiot lights to all installs. Add an extra few bucks for doing so, and a few hundred because I know how to do so. Keep making sure I am not the lowest bidder then retire.


  4. cnygeo

    cnygeo New Member

    Electric and gas rates?

    Looks like your electric rate is $0.17/kWh? That's pretty high, with average heat pump performance it is about equivalent to buying gas at $1.30/therm. Unless your gas is a lot more than that, that's why you're not seeing any $ savings.
  5. captain

    captain New Member

    CDD etc

    This is the first I've ever heard of cooling degree days and heating degree days. I read a little about it and it does seem like a good measure. So my summer cooling IS SAVING MONEY. That's good. But it should save money in the winter also right? Gas around hear runs in the neighborhood of $1.10. The Aux heater is definitely not coming on.

    What about the possibility of a leak in the loop. Where should I get a pressure gauge? The loop does not run all the time. It runs periodically.
  6. geome

    geome Member Forum Leader

    Any idea about the 1870 kWh? Heating savings will vary depending on the cost of gas and electricity.

    In a pressurized closed loop, pressure varies with the seasons (higher in the winter, lower in the summer.)

    I don't know the extent to which low pressure can adversely effect performance in a system designed to be pressurized. We were told by our installer that he likes to make sure our pressure is in the range specified by WF as lower pressures can result in the loop pipe (in our horizontal loop) losing some contact with surrounding dirt.

    Our installer also told us that it is common for loop pressure to need adjusting several times after installation, so you may not have a leak.

    Here is a link to a thread on a pressure gauge that was originally designed by Looby. Cheaper gauges are available, but no one else here that I am aware of has fully spec'd the gauge and adapters needed.
  7. cnygeo

    cnygeo New Member

    I think this may be the problem (if it can be called that). At $1.10 a therm and $0.17/kWh, you would need an exteremly efficient geo system (COP>3.5) just to break even, let alone save any money over gas. Your system could be working fine - it's just that your gas is very cheap compared to electricity so no matter how well it's working you won't see much savings. This should have been made clear to you up front.
  8. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader


    where do you live?
  9. ChrisJ

    ChrisJ Active Member Forum Leader

    Outside Philly PA
  10. shale gas = cheap natural gas

    Thanks to the vast shale gas resource now being accessed in the U.S. natural gas has become a cheap fuel that makes it difficult for geothermal to compete. However, there is hope as our expensive coal electric generation plants convert to cheap natural gas reducing electric cost and also new geothermal heat pumps that are driven by natural gas rather than electricity.

  11. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

  12. Looby

    Looby Member Forum Leader

    So, GPM is of no concern with non-pressurized flow centers?

    "Make things as simple as possible, but not simpler."
    -- Albert E.

  13. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    Who said that? GPM has the same concern, wether pressurized or not. May be you did not fully understand that one of the issues was that the installer had to come back here to adjust the pressure, something a non-pressurized flow center usually eliminates.
  14. Looby

    Looby Member Forum Leader

    Maybe you didn't fully understand that the dirt-cheapest pressure gauge
    you can find is more than good enough to check the static pressure in a
    pressurized loop. A $3.00 tire gauge is vastly better than necessary.

    The ONLY reason to consider a high-resolution pressure gauge is to
    accurately measure small pressure differences in the presence of high
    (and fluctuating) background pressures. For example, estimating flow
    with an accuracy of +/- 1 gpm requires a pair pressure measurements
    each good to within a few tenths of a psi.

  15. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    So what has a dirt cheap pressure gate or anything you are saying there has to do with the fact that the use of a non-pressurized flowcenter helps eliminate pressure adjustment issues (in contrast to pressurized loops). May be you really did not understand...
  16. Looby

    Looby Member Forum Leader

    So what do "pressure adjustment issues" have to do with the link YOU re-posted
    regarding a digital pressure gauge?

    Last edited: Mar 21, 2011
  17. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    "Our installer also told us that it is common for loop pressure to need adjusting several times after installation, so you may not have a leak."

  18. geome

    geome Member Forum Leader

    A $64 pressure ram (7/2010 price) was worth it to me to avoid having the installer come out, but I like DIY maintenance. (A hose is needed as well.)
  19. zach

    zach Member Forum Leader

    I am very happy with my non-pressurized flow center. I have no worries about loop pressue fluctuating or needing to have my installer come back and adjust the pressure.

    I see non pressurized flow centers as the future of the industry. I am hands on as well but also busy with life. I'd rather not have to worry about fluctuating loop pressure.
  20. ChrisJ

    ChrisJ Active Member Forum Leader

    I looked again at Captain's picture of the electrical tag from his unit. Under loop pump it said 1/2 HP pump at 5.4 amps, Is that a typical size pump for a pressurized system. My system (non-pressurized I think) uses a 1/6 HP pump, 1.2 amps something like that. Does it take more pump to run a pressurized system? Or maybe vertical closed takes more pump. I don't think Captain said what type of closed system he has. Mine is horizontal, for 5 tons.

    Down2earth, I won't be holding my breath waiting for the electric co to lower their rates.


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