2008 dual stage to 2017 variable speed conversion

Discussion in 'General Discussions' started by docjenser, Jan 31, 2017.

  1. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    I thought I post an interesting little case report.

    5200 sqf old farmhouse
    This is the coldest property we have, at higher elevations about 50 min south of Buffalo, a couple years ago this was at -26.8F.

    Installed a 6 ton dual stage Climatemaster TT27 in 2009, reduced the heating bill from $5000 (propane) to $1800 (increase in electricity), dual pump flow enter (2x 26-99)


    Customer's son got a variable speed 7 series a couple years ago,
    http://welserver.com/WEL0834/, now the father wanted one too.
    Now we replaced the 8 year old dual stage 6 ton with a new 5 ton WF 7 series with a single 32-140 variable speed flow center.

    Interesting to compare the performance.

    With very similar heating degree days, the daily KWH usage went from 110 down to 70, about a 35% reduction.

    Even more interesting, the balance point was around 20F for supplement heat, but so far, despite 10F night, the supplement heat did not engage, so it appears that we are getting a higher capacity out of it.

    An anecdote, not more, but interesting to see the evolvement of the technology in the last 7 or 8 years. DailyKWH.png Screen Shot 2017-01-31 at 3.16.30 PM.png
    urthbuoy likes this.
  2. ChrisJ

    ChrisJ Active Member Forum Leader

    So is the WEL hooked up to the 7 Series or just a few of the sensors?
  3. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    The WEL 447 is hooked up to the 7 series, but it also has a Symphony. I just have to tweak some of the graphs since I lost some signals.....on/off being one of it.
  4. Deuce

    Deuce Member

    I really like the comparison.
    ChrisJ likes this.
  5. ChrisJ

    ChrisJ Active Member Forum Leader

    I do too. Interesting that an 8 year old heat pump gets replaced long before it's life span.

    I replaced an 8 year old unit last year, just didn't have the money for the 7 series and a variable speed loop pump.

    I look forward to seeing what sort of payback the customer will get with the savings on the new unit.
  6. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    If you assume a 40% reduction in his now $2000 (giving the lack of supplement heat use so far), that is $800/year. I think we sold it to him for about $13,600 installed, minus the tax credits, so he is at about $10K out of pocket. So roughly a 10 year payback. Without factoring in interests if any, inflation, increase in electricity rates etc. Just some ballparks. Plus new 10 year warranty.
    Giving the increase in efficiency, and about a simplified 10% ROI, you could make the argument that everyone should upgrade after 1o years. :rolleyes:
    ChrisJ likes this.
  7. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    Feb 2016 KWH usage = 2963 KWH (6 ton CM TT27)
    Degree days: 1063

    Feb 2017 KWH usage = 1630 KWH (7 series WF)
    Degree Days = 845

    Normalized for weather, the 7 series uses 69.2% of the energy compared the TT27.
    ChrisJ likes this.
  8. bdbsenji

    bdbsenji New Member

    I just replaced a Waterfurnace Envision with a Waterfurnace 7 Series unit. I had a WEL installed on the old unit. It doesn't seem as if the WEL 24 volt thermostat interface is compatible with the 7 Series. How did you install the WEL on the Series 7? Is there a way to tap into the units data or did you install the normal WEL sensors? Thanks!!
  9. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    You are right, the thermostat signal is proprietary to WF and cannot intercepted, thus you don't know what stage the unit is in. We lost that information.
    You can see the power draw of the unit, so you get a bit of an idea what stage is running, but you cannot use it for computations.

    But now you have the Symphony:)
  10. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    I could not resits and run the whole dataset, and the 12 month period in 2013,2014,and 2015, and compared it with a 12 month period in 2017/18after the conversion.
    6 ton TT27 Climatemaster fully functioning with a dual pump 26-99 flow center, installed in 2009, replaced by a 5-ton 7 series with a single Grundfos 32-140 ECM loop field circulation pump at the end of 2016.
    Both desuperheater, same occupancy, same thermostat settings.
    Then I normalized the weather data to adjust for the slightly different heating degree days, to take the impact of different weather out of the equation.
    So all the variable factors were excluded, and what is left is that you have a direct comparison of the highest efficient heat pump of 2009, and compare it to the state of the art in 2016, which is a testament how the technology emerged in the last 8 years.
    The result is that the WF 7 series consumed 58.8% of the energy the dual stage climate master did for exactly the same load.
    I though this was going to be good, I did not expect this to be that good.
    I am officially impressed.
    Homeowner had average cost of $3120 annually, down from $7,000 in propane, but is now down to $2,020, saving $1,140 /year in electricity. Brings up the question of payback for the 7 series.

    Attached Files:

  11. Stickman

    Stickman Active Member Forum Leader

    Compelling analysis Doc - kudos and thanks for running it. Makes me wonder about those of us with smaller than 6 ton systems. My kWh usage is less than what it was with your client’s CM. If the 58.8% is applied to a smaller number, the end result (savings) would be smaller (less), wouldn’t it? Or is my late-in-the-day math off? Maybe the unit/installation is somewhat significantly less for a smaller system, helping the ROI timeframe?
  12. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    Certainly, when the load is less, the $$$ savings are less. Extremely put, if you house does not need any energy, you are not going to save much. But I would say the 60% ratio is fairly accurate.
    So here are the tricks.
    1) use a ECM 32-140 single pump (in the example the old setup was with a dual pump). Have a loopfeild design for low pressure drop. Use methanol.
    2) adjust the pump setting in symphony to reduce the pumping power so you have about 2.5 gpm/ton
    3) throttle back the fan so you see about a 23F delta T over the air coil. Ductwork should have been designed for low pressure drop.
    4) put in a 7 series
    gsmith22 likes this.

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