Normal Loop Temps

Discussion in 'General Discussions' started by Altnrgy, Aug 6, 2011.

  1. Altnrgy

    Altnrgy Member

    I searched the forum and didn’t find a thread on normal loop temps. I did see it mentioned that ground temp +/-20 was a rule of thumb for EWT’s depending on the season. It was not clear if that rule was for normal or max though. I just measured and my well water is 65f which I assume is that is nearly same as the ground temp.

    We installed a 3 ton Climate Mater Tranquility 27 in early June are loving it so far. Two 300’ vertical loops and a desuperheater. It spends 90% of its time in 1st stage and is able to keep our house comfortable 24/7 unlike the system it replaced that barely kept up most of the time.

    Total house energy usage is down at least 15% from the same period last year and geo is the only thing different. Like many across the country our cooling degree days are up at least 10% from last summer. In summary; I’m tickled pink - cooler house, hotter days and noticeably lower energy usage.

    I’ve been data logging the EWT and LWT. We started off the summer with morning EWT’s just under 70f and rarely got much above 75f. Now were starting the mornings just over 75f and are hitting 85f every day. Of course the outdoor temps have been over 105f 7 out of the last 10 days here along with some all time records.

    I watched them grouting the wells and it seemed like they got a lot less grout in one than they did the other. Perhaps as much as 90% less but I didn’t babysit them every second so I can’t really be sure. Yet, I’ve still been suspicious that one of the loops is far less effective than the other. I’m wondering if my loop temps are indicative of one of the wells being less effective or if they are normal given the record setting heat lately? It still keeps the house comfortable and energy usage is still lower than last year so it certainly passes that test.

    Can any of you veterans speak to what I should expect loop temps to be?

    Thanks, T
  2. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    Hi and welcome,
    Since you allready have paid for the system getting the required info should be easy. It is all about the design. Call your installer and request a copy of your manual j, and the subsequant desing that the manual j generated. All the info you need is in there. Outdoor design temps, run times, anticipated loop swing ect. All that being said this heatwave has put a crimp in a lot of designs, or your system could be right on the mark and functioning as per the design.
  3. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    Industry norm is 90F max and 30F min entering water temperatures.
    That is likely where you are designed and you needn't worry if you stay within those lines.
  4. cschmelz

    cschmelz New Member

    My loop changes fairly quickly to extreme heat outdoors. My EWT has gone up 5 degrees over the last 10 days during very significant cooling load. The impressive thing is, a few days of lower temps results is a fairly significant decrease again toward the summer norm (this summer, my typical EWT has been 65-67dF and recently have been up to 72dF) This is a very good loop thus far.

    Lowest of the winter was 32dF EWT.It sounds to me the loop is just responding to record heat and is, as others have pointed out, well within acceptable norms.
  5. Altnrgy

    Altnrgy Member

    Thanks Cschmelz,

    I'm seeing the same thing regarding a quick drop in EWT's as soon as the load drops for more than 24hrs (or so). Are you a closed loop? Any idea what your ground temp is? I'm curious if it's noticebly lower than mine in the southern most part of Missouri.

    I'm a closed loop and my well water is currently right at 65f so EWT's much under 70f is unlikely I think.

    Thanks, T
  6. Altnrgy

    Altnrgy Member

    Thanks for all the replies. I'm not terribly concerned that anything is wrong and your replies have really reinforced that.

    We've set record highs something like 9 out of the last 15 days and not just barely, but smashed them by noon. So the fact that my house still stays quite comfortable with very little 2nd stage operation and over 20% lower total house electric usage than last year’s milder July is all the proof I really need. I’m really just curious about what this summer’s record heat wave has done to people’s EWT’s vs. a “typical” summer.

    One of my big questions when I really started thinking seriously about going to Geothermal was would I be able to see the EWT trend up all summer long. While I have been able to see it trend up, it’s not nearly as pronounced as I thought it would be or for the reason I assumed; which was the ground would become increasingly saturated with BTU’s thus leading to higher and higher EWT’s.

    In reality, what I’m pretty sure I’m seeing is that the higher EWT’s are much more a function of increased load on the system because the average daily temp continued to rise. The record heat wave broke just a few days ago and my EWT immediately started out the next day under 70f just like it was nearly 8 weeks ago. Had my loop been saturated with BTU’s I theorize that it would have trended down. IE; 74.5, then the next morning 74, then the next morning 73.5, and so on over a period of weeks. That pretty much dispelled in my mind that ground was saturated with heat.

    Great thread. Thanks everyone!

    Cheers, T
  7. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    you now have a better understanding of moving btu's around than some of the proffesionals I speak with on a daily basis.
  8. AMI Contracting

    AMI Contracting A nice Van Morrison song Industry Professional Forum Leader

    :eek:I'm sure you weren't refering to anyone around here:D
  9. engineer

    engineer Well-Known Member Industry Professional Forum Leader

    Sub-85 EWTs in the context of 105*F highs mean your geo is likely delivering the goods at substantially higher efficiency than air source heat pumps.

    Don't worry, be happy!
  10. Altnrgy

    Altnrgy Member

    I'm quite happy. I couldn't have seriously considered geothermal had it not been for a 50% state rebate. Couple that with the 30% Federal tax credit and $300/ton rebate from my utility and I'm going to end up net discount of over 75%!

    Best, T

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