Geothermal Monitoring?
Last Post 28 Mar 2014 10:11 PM by docjenser. 22 Replies.
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Ground EnergyUser is Offline
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27 Mar 2014 06:58 AM
Once you put them on pipes, you have to recalibrate them anyway, so what is the point to have them calibrated already.


We have found a few problems with this approach. First, there is a small bias introduced from mounting them on the pipe surface. However, because the bias applies to both the EWT and LWT, its affect will be small (less than 5% error in delta T), if properly installed -- using the methods similar to those described by Bill. The sensor offset is a different source of error and, because it is temperature dependent (as shown in DS18B20 datasheet and App note cited above), both the slope and offset need to be incorporated into calibration. The final challenge with calibration in the field is that temperature probes that are available for P/T ports are typically either very expensive or not very accurate (in spite of some manufacturers claims).

Here is a link to a fact sheet we've put together that summarizes these issues. http://groundenergysupport.com/wp/docs/datasheets/GxTracker_DataSheet_OnPipeTemp_rev1.1.pdf
Bill NeukranzUser is Offline
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27 Mar 2014 09:33 AM
Posted By docjenser on 27 Mar 2014 12:48 AM


Sorry, I misspoke, it is 0-5 volts....

I saw it though.  The 0-5 VDC ammeter simply won't take advantage of the 0-10 VDC input range of the WEL.

I thought about ordering a 30 A ammeter instead.  But, I was fearful there'd be times, particularly when both units are running, and one or both might be running is Stage 2, where current is greater than 30 A.  So I ordered a 50 A unit just like yours.

Thanks.

Best regards,

Bill
Energy reduction & monitoring</br>
American Energy Efficiencies, Inc - Dallas, TX <A
href="http://www.americaneei.com">
(www.americaneei.com)</A></br>
Example monitoring system: <A href="http://www.welserver.com/WEL0043"> www.welserver.com/WEL0043</A>
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28 Mar 2014 10:11 PM
Posted By Ground Energy on 27 Mar 2014 06:58 AM
Once you put them on pipes, you have to recalibrate them anyway, so what is the point to have them calibrated already.


We have found a few problems with this approach. First, there is a small bias introduced from mounting them on the pipe surface. However, because the bias applies to both the EWT and LWT, its affect will be small (less than 5% error in delta T), if properly installed -- using the methods similar to those described by Bill. The sensor offset is a different source of error and, because it is temperature dependent (as shown in DS18B20 datasheet and App note cited above), both the slope and offset need to be incorporated into calibration. The final challenge with calibration in the field is that temperature probes that are available for P/T ports are typically either very expensive or not very accurate (in spite of some manufacturers claims).

Here is a link to a fact sheet we've put together that summarizes these issues. http://groundenergysupport.com/wp/docs/datasheets/GxTracker_DataSheet_OnPipeTemp_rev1.1.pdf


Respect...you obviously put a lot of work into this. I am not only looking at the delta T, actually it is the lesser important thing I am interested in. I care more about the real temps, An since I don't know the ambient air bias or influence, I need to calibrate it anyway once it is mounted. Plus not every mounting is the same, and not sensor insulation is the same, so the amount of bias varies. But again, congrats for looking into this more.
www.buffalogeothermalheating.com
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