Measuring Heat Pump Performance - Data Logger?

Discussion in 'General Discussions' started by Eric D, Feb 4, 2008.

  1. Eric D

    Eric D Member

    Anyone using a data logger to monitor the performance of a geothermal system? If yes, what type and how well is it working?

    I have a number of geothermal systems I would like to gather data from to allow for a baseline of performance. This data would then be used to compare performance numbers of different systems and to help identify future degradation in a system over time.

    The system should be compact enough to allow easy portability, and easy setup. I would like it to record for at least a week without needing any attention. I want to record at least 8 temps, measure A/C current on two channels, and maybe a couple of pressures. Two measurements per channel per minute or better.


    Eric D
  2. saeheumsong

    saeheumsong New Member

    Performance measurement.

    Dear Eric,

    Would you please teach me how to measure heat-pump performance and cost of doing it?

  3. Eric D

    Eric D Member

    Mr. Song,

    Did the calculations help out any?

    Eric D
  4. saeheumsong

    saeheumsong New Member

    Dear Eric,

    It was indeed helpful understanding the concept. I need to measure COP of my invention in near future. My system is not DX not water based system. However, the principle should hold.

    Kind regards,
  5. Rgausman

    Rgausman Member


    I have just installed a Hydron 4-ton GSHP which I am beginning to collect data on. I am using the "Web Eergy Logger" (WEL) which uses a '1-wire' bus network of thermisters to collect data. The logger uploads the data every minute to the WEL Server website which the collected data can be overlay a drawing and graphs created.
    See for the main page. Check out the samples.
    This is my page:
    It does a great job in gather large number of temperatures and electrical power. However, pressure reading is a problem. For Heat Extraction, you can measure/calculate the pump flow and plug the value into a formula as a constant.
  6. Eric D

    Eric D Member


    Welcome to the GeoExchange Forums! Wow! Your data is awesome! Did it take you long to get the data logger system up and running? How do you like the logger system and the GSHP so far? Are they performing to your expectations?

    Looking at your ground loop temps, they seem somewhat low. What style GL did you end up with?

    Sorry for all the questions, but my geeky engineering side really enjoys this type of stuff.:D


    Eric D
  7. Rgausman

    Rgausman Member

    The WEL logger is a very easy thing to setup. The 1wire thermisters are about +- 1 degree F. I place all my new thermister on a breadboard inside a cooler in the basement to see what temperature differences. This is what the T02-T10 temperatures are. You can modify thermister's display temperature with an offset. I matched thermisters were delta T's were critical like EWT/LWT. The '1Wire' network is great and inexpensive for monitoring temperatures. However, there does not seem to be any pressure sensors for this system. With the WEL, you can also use a 'WattNode' to measure current flow for power calculations and it has eight contact closures to monitor/count on/off state. This would allow you to hook up a flowmeter which clicks off for X number of gallons of flow.

    The loop field is 2000' x 3/4" PE, 36" pitch horizontal slinky in 4 x 100' trenches at 6' to 7' average depth.

    My install has only been up and running for two weeks now. The low temps are due to soil not being totally compacted yet and when I backed fill we where having 20 degree weather. When circulating the loop before actually HP start up, the loop temperature was 40-42 degrees.

    I first excavated in October and watched all the heat in the soil escape :<. Had rock issues which result in loosing a month. Also the inspector wanted everything exposed for the hydrostatic testing. Looking back, I would have ask AHJ to header up the loop field, test and back fill first then worry about the header trench. The loopfield is basically holding steady. Should improve next season. This is another advantage of a vertical loop which are not effected by surface temperatures.

    Take care, Bob
  8. Eric D

    Eric D Member


    Thanks for the update on your system. This spring I hope to install a ground loop. I'm currently running open loop. The system is doing a good job but I would really like to go closed loop.


    Eric D
  9. Guest

    Guest Guest

    Hello Eric,

    You won't much if any Delta in temperature over a week. The pressure differential only confirms the flow rate from the pump(s) and the confirms minimum reynolds number.

    You need a data logger that takes perhaps a weekly reading over an entire year. The seasonal cycle is what you want to study. ie-How well does it respond to both heating and cooling cycles. Is the comfort level and cost saving sufficient?
  10. Waukman

    Waukman Member

    I am using a home grown logger. I have a 2 temperature sensors and total power consumption. I use a 8 port serial temperature monitor that uses DS1820 devices. I have a wattnode meter that I use to capture electrical usage. The basic parts are the same as with the WEL. At the time I did the install I wanted to install the WEL unit but the total cost was beyond what I could justify at the time. I already had the serial monitor so I only needed to purchase the wattnode. In time I plan to add the WEL unit using the existing equipment.

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