Vermont Sensors

Discussion in 'Maintenance and Troubleshooting' started by Grant, Mar 4, 2015.

  1. Grant

    Grant New Member

    I have a new ground source system and have some issues that I am trying to sort out and was looking for some advice on sensors. The system was installed using strap on sensors (Tekmar) for providing data to the control units/data recording and some solar digital thermometers. These are located away from the unit on parts of the piping. My source delta T was about 6 degrees back in mid January in the recorded data. At the end of January I developed a refrigerant leak from the reversing valve. Finally got that replaced and the system recharged. However now the delta T is only a degree or 2 according to the sensors. The system runs and eventually gets to temperature. I checked the HE using the flow meters and the delta T. That indicated low charge. The digital thermometers read a higher delta T, but I question their accuracy as the combined source temp reads lower than any of the individual sources. I do not think that their wells were installed correctly.

    I am down to that I have either bad sensors or I have low refrigerant. There are no P/T ports on the system, but I am willing to make changes so that I can get more accurate data. I have tried using a strap on TC on the source fittings, but I get a lot of variability. Trying to get the tech back here to check superheat, but frozen systems are taking priority.

    So any advice on sensors would be appreciated.
  2. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    Borrow a clamp on temperature reader and check the accuracy of the sensors.

    Strap on sensors not reading representative temperatures is not uncommon.
  3. dgbair

    dgbair Just a hobby Forum Leader

    That's pretty sad.... seems like a basic thing that every system should have.
    Palace GeoThermal likes this.
  4. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    agreed...a major lack of effort by the installer for both the homeowner and any future service tech
  5. Stop gap measure only, get a couple of cheap probe thermometers (try $4 meat thermometers) and stick them through the insulation on the i\o loop lines close to the unit making sure the tips touch the pipe.

  6. Grant

    Grant New Member

    "stick them through the insulation on the i\o loop lines close to the unit making sure the tips touch the pipe." What insulation? None of my piping is insulated until the PEX is under the floor. What is typical for an installation? I would love to see someone else's system. Anyone have a typical instrumentation plan to share?

    Sorry but this is my first exposure to a geo system,but I thought that my installer would take all the proper measures for instrumentation and necessary insulation if needed.
  7. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    Are your strap on sensors on PEX?
  8. Grant

    Grant New Member

    No not on PEX.

    The strap on sensors are on brass fittings in the 2" Schedule 80 PVC. The source in one is attached just after the pump. The source out is attached to the brass fitting for the digital thermometer not directly in the flow stream, but on the T for the thermometer.

    All the source piping is 2" schedule 80 PVC. There are 4 sources which get T'd together just before the pump.

    The load side is 2" PVC up to the zone valves. From the zone valves it is either PEX or copper of different sizes depending upon the amount of flow required for the individual zone.

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