Sunday, April 18, 2010

Measuring up for Datalogging

17 April : Blaise came round to discuss where we would fit thermocouples for the datalogger. He is the engineer who is also a PhD student in our school studying heatpumps, and will be at Shanghai to present my sunboxes (and a couple of other things too, including PVT).
  Seeing it in action on the sunniest day of the year, he really did seem to appreciate how they worked and the thermostat was working wonderfully to display the temperatures. As a heatpump engineer, he has  focused on the mechanics and the COP, whereas I have this larger idea about how the product might be extended as an
  He suggested moving the Cold sensor to the pipe that comes from the loft, and I did that.... It's useful to have an accurate display of that pipe coming down from the sunboxes - but I changed it back after he had gone because I remembered that the sensor has a double function - it needs to be in the COLDest location, or it will not switch on the sunboxes. The only temperature that should trigger it is the Ground loop temperature.
  I realised this when I found that the sunbox pump was still working at sunset, but by now pushing glycol through the loop colder than the loop had been earlier. By moving it to the position I had originally put it in, the Sunbox can Never cool the loop.

Time for a Better Datalogger
The datalogger I had originally been loaned is a DT50 and only really records 4 channels. We identified FIFTEEN important temperatures that must be recorded:

  • 2 - The flow and return to the Sunboxes
  • 2 - The flow and return from GSHP to the Groundloop
  • 2 - The flow and return to the underfloor heating
  • 2 - The cold water main and the hotwater supply pipe
  • 1 - The combined temperature of outgoing pipe and incoming sunbox pipe where the Trigger-Sensor is located.
  • 3 - the Air temperatures in the House, externally in the shade, and inside the Sunbox.
 3- We also need Lines in from the Energy Flowmeter on the Sunbox circuit, the Hot water flowmeter and the future Energy Flowmeter to the PVT sunbox that is not yet built.

2 - We also need a line in from the thermostat and the heatpump simply to record WHEN the devices go on and off. As they seem to track each other, this is valuable information.

So we need a better datalogger, and Blaise will bring a more powerful one next week - probably a DT500. We will put it on the roof of the GSHP, and ask Chris to weld us up 12 thermocouple cables.
My laptop had a problem with loading the software - I have an old virus checker on it that has become worse than a virus - it can't be upgraded, but it won't allow me to install another, or de instal it.
   So he will try to get an old laptop from the Uni. Actually... I just remembered, I have one in the office at the Uni. So I will bring that back.

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