Saturday, February 19, 2011

Under performing in East Leake

19 Feb '11: We are not getting such good figures from the new installation. Although it should do better than the Peveril house, in theory, this demonstrates the better feedback one can get from a real life real time installation.
   From 2-16 Feb, the Peveril Sunboxes captured 90 kWh, and the East Leake ones only 46 kWh. There is a difference in the plumbing layout, but I don't think that should be the reason. We are trying a number of things:
1. Reduce system losses. Need to fully insulate the pipes from the sunboxes to the heat pump now that we have checked for leaks (and there are none).
2. Check that there isn't a lot of cold air getting into the box somehow, eg the back of the box is against a slightly uneven wall and there is a case for some duct tape to do some sealing.
3. Check that the two sensors are correctly positioned. I am not sure if the Cold sensor against the ground loop is strongly enough taped with thermally conducting paste. Perhaps the warm sensor needs to be positioned higher in the box, so it detects a rise in temperature more quickly (eg when the sun comes out from a cloud) On my system, the sensor is at the highest point of the box where heat rises first, but has a foil hood to stop it being triggered by direct sunlight.
4. Reduce the pump speed. If it is slower there is a more distinct temperature difference between the flow and return, if it is too fast, then the energy flowmeter isn't precise enough to measure the temperature difference. In my case, it can run at middle speed, as the pipe length is longer and the volume is about 60 litres. In E Leake's case, with the compact radiators and small pipes, the volume is smaller.
     As if that wasn't enough we also had the Energy flowmeter stopping recording for a few days, it was showing an error earlier in the week and with a bit of tapping and shaking, it worked again.... new technology, huh!?

Postscript 27 Feb '11: I visited the site and the main problem seems to be a large gap at the top letting warm air escape. There is a smaller gap at the bottom, and rain penetrating from the top - needs a flashing.

3 comments:

  1. David,

    Just a few points to consider:

    1) it appears that the east leake installation is more shaded - especially because its low level.

    2) It would be worth while comparing your data directly against the east leake data. (though i am not sure you record this type of data, whihc you will need.). If you compare the average glycol temperature when the heat pump is running and going through the sun boxes. Remember you have different boreholes (and heat pumps etc). It may be the case that on average your glycol temperature is lower for other reasons goverened by the installation and the heat pump load profile. If this is the case a lower mean glycol temperature would mean that you will have a greater energy yield from the sun box.. It doesn't mean that your sun boxes are better performers, just that the situation dictates that there is a greater temperature dufference between the mean glycol temp and the air / (and panel temp due to irradiance.) You really need to assess the peculiarities of both installations to make a judgement.

    Chris

    ReplyDelete
  2. Thanks Chris,
    We will continue to monitor and compare. At the moment we dont have the E Leake spreadsheet visible, but i could ask David about this.
    Or perhaps make it available to you as a viewer.
    David's boreholes appear to be twin 60m boreholes (at first he thought it was 3 holes, but now thinks that the drillers aborted drilling on the middle hole for some reason)
    I have asked him to put the pump on a slower rate.
    ==david

    ReplyDelete
  3. The E Leake panels have shading at lower levels from East (Trampoline) and West (House shape). But they havent got the overwhelming shape of Sharp Hill that I have south of my house during Winter months.

    ReplyDelete

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