Saturday, March 27, 2010

Sunny days in March: time for gardening

27 March: I noticed today that the OWL meter (which displays the flux through the main house electricity meter) was showing 2.75 kilowatts. I rushed round the house furiously trying to find what could have been left on, this was more than a kettle or immersion heater or oven! I then realised that the meter was actually working in reverse, and the total going from our roof to the grid, minus what we were using was 2.75 kWatts. Haha! Hope we have more days like this during the summer!
   For our temperamental GSHP, we turned off the pasteurization function altogether, and I also discovered that the water tank inside the inner casing is inadequately insulated - the whole bottom panel of a 50cm diameter hot water tank is bare metal! So I used some thin super-insulation to make a disc of insulation to slide under the tank and taped it to the sides. Also insulated some of the pipes inside the unit which presently allow heat to disperse in the cabinet. Today, the water system has been quite stable, the temperature going no higher than the hysteresis range of 5º, and not losing heat once it gets to target temperature.
  I have neglected the garden for too long, as this project has preoccupied me tooooo much - my wife is beginning to think I have 'Heat-pump Aspergers'... ! And I do wish the scaffolders would come to take their stuff away so we can have a nice photo of the finished work.
    But if I am allowed to make one observation, it was that mid afternoon, when the GSHP came on to top up the house heating, the outgoing glycol temperature was 9.4º and the returning temperature was a steady 12.9º - this is higher than the ground is ever expected to get normally even after a summer's recovery time. The Surya Sunboxes had put 12 kWhrs down below by 3pm, with more sun to come for the rest of the day! So this is working!
28 March: another sunny day and time for more gardening and time spent on some forestry up in Sharp Hill wood. Went out for three hours in the afternoon, leaving the Heatpump Off and the Sunboxes On. Air temp. is still only about 9-10. On my return, tested the ground temperature (when you turn it on, the initial glycol pulled in reflects the ground temperature if you wait about 5 mins, and when it begins to go down, that is the effect of the new outgoing colder glycol.) The ground temperature was 15.0 !
  The reason for leaving it off was not just to test the ground - it is that this particular pump cannot be trusted until it has its controller replaced. After writing the paragraph above, I went down only to find that yet again, it had run amok pushing the water temperature up into the 60s, with the red panic-light showing. Rebooted, and it was calm again, saying that no heating or HW required.

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