Wednesday, December 1, 2010

Floor pump Thermistor on a Timeclock

1 Dec '10: I now managed to get both the heat pump and floor circulating pump to switch itself on and off due to time as well as to temperature.
   Although the GSHP has its own timeclock to turn it off at night, that doesn't stop the floor circulating pump from whirring all night if the external air temperature is below 15º. A few months ago, I rigged up a 2 way switch that we could use manually, so that we could fool the GSHP and the floor pump into thinking that the temperature externally was 25º - so that neither could come on. I did this by installing a fixed resistance of 4.7 kohm which is what the external thermistor would return at 25º.
   With these cold days, we have been wanting the GSHP to start a bit earlier than usual (like 8am), and not wait for us to get downstairs for breakfast. So I have taken a 220 vac line to the original switch, and from there, it goes to an Omron relay below, and this has a 2-way switch function, so it can switch the temperature sensing between the real external thermistor and the fake one. Now, with a little B&Q timeclock, we can have the sunboxes and the GSHP+floorpump turned off and on at the same times.
  Please, Navi tron expert critics, do not attack my wiring, this photo was just after I got it working, and I will tidy it up. And yes, I don't like using an adaptor but it is only driving 50 watts. And the little wires around the Omrons are mostly datalogger cables.

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