More control tuning

Well I have managed to stop it intermittently alarming on overheated return from the heating circuit (though it still cycles OK in this state the output is reduced and the house cools). This by reducing the speed setting on the house circulation pump (max to min of 3) and putting on more radiators (top floor /3 was off whilst we painted). The house radiators are still all hot. Also by backing off the 'slope' to the factory 4.0.

Perhaps counter-intuitively this actually raises the house temperatures (to normal, meaning 19+-0.3 for rooms) and raises the GSHP output (drops the cool ground circuit temperature), partly of course by cooling the return heating loop - but the controls are strange all the same. I see that it is possible to have a temperature-dependent slope; this may be the answer, 4 when it is cold, more when it is warmer.

FTR external 2m above ground temperature is -3 to -3.5C, the same as last night.

Note added 28/11/10:-
This seems to have worked well; mainly because the GSHP cycle time is for unclear reasons shortened (by about 20% for a slope change from 4.5 to 4) though the change in house pump circulating speed may play a role. External temperature last night fell to -4.4C but we are still some distance clear from the return 'limit'.

Problems in the cold.

Well last night was fairly cold (-2.5C at 2m above ground) and the heat pump started returning an intermittent (self-resetting) error condition. This is because the return temperature of the heating fluid into the heat pump from the mixing 'accumulator tank' is too high. When this cools the HP restarts. Indeed the temperatures are quite high (I have now added monitoring sensors) and the mixing in the accumulator tank means that the GSHP sees higher temperatures than the house heating loop (for this reason I have never been so keen on this tank!).

The system suggests backing off the 'slope' to reduce this, or that the circulation over the heat pump is greater than in the house circuit (which must be true if the GSHP's circulating pump is similar). I have backed off the slope to 5.5 and the sensitivity to house temperature to 8. We shall see - tonight should be as cold.

Tarmac Man

OK - so the final electricity team came and filled in the hole with tarmac. And the final bill came, too, bringing the total cost close to £42k, less any grant (~£1.5k, in a few weeks maybe).

This is set against a reduction in heating bills which is on track to be £700pa or so (as expected) though we shall have to see in a full winter. If the Renewable Heat Incentive (RHI) comes through (as is still promised before April 2011) this could help a good deal with running costs. And there is the convenience of having a heating system which can manage on its own - remember we had solid fuel. And the last of the anthracite has gone (to a village Welshman and his family, who have a Rayburn, with a wheelbarrow!).

Plastic Jerry cans

One point to be clarified still - we were left with 11 20l plastic jerry cans by the installer - 5 empties but 2 unopened and 3 with pre-mix in them (& one 'rubbish' containing some kind of fluid). I am not clear whether this is because the circuit fluid is less concentrated than expected (the pre-mix is labelled '-18' whereas the certificate says '-14' ) of smaller volume than expected or just that the glycol was over-ordered.

Old Cable goes.

Well that is almost it - the old single-phase cable is out of the house and cut back to a point below the pavement. One surprise is that there is an existing dividing point in it (ie resulting in a second cable) just below pavement level. I note that this surprises them, too - so records of the 10-year-old installation are clearly patchy!. The second cable heads up the road in the direction of the neighbor's round the bend, though in this case the new installation should have encountered it.

And naturally the cable-remove crew can dig the hole but we need another team to fill it in and cover over - probably in a day or two..

Note added 20/11/10 - make that TWO more teams to visit! One has been and filled in the hole, but we still await the team that covers it with tarmac.

Another eon - the meter man comes (again..)

Well we have had a man to read the new meter - of course the carefully-left message that he does not need house access did not get through but the multiple mobile texts asking me to be in (on an un-agreed date) are something I suppose.

He tells me it is a 'smart meter' - which it isn't (smart meters can be read remotely - we should be so lucky!) though it may be able to accommodate feed-in power (if we had any). One dreads to think what the bill will look like whenever it comes in; though in fact the GSHP is performing well. Using nominal flows COP looks to be 3-4, and the mark-space ratio for pump operation only went to a bit over half with our first below-freezing period (at 2m under-eaves where the sensor is - plenty of ground frost before).

Next excitement is Thursday when they come to remove the old single-phase cable.

More sensors - and more electrics!

Well the monitoring system referenced below now has an extra batch of sensors connected; it also has 4 buses radiating from the box, which must skew the impedance a bit but it seems to work well. I think this is enough for the moment (we have an independent electric power measuring system - one could integrate temperature and power monitoring using another system which we may try sometime). We have learned a lot but there might be more real added value in knowing the heat output by the GSHP into the house heating (to compare with the electricity used) but this seems quite hard. Independent heat meters exist (for metering heating in collectively-heated blocks of flats) and of course measure water flow (using impellers or ultrasound) as well as temperature and are quite expensive (£100's).

And I have just had ANOTHER call from eon (suppliers) who want to send yet another man to have a look at their newly-installed meter box! It appears that they have got confused between two slightly different versions of our postal address (no matter that we always gave their reference number as well!) and somehow have two accounts. In addition they have somehow got the brand new 3 phase meter with its serial number as here since 2005! Unless they are clever enough to get the old serial number fitted to the new meter (doubtful - and why, anyway?) their system seems as confused as ever. I cannot see what they learn by looking at the meter, either, but they are welcome!