Fan convectors

We have replaced the lounge fan convector (admittedly 27 years old!) with a new one with half as much again nominal capacity. This (Myson) unit also has newer controls that are adapted to GSHP in that the cut-off for low water circulation temperature can be reset to a lower (32C) value. With various other changes this has raised the lounge temperature a bit, and stopped the convector blowing cold air when the GSHP goes off! FTR our fan convector is in a screw-closed box behind a decorative brass grille, and we leave off the official fan convector casing (just as with the old one) as this increases output significantly. The new unit also has a room temperature sensor (as opposed to a thermostat) which comes built-in but is quite easy to rewire to a remote location in the room (that is outside the wooden box!).

All the same we may still be limited as much by water circulation as fan nominal capacity, and I have raised the house circulating pump one notch (to middle of 3) which seems OK for now, though it is not very cold (-1 or so) at present so we shall see.

The Electricity Bill

Well it did come in and it does come to thousands! - but that is because it goes back to 2005; since it also credits us with payments since then we actually do not end up owing anything net - but the sheer complexity of the system (not to mention the length of the bill) is astonishing! Maybe it is not so bad to have it all itemized in one place - but why, exactly?!

Otherwise the sensor system now includes a switch on one of the GSHP-only phases (ie on if on & VV) so the average power it consumes can be monitored, on the assumption that it always draws the same if on (which seems true).

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!

Well we now have a weblogger monitoring our Heat Pump. You can see the results here:-

http://www.welserver.com/WEL0412/

Electrical games

Having commented before on the amazing complexity of dealing with the electricity suppliers we have had a rather surreal experience with them.

Having had the 3 phase set up and connected we needed the single phase meter read and removed. This is fine in principle - one calls eon as before and asks. I then find that, even though we called the same number to get the 3 phase meter fitted THIS bit of eon does not know about that. So I have to register the system in order to get the (same) man to remove the old meter (then one calls another bit of the suppliers to get the cable removed - in about 3 weeks).

Not ten minutes after he left I got a call asking me to please tell them the serial number and reading of the 3 phase meter they have just installed ('hey, your man just left...'). Still - this is fine except that the person I am talking to does not know how to read the new meter (clearly labeled 'property of eon') - he feels it should just show the 2 readings alternately (actually it alternately shows time and date). But by pushing various yellow buttons I can get two numbers (but would not a new meter start from zero anyway?). Reading instructions on the meter itself might have been a thought...

I have no faith that there will not be more issues here; for example I pointed out that we are on dual-rate so there are two readings - but he seemed not to be listening. We shall see!

And a detail of useful stuff - there are inevitably small parts of the cold ground circuit showing near the pump - valves, access points etc. These collect condensation and drip a little. But plastic disposable cups mounted on garden wires can collect the drips - which then evaporate anyway from the warm cups!

Fiddling with the controls

Well it all works pretty much, but we have had a fine time fiddling with the settings and may have to make more adjustments before we are done. For unexplained reasons (?concern over local disturbances) the controls favour indirect 'feedforward' control via an external temperature measurement and a fudge factor ('slope') to estimate the heat needed (rather than direct feedback control using the house thermostat). The machine comes with a generic fudge factor of 4.0 programmed, but radiator systems expect a larger factor and we have raised this to 6.0, which may be a tad too high as there may be a slight (less than 0.2 degrees) tendency for the house to warm as the temperature falls, though with a time constant of several days (with up to metre thick stone walls) experiments are not so easy!* We need our WEL data logger. The Alertme power logger works OK (with a few glitches on the software).

And the long time constant gave us an initial problem - the house was very slow to warm up and the HP was not putting in enough extra effort. Raising the fudge factor on the internal house thermostat from 4.0 to 9.0 (in the special menus) to make the system more responsive to house temperature (after all that is what we really want!) helped, as did moving the 'radiator return' temperature sensor (which seems important) onto the radiator return arm and away from the accumulator tank where it was originally sited, but we are warmed up now anyway. The system now thinks the house temperature is 19.5, though 2 local thermometers think only 18.6, but anyway it is quite comfortable.

Other details are that the two oldish Myson fan convectors we had do not much like the water temperature being low - they have a switch to shut them off if the circulating water temperature falls too far (ie in summer as normally arranged). But they have a panel switch that I supposed by-passes this in case you want summer air flow. This is fine but the switch is very counter-intuitively marked, so you need to select the red 'hot' setting (?summer) rather than the blue 'cool' one. We have external room (ie some metres away) thermostats on both units anyway.

I am not sure that the radiator circulating water pump runs 24/7 (as we would wish), though it is mostly on.

Since the HP cycles I am not sure to what extent the efficiency (by physics a function of the temperature increment from the ground and thus of the circulating water temperature) is affected by the mark/space ratio on the cycle, which is what actually varies.

* FYI if you have a similar IVT system we have ended up with a 'slope' fudge factor of 6.0 (default 4), a target room temperature of 20.5 (actually ~19.5) and a sensitivity to room temperature of 9.0(default 5). This seems to work fine.

It works!

So far anyway! I was out this morning whilst it was commissioned but it seems fine and the house is gradually warming up.

Noise is quite moderate, like a loud fridge (& may be above normal anyway).

And the pipe holes are mostly filled and the street hole filled and tarmaced over - so all is well really!

More electricity

Well we are back to commissioning tomorrow (when I will not be here but the plumber and electrician will be), which is probably just as well as the electrician did not in fact change us over to the 3 phase until 5.00ish!

Dealing with the electricity remains by far the most complex task - we now have a single phase meter connected to source but not to our systems and a fully-connected 3-phase system (the inverse of yesterday of course). From here nothing is so urgent but we had to arrange (by ourselves calling yet another bit of eon with yet more numbers - MPAN this time) to get the old single phase meter removed (next week). Only then can we again call the project manager at Morrisons (working for eon) for him to arrange a disconnection crew to take out the old cable (we wonder how much of it - surely not right across the road?). And of course there is also the hole in the road where the joint is to be filled in (see below).

I cannot help feeling that eon would be much better off doing internal central project management, including the ability of any single point of contact to see the whole status on screen and set everything up; easier for them as well as us. The attempt to get the customer (us) to make all the phone calls to different people to set up different jobs in sequence surely just adds to the confusion!

Almost there!

The connect team did connect the 3-phase power as far as the meter box yesterday (fortunately/kindly they did not disconnect the single-phase as their jobsheet said!); but the quick meter-install that sounded so good was much more problematic.

I spent a prodigious amount of time on the phone yesterday to various parts of our electricity supply company (eon) in multiple calls. Everyone (particularly Sean & Rosie) was very helpful but the system is deeply flawed - several degrees below shambles! No-one seems to know who can authorize what and people are on the phone to endless lists of other people who keep passing them on! Frustratingly but fortunately we did have the direct phone of the emergency team who put in meters but they need authorization...

We did finally get a call at nearly 5.00pm to say a meter installer would call in the next 4 hours! This may have been more the effect of the original meter-installer's report than of our calls. Unfortunately I was by then at a meeting in London (ironically on the resilience of UK infrastructure!), and our electrician was running out of time.

But they did come about 7.45pm - no-one here of course, as we had pointed out, but the box is outside so he did not need access. Unfortunately no-one had told him that so he left a card! Thank Rosie we knew the direct line for the emergency people and were able to recall him - and it finally got fitted 10.30-11.30pm last night. He was helpful (it seems he does nights on a rota and was heading home afterwards) and we plied him with coffee and we are potentially on course for commissioning today!

Not such a good day!

Well the crew came back (albeit not exactly 'first thing'!) but were unable to get the right cable into the wrong duct - it is a pretty tight fit. They also managed to leave it with no rope through.

After they left another crew came who also could not get the right cable through the wrong duct. They stayed for some hours after which another crew came who could not do it too, and are now digging up the road again (without lights this time) to put the right duct in.

Oh - and the meter box was the wrong way up - but we have now fixed this!

Meanwhile the existing boiler is out - so no heating!

And the man came to change the meter - helpful but obviously nothing for him to do (so the initial crew did not tell him as promised). Still, they have been quite helpful and we have a number to call to get an emergency meter fit at 3 hours notice.

***

Well the self-proclaimed A-team did get the correct cable and duct in OK, and the joining team should be back 8.00am tomorrow, so we are about 24 hours behind on the 3-phase supply but should still be OK. Meanwhile the plumbing is pretty much done and the circuits filled. So we have ended on a more positive note!

First signs of 3-phase

Well they have dug the hole across the road and covered it over - though I noticed that the cable they had installed was single-phase! They agree and now expect to be back Monday am to replace it - they hope by pulling the (rather fatter 3 phase) cable through the duct. I note that their duct is considerably thinner than the 100mm one they got us to put in!

Our electrician has put in a good many cables but was not back today as anticipated - he thinks he is OK to complete Monday am (looks a bit tight to me!).

Commissioning on Thursday! ICE tried to change this to Wednesday or Friday but we said no - too many other people involved.

Pipework started

Well after a hiatus (not quite as long as it looks - the plasterers have been fitting foam-insulated plasterboard under the sloping roof ceilings that are universal on the top floor as this is the only way to improve the insulation) the plumbers are back and fitting this Tardis-like arrangement. It is fine except that the elaborate effort to make sure that the ground loops nearest the house are on the return (warmer) side went wrong so they will have to fit pipes swapping this round!

The heat pump has fittings for hot water that we are not using (which seems a waste) & we will just join these up to seal them (Ice Energy say one could blank them). The programming should ensure that they are never used.

3 phase power is due on 18th, with commissioning on 21st (the old boiler will need to be removed between these dates).

Manhole covered

Well just FTR the manhole cover is now on and the trenches topped up and gravelled over (as is the manhole cover).

So things really do look just like the 'front-of-house' picture above, except for the Wisteria flowers (we do have yellow pansies again!). Strange really to do all this work and end up with nothing to see - but that is the idea!

Delays!

It appears that we cannot get the three phase power in until mid-October, creating some issues of timing since we will need heating before then (& the systems will share the radiator circuit).

FTR the process involves a lot of cooks and dairymaids - we approached the supplier (e-on), were passed to the planning bit of Central Networks who were helpful but not so fast (& heavily into snail mail!). AFTER the full amount for the job (£3k) has been paid this gets passed to the operating bit, who pass to their contractors, who appoint a project manager who visits. He then sets up an appointment six weeks hence after he has talked with someone else. It remains our responsibility to then go back to the suppliers to get them to put in the meters required on the same day (& of course our electrician...). It all makes work....

Meanwhile the manhole covers are still missing and the trenches still sunk a bit but we have unpacked the pump.

Not all together

So the contractor project manager for the 3-phase installation has called and will phone in a day or two with a specific date. The good news is that, contrary to earlier advice, the work can go forward on its own, with the house electrical work and the meter installation following. This requires a second visit to disconnect the single phase cable but this seems fine!

The pump arrives!

Well the pump and exchange tank have been delivered. There might be a small expansion tank missing or not.

The trenches have sunk 70mm or so in places (which is a pity for the re-seeded grass). The 3-phase electricity installation grinds forward; it has been passed to the contractors and they have appointed a project manager who wants to see the site, with luck this week. Expect more delays before an actual date can be agreed!

We did think about using the cold ground in summer to provide 'free' cooling by circulating the coolant from the ground loop into special fan convectors or a 'VBX' system. Apparently this is normal anyway in Scandinavia in order to re-heat the ground, though not here. With thermal timescales of centuries (?) for the boreholes we maybe should keep watching the coolant return temperature for a few years! The cooling of the house may be a marginal value except for a few days each year.

Drive back to normal

Well the drive is at last restored (almost - the manhole frame is here but not the actual cover, supposed to be next week...). With August meaning holidays and jobs to be done in school breaks things take time.

Many delays and glitches getting the right gravel and tiles for restoration but all seems now OK and there is access almost everywhere.

The 3 phase power may be a while as the various bureaucracies grind forward (that is the power company, the meter/supply company and the electrician, all of whom need to come the same day, and the local authority who need to approve the traffic controls needed.)

The heat pump itself is supposed to be delivered next week, after which there is still plumbing, connections etc. It appears that a web interface for the heat pump that enables monitoring (but not control) is imminent - seems a bit behind the curve for a new machine (Swedish at that!). So actual controls are via clunky up-and-down and select menus like an old-fashioned mobile phone. We will have smart meter monitoring on each phase via our Alterme system - not sure if it is worth having monitoring of the heat pump alone (though it may be the only unit on one phase).

More filling

Well it progresses but fairly slowly. It is August and the builder has people on holiday and doing school jobs (top season for these) so we had no-one until today but the one man here today has filled in a good deal and started the manhole with the bricks, sand and lintels delivered yesterday and Monday.

The rain no doubt contributes to the Somme-like surfaces but all should be well some time next week when the gravel may come. The external electric box has come (white of course!).

It is striking how much less one can get back into a hole than one took out of it - even allowing for the manhole and the sand!

The Drive reappears

Well the pressure test was OK and infilling has started - stopped by the need for more sand to cover the pipes!

Things will probably speed up from Tuesday, with more gravel we hope coming Wednesday (from beds near Peterborough). There will need to be rather a large manhole covering the manifolds because they have ended up at right angles (see the previous post), and the cover will thus need to be a steel one fabricated to order. We should be able to lightly cover it with gravel like the other one.

The builder thinks the infilled trenches will drop a bit and may need topping up in 6m or so.

Pressure testing

Hum

Well it looks the same but it has taken a couple of re-runs to get the whole complex pipework to hold pressure fully. The initial installation changed from 4 to 1 bar in a couple of days, but after some joint re-making and two pipe replacements (the seals are rubber o-rings onto the pipes, so a scratch on the pipe can cause leakage) we seem to be holding >3 bar for 24 hours. The Ice Energy book well describes the test procedures but does not quite give criteria for a 'pass'! Since the final circuit is not significantly pressurised I think we are now OK.

However I fear that we have now lost our builders to another job for a while - I wonder who is paying for the hired machinery?

Pipes in

Well that is all the ground loop pipes in. Pressure testing still seems to show some decline (5 bar to 4 in an hour or so) so we shall see.

The missing valve came in OK.

The actual heat pump delivery is now scheduled for 3 weeks time or thereabouts.

It will be good to get the drive back!

It is interesting to see that the soil/clay/rock in the drive bed is quite layered and varies with position. I suppose the area has been a yard for centuries and must have seen a good deal of change.

Plumber Day 1

Well much of the connecting is done - should be finished tomorrow. We did have to call to get them to come (about midday in the end) and we seem inexplicably short of one manifold valve (IceEnergy will ship another) but apart from that all seems well.

Ready for the plumber

Well we now have a fine dig in the drive and a big spoil heap elsewhere (to the left of shot). The work looks good and we can still, just, get round to the garden.

All the trenches

Well that is all the trenches dug - and dampened by the rain.

More trenches

Well there are a good many more trenches, now sanded, and space for spoil is getting tight. And we have drains we did not know about and the drains we did know about run in different places we did not know about (probably!).

The plumber thinks he needs wider trenches to work more easily but this generates far too much spoil so most of them will be narrower. The builder tells me plumbers are like that. Because all the connecting pipes are to be insulated we can at least run them beside each other, or we would need to take the whole drive away....!

Predictably much more disruptive than the hole boring; and now we really realize the problem with having 8 rather than 4 holes. Let us hope that things are back to normal in a couple of weeks!

Trenching Starts

Well there is some progress, but it is limited by the unavailability of the expected digger, delayed by the failure of the transport for it.

But work has started on the manual-dig bits, essentially into the washroom where the heat pump will be located under its wall. The terrace tiles are mostly damaged and will need replacement - and the original makers no longer do them but know a man that does....

The plumber is fairly satisfied that he has what he needs except for the considerable amount of insulation needed (for all the connecting pipework - otherwise it would need to be very deep and all go and return pipes would need to be 1m separated). The Ice Energy book is usefully specific.

Heat v depth

I note FTR that geothermal heating (ie mostly radioactively-generated heat from the hot core of the earth) should be about 1 degree at 39m (of course this does not mean that geothermal is a significant contributor to the heat pump - it is very small - about 40W for the house and pump area compared with 15kW peak for the pump). The temperature change due to heat pump heat extraction over a year might be similar.

But the daily temperature fluctuations reach down a few cm, annual fluctuations 2-3m and on the same basis at 39m we are talking 400 years or so! (quadratic with depth). Though groundwater movements might reduce this a good deal I imagine.

Trenchers

Are now expected Monday - the office 'was supposed to have called and told me that things were slow on the previous job' - I suppose builders are like that...

8 holes!

Well that is the full set of 8 holes done, all at 37-38m or so, and they all hit 'voids' (meaning abrupt loss of return water) at 32-39m. In all cases they hit harder rock-like material first, which returned fragments of what looked like creamy-white limestone. After this the drillers went on a few metres using a fire hydrant as a water supply to allow for no returning water! For these last few metres drilling was mostly clay-like in terms of resistance to drill, with intermittent rock-like resistance. The void holes if any were not so apparent except insofar as the drilling water flowed away at a considerable rate.

Anyway we have enough pipe in the ground and they have 'grouted' it with some sort of sloppy 'bentonite' material that apparently semi-hardens.

The drillers (Geocore) were as good as their word in terms of leaving the site clean and tidy - the plastic sheet is very effective at containing the mess. And they were polite and sensible always.

Slight glitches (apart from the voids!) were the eventual need for 3 skips (some extra cost), partly to clear the drive for the intermediate weekend and partly because the 2nd skip got full of unwanted pump water. This caused some fun for the skip driver when he later stopped quickly and covered his lorry in clayey water!

But basically OK so far. The picture is a fisheye, and boards cover pipes cut off a bit lower to allow drive usage. We expect the builder late next week to start cutting trenches and connecting the ground loop up, using a new manhole. The pipes and bits (but not the insulation needed) were supplied by the heat pump supplier and seem all here.

4 holes

Well after a busy Monday we now have 4 holes, which is more promising, though all 37-39m deep. So the definite plan is to go for 8 holes and we have the requisite extra pipework coming tomorrow.

My geologist Professor friend signs up to the 150M yr old blue-grey lias clays OK but the underlying creamy limestone containing the voids is not really what the UK geological map says. Next hole we will get him a sample!

They now hope to be away late Thursday if all goes well.

The big family party went well - we got 3 cars in the other drive section (with some care) and the other 9 or so cars used the road. Perfect weather anyway!

2.1 holes

Well we do have some holes - but they are 36-38m deep only so there may be a 'void' everywhere around here! My geologist brother-in-law will be consulted this weekend! Anyway we now need 8 holes, and there has been some tree-trimming to accommodate this.

The existing holes have plastic pipes in - with blue end caps - and are both in the grass at left. The machine is starting on hole 3.

Note that 'voids' may well be full of water rather than air, but the drilling fluid still flows away. There are granular materials that are put down in the fluid that can block small cracks - but they did not work here so we may have a more fractured-rock (limestone) environment. They used to use compressed air instead of water - much messier but you do not run out of it if you hit a void! We will now be OKish provided that the remaining holes run to 37.5m or thereabouts (the existing ones are 38 & 36). The current 3rd hole is unlikely to get to this depth today anyway (they stop drilling at lunchtime).

The drillers blocked off the hole base with grout as they put the pipes in - and the hole then fills with water from a gravel/sand layer that is quite close to the surface.

The top picture is of the actual drill bit.

We hit a void

Well this morning we hit a void at about 37.5m - possibly a cave in the relatively thin ('10 ft') Marlstone bed indicated in the geological maps - there was a harder region first. At all events this is a problem - all the drilling water flushes away rather than returning with the debris. If we had a fire hydrant amount of water available one might live with this (one thinks of that burst main..) but otherwise options are limited. Drilling 8*37.5m rather than 4*75m holes would be simplest - if there is enough room, which looks a bit tight. Experience apparently suggests that if one hole hits a void others around it are also likely to. Pic is of the drilling system running before hitting the void.

First half-day 30m

Not so fast but looks OK so far. Mostly grey clay and a bit of sand coming up. The pictures show the rig in use and the 3-segment tank separator (not in use). The theory is that the water is pumped down the drill pipe (smaller pipe) and comes back up the hole into the larger pipe, flowing out into the separator tank. The debris is brought up and left behind,then shovelled out of the first section - the pump then takes cleaner (well flowable anyway!) water from the 3rd tank section and recycles it.

The water spout is absolutely nothing to do with us (about 300m away) but is an impressively burst water main with a 30foot spout!

Drilling at last!

Well we are drilling!

Only down a few metres so far but still clay, which is fine. A clay hole should be self-supporting (there are steel sheaths if necessary). The drill cuts up the stone/clay etc. and a water flow sucks up the debris (hence the big orange pump) into a tank where the water is recycled and the debris shovelled into a skip. The big white tank of reserve water was filled from a hose.

The drilling machine is fairly compact (small-car-footprint) but tows a trailer with the huge orange water pump on it. The plastic sheets should limit the mess but in fact a short length of steel sheath seals the hole to the machine to enable water circulation anyway.

The low-loader turned up as expected, preceded by the two-man drilling crew (8.00am) who seem competent, friendly and efficient. All the same we will not be finished by Friday so the skip will be collected Friday afternoon and a new one delivered Monday.

The machine is real - they say!

But it will not be here until 8.00 am Tuesday. The driller himself will call tonight if he can manage it!

Still no driller!

It appears that the machine in transit last week was the wrong one - the right one is just finishing the last hole near Southampton and might make it here by CoP today (we are not taking any bets, though!). The chances of being clear by CoP on Friday for the family do on Saturday will depend upon how things go here, but do not look so good. I am assured that the driller is 'the neatest they have' which may be something!

No Driller!

Right - we were all ready yesterday, and then today, for the drillers to arrive but they hit chalk on a previous job and that is a problem - the water flow process does not work well it seems and this slows things down. So the machine was on a low-loader last night but the driver hit his hours limit (@3.00am!) somewhere W of London on his way from Hampshire and we now expect them Monday morning.

Well, here are the ground loops and associated pipework! Delivered as expected today but for some reason in two lots by two different delivery companies, on two pallets. In fact all 4 pipes on one pallet was too much for the system and this one fell apart in the lorry but seemed easily rolled in by hand. In spite of strictures not to drop them on the labels this seems unlikely to have done much harm to the plastic pipe!

Of course we have the usual issues with pallet trolleys and gravel drives (can't do that mate!), but in fact this also seems fine in practice - or maybe rolling is not such a bad idea anyway....

Next excitement on Thursday when the drillers show up (we hope). Parking outside is interesting considering all the cars (none ours) that conventionally park in front of the house - and the grass harvest tractors and milk lorries going through. But OK so far. The drillers' low-loader, skip and presumably van, plus our cars moved outside, may be interesting later in the week!

House picture

This is the house before the drillers arrive (taken in April in fact). The flat area in front is where the holes will go, and yes they have to avoid the topiary and the giant chessboard (lower right)! The heat pump will go in the washroom/study building on the right (with the balcony) and the heat pipes run through to the main house via the (unheated) garden room/conservatory. The washroom/study is also formally unheated (just machines etc. & the S-facing balcony doors) but is very well insulated - OK for the comparatively cold-blooded!

Geology

In advance of the drillers we did look into this. They are after all proposing to go down a good way (75 metres down!). Our house is built of 'marlstone' (a warm orange limestone-plus-sandstone mix) with some cotswold oolitic limestone. There is an old quarry at the edge of the village. But we did get the gelogical survey map for the area (from the London Natural History museum) and these stone layers are remarkably thin, at any rate much thinner than 75m! Apart from this we are most likely on various forms of 'clay'. The drillers are not concerned, indeed on the whole prefer stone, but we shall see. They do not like running sand, nor it seems chalk, nor artesian water - meaning a spring I think).

I note that 75m down is more than half-way down to sea level here (we are at 130m)!

The Beginning

This is a story about our experiences of substituting a heat pump for our venerable-but-reliable solid fuel heating system in our ancient (supposedly 16C) thick-stone-walled house in rural Northamptonshire, UK. I hope it will help others who might also be looking at this.

Right now (June 2010) nothing new is installed, but the first actual action (drilling the holes for the ground loop) is due next week.

Why are we doing this at all? Well I am a physicist by training and I understand the way that heat pumps work - they pump heat out of the ground into the house, using electricity in the process, a bit like a backwards fridge (you will note the coils behind your fridge that get warm). The trick is that the amount of heat it pumps is about 4 times the energy needed to do the pumping (which also ends up as heat). So 80% of the heat energy actually delivered to the radiators in the house is renewable (in fact mostly solar heat accumulated in the ground - you have to go kilometres down round here to get much geothermal!). The other 20% comes from the electric power used by the heat pump. Even using electricity that is a big Carbon gain compared to our solid fuel system.

Why do we use solid fuel? Well there is no gas in the village and when we put the system in 25 years ago solid fuel looked better than oil. And it does mean that I know exactly how much Carbon we use, as I carry it in from the store in hods twice a day! (about 5 tons pa). So if we are away the heating gets shut down, and even then the boiler will go out if left for more than a weekend. We estimated a peak heat output of our solid fuel boiler at about 15.5kW based on daily fuel usage.

So a replacement seemed a good idea! And we have some advantages. The heavy walls mean that changing the temperature during the day is hardly possible - it takes literally days to change much. And because solid fuel systems deliver hot water at the same temperature as the radiators we have bigger radiators designed to work at 55 degrees C. This is OK for a heat pump which gets much less efficient as the temperature difference it is pumping into goes up (as is also true for your freezer). 35C undefloor heating would be better still but impractical for our retrofit.

So we did some research on systems and grants (basically £1.5k to help fit - which does not go very far - and perhaps £2k pa support under the renewable energy scheme from next April). We aimed to get quotes from 3 suppliers selected from the certified installers list (http://www.lowcarbonbuildings.org.uk/Microgeneration-for-your-home/Certified-installers-and-products). These were otherwise selected on location, apparent track record (eg old building experience etc) and in one case because a friend in the next village who is also installing a heat pump recommended his supplier.

The quote bases varied (there seems no way to know this without asking). Two quoted for the heat pump and associated bits supply, and commissioning and 'design'. They could suggest the builders, electricians and plumbers also needed (insofar as this is not DIY) but this system seems little used. The third did a site survey (the only one who did pre-quote, the others quoted from plans) and would have quoted an all-in price. But in fact he never actually quoted at all, in spite of promises. The other two quotes were similar.

So we accepted one of the first two, as it happens the one also being used by our next-village friend, mainly because they were much more convincing and quick to answer questions. We had done 2-3 weeks of checking things and asking questions before signing up and starting to pay, for the following reasons:-

Electricity supply. The systems we needed, with a nominal output of up to 17kW or so (5kW electric power) required, all needed a 3-phase electricity supply. We, like most people in the UK, only have single phase, though there is 3 phase buried out in the street. This proved fairly complex - our supplier (Central Networks) can fit the supply for £3k to dig all the holes, bring it across the street, control the traffic etc. But they could not bring it in where the old supply comes in because the rules now require it to come in underground (under the thick stone wall) which is OK except that this passes over the house heating pipes and that is not good anymore. So we will come in to a box on the end of the house, which looks OK. We will also pay a builder and electrician to install this (I did the original wiring) to get the system in quickly.

Ground loop - that is the plastic pipe that draws the heat from the ground, supplied as part of the heat pump system. You could spread this around in trenches about a metre underground, and this is what most people do - it is cheapest. Our friend in the next village has a convenient field and has dug the trenches (with a digger!) himself. We drew up maps and we could just get the required 250m of widely[5m]spaced trenches into our lawns, but access is very difficult and the disruption would be impressive. On the other hand we have a flat 13m-square drive-plus-lawn area in front of the house and have chosen instead to have 4*75m deep 6" holes dug in it instead. This is more expensive (~£12k) but of course needs less space. The driller is recommended by the heat pump supplier but in effect we end up project managing this - arranging delivery of the pipes and setting up the skip(s) for the 7 yards or so of spoil (the holes are refilled with 'grout' supplied by the driller). The driller was very helpful in terms of supplying sizes for his machines so we know we can get them in and commenting on maps from us of service and drainage arrangements (one needs to keep clear in case they got damaged, or froze later - the ground should not freeze but in winter and at shallow depth it might). So far so good!

The friend's system is working!

We have chosen only to use the heat pump for heating; not for hot water, which will continue to be heated by an existing immersion heater, which we use anyway in summer when the boiler is shut down. The problem is that the 'standard' hot water tank supplied by (each of) the heat pump suppliers is vast, ~300 litres against 180 standard in the UK. This is compounded by the strange design which adds another 180l of water in a surrounding heat jacket. The result is a vast and extremely heavy unit, bigger even than the heat pump itself (which is about the size and shape of a big upright freezer). This presumably reflects a different way of life somewhere else! At all events we could only accommodate this in an outhouse >10m away, and then we would have to pump-circulate the hot water loop (like a hotel) to avoid long delays in getting hot water from the tap and then... it all seemed not worth it. We might put solar hot water in later. And FWIW we did check our actual hot water usage over a week using our 'alertme' energy monitor and found we only spend about £250 pa, which is also much less than estimated (this seems to be because we power-shower rather than bath and have a cold-fill washing machine).

So - so far so good! We have the pipe coming on Monday and the drillers on Thursday (they were very quick once asked - 50% paid in advance). They expect to be out and clear by the following Wednesday at the latest - leaving not much mess and a few pipes sticking out of the ground. As we have a big family party that weekend we hope they are right! We are expecting a quote from our builders for connecting these to a buried manifold and thence into the washroom where the heat pump will go. (We had the heat pump surveyor & the builder with his electrician and plumber in together). The builder is known to us for stone repair work and seems reliable - it emerges that they have done heat pumps before.

I will report!