Bonne chance! B^>

24 August 2010. Report 3.

Due to the house layout, the best position for the heat pump and 200 litre inertia tank is in a loft space on the first floor. There is plenty of room in the loft space, but it needed 5 people to lift the heavy heat pump up the stairs. This was done with efficiency and good nature by the team.

Today, Dominique and Pierre are connecting lots of pipework. Tomorrow a new person will be digging the trenches for the borehole pipes to be connected to the manifolds and then through the wall, into the house and up into the loft space. I will be connecting a 'Current Cost' energy monitor (Model CC128 ENVI) to the three phase supply to the heat pump. I hope to record every single watt that it consumes

Tony, Yes, I am very aware of the huge loudspeaker that the floor of the roof space makes to the visitor's bedroom below. Previously I was planning to have a heat pump made by a French Company called GéoThermic. I visited the factory and listened to the noise it made, it was significant. I was planning to have it mounted on hangers on the very solid wall (1 meter thick) with insulating pads. I also visited a neighbour who had a very noisy heat pump (much louder than a fridge) in their kitchen. They were annoyed about the noise, but had grown used to it.

Then I discovered Atlantic - they import Nibe heat pumps from Sweden. I was able to visit the classroom where they teach installers about the product. Using the inaccurate measurement of my ears, they are as quiet as a fridge. The compressor and heat exchangers are inside a sealed metal box. It must have a great deal of sound insulation. The heat pump will be on additional sound insulating feet on a thick base of high density chipboard which will be on the floor of the roof space. The Atlantic spec says the noise level is 21 dB(A)

I hope I will have a quiet heat pump. Wish me luck.

Mark, Thanks. I will have to accept a less accurate measurement than I had hoped for. However I am comparing with propane gas which a year ago cost me (assuming my maths are right) 0.108 €/Kw Hr. With my old gas boiler (estimated efficiency 70%) that comes up to 0.1543 €/KW hr. I was using on peak electricity* at 0.0495 €/Kw hr in place of the gas. So if my heat pump has a conservative efficiency or COP of 4.0 then 1 Kw of heat will cost me 0.0124 €/Kw hr. To good to be true eh?

I hope to find out.

* EDF (French sole domestic suppler of electricity - 85% nuclear) have a brilliant tariff called Tempo. The prices given above are for the summer daytime rate - night is even cheaper. But they can really whack you in the winter time when on some days the cost is 9 x the summer rate. If you are interested, look at http://www.frenchentree.com/france-lot-quercy-services-contacts/DisplayArticle.asp?ID=10263

Damon, Yes Tempo is very clever. If you were running a nationwide electricity company and did not want to have excessive capacity (= expensive generators) just for the odd peak demand, you would invent a way of discouraging the peaks. In the UK the big users have price which varies with demand. EDF just look at the weather forecast and if it is going to be cold, declare that tomorrow will be a red day. I am sure they have a max demand pricing for the big users too.

Imagine all the French domestic users getting the news that tomorrow is to be a red day. The price is now going to be about 9 times normal. Do the ironing another day, wash up by hand, turn the imersion off it will probably just last for 2 days before a reheat, cook on the gas hob, not the electric oven . . . . and so on.

It is done with an electronic consumption meter. EDF send a signal to tell it what tariff to use. The whole thing is entirely in the interests of EDF, but has some benefit for the users too. The year when I switched to Tempo, I got a rebate of about 100 €.

I work for EDF as an asset manager (wind farms) and I agree 100%,
Gusty.

Sounds like your driller is pretty honest admitting one borehole is not as deep as it should be - very good sign.

15kW from essentially 2x100m boreholes is a big ask. Twin loops will help to a degree but you are expecting 75w/m. This is normally only achieveable in the very best of scenarios. I would ask who designed your ground loop what ground conditions they were expecting and also what minimum entry water temperature they have entering the heat pump. One other question would be the grout - is it thermally enhanced. Also, check that the boreholes are well spaced (with the load I woud expect 10m or so).

Hope all goes well for you.

Regards

Mike

Mike and Paul,

Thanks for your comments. Very interesting. Let me tell you some history and some facts.

First, the Atlantic France (really Nibe in Sweden) 15 Kw heat pump manual says it needs two boreholes of 100 to 120 meters depth. It was me that said that I needed 2 x 100 meters, this is because I was dealing with GeoThérmal, the previous supplier and they said 2 x 100 meters for a 12 kw heat pump. I missed the point that with Nibe, I was on a 15 kw machine, and it might need more. My mistake. Doh!

It was easy to see that one bore hole was 95 and the other was 102 meters because the pipe is marked with its length, every meter, from about 5 meters (next to the 'U' bend) to 120 m at the opposite end. The bore hole driller told me that the first hole was 98 (he misread 95), so he drilled the 2nd hole to 102. Not bad really.

Going downward from the shallow topsoil, first is bright red clay to about 15 meters, then it is gray shale and some layers of quartz. The two boreholes are about 15 meters apart and both were drilled where there was an aquifer - I had a water diviner (cost me 65 €) to tell me where the water sources were, and he was right. Hooray! Water is at a depth of about 40 meters and the flow is 3 to 5 cu meters per hour - I have the exact numbers somewhere.

The other interesting thing is that the company that bored the holes put in a shorter 5th pipe so that water could be added if the bore holes became dry. My installer will put in inspection covers so that I can add water from a garden hose if needed. I am hoping that both bore holes are always wet, giving good heat transfer. The bores are not grouted, it is not yet current practise in France, and I was unaware of the process or its advantage until recently. I understand that next year it will be compulsory here. However they did seal the top of the borehole with a special product which expands when wet and forms a seal. It is wet.

So with fingers crossed, I hope I might be able to get enough heat from the ground.

The heat pump COP is quoted as 4.25 at 35 deg Celsius. I have underfloor heat so I will run at 35 deg or less. At 35 deg, the heat output is quoted at 15.42 Kw. So if I understand correctly, I will take 15.42/4.25 = 3.63 Kw from the electrical supply and 15.42 - 3.63 = 11.79 KW from the 95 and 102 meter bore holes.

I will be very interested in your thoughts. Regards,..........Topher.
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28 August 2010. Report 6.

I was right. Installation was not completed on Friday evening as planned. However, Dominique worked his socks off pushing himself very hard all day long. There was power cut in the afternoon, heavy rain in the morning, and a broken underground rainwater pipe to be repaired - not helpful.

Each bore hole loop is filled with the pink antifreeze mixture. When the pipe loops were put down the bore holes, the drillers put water in the pipes to make them heaver and assist their descent. At this stage of the installation, a small electric pump is used to force the pink mixture into the pipe. When clear water coming out the other end, turns pink, both ends are sealed. The next step will be connection to the manifold. Fortunately each pair of pipes has one plain and one with a longitudinal stripe. In this way, as long as all the stripes are connected to one side of the manifold, and the non-stripped to the other side, all will be well. Finally antifreeze will be pumped by hand into the closed system and the circulation pump started. Air will be bled out of the system and the correct pressure set.

The neat glycol has to be premixed with water before being put in the pipes. Apparently if neat antifreeze is put in the pipes and expected to mix with the existing water, it does not. Slugs of antifreeze circulate with slugs of water. This is not like adding inhibitor to a radiator circuit.

Work will re-start on Monday and take 2 or 3 days I expect. I am concerned about the garden being left in the best possible state. The trenches have taken up lots of space and clearly they will have the bright red clay surface. I would like the non trench areas restored as well as possible. There are some piles of soil - for example near the bore holes where the fine material was pushed out from the drilling process. I am hoping I can get Dominique to encourage the digger driver to do the best he can to get a good result.

When the installation is finished and the heat pump commissioned, a stage payment is due. The final payment will be made on the 1st December when the system is working correctly and keeping the house warm.

Interesting that you are using a Swedish NIBE heat pump. A close neighbour here in Sweden installed a Thermia pump last summer 2009, but he only used ONE hole, about 120 meters, which was drilled the first day, no problems as the going was good thru granite. The second day the piping was installed in the hiole and into the house, pump connected etc etc etc, and on the 3rd day it was up and running. For the first year up until the end of July 2010, it took approx 3000KWh for running, and supplied heating for the house, water rads, and hot water. He has about 170 sq meters , ground floor plus basement. Tap water is about 72C, and the pump runs for about 1 hr each day during the summer months to top up the hot water cistern. Last winter was our coldest since 1986, and we had below zero for about 3 months. He estimates he will get his money back inside 7 years at this rate

Damon,

I don't know the geography of your house and garden, but just as an idea for you to consider - the whole area around the house might be suitable for drilling the bore hole (the driveway?). The pipes to the house can go over or under existing services like gas, electricity, and so on. Once the pipes are in place, everything can be restored, you just need an inspection cover to view the manifold.

The only place I was not allowed to drill was within a certain distance of the septic tank and its filter bed.

Posted By: topher
It is done with an electronic consumption meter. EDF send a signal to tell it what tariff to use. The whole thing is entirely in the interests of EDF, but has some benefit for the users too. The year when I switched to Tempo, I got a rebate of about 100 €.

In Scotland at least there is a system called "Total Control" which uses a radio signal to turn on/off groups of domestic storage heaters and immersions to manage capacity and load. This supply is separately metered and has a lower unit price.
Even though we have a good amount of "peaking" hydro and pumped storage, it is beneficial for them to do this.

Damon: Good idea. When the hole is drilled, quite a bit of spoil comes out. My bore hole driller did not have a means of removing the spoil, but I think such machines do exist. In any case a bloke with a wheelbarrow and a skip would probably work. The footprint of the spoil would be bigger than the 1m x 1m that mention. May be borrow a bigger space for the spoil, then hand it back when the site is cleared.

When the drill is working, it is not safe to stand very close. Soil, stones and perhaps water (in my case) come shooting out up to 15 feet in the air. Is is the powerful compressor that causes this.

You should research the ground down to 100 meters to find out what it is. Different soils have different thermal transmission characteristics, may be you wont need 100 meters, maybe you will need 120 meters.

The trench that takes the pipes to the heat pump will be 1 to 2 meters deep rising to half a meter as they enter the house. This size of trench means that you will have a lot of soil to deal with; much more than the boreholes, unless the trench is very short.

Amicalement,...........Topher.

It's definitely possible. Here's a photo of the drilling machine in the front of our house. We also didn't contract the clear-up of the drilling debris (due to ignorance) ... ended up shifting about 20 barrow-loads of gravel-sized rock - luckily the alley between us and the lower neighbour (which had got covered with a slick of clay from the drilling) was the recipient of all of this - solving the disposal problem and the slick all at the same time.

Paul in Montreal.

31 August 2010. Report 6.

We are at the beginning of day 7. Virtually everything is connected up. The primary (bore hole) and secondary (underfloor) circuits are pressurized to just over 1 bar. Outside the inspection chambers for the two bore holes and the manifold remain to be completed. Dominique worked hard on the digger yesterday to try and make the site as good as possible. There is lots for us to do to get it flat and in a state for the grass to regrow.

The heat pump (made by Nibe, Sweden) is not yet connected to the supply. It has a very super little facility - three current transformers for the three phases, they go over the incoming supply wires to the house. The heat pump is set with a max incoming current value, which is the same as the rating for the supply. If the heat pump load were to cause an over current, hence a blackout in the house, it reduces and redistributes supply across the phases to ensure that the max current is not exceeded. Cool eh? Only on the 3 phase machines.

In France, one factor that affects the tariff is the max Kw of the supply. If you exceed the max, it trips, and you have to switch off the offending device before re-closing the circuit breaker. Some people have relatively low supply to save money and do their load regulation manually. When we bought the house we had a 12 Kw (3 phase) supply and would ofter exceed the max of 4 Kw per phase. When we switched to the Tempo we upped it to 18Kw and now have no problems. It is another example of the way the French control their maximum demand.