Posted By: DamonHDenvironment minister's priorities

His priorities are his estranged wife and liberty at the moment I think.

Posted By: SteamyTeaBut back to the -10C and COP, this is not really relevant as it is an extreme event. What you need to calculate is the COP when you need the heat. This can be split into two parts, Space Heating and DHW and compared to HDDs for your area. Then pick a system that fits that profile best.

COP isn't the problem at low temperature, it's output capacity (for ASHPs). This does drop quite significantly with temperature, plus you lose even more capacity once you hit the need for defrost cycles. Sizing your heatpump for enough capacity at very low ambient temperatures could mean it's oversized for more normal conditions, leading, potentially, to short cycling. Plus a larger capacity machine will cost more. You'll have to do a calculation to find the best compromise between sizing of the heatpump versus the additional cost of auxiliary heating to cover those extreme days.

Paul in Montreal - now in cooling mode for the GSHP

Because the air is still coming out of solution, in the same way that bleeding radiators in a CH system is not a one-off task?

Rgds

Damon

I suspect that you have a two or more very slow things going on that is confusing diagnosis, eg air coming out of solution, maybe ground settling changing pressure in the pipework, possibly a very very small remaining leak, etc, etc.

Rgds

Damon

Damon, Dantenz,

Thanks. I am occupied with visitors at the moment. In a week or so I will re-presurise to 1.5 bar and do as you suggest.

Thanks,...........Topher.

I re-pressurised the primary circuit to 1.5 bar a few days ago. It has stayed rock solid. Yesterday I put the primary pump on for 10 days. It has still remained at 1.5 bar. The air vents are open to let the air or hydrogen (djh) out. So it still looks like a air bubble that had been there for a long time.

The temperature of the primary started at ambient, about 22 degrees, then quickly after the pump had been running, it reached 13.6 degrees - the temperature deep underground. Before I decided to have the installation, I considered cooling in summer, I was persuaded against it because one person said that as I did not know the spacing of the underfloor pipes, I might have 'stripes' of cold floor with condensation. As my floor tiles are very slippery when wet, I decided against it.

Now I am thinking again - how much would it cost to put in a valve to link the two circuits, and get more antifreeze to put in the primary circuit - it should not be too expensive, and very cheap to run.

I know that Paul in Montreal has his system in a cooling mode. I would be interested hearing comments from Paul and anyone else who has such a system. Does it really work? Do you have condensation problems? Does it have any form of temperature control?

Regards,...........Topher.

I have run the pump for 10 days now and the pressure has remained at 1.5 bar. So I have shut everything off and will await the start of the heating season.

For the entire 10 days, the temperature of the primary circuit was 13.6 degrees. I wonder if this tells me anything about the COP that I will get when I first turn it on. Is there a 'guide' formula which shows how the COP varies with primary temperature, temperature difference, secondary, and secondary temperature difference? Anyone know?

Regards,.........Topher.
.

Found the spreadsheet - will attach it here.
Substitute your own GSHP COP at 35 degrees and your own brine and UFH flow temps.
Make of it what you will though, it was just an experiment.

Ah - GBF won't let me add an attachment. Why is there a button for it then?
If you can whisper me your email address I can email it.

Hi Gusty

We're in Somerset.
I don't really know. It's dissappointing that the domestic part isn't up and runnning yet.
The premium payment (a one-off subsidy for installation if I understand correctly) is about to start. You can "register interest" over at the Energy Savings Trust website (they will admin the scheme IIUC) but you can't quite claim it just yet. Expected next month is last I heard for that.
But the full incentive for domestic users looks like it won't happen until next year now.
Only info on tarrifs is things like this (and still could change before it starts):-

http://www.rhincentive.co.uk/eligible/levels

Looks like 7p/unit for 23 years is best guess to me.

Someone else here hopefully knows more?

I like to think it looks a fairy safe bet but who knows :-/
I cant see that this government has much to gain by changing those proposals much... not compared to solar-pv anyway. Our install costs for heatpumps are not changing much. Neither are there 1000s of people rushing to set up heatpump farms and claim massive subsidies.
There is a "Any news about RHI" thread over in the renewables forum here.
Which reminds me - I had a question to ask about solar over in that topic too.

What is the air temperature just above the floor?
Or were you after comments of the speed it may take to be fitted

Posted By: topherI was wondering if cooling the floor would help in improving the house comfort in warm and/or humid weather. I would circulate cool water - around 15 degrees in the underfloor pipes. This would cool the large lumps of concrete that are the ground floor and the first floor. The house has very thick stone walls with additional internal insulation. It would not reduce the humidity, and perhaps when the humidity was high, water might condense on the cool floor causing falling down accidents!

Today the weather is cloudy, rainy, thundery, and a bit humid, but not too unpleasant.

The temperature just above the floor is 23 degrees and the RH is 68%.

According to http://www.decatur.de/javascript/dew/index.html the dewpoint is 14.82 C, which is rather close to 15 C!

So whether you would get condensation or not depends on how lucky you feel

It sounds like you would definitely get condensation on days when it does feel unpleasant. I think that's one reason why air-conditioners cool the air rather than surfaces.

Report 24. 30 August, 2011.

I am now on my third leak in the primary circuit. The first was some time ago, during the heating season, and was caused by a broken pipe fitting in the manifold connecting the black high density polythene pipes from the bore holes to the main flow and return to the heat pump. The broken fitting was caused by over tightening or defective brass in the fitting. The installer claimed the latter, everyone else said it was the former!

The second was during the summer - there was a sudden loss of pressure. It was thought to be an air bubble because when the pressure was restored and the circulation pump run for 10 days, the pressure stayed up.

About 8 weeks later, I noticed that the pressure was zero again. This time I could not get more than 1.0 bar because I ran out of the pink antifreeze. When I looked at the manifold, it was surrounded by the pink coloured water. I am now waiting for Dominique to find the leak and repair it.

The inspection chamber is about 60 centimetres deep and has a small cover. It is very difficult to work on the manifolds because the space is so restricted and the pipes are very stiff. Four smaller pipes are connected to one big one and one manifold lies on top of the other. I am going to have a much larger inspection pit made, since it seems to need frequent visits.

In hindsight I should have insisted on a plastic manifold with the pipes heat welded together. It might have been more expensive, but it would have been much more reliable. I am not sure about a pressure test, because the pressure has held up for weeks between failures.

If you are having pipes jointed underground, I would strongly recommend all plastic fittings with the pipes heat welded. It would be interesting to read about other's experiences.

I agree Topher. I have just had mine fusion welded and as much, including the manifold is inside the house. Very little is outside so it improves access etc. I think this is a fairly new approach though,
Gusty.

Report 25. 7 September 2011.

Dominique came today to investigate the third leak. It was found to be a brass fitting. What I would call a straight one inch coupling, male to female. The flow and return manifolds are made up with one of these on each side. If you look at picture 10, dated 5 October 2010 you will see it. It is on the right hand side next to the elbow. So now both the flow and return have had the same fault. You can clearly see the crack on the fitting. I hope to post a picture in a few days. Both fittings have had the same longitudinal crack. So I seem to be the unfortunate recipient of two defective machined brass castings.

Dominique has taken the fitting to his supplier to complain. He has borne the cost and time of making two repairs because of these defective parts.

The system now has the primary pump running 24/7 for a few days at 1.5 bar. Fortunately there is a builder on site doing various projects. Tomorrow he will construct a new inspection pit, much larger than the old one which will make any future leaks much easier to fix.

P.S. Have you guys come across a 'Puit Canadianne' or earth tubes? There is a section on this forum. Very interesting. Almost free cooling in summer and almost free base heat in winter. Not expensive to install in a new build. Have a look at . . . .
http://www.builditsolar.com/Projects/Cooling/EarthtubeNotes.htm
http://www.greenbuildingtalk.com/Forums/tabid/53/aff/14/aft/58831/afv/topic/Default.aspx
http://www.greenbuildingforum.co.uk/forum114/comments.php?DiscussionID=1026&page=1#Item_0