Navitron Renewable Energy and Sustainability Forum

HEAT PUMPS & Geothermal Energy => Heat Pumps => Topic started by: stumpy on August 29, 2006, 04:55:21 PM



Title: PIPE
Post by: stumpy on August 29, 2006, 04:55:21 PM
Hi all

I've been investigating GSHPs and have had a couple of quotes from 'reputable companies'.  For my house (220m2) their quaotes are between 6500-8000 for the pump and c1000 for the pipe (400m - 2 x 200m lengths).

They are also quoting c700 installation of pump and commissioning.  The groundworks for the pipe's installation is additional, and I'd probably do that myself.  Fortunately I have a reasonably sized rear garden to accommodate this pipe.  This would be c750 for a machine for a couple of days + sand.

One of the systems will supposedly give me a CoP of 4.83, as it requires 5000kWh/a, and will deliver 24,000kWh/a which I understand is pretty good?

If I chose to DIY, and purchase Navitron's 9kW pump, does anyone know of a supplier of the appropriate pipe, and approx cost?  I'm sure I saw a thread on here somewhere but can't find it now!  Also, does anyone know an installer?  Not something I could manage myself... Location = Kent.

Any responses from individuals who have installed their own GSHP's and how well they work with wet UFH systems would be greatly appreciated.  I'm having a few problems convincing the missus it would be better going this route than using a traditional gas boiler!


Many thanks
Carl


Title: Re: PIPE
Post by: ecogeorge on August 29, 2006, 10:26:35 PM
Use 32mm MDPE "normal" waterpipe. Usually rated at 12 bar. Choose black colour -donates non-potable water. Available in 100m or larger rolls (remember you have to handle them). Use heavy duty cable ties to hold slinkies in place. Fusion joining of pipes is best - use good quality Philmac or Plasson water fittings if fusion not an option.Minimise no. of joints.
I bought pipe 12 mths ago for less than 50p / m (incl vat) but that was cost price (I work for a large Agricultural co.). I can check price tomorrow if you require.
rgds George.

ps Keep pipe lengths on multiple runs exactly the same length - stops the pump favoring one section .


Title: Re: PIPE
Post by: stumpy on August 30, 2006, 09:02:46 AM
Thanks for that George

Yes please do get a quote for me.

Thanks again
Carl



Title: Re: PIPE
Post by: madandy on August 31, 2006, 03:36:02 PM
Ref the above - 32mm pipe. I'm am putting in navitron's 5 Kw GSHP and plan to use 200m of 25mm slinkies (is that how you spell it?). After reading your comments I am now worried that this will not be up to the job - please advise if you can :-\ Thanks

madandy


Title: Re: PIPE
Post by: stumpy on September 01, 2006, 02:58:08 PM
I've heard that slinkies are generally used where there may be insufficient space to run long single lengths of pipe in the garden.  Slinkies being closer-packed therefore can be placed in a smaller hole.

I also understand, it's the length of pipe that is important as I guess this is what gets heated up - the longer the pipe the more heat that is generated...?

Certainly do not profess to know very much...!

Carl


Title: Re: PIPE
Post by: Bargeman on September 01, 2006, 11:07:38 PM
Hello madandy,

My understanding is that the 'rule of thumb' for slinkies is 10m of trench for every kW power installed, so 200m for a 5 kW pump seems more than adequate. One thought occurred to me - my understanding (please check with Ivan) is that the navitron 5kW model is ground source to air, meaning that your internal domestic heating system probably needs to be air blown ? Sorry if this sounds patronising, but I thought it might be worth checking. The 9 kW model is ground source to water which would link to most wet domestic heating systems.

Hello Carl,

I'm also based in Kent (Faversham). I did quite a lot of research, obtained Clear Skies funding and took part in the installation of a large (24 kW)system, supplied by Kensa, at my daughter's local primary school. I'm also considering the navitron 9 kW. Depending upon how close we are, I'd be happy to help you out just to get some hands on experience with the navitron system. If you're interested please send me a message offline.

regards


Title: Re: PIPE
Post by: Ian on September 02, 2006, 09:31:23 AM
Just when you thought all was clear, along comes another guy and tells you the exact opposite!

There is no way that I would factor 100 watts per metre in any installation that I would undertake -even sunk in a lake!

Guys that try to sell the kit tell you that you can get somewhere between 30 - 50 watts per linear metre. Personally,I work to 20 watts per linear metre and I have never had a poblem. Am I OVERspecifing ? maybe - and there is no real way of finding out without trying something different.

In my opinion, 200m for a 5 kW GSHP should be fine (25 watts per linear metre) unless you live on a very dry sand dune.

If I install a slinky (helix) rather than linear pipes, then I allow a greater de-rating and I would never use more than 20 watts per metre of pipe.

I would also try to use a thin bore pipe. 32mm is OK but is on the large side. 20 - 25mm is what I normally propse. It is all a game of compromises. Too small a diameter means that the pump has to work harder and airlocks are more likely; too large a diameter and the surface area to volume is lower so more water has to pass through the heat exchanger in order to extract the same energy.

I hope this helps.

Regards,
Ian


Title: Re: PIPE
Post by: Bargeman on September 02, 2006, 01:59:01 PM
Hello Ian,

You're right that the 10m:1kW 'rule of thumb' cited is sourced from a heat pump manufacturer, in this case Kensa Engineering in Cornwall. They apply it to slinkies laid in 1.8 m deep trenches in favourable soil conditiions. To be clear it refers to the trench length, not the pipe length.

If you can find the time, take a look at some of the case studies (for slinky installations) available on the Kensa (www.kensaengineering.com) web site, e.g. Auldyn School, Sevenoaks barn conversion, Aberdeen, Cucklington, Honiton. Those which give data for the closed ground loop collectors with slinkies are consistent with the 10m:1kW rule. Having followed up references for a number of their installations, I found that their customers were in general satisfied with outcome. At our local school we have proceeded on this basis, with 5 x 50 m x 1.8m trenches laid out across the school playing fields to supply a 24 kW pump.

regards





Title: Re: PIPE
Post by: madandy on September 04, 2006, 03:27:12 PM
Ian & Bargeman

Thanks for the info above, I now feel happy with my choice of pipe. Am I correct in thinking that a straight run of pipe is more efficient than a slinky? I am lucky enough to have the space to do this if required but had been led to believe that a slinky is more efficient ???

Thanks for the reminder about the 5Kw pump being water to air - yes this is what I am after as I plan to link this into my HRV system.


Title: Re: PIPE
Post by: Ian on September 05, 2006, 09:09:04 AM
Madandy - it depends how you define efficiency!

Slinky (coiled) is more efficient if you measure :
Time and labour taken to dig the trench
Amount of space required to bury the same linear length of pipe

Uncoiled linear is more efficient if you measure :
Absolute ability to extract as much energy as possible from the ground loop
Minimum physical linear length of pipe
Reduced depth of trench
Hassle
Cost of pipe.

I would agree that in a normal conversation that a single run of pipe would be regarded as more efficient. If space were not an issue, and all other things were equal, I would install a single (uncoiled) run of pipe (but there is not a lot in it really).

I hope this helps.

Regards,
Ian