Minimum ground needed for Ground Source Heat to work?

[fixit9660]

Hi,
This is my first posting here so apologies for any transgressions, upsets, etc.
I'm going to renovate a house and it's got a fairly large garden. I want to install a Ground Source Heat Pump/system but I've no idea of the minimum size/shape I need to make it work.
Can anyone answer my immediate question (what's the minimum size/shape required?) and point me at some form of Reference website/docs please?
Thanks
Andy.

 

[Worcester]

Not a simple calculation - it's about 6-8 hours to do properly - when you know what your doing.

#1 Need to know the heat loss and and heat load of the house - carry it out to BS EN 12831 (about 4 hours)
#2 choose your heat pump (from your knowledge of that that can deliver the load and provide quality support )
#3 calculate the full load run hours equivalent
#4 do a geophysical survey to ascertain ground conductivity levels based on actual location (OS Grid, altitude) ( 2 hours)
#5 calculate length of pipe run required based on actual location
#6 make sure you can get turbulent flow in the pipes. !!**!! (for anyone that had to juggle loop lengths you'll know what I mean) (2 hours)

Minimum 6 hours when you know what you're doing on a good day normally allow a full day with no interruptions.

Or about 200 hours of self study and knowing where to find the reference material and how to intepret it (and then you'll still need it done again for MCS)

Or £500 no obligation fee.

Length varies by over 100% between sites easily. So you could be way way out if you haven;t put the right information in at the start.

This is why the process is the way it is, far too many systems installed > 18 months ago are creating permafrost by taking too much heat out of too short pipe runs

Here are the documents:
Microgeneration Certification Scheme - Installer Standards
and here:
Microgeneration Certification Scheme - Heat Pumps

 

[Richard Burns]

Worcester has the detail for you but the energy saving trust gives some basic information about GSHP.
This may be useful on a more basic level.

 

[fixit9660]

Hi Worcester.
Thanks, that's perfect, exactly what I wanted.
I'll do it myself first for two reasons; 1) I like to understand the technology and systems involved, so I can if obsolutely necessary, maintain and fault-find/fix. 2) To make sure that my figures match the professional bloke doing his survey and not be "baffled by science" by blokes who only know half their job and BS the rest of their way through it. ;-)

 

[Worcester]

Hi Worcester.
Thanks, that's perfect, exactly what I wanted.
I'll do it myself first for two reasons; 1) I like to understand the technology and systems involved, so I can if obsolutely necessary, maintain and fault-find/fix. 2) To make sure that my figures match the professional bloke doing his survey and not be "baffled by science" by blokes who only know half their job and BS the rest of their way through it. ;-)

Our experience is that unfortunately despite being mcs certified there are still a lot of organisations that are incapable of doing a proper collector design. And I can gaurantee that at least 90% of the salespeople that visit you won't know what a reynolds number is or even why it is so critical to get it right for correctly designed collector loops.
p.s. we'd be happy to quote

 

[fixit9660]

"Our experience is that unfortunately despite being mcs certified there are still a lot of organisations that are incapable of doing a proper collector design" - that's exactly the reason I want to learn for myself.
"Reynolds number"??? They're to do with aircraft wings I thought!

 

[BruceB]

Reynolds number is simply a dimensionless variable which is used when modelling fluid flows. If you plough through the MCS references Worcester has cited, you will find it stated that if you keep the Reynolds number of the 'brine' flowing through the collector loop above 2500 then you will be in the turbulent flow rather than laminar flow regime. This uses slightly more circulating pump power but the transition from laminar to turbulent flow significantly improves the transfer of heat to the brine through the pipe wall. Designs which are to meet the MCS standard require a Reynolds number of 2500 or higher.

 

[fixit9660]

Priceless!
I would have thought that they'd be making special plastic pipe with a corrugated surface inside and out to increase the amount of soil contact area on the outside and encourage turbulent flow on the inside?
This website is a mine of information. Thankyou!

 

[BruceB]

Like Worcester, I charge to do a full heat loss calculation and sizing calculations - there is simply too much detailed and tricky work not to. I appreciate that does make it difficult for potential customers to amass a number of 'free' quotes to compare. But for people close geographically I am normally happy to give a couple of hours free to give advice on likely options. I am based between Bath and Bristol so might be close to you. If you are interested send me a PM.

 

[The Solar King]

Having done the Logic Certifcation training course and seen people going away thinking they knew what they were doing, I can confirm that this is only the start. Alot of installers especially with Air Source will simply rely on the manufacturer to do most of the work. To do this properly is like crossing a minefield. It has made me think twice about entering this market.

Heat pumps are brilliant and will play a major role in the future of space heating, but there is no 'for dummies' approach to getting it right. It is a whole skill set as Worcester rightly points out.

 

[TeamIneedexpert]

Hi there,

You could contact UFW Limited they will do a site visit for you they deal with all renewable technologies. You will need a lot of land to install a ground source heat pump an alternative is an air source heat pump. Not sure if you have looked at this option?

 

[Worcester]

You will need a lot of land to install a ground source heat pump

No you don't! All you need is an average 3 bed semi back garden, with good access.

an alternative is an air source heat pump.

ASHP is rarely an alternative to a GSHP, as the CoP goes through the floor when it gets cold outside, whereas GSHP's work all year round from the stored energy in the ground.

ASHP's work well with well insulated properties, whereas a GSHP can stack up against a Biomass boiler when you get the heating design correct.

In all circumstance the 4 golden rules are:
1) Insulate
2) insulate
3) Insulate
4) Consider the options.

 

[shanky887614]

Hi there,

You could contact UFW Limited they will do a site visit for you they deal with all renewable technologies. You will need a lot of land to install a ground source heat pump an alternative is an air source heat pump. Not sure if you have looked at this option?

you dont need a lot of land at all, if you have enough land its cheaper for a grid like system than drilling straight down