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5.9 GRoUnD ColleCtoR InfoRmatIon
TYPICAL GshP GROUND COLLECTOR sPECIFICATIONs FOR UK DOMEsTIC INsTALLATIONs
Ground source heat pump systems require that geological ground conditions and preferred heat extraction methods
are considered strictly in association with the thermal load requirements of the load dwelling and the heat pump
coefficient of performance.
Geological conditions vary significantly around the UK and the following tables are presented solely as a guide to
assist in pre qualification formatting.
Underground Geology
General guideline values
underground (dry sediment)
Normal rocky underground with water
saturated sediment
Consolidated solid rock with high thermal
conductivity
Individual rocks
Gravel, sand, dry
Gravel, sand, saturated water
Strong groundwater flow in gravel and sand,
for individual systems
Clay, loam, damp
Limestone (solid)
sandstone
Acidic magmatite (e.g. granite)
Basic magmatite (e.g. basalt)
Gneiss
Illustrated extraction values are approximate guides only. Actual values can vary significantly due to rock fabric such
as crevices, foliation, weathering etc.
Ground Conditions
Underground Geology
Dry, non- cohesive soils
Wet, non - cohesive soils
Cohesive (loamy) soils, wet
Water saturated sand/gravel
House floor Area m
Up to 90
80-130
heat pump capacity
Borehole depth m
Groundhose length m
Ideal slinky collectors m
The above information is offered as guidance only and Ideal recommend that professional technical advice is sought
prior to design and selection of system components.
Groundtherm - Ground Source Heat Pump -
Borehole Collector Heat extraction Guide
Horizontal (flat) Collector Heat Extraction Guide
Slinky Collector Heat extraction Guide
2
240V single phase - for 1800 hours
Specific Heat Extraction
1800 hours
25 W/m
60W/m
84 W/m
<25 W/m
65-80W/m
80-100 W/m
35 - 50 W/m
55 -70 W/m
65 - 80 W/m
65 -85 W/m
40-65W/m
70 - 85 W/m
Specific Extraction Output
For 1800 hours
10 W/m
2
15 - 20 W/m
2
20 -30 W/m
2
40 W/m
2
heat pump
nominal output
trenches required
3.5kW
5.0kW
Comparative examples
3.5kW
60 - 80
150 200
2 x 30
Installation
2400 hours
20 W/m
50W/m
70 W/m
< 20W/m
55-65W/m
80 -100 W/m
30-40W/m
45-60W/m
55-65W/m
55 -70 W/m
35-55W/m
60-70W/m
For 2400 hours
8 W/m
2
12 -16 W/m
16 - 24 W/m
32 W/m
2
Number of
Length of
slinkies
2
30 metres
2
40 metres
5.0kW
70 - 90
200 300
2 x 40
Poor
2
2
25
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