Geothermal Probe - Viessmann VITOCAL 300-G Technical Manual

Design information

Geothermal probe

RL
VL
RL Primary return
VL Primary flow
A Bentonite-cement suspension
B Protective cap
On smaller plots, geothermal probes are an alternative to geothermal
collectors when retrofitting existing buildings. In the following we con-
sider the double U-shaped tubular probe.
One version would be two double U-shaped tubular loops made from
plastic in one borehole. All cavities between the pipes and the ground
are filled with a highly conductive material (bentonite).
We recommend the following spacing between 2 geothermal probes:
■ Down to 50 m depth: 5 m (min.)
■ Down to 100 m depth: 6 m (min.)
For systems such as this, notify your local water board well in advance
of commencing such installations.
The geothermal probes are installed either by drilling or by ramming,
subject to their respective design. Systems of this type require a permit
from your local water board.
Further information can be obtained from the geothermal probe man-
ufacturer (see "Manufacturer's addresses" in the appendix).
We recommend arranging the sizing to match the regional conditions
and the drilling service to be carried out by the contractor suggested
by your local Viessmann sales office.
Required geothermal probes and brine distributors at ³
Heat pump type
²
K
kW
Single stage heat pump
BW 121
BW 129
BW 145
Two-stage, both stages with the same output
BW+BWS 121+121
BW+BWS 129+129
BW+BWS 145+145
Two-stage, stages with different output
BW+BWS 121+129
BW+BWS 121+145
BW+BWS 129+145
VITOCAL 300-G
(cont.)
= 50 W/m, probe (to VDI 4640) for 2000 operating hours (estimated sizing)
E
PE 32 × 2.9
Overall pipe length
m
17
23.3
34.2
34
46.6
68.4
40.3
51.2
57.5
Possible specific extraction rates q
probes (to VDI 4640 sheet 2)
Substructure
General guidelines
Poor ground (dry sediment)
(λ < 1.5 W/(m · K))
Normal solid rock subsoil and
water-saturated sediment
(1.5 ≤ λ ≤ 3.0 W/(m · K))
Solid rock with high thermal conductivity
(λ > 3.0 W/(m · K))
Individual rocks
Gravel, sand (dry)
Gravel, sand (aquiferous)
Clay, loam (damp)
Chalk (solid)
Sandstone
Acidic magmatite (e.g. granite)
Basic magmatite (e.g. basalt)
Gneiss
Rough sizing
Basis for sizing is the refrigerating capacity ²
operating point B0/W35.
Required probe length l = ² /³
K
to ground conditions).
The detailed sizing depends on the ground structure and the water-
carrying ground strata, and can only be determined following a local
inspection by the drilling contractor.
Note
The reduction of the number of drilled holes in favour of probe depth
increases the pressure drop to be overcome and the required pump
rate.
Information regarding dual mode parallel and mono-energetic
operation
In case of dual mode parallel and mono-energetic operation, consider
the higher heat source load (see "Sizing"). As a guide, a geothermal
probe system should not exceed an extraction of 100 kWh/m
Geothermal probes
Length in m
340
466
820
820
1120
1640
970
1230
1380
for double U-shaped pipe
E
Specific
Extract rate q
W/m
of the heat pump at
K
(³ = average extraction rate subject
E E
∙ a p.a.
Brine distributor
Part no.
4 × 85 2 × 7143 763
5 × 93 1 × 7143 763
2 × 7373 329
8 × 103 4 × 7143 763
8 × 103 4 × 7143 763
11 × 102 on-site
17 × 96 on-site
10 × 97 on-site
13 × 95 on-site
14 × 99 on-site
VIESMANN
in
E
20
50
70
< 20
55-65
30-40
45-60
3
55-65
55-70
35-55
60-70
39