Calculating The Required Groundwater Volume; Permits For A Groundwater/Water Heat Pump System; Sizing The Heat Exchanger, Primary Circuit - Viessmann VITOCAL 200-G Technical Manual

Design information
(cont.)
Water/water heat pumps achieve high performance factors. Ground-
water offers an almost constant temperature of 7 to 12 °C all year
round. Therefore the temperature level needs to be raised only a little
higher (compared to other heat sources) in order for it to be able to be
utilised for heating purposes.
Depending on the design, the heat pump cools the groundwater by up
to 5 K, although its consistency remains otherwise unchanged.
■ On account of the costs for pumping systems, for detached houses
and two-family homes, we recommend the pump groundwater from
depths of not more than approx. 15 m (see the above diagram). For
commercial or large scale systems pumping from even greater
depths could still be viable.
■ Maintain a distance of 5 m between the point of extraction (delivery
well) and the point of re-entry (return well). Delivery and return wells
must be located in the line of flow of the groundwater to prevent a
"flow short circuit". Construct the return well so that the water exits
below the groundwater level.

Calculating the required groundwater volume

The flow rate, i.e. the volume of water passing through, depends on
the appliance rating and the rate of cooling.
See the datasheets for the required minimum flow.

Permits for a groundwater/water heat pump system

This project requires permission from the "local water authority" [check
local regulations].
Where buildings must be connected to the public water system, the
utilisation of the groundwater as a heat source for heat pumps must
be authorised by your local authority [check local regulations].

Sizing the heat exchanger, primary circuit

10 °C 8 °C
A B
6 °C 4 °C
A Water
B Brine (antifreeze mixture)
Selection list for plate heat exchangers for water/water heat pumps
Plate heat exchanger, soldered (do not clean; replacement part)
Heat pump Cooling capacity
Type kW
BWP 106
5.9 (4.6
BWP 108
7.7 (5.7
BWP 110
9.5 (7.3
Plate heat exchanger, threaded (requires cleaning)
Heat pump Cooling capacity
Type kW
BWP 106
5.9 (4.6
BWP 108
7.7 (5.7
BWP 110
9.5 (7.3
*14 230 V appliances
VITOCAL 200-G
Flow rate
Well circuit Primary circuit
(water) (brine)
3 3
m /h m /h
*14 1.1
)
*14 1.3
)
*14 1.6
)
Plate heat
exchanger
Part no.
*14 7248 331
)
*14 7248 332
)
*14 7248 333
)
■ Due to fluctuating water quality, we generally recommend a system
separation between wells and heat pump.
■ The groundwater flow and return lines to/from the heat pump must
be protected against frost and must slope towards the well.
For the Vitocal 200-G, type BWP 110, the minimum flow rate is, for
3
example, 1.8 m /h. Increased flow rates lead to a higher internal pres-
sure drop. Take this into account when designing the pumps.
Permits can be subject to certain stipulations.
Note
Fill primary circuit with anti-freeze mixture (brine, min. –5°C).
The operational reliability of a water/water heat pump improves when
it is used with a primary circuit heat exchanger. Subject to the correct
sizing of the primary pump and the optimum layout of the primary cir-
cuit, the coefficient of performance of the water/water heat pump will
be reduced by a maximum of 0.4.
We recommend the use of the threaded stainless steel plate heat
exchanger from the Viessmann Vitoset pricelist (manufacturer: Tranter
AG); see the following selection table.
Pressure drop
Well circuit Primary circuit
(water) (brine)
mbar mbar
1.2 55
1.46 28
1.81 44
Flow rate and pressure drop in the intermediate circuit are safeguarded
by the integral circulation pumps, provided the total pressure drop from
the separating heat exchanger and pipework does not exceed the
maximum external pressure drop of the heat pump (see "Specifica-
tion").
6
Vitotrans 100
plate heat
exchanger
Part no.
55 3003 492
33 3003 493
52 3003 493
VIESMANN
43