Installation manual
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Brine-to-Water Heat Pump 3.1.3
Fig. 3.1: Freezing curve of a monoethylene glycol/water mixture in relation to
the concentration
Pressure protection
Brine temperatures between approx. -5°C and +20°C can occur
when heat is exclusively extracted from the ground. These
fluctuations in temperature result in a change in volume of
approx. 0.8 to 1% of the total volume of the system. In order to
keep the operating pressure constant, an expansion vessel with
an admission pressure of 0.5bar and a maximum operating
pressure of 3bar is necessary.
ATTENTION!
For protection against overflowing, a tested membrane safety valve
should be installed. The air outlet pipe of the safety valve must, according
to DIN EN 12828, end in a collection tank. To monitor pressure, a pressure
gauge with minimum and maximum pressure designation is necessary.
Filling the system
The system should always be filled in the following order.
Mix the required concentration of antifreeze and water in a
container.
Check the antifreeze/water concentration with an antifreeze
tester for ethylene glycol.
Fill the brine circuit (at least 2bar to a maximum of 2.5bar)
De-aerate the system (install a micro-bubble separator)
ATTENTION!
Even following lengthy operation of the brine circulating pump, filling the
brine circuit with water and then adding antifreeze does not create a
homogenous mixture. The unmixed water column freezes in the
evaporator and destroys the heat pump!
Relative pressure drop
The pressure drop of brine is dependent on the temperature and
the mixture. The pressure drop of the brine increases with
sinking temperatures and increased concentrates of
monoethylene glycol.
Fig. 3.2: Relative pressure drop of a monoethylene glycol / water mixture
compared with water, dependent upon the concentration at 0 °C
and –5 °C
Insufficient brine solution and leakage
A "low-pressure controller" (available as an accessory) can be
installed in the brine circuit to diagnose a lack of fluid, a leakage
in the brine circuit and to comply with the regulations of the local
authorities. In the event of a drop in pressure, the low-pressure
controller sends a signal to the heat pump manager, which is
then either indicated in the display or blocks the heat pump.
1) Section of pipe with internal and external threads
2) Pressure controller with connector and connector seal
Fig. 3.3: Low-pressure controller for the brine circuit (assembly and wiring)
Table 3.1: Total volume and quantity of antifreeze per 100 m pipe for different
types of PE pipe and frost protection down to –14 °C
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Pipe DIN 8074
(PN 12.5)
[mm]
Volume
per 100 m
[l]
Antifreeze
per 100m
[l]
Maximum
brine flow
rate
[l/h]
25 x 2.3 32.7 8.2 1100
32 × 2.9 53.1 13.3 1800
40 × 3.7 83.5 20.9 2900
50 × 4.6 130.7 32.7 4700
63 × 5.8 207.5 51.9 7200
75 × 6.9 294.2 73.6 10800
90 × 8.2 425.5 106.4 15500
110 x 10 636 159 23400
125 x 11.4 820 205 29500
140 x 12.7 1031 258 40000
160 x 12.7 1344 336 50000
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