Fronius Ohmpilot - Application Example 3: 1-Phase Heating Element with Heat Pump Control

26
1
INPUT - grid supply 1x 230 V
Spring balancer 1.5 - 2.5 mm
2
NOTE! Phase and neutral con-
ductors must not be mixed up.
Residual current-operated circuit
breaker is triggered.
WARNING! If signal cables are
connected, the individual wires
must be bound together with a
cable tie directly upstream of the
terminal. This prevents any wire
making contact with dangerous
voltages if it works loose.
2
Multifunctional relay output
3
OUTPUT up to 3 kW variable, max.
13 A resistive load
Spring balancer 1.5 - 2.5 mm
2
NOTE! The voltage must be at
least 15 V and the current at least
2 mA, so that the relay contacts
do not oxidise.
4
Hot water boiler
5
PT1000 temperature sensor
6
7
8
9
10
Heat pump with SG Ready
control input
Heating element (max. 3 kW)
Residual-current circuit breaker
Circuit breaker max. B16A
Ferrite (included in delivery)
Functional
Description
The Fronius Smart Meter records the current power at the feed-in point and transfers the
data to the Datamanager. By controlling the Ohmpilot, the Datamanager adjusts any sur-
plus energy that is available to zero. In detail, this takes place by continuously adjusting
the heating element connected to the Ohmpilot and by targeted switching on of the heat
pump.
For activation, the heat pump must have a control input (e.g. SG Ready or DSO release).
The heat pump can, for example, be switched from operating status 2 (normal operation)
to operating status 3 (increased operation) as a result of activation of heat pump input 2
by the relay. However, the heat pump can also be switched from operating status 1 (DSO
block) to operating status 2 (normal operation) as a result of activation of heat pump
input 1 by the relay.
A description and list of SG Ready heat pumps can be found at:
http://www.waermepumpe.de/waermepumpe/qualitaetssicherung/sg-ready-label/
Relatively small surpluses are consumed with the heating element in a continuously vari-
able manner. From a certain surplus power, it makes sense to activate the heat pump, as
it is more efcient (e.g. COP for hot water preparation up to 53 °C = 2.5).
The optimal switching thresholds depend on:
- COP of the heat pump. The higher the temperature to which the hot water is
heated, the lower the COP
- Electrical output of the heat pump
- Feed-in tariff and the costs for purchasing electricity
- Reduction of the heat pump’s start-up cycles = increase in service life of the heat
pump
- Thermal losses from the heat pump and the pipes
If no temperature sensor is installed, the heat pump must ensure the minimum tempera-
ture is maintained. Alternatively, the Ohmpilot can also ensure the minimum temperature
through activation of the heat pump. This may result in electricity being sourced from the
grid.
The maximum temperature must be set on the heating element thermostat and on the