Dhw Heating - Siemens LMS14 User Manual

Charging with
controllable heat
sources
Charging with
uncontrolled heat
sources
Building Technologies Division

6.7 DHW heating

The LMS14... makes possible the following types of DHW heating:
1. Charging with oil- or gas-fired boiler
2. Charging with electric immersion heater
3. Charging with solar collectors
4. Charging with solid fuel boiler
Heat generation with an oil- or gas-fired boiler or electric immersion heater can be
controlled. If there is demand for DHW, these heat sources can be switched on at any
time. The strategy is to produce the amount of heat required at a certain point in time –
and no more. For that purpose, switching programs, different setpoints and release
criteria are available. If several heat sources and an electric immersion heater are
available at the same time, they are used alternately, e.g. after summer/winter
changeover.
Heat generation with solar collectors and solid fuel boilers is not controllable. This
means that with these types of heat sources, the DHW is not heated when there is
demand, but when heat is available. The strategy is to fully charge the DHW storage
tank whenever possible. Here, switching programs, setpoints and release criteria do not
exist. Charging takes place whenever there is a sufficient temperature differential
between solar collector or solid fuel boiler and storage tank, and when the DHW
storage tank is not yet fully charged.
Since it is not always possible to satisfy the total demand for heat via the solar
collectors, the deficit must be covered by a controllable heat source (boiler or electric
immersion heater). So boiler or electric immersion heater are only used to compensate
for the heat deficit. This deficit is calculated from the storage tank's current temperature
and the required setpoint. In that case, the switching program and the release for
recharging should become active during the night when it is certain that solar energy
alone is not able to ensure the required temperature level.
Note!
DHW storage tanks are usually designed such that the lower part of the tank is
reserved for solar energy.
Warning!
To prevent scalding, the pipe to the tap must have scalding protection
integrated.
User Manual LMS14...
6 The settings in detail
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CC1U7471en
07.05.2014