Configuration parameter
[BufferFlex] function block
13
Explanation of [Return from consumers]
This temperature is the mean return temperature of all
consumers connected to the buffer. For example:
heating circuits, hot water tanks, external heat
consumers fresh, water modules...
This temperature forms the basis for calculating the
buffer charging status. If the buffer is charged
uniformly with this temperature (e.g.: 35 °C), this is
equivalent to the charge status "0%".
The average should be set for fluctuating return tem-
peratures.
Explanation of [Buffer min.]
This defines the minimum temperature of the buffer
within the configured time window at the allocated
temperature sensor.
The higher this minimum temperature is set, the
larger the heat reserve in the buffer. At the same
time, however, higher temperatures in the buffer
reduce the solar yield. This is because the buffer is
kept at the minimum temperature using energy from
the boiler, even if there is no demand from the
consumers.
The factory setting can remain unchanged as long as
all components of the heating system are controlled by
the ETA control system. A higher value is required if
peaks in output have to be covered or very fast heat
availability is needed.
Explanation of [Buffer off]
This sets the shutdown temperature for the buffer
charge through the boiler. If the temperature sensor in
the buffer has exceeded the shutdown temperature,
charging of the buffer by the boiler is stopped.
The value should be at least 5 - 10 °C above the
average return temperature of the consumers,
but no more than 70 °C. A high shutdown temperature
reduces the number of boiler starts and improves
boiler running time.
Explanation of [Starting after output] and [Output
via]
In most cases, the buffer starts charging as soon as
the temperature sensor has dropped below a minimum
level. Then the boiler starts and, as soon as this is
warm enough, buffer charging begins. These delays
are usually not noticed.
However, these delays may be disruptive for
systems (e.g. district heating) which have to hold
a certain minimum temperature. Therefore, this
parameter can be set to [Yes] in such cases. Then the
boiler starts as soon as the control system calculates a
request on the buffer.
Previously collected control data is used for this
calculation and adjustable factor [Output via]. If the
total of the calculated output multiplied with the factor
[Output via] is greater than the output of the first boiler
to be started, this is switched on for buffer charging.
Example:
Boiler output: 200 kW
[Output via]: 70%
=> If more than 140 kW (200 x 0.7) is calculated, the
first boiler is started in order to load the buffer.
Explanation of the [Extra charge] function
With this function a daily point in time is defined
(=[Start time]) and an upper limit for the outdoor
temperature (=[Charging under outside temperature])
to additionally charge the buffer. This buffer charging is
done independently of the actual consumer require-
ments and independently of the set time windows.
A separate minimum temperature [Charge buffer min
extra] and shutdown temperature [Charge buffer from
extra] can be set for this charge. Charging ends as
soon as the buffer reaches these temperatures.
The function is turned on or off with the parameter
[Activate time programme?].
For an immediate start, the [Immediately charge]
parameter must be set to [On].
Explanation of [Res.heat difference]
This sets the minimum temperature between the heat
producer (e.g. boiler) and the temperature sensor
assigned in the buffer, so that the heat producer may
transfer its residual heat to the buffer. If this difference
is undershot, no more residual heat is fed into the
buffer.
Example: the assigned temperature sensor for the
residual heat is the lowermost buffer sensor and the
temperature here is currently 35 °C.
[Res.heat difference]: 8 °C
=> The boiler may continue to feed its residual heat to
the buffer until the boiler temperature is at only 43 °C
(=35°+8°).
Explanation of [Flow temp raise]
The target temperature of the buffer [Buffer target] is
increased by this value when the buffer is demanding
heat from the boiler.
This ensures that the boiler temperature is sufficient
for reaching the target temperature in the upper
section of the buffer. As long as the boiler has not
reached the target temperature [Boiler tgt.], the boiler
is operated in the high-output range.
