Buffer Discharging Control

External un-controlled loading usually loads the buffers down to the lower sensor.

For discharging control the input “ExtLoading” shall be set to “1” only when external load happens. During external loading all the bypass valves will be opened to charge the buffer as much as possible.

In this case the bypass valves will switch to bypass only

In this configuration a buffer changeover valve is automatically configured.


If the heat in the buffer is insufficient and the temperature of the upper sensor falls below the heat demand – DCHG.02:

BufUpperTemp < HeatDemandIn - DCHG-02(5K)


When the effective lower temperature will be higher than the heat demand + DCHG-01:

EffLowerTemp > HeatDemandIn + DCHG-01(8K)

The effective lower sensor is the same as described in charging control. The engineer can decide about the lower sensor, setting the input “BufLoadLevel“.


With big values of DCHG-02, you save more heating energy and use the buffers heat as long as reasonable, even if we cannot reach the heat consumers setpoint. We have to find a reasonable balance between heating and electric energy costs.

In configurations where the heating strategy, a solar control or a solid fuel boiler charges the buffer, one buffer lower sensor is mandatory.


During external loading if the input „ExtLoading” = 1, the heat demand (if transmitted) will be decreased by the value defined in the parameter SOL-01 and the output “Buf_SpShift” will display the effective value of SOL-01.

When the input „ExtLoading” switches back to “0”, the heat demand at the input “HeatDemandIn” will be transmitted to the output and the output “Buf_SpShift” will be “0” after the delay time defined in the parameter SOL-02.

Table 4.   Parameter List

Description

Value Range

Default Value

Unit

DCHG-01: switch to buffer hysteresis

0 … 50

8

K

DCHG-02: switch to boiler(s) hysteresis

0 … 50

5

K