Electric immersion heater in the flow
Relays K25 and K26 are intended for using an electric immersion heater in the flow.
They are controlled by 2 appropriately configured multifunctional relay outputs QX1 –
QX6.
If both relays are present, the electric immersion heater is controlled in 3 stages (1st
stage K25, 2nd stage K26, and 3rd stage K25 and K26).
If a flow temperature sensor (B21) is connected, it is used for control to the flow
temperature setpoint. The switching differential is 1 °C.
If the flow temperature sensor is missing, but a common flow temperature sensor (B10)
is available, that sensor is used for conrol.
If no flow temperature sensor is present, the electric immersion heater is controlled
based on the return temperature (B71) and the return temperature setpoint. The
switching differential is set with parameter "Switching diff return temp" (2840).
Electric immer
sion heaters in the flow are also locked during an electrical utility lock.
Line no. Operating line
2880 Use electric flow
2881 Locking time electric flow
2882 Release integr electric flow
2883 Reset integr electric flow
2884 Release el flow below OT
Control of the electric immersion heater is dependent on the selected kind of use.
Use electric fl
ow
Substitute
The electric immersion heater is only used in emergency operation (parameters 7141,
7142), when breaching the minimum source temperature (parameters 2815, 2816) or
outside the employment limits for air/water heat pump (parameter 2812, 2813).
When activating emergency operation (manually or automatically), the electric
immersion heater is immediately released to ensure control to the current setpoint. No
consideration is given to "Locking time electric flow" (2881) and to "Release electric
flow below OT" (2884).
If there is no control sensor (B21, B10,
B71), the electric immersion heater is switched
on in emergency operation when there is a valid temperature request. In the case of a
3-stage electric immersion heater, both stages (K25 and K26) are switched on at the
same time.
Control of the electric immersion heater must take place by an external thermostat.
Complementary operation HC
Complementary operation DHW
Complementary operation HC+DHW
The time entered on parameter 2881 'Locking time electric flow' started to run as soon
as the compressor switches on if the electric immersion heater in the flow is released to
support the heat pump (complementing the compressor). The calculation of the release
integral (parameter 2882) after the lock out period expires. The electric immersion
heater is released as a compliment to the compressor
if the release integral expires, for
heating only, for DHW charge only or for both application, depending on the setting. In
this case, the electric immersion heaters act as an additional stage.
In the follo
wing cases, setting "Use electric flow" has no impact on the use of the
electric immersion heater:
• With frost protection
• With air-to-water heat pumps during the defrost process
• During active limitation due to too low source temperature (see "Time limit source
temp min" for water-to-water heat pumps (2822))
124/258
Siemens Switzerland Ltd User manual RVS61.843, RVS41.813 CE1U2355en_02
HVAC Products 6 The settings in detail 28. September 2009
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