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Building Technologies Division User Manual LMS14… CC1U7471en
6 The settings in detail 28.01.2015
Instantaneous water heater with secondary heat exchanger without water outlet sensor (aqua booster)
When using an aqua booster, sensor B38 is not installed by the water outlet, but in the
heat exchanger itself, close to the cold water inlet. Configuration of an aqua booster
requires option Yes, using parameter Aqua booster (5550).
Special features of aqua boosters:
DHW consumption is detected by sensor B38, based on the heat exchanger’s
temperature gradient
When DHW is consumed, the burner’s output is controlled depending on the boiler
return temperature (from the heat exchanger to the boiler)
To ensure that DHW consumption can be detected via the heat exchanger’s
temperature gradient, the heat exchanger must always be kept at a certain
temperature level. For this reason, the Keep hot function for the aqua booster is
always enabled
Detection of DHW consumption with the aqua booster is performed via the temperature
gradient at sensor B38. With the aqua booster, that sensor B38 in located in the heat
exchanger itself, close to the cold water inlet. When DHW is consumed, the
temperature acquired by that sensor drops when cold water enters the heat exchanger.
If a flow switch is connected and configured, DHW consumption can also be detected
by the flow switch. DHW consumption is detected when either the flow switch or the
temperature gradient indicates consumption. The end of consumption is detected when
neither the flow switch nor the gradient indicates consumption. If DHW consumption
shall be indicated by the flow switch only, parameter Aqua booster (5550)offers option
Yes, wo gradient detection.
When DHW is consumed, the burner is controlled depending on the boiler return
temperature (sensor B7). The boiler return temperature represents a good indication of
the DHW outlet temperature. The burner is switched on when the boiler return
temperature drops one switching differential below the setpoint of consumption. The
burner is switched off again when the boiler return temperature exceeds the setpoint of
consumption by the current switch-off differential. The switch-off differential is
calculated dynamically, based on the parameterized minimum and maximum switch-off
differential.
When DHW is consumed, the burner is controlled depending on the boiler return
temperature (sensor B7), but the boiler temperature is limited. Parameter Boil temp out
red (2527) is used to set the temperature limit. The associated switching differential is
set via parameter Swi diff output red (2528).
Line no. Operating line
1610 Nominal setpoint
2460 Switching diff on DHW
2461 Switching diff off min DHW
2462 Switching diff off max DHW
2463 Settling time DHW
2527 Boil temp out red
2528
Swi diff output red
5020 Flow setpoint boost
5550 Aqua booster
DHW consumption
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