Bosch HP270-2 Technical Manual page 40

Note: For Software HP1501 / 1701 (HP270-3) and 2501 (HP200/250-1)
Only "dTon" needs to be defined and automatically the dtoff is set up to dton + 2ºC
"dTon" – setting for temperature differential at which the HP is switched ON
- default setting is 6ºC (available range from 2ºC – 10ºC)
"dToff" – parameter not existing in Display but assumed as dton + 2ºC
Operation Principle:
 If the boiler mode is active and the HP appliance needs to switch ON the E-heater
(example: to assure set point @ T bot>55ºC, Legionella Mode, Tank antifreeze, FULL, AUTO-FULL, air
temperature out of the range):

The relay is closed allowing the boiler to read a tank temperature (ZS type boiler with NTC
connection 10 kΩ).

After 3 minutes the T_dif is checked:
 In case we have Tdiff < dtof and Tdiff > dton we detect following behavior:

If E-heater is On, keeps On

If E-heater is Off, keeps Off
 Hysteresis time: 3 minutes for both conditions
 If T tank < TMin, HP Switch ON
Note: For both Solar and Boiler Combination with heat pump consider following coil data:
* Continuous output according to DIN4708, part 3, for Mh=2600kg/h; ΔT=35ºC, inlet coil temp=80ºC.
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 if T_dif > doff, E-heater is switched OFF, the boiler is ON
The boiler operates to ensure fast recovery and hot water instead of electrical energy as a
backup to the compressor.
 if T_dif < don, E-heater is switched ON, the boiler is not producing enough energy
The boiler is not ensuring energy (for example when enters in lockout due to absence of
combustible, etc), so the E-heater is requested as backup.
Description
Coil area (m 2 )
Max. Power (kW)
6-720-821-364 SM HP270 – 250 - 200 2016/12 en
FD > 306 FD ≥ 454
1.3 1.0
42 31.8