Boiler Mode - Bosch HP270-2 Technical Manual

"dTof" – setting for temperature differential at which the HP is switched OFF
- default setting is 10ºC (available range from 4ºC – 15ºC)
Note: the differential temperature for comparison with defined/default "dtof" is measured as:
T dif = T coil – T tank
- T tank = minimum value measure by T top in HP or T tank (supplied sensor assembled in pocket at middle
of the tank)
- T coil = value measure by supplied sensor assembled in inlet of indirect coil.
Attention: The differential between "dton" and "dtof" must be at least 2ºC:

doff - don ≥ 2ºC (hysteresis)
Operation Principle:
 Heat Pump Switch OFF: if T dif > doff for more than 20min, the HP is switched OFF and only the Solar
thermal input assures DHW production. The solar gain has priority, so the display will display "Syst" as a
warning message indicating the external source active.
 Heat Pump Switch ON: if T dif < don for more than 3 min, HP starts, so the HP will operate in parallel to
compensate the Insufficient Solar Gain.
 In case we have Tdiff < dtof and Tdiff > dton we detect following behavior:

If HP is On, keeps On

If HP is Off, keeps Off
 If T tank < TMin, the HP Switch ON
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

5.3) Boiler mode

The main advantage of this mode is to ensure back-up by an alternative energy source (gas, oil, wood) instead of
electricity as generally is more costly. It will be activated when:
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