Auxiliary Heater - Danfoss DHP-R 7Ua User Manual

therefore has the unit degree minutes and represents the plant's energy ba-
lance. If the primary supply temperature is one degree above the set point for
one hour straight the integral value will grow to 60. If the supply temperature
is too low, the integral value will decrease and become negative. When the
temperature is precisely right the integral will not change at all.
There is a setting in the controller called Start hp1. This setting is for the inte-
gral value at which the first heat pump should start. It is a negative number.
When the heat pump starts, it may be that it produces more heat than neces-
sary. The integral value will then increase, and when it passes zero the heat
pump is turned off. The primary supply temperature will, at average, have had
the same temperature as the set point. Since a building's temperature changes
slowly, the variations in the primary supply will not make a noticeable diffe-
rence in room temperature.
The setting Delta start hp decides how much below Start hp1 the integral must
drop before the next heat pump is started, and how much below that before
the third starts, and so on, if the plant has multiple heat pumps.
If all the heat pumps are running but the integral still drops, then the auxiliary
heater is needed. Start extra heater decides how much below the starting va-
lue for the last heat pump the integral must drop before the auxiliary heater is
started. When it has dropped to the limit Full extra heater below the start limit
or the last heat pump, the auxiliary heater will work at maximum power. Exac-
tly how the auxiliary heater works depends on what type it is.
The integral is allowed to drop a little bit more according to the setting Integral
dead zone, but then it is not allowed to become lower. On the positive side it is
limited by the setting Integral max limit.
The integral value can be read on the pump display.
2�1�3 auxiliary heater
The control system has one relay output Block. extra heater and one analogue
0 to 10 V output Extra heater, which can be used to control auxiliary heating of
different types. When the plant is commissioned, the type of auxiliary heater, if
any, is defined in the control system.
2�1�3�1 Burner
The auxiliary heater can consist of a burner for oil, gas, wood chips, or some
other fuel. The burner must have its own control system and be capable of ge-
nerating a constant high water temperature. The signal Block. extra heater can
be used to turn off the burner completely. The analogue signal Extra heater
8 – Danfoss