Heating The Dhw Tank; Appliance Operation Outside The Application Limits; Frost Protection - STIEBEL ELTRON Accelera 220 E Operation And Installation Manual

OPERATION
Appliance description
3.1

Heating the DHW tank

1
2
1 Dome sensor
2 Integral sensor
The appliance is equipped with two temperature sensors.
- The dome sensor captures the water temperature in the
upper section of the tank.
- The integral sensor is a temperature sensor affi xed over the
entire tank height. The integral sensor determines the aver-
age tank temperature.
The appliance display indicates the temperature in the upper sec-
tion of the tank. The appliance control unit operates using the
average tank temperature.
The appliance may start to heat even though the display indicates
that it has reached the set temperature. In this case the deviation
of the average tank temperature from the set value is greater than
the start hysteresis.
For information on the heat-up time, See 15.3, "Data table", pg.
29. The calculation of the available amount of mixed water is
based on the average cylinder temperature. The amount of mixed
water is only calculated if the water temperature in the upper
section of the cylinder is higher than 104 °F / 40 °C.
DHW is normally heated by the heat pump of the appliance within
the application limits (See 15.3, "Data table", pg. 29).
3.1.1 Electric booster element
Heat pump operation will be interrupted if the application limits
are exceeded in heat pump mode. The electric emergency/booster
heater takes over the DHW heating using the selected set tempera-
ture. Once the appliance is back within the application limits, the
electric emergency/booster heater switches off and DHW heating
continues with the heat pump.
In emergencies you can start the electric emergency/booster heat-
er should the appliance develop a fault and the fault code is higher
than 256. See 4.4.1, "Comfort heating", pg. 13.
In the event of an unexpectedly high hot water demand, the emer-
gency/booster heater can be activated with the rapid heating key
in addition to the heat pump. See 4.4.2, "Emergency back up
mode", pg. 14.
www.stiebel-eltron-usa.com
3.2 Appliance operation outside the application
limits
3.2.1 Ambient temperatures below the application limit
If hoar frost is growing on the evaporator fi ns, the hoar frost
temperature monitor switches the heat pump compressor off.
The compressor switches on automatically once the evaporator
defrosts.
 To guarantee fault-free operation of the appliance, make sure 
you operate the appliance within its application limits (See
15.3, "Data table", pg. 29).
Note
Heat-up times are longer while the evaporator is defrost-
ing.
3.2.2 Ambient temperatures above the application limit
The safety equipment switches the appliance off if the upper ap-
plication limit is exceeded.
Following a cooling time of several minutes, the appliance is
switched back on automatically. The appliance is switched off
again if the ambient temperature rises above the permissible tem-
perature value again.
 To guarantee fault-free operation of the appliance, make sure 
you operate the appliance within its application limits (See
15.3, "Data table", pg. 29).
3.3

Frost protection

The appliance activates a frost protection function if the integral
sensor in the DHW tank detects a temperature below 50°F/10°C.
The appliance then heats the water in parallel mode by using both
the heat pump and the electric booster element. The heat pump
and electric booster element switch off once the temperature de-
tected by the integral sensor is more than 65°F/18°C.
Accelera® 220-300 E | 11