Heating The Dhw Tank; Appliance Operation Outside The Application Limits - STIEBEL ELTRON accelera 220 e Operation And Installation Manual

OPERATION
Appliance description
The electronic control unit makes energy saving adjustments eas-
ier. Subject to the power supply and usage pattern, the water is
heated up automatically to the set temperature.
Heat pump operating principle
A hermetic circuit within the appliance contains refrigerant (See
16.3, "Data table", pg. 33). This refrigerant evaporates at low
temperatures and collects heat from the ambient air.
In the evaporator, the refrigerant changes from its liquid into its
gaseous state. A compressor draws in the gaseous refrigerant
and compresses it. This increase in pressure raises the refrigerant
temperature.
The compression process requires electrical energy. The energy
(motor heat) is not lost, but is discharged to the downstream con-
denser. There, the refrigerant indirectly transfers heat to the DHW
tank and the liquid refrigerant is routed to a a fi lter dryer. An ex-
pansion valve reduces the still prevalent pressure. The refrigerant
is routed to the two-fl ood evaporator and the cycle starts again.
Note
In the event of an interruption of the power supply, the
compressor is blocked from operating for at least one
minute. The electronic control board (ECB) delays elec-
tronic starting for one minute while the appliance goes
through its initializing process.
If the compressor subsequently fails to start, it may be
blocked by additional safety devices (Klixon and/or high
pressure switch). If the compressor is switched off due
to the Klixon, the pressure difference between the high
and low pressure sides of the refrigerant circuit may be
the cause. When the pressure difference is equalized
(approximately 5 minutes), the compressor turns on. If a
tripped high pressure switch caused the blocking of the
compressor, this may be due to a failed thermostat or
high ambient air temperature. After the power supply has
been re-established, the appliance continues to operate
with the parameters that were selected before the power
supply was interrupted.
4.1

Heating the DHW tank

1
2
1 Dome sensor
2 Integral sensor
www.stiebel-eltron-usa.com
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 the thermostat is fulfi lled. In this case the deviation of the
average tank temperature from the set value is greater than the
hysteresis of the integral sensor thermostat.
At ambient air temperatures lower than 46 °F (7.8 °C), the unit will
automatically enter defrost mode from time to time to remove ice
buildup on the evaporator.
For information on the heat-up time, See 16.3, "Data table", pg.
33. 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 16.3, "Data table", pg. 33).
4.1.1 Electric booster element
The electric booster element is used for times of unexpectedly
high hot water demand. The element is activated manually via
the red dot push button located on the front display panel (See
5.1, "Display and controls", pg. 12, item no. 8, "Rapid heating
key"). It is also activated automatically when the appliance is in
Automatic Mode (See 5.3.1, "Automatic Mode", pg. 14).
In case of a heat pump failure you can start the electric emer-
gency/booster heater should the appliance develop a fault and
the fault code is higher than 256 )See 5.5.2, "Emergency back up
mode", pg. 15).
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 5.5.1, "Comfort heating", pg.
14.
4.2 Appliance operation outside the application
limits
4.2.1 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. Defrost only works if the ambient air temperature is
more than 38 °F (3.3 °C)
 To guarantee fault-free operation of the appliance, make sure 
you operate the appliance within its application limits (See
16.3, "Data table", pg. 33).
Note
Heat-up times are longer while the evaporator is defrost-
ing.
Accelera® 220-300 E | 11