andrews CWH30/100 Installation Manual, Operation And Maintenance Manual page 18

SECTION 3 INSTALLATION
TEMPORARY It is possible to change the water heater temperature remotely via a timer programme.
First of all the new, desired water heater temperature is set at a value higher or lower
WATER
than the water heater temperature during normal operation. This makes it possible, for
HEATER
example, to carry out legionella flushing. See page 31.
TEMPERATURE
The water heater temperature changes when the contacts connected to terminals BT1-
CHANGE
BT2 are closed. The water heater temperature goes back to normal operation when these
contacts are opened again.
If the temperature change is used for legionella flushing, it is possible to return the water
heater temperature to normal operation before the timer programme finishes. This
happens on the basis of a temperature measurement, for example at the end of a
circulation line (secondary return). For this purpose a 10K NTC temperature sensor (part
number E674) must be connected to the terminals LS1-LS2. The water heater
temperature now goes back to normal operation if the temperature is higher at the
measuring point than the secondary pre-set water heater temperature minus 5ºC for 20
minutes. If, for example, the secondary pre-set water heater temperature is set at 70ºC,
the water heater temperature returns back to normal operation as soon as the
temperature at the secondary measuring point has been above 65ºC for more than 20
minutes.
CIRCULATION
A circulation pump (maximum 0.7 A) can be connected at the terminal pump L - pump
N. The circulation pump can then be controlled by a thermostat connected to terminals
PUMP AND
TH1-TH2. Connecting the contacts of the thermostat then activates the circulation pump.
STORAGE
TANKS
The application can be used when the water heater is combined with a separate storage
tank.
As soon as the temperature in the tank gets too low the thermostat will activate the
pump so the tank is heated up again. Matching storage tanks are available
in 200 and 300 litre sizes, models HWST200 and HWST300, these tanks are fitted
with a thermostat for use as above. See below for schematic system design, and
page 17 for tank dimensions and wiring diagram.
Fig. 6
Sc hematic
System Design
16