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CAHA Midi
Installation, Usage and Maintenance Instructions
4.3 DOMESTIC HOT WATER (DHW)
4.3.1 EXTERNAL STORAGE TANK WITH THERMOSTAT (ELECTRIC 3-WAY VALVE)
As standard the DHW configuration is factory pre-set for an external storage tank + tank thermostat.
For hydraulic connection of an external storage tank to the boiler via an electric 3 way valve one should either use :
- the default configuration 2 pumps: 230 VAC DHW pump (terminal strip C1: 12,13,14) and CH pump (terminal strip C1:
15,16,17)
- an electric 3-way valve with a maximum travel time of 255 sec. (terminal strip C1: 13,14,15,16). At the end of the travel
time in either direction DHW or CH the 230 VAC on the 3-way valve will be switched off.
The 2 wires of the tank thermostat must be connected to numbers 7 and 8 on terminal strip C2.
In the case of using an electric 3-way valve adjust the setting in the technician menu, system settings, boiler parameters,
number of pumps to: pump and 3-way valve.
The 3-way valve travel time can be changed in the technician menu, system setting, boiler parameters, 3-way valve travel
time.
4.3.2 EXTERNAL STORAGE TANK WITH NTC SENSOR
In case the storage tank is equipped with an NTC sensor, adjust the setting in technician menu, advanced DHW settings,
DHW request to sensor.
Note: The resistance of the NTC sensor must have a value of 12 kOhm at 25 °C.
The 2 wires of the tank NTC sensor must be connected to numbers 7 and 8 on terminal strip C2.
The set point temperature of the storage tank is adjustable (default set at 60°C,the flow temperature is DHW se
20K). Warning : if a CH heat demand exists immediately after finishing the heat request for DHW, it is possible for high tem
-
peratures to flow into the CH system regardless of CH set point (hot shot).
4.3.3 DHW PRIORITY/GENERAL BEHAVIOUR WITH EXTERNAL STORAGE TANK
Disabling hot water operation : press Summer-Winter button R2-C4( not active in main screen). See later in manual for
further explanation.
Enabling hot water operation : press Summer-Winter button R2-C4 (active in main screen). See later in manual for further
explanation.
In the default boiler configuration, (2 pumps-DHW and CH pump), a DHW request has priority over CH request
In the technician menu, advanced DHW settings, DHW priority, the DHW priority over CH can either be disabled or a maxi-
mum DHW priority time can be set.
In the case where the DHW priority is disabled and both demands are active at the same, both pumps (CH and DHW) will
be activated. During this time the flow temperature is set to either 80 °C (tank thermostat) or DHW se 20K (NTC
sensor).
Notice : In some countries, at outputs ≥ 40 kW double separation between exchanging media is required. Please
check your local regulations.