Fondital Tahiti Condensing 24 kW Combi (KC), Installation, Use And Maintenance Manual

11

WARNING
In KC model, a special adjusting device is installed, which limits domestic hot water flow rate to 13 liter per minute (KC 24), to 14 
liters per minute (KC 28) and to 16 liter per minute (KC 32).
Domestic hot water temperature supplied, depends on no. 3 DHW thermostat, on the quantity requested by the user and on 
water mains supply temperature.

In KC model, DHW liter per minute flow depends on the boiler’s thermal capacity and water mains supply temperature, according to the 
following formula:

K

l = DHW liter per minute = --------
                                             ΔT

K

 represents:

-  401 in KC 4 model
-  444 in KC 8 model
-  507 in KC 3 model

ΔT = DHW temperature – water mains supply temperature

E.g. in KC model, when water mains supply temperature is 8 °C and DHW is required to be 38 °C, in order to have a shower, the value of 
ΔT is:

ΔT = 38 °C – 8 °C = 30 °C

and DHW liters (l per minute) available at the required temperature of 8 °C are:

I = 401/30 = 13.4 [liter per minute] (mixed water at the tap).

In contrast, in KR model equipped with an external cylinder (optional equipment), available DHW flow depends on the cylinder capacity.

In KR model with external cylinder (optional equipment), every 15 days, the anti-Legionella function is activated. It consists in heating up 
the cylinder to 65 °C for 30 minutes; regardless of boiler mode setting.

2.4.4  ANTI-FREEZE FUNCTION

The boiler is equipped with anti-freeze function, which is active in SUMMER, WINTER and ANTI-FREEZE modes.

Anti-freeze function protects the boiler only and not the whole central heating system.

Central heating system is to be protected by means of an ambient thermostat, although this is disabled when the boiler  

is set to the ANTI-FREEZE and OFF modes.

Should anti-freeze protection be necessary for the boiler and CH system, select WINTER position 

 through no. 2    

knob.

When central heating water temperature sensor detects a water temperature of 5 °C, the boiler is switched on and stays on at minimum 
heat output until central heating water temperature reaches 30 °C or 15 minutes have elapsed.
Should boiler shut down, pump operation is still granted.

In KC model, anti-freeze function protects the domestic hot water system as well.
When domestic hot water probe detects a temperature of 5 °C, the boiler ignites and stays on at minimum heat output until domestic hot 
water temperature reaches 10 °C or 15 minutes have elapsed (the deviating valve is set to domestic hot water position).
Should boiler shut down, pump operation is still granted.

In CH only boilers equipped with a DHW supply external cylinder, anti-freeze function protects the cylinder as well.
The function is active only for cylinders equipped with 10 kΩ @ ß=3435 type NTC probe (refer to cylinder technical data).
When cylinder water temperature probe detects a water temperature of 5 °C, the boiler is switched on and stays on at minimum heat 
output until cylinder water temperature reaches 10 °C or 15 minutes have elapsed (the deviating valve is set to domestic hot water 
position).
Should the boiler shut down, pump operation is granted.

In model KR, with an (optional) external storage heater for the production of domestic hot water, which incorporates a temperate sensor 
similar to a thermostat, the anti-freeze function DOES NOT protect the storage heater.
In this case the storage heater is protected by setting the boiler to SUMMER  

 or WINTER  

  (via selector ), by enabling the storage 

heater (via regulator 3) as detailed in the previous subsection, and by selecting a temperature on the thermostat  above 0°C.

CH system can be effectively protected from freezing by means of specific anti-freezing addictives suitable in multi-metal systems.

Do not use automotive anti-freeze products, and periodically check anti-freeze product effectiveness.