Year-round DHW heating using heating water from a gas boiler for connection with priority DHW heating. For the OKC x NTRR type, a combination of a gas boiler and an alternative energy source is possible, or, when connecting both heat exchangers in series, an indirect-heated storage tank for boilers over 24 kW.

A newer line of enamelled indirect-heated floor-standing water heaters in volumes of 100–300 litres with an enamelled tank and a powerful single heat exchanger, or from the 200-litre type upwards with two heat exchangers for DHW heating from an external source or a combination of different sources. By connecting both heat exchangers in series, a DHW source with an output of up to 57 kW can be achieved. The water heater is equipped with DHW temperature control (thermostat for controlling a three-way valve or circulation pump) for a voltage of 230 V/50 Hz, and up to 200 litres a safety valve and a circulation outlet.

In the lower part of the water heater there is an inspection flange opening for cleaning the inside of the tank and possibly inserting an auxiliary electric heater of the TPK series from the accessories. For using the water heater in a solar system, water heaters over 200 litres have a 6/4" socket available, located above the solar heat exchanger, for the TJ electric heating unit from the accessories section.

Type	OKC 100 NTR/BP	OKC 125 NTR/BP	OKC 160 NTR/BP	OKC 200 NTR/BP	OKC 250 NTR/BP	OKC 300 NTR/BP
Volume [l]	95	120	155	210	250	300
Weight [kg]	59	72	82	97	106	111
Water heater height [mm]	815	980	1 018	1 328	1 508	1 597
Water heater diameter [mm]	524	524	584	584	584	670
Maximum operating pressure of the tank [MPa]	0.6	0.6	0.6	0.6	0.6	0.6
Maximum operating pressure of the heat exchanger [MPa]	1	1	1	1	1	1
Maximum heating water temperature [°C]	110	110	110	110	110	110
Maximum DHW temperature [°C]	80	80	80	80	80	80
Heating surface of the lower heat exchanger [m²]	1.08	1.45	1.45	1.45	1.45	1.5
Heating surface of the upper heat exchanger [m²]	–	–	–	–	–	–
Output of the lower/upper heat exchanger (LHE/UHE) [kW]	24	32	32	32	32	35
Continuous DHW output*/LHE ./UHE . [l/hour]	610	990	990	990	990	1 100
Heating time from 10 °C to 60 °C (by heat exchanger) [min]	14	14	17	22	28	24
Heating time with electric energy from 10 °C to 60 °C (2.2 kW) [hours]	3	3.5	4.5	5.5	7	8.5
Heating time with electric energy from 10 °C to 60 °C (3–6 kW) [hours]	–	–	–	–	–	6–3
Electrical protection rating	IP 44	IP 44	IP 44	IP 44	IP 44	IP 44
Heat losses [kWh/24 hours]	0.9	1.05	1.39	1.4	1.72	1.86