Dražice Stationary Hot Water Tanks

About the Product

Družstevní závody Dražice - strojírna s.r.o. thanks you for choosing their product. This manual will familiarize you with the operation, construction, and maintenance of these water heaters.

The product is not intended for use by persons (including children) with reduced physical, sensory, or mental capabilities, or those lacking experience and knowledge, unless supervised or trained.

The manufacturer reserves the right to make technical changes. The product is designed for continuous contact with drinking water.

It is recommended to use the product in rooms with an air temperature between +2°C and +45°C and relative humidity not exceeding 80%.

Product functioning and safety have been tested by the Institute of Mechanical Engineering in Brno.

Manufactured in the Czech Republic.

Pictogram Meanings:

• [Information Icon]: Important information for the user.
• [Recommendation Icon]: Manufacturer recommendations for uninterrupted operation and long service life.
• [Warning Icon]: Important warning that must be observed.

1. Technical Characteristics

1.1 Function Description

The OKC 160-500 NTR(R)/BP water heaters, due to their construction and numerous variants, allow for economical preparation of hot water (GVS) using various energy sources. Their nominal output guarantees sufficient hot water for residential buildings, commercial premises, restaurants, and similar facilities. For heating GVS, you can choose electric energy, various types of central heating boilers, renewable energy sources (heat pumps, solar collectors), or a combination thereof.

Heating Domestic Water via Heat Exchanger

Shut-off valves on the heat exchanger must be open to ensure the flow of heating water from the heating system. It is recommended to install a safety valve along with the shut-off valve at the heat exchanger inlet, which can be used to vent air from the heat exchanger if necessary (especially at the beginning of the heating season). The heating time by the heat exchanger depends on the temperature and flow rate of water in the heating system.

1.2 Operation and Installation Instructions for Types: OKC 160 NTR/BP, OKC 200 NTR/BP, OKC 200 NTRR/BP

1.2.1 Product Description

The tank body is welded from sheet steel, heat exchangers are made of steel pipes, and are coated with enamel resistant to hot water. For additional corrosion protection, a magnesium anode is installed in the upper part of the tank, regulating the electrical potential inside the body and thus reducing the risk of corrosion. Hot and cold water outlets and a circulation opening are welded to the body. On the side of the tanks, under a plastic cover, there is a cleaning and inspection opening closed by a flange, where an electric heating element of various power ratings can be installed. The 200L reservoir has a G 6/4" opening for installing a TJ G 6/4" series heating element. It is used when the reservoir is connected to a solar system or a heat pump system for heating water in the upper part of the reservoir to the required temperature. The tank is installed on the floor next to or in close proximity to the hot water source. The tank and heat exchangers are tested at 1.5 times the working pressure. A temperature indicator is located on the heater casing. The tank insulation consists of 42 mm polyurethane foam. The heater casing is made of sheet steel, powder-coated.

The NTR version has one heat exchanger located at the bottom of the tank, and one hot water source is used for heating.

The NTRR version is equipped with two heat exchangers for any combination of two heat sources. Both heat exchangers can be connected in series. NTR/BP and NTRR/BP types do not have a heating element. The reservoir cannot be used for continuous heating of hot water in the heat exchanger.

1.2.2 Construction and Main Dimensions

Figure 1: OKC 160 NTR/BP Dimensions

Diagram shows side and cross-sectional views of the OKC 160 NTR/BP water heater with labeled dimensions.

Figure 2: OKC 200 NTRR/BP Dimensions

Diagram shows side and cross-sectional views of the OKC 200 NTRR/BP water heater with labeled dimensions.

Figure 3: OKC 200 NTR/BP Dimensions

Diagram shows side and cross-sectional views of the OKC 200 NTR/BP water heater with labeled dimensions.

1.2.3 Technical Parameters

Table 4: Technical Parameters for OKC 160 NTR/BP, OKC 200 NTR/BP, OKC 200 NTRR/BP

1 Hot water 45°C. 2 These data do not apply to NTR/BP types which do not have a casing. * Heat exchangers connected in series.

1.3 Operation and Installation Instructions for Types: OKC 300 NTR/BP, OKC 500 NTR/BP, OKC 300 NTRR/BP, OKC 500 NTRR/BP

1.3.1 Product Description

The accumulator body is welded from sheet steel, heat exchangers are made of steel pipes, and are coated with enamel resistant to hot water. For additional corrosion protection, a magnesium anode is installed in the upper part of the accumulator, regulating the electrical potential inside the body and thus reducing the risk of corrosion. Hot and cold water outlets and a circulation opening are welded to the body. On the side of the tanks, under a plastic cover, there is a cleaning and inspection opening closed by a flange, where an electric heating element of various power ratings can be installed. The reservoir has a G 6/4" opening for installing a TJ G 6/4" series heating element. It is used when the reservoir is connected to a solar system or a heat pump system for heating water in the upper part of the reservoir to the required temperature. The reservoir is installed on the floor next to or in close proximity to the hot water source. The tank and heat exchangers are tested at 1.5 times the working pressure. A temperature indicator is located on the heater casing. The tank insulation consists of 50 mm polyurethane foam. The tank is covered with a plastic casing (reinforced polystyrene).

The NTR version has one heat exchanger located at the bottom of the tank, and one hot water source is used for heating.

The NTRR version is equipped with two heat exchangers for any combination of two heat sources. Both heat exchangers can be connected in series. NTR/BP and NTRR/BP types do not have a heating element. The reservoir cannot be used for continuous heating of hot water in the heat exchanger.

1.3.2 Construction and Main Dimensions of the Tank

Figure 4: OKC 300 NTRR/BP Dimensions

Diagram shows side and cross-sectional views of the OKC 300 NTRR/BP water heater with labeled dimensions.

Figure 5: OKC 300 NTR/BP Dimensions

Diagram shows side and cross-sectional views of the OKC 300 NTR/BP water heater with labeled dimensions.

Figure 6: OKC 500 NTRR/BP Dimensions

Diagram shows side and cross-sectional views of the OKC 500 NTRR/BP water heater with labeled dimensions.

Figure 7: OKC 500 NTR/BP Dimensions

Diagram shows side and cross-sectional views of the OKC 500 NTR/BP water heater with labeled dimensions.

1.3.3 Technical Parameters

Table 9: Technical Parameters for OKC 300 NTR/BP, OKC 300 NTRR/BP, OKC 500 NTR/BP, OKC 500 NTRR/BP

1 Hot water 45°C. 2 These data do not apply to NTR/BP types which do not have a casing. * Value obtained by calculation.

2. Operation and Installation Information

2.1 Operating Conditions

The tank must be used strictly according to the conditions specified on the rating plate and in the electrical connection instructions. Each separately closable heater must be equipped with a shut-off device on the cold water inlet, a control tap or test plug for checking the non-return valve, a non-return valve, and a safety valve. Heaters with a volume of 200 liters or more must also be equipped with a manometer. In addition to generally accepted national rules and norms, comply with the connection conditions established by local electricity and water supply organizations, as well as installation and operation instructions.

The temperature in the tank installation location must be above +2°C; the room must not freeze. The appliance should be installed in a suitable place, i.e., easily accessible for possible maintenance, repair, or replacement.

For water with high lime content, it is recommended to install a standard descaler (water filter) before the accumulator or set the thermostat to a working temperature not exceeding 60°C (set to "60"). For correct operation, drinking water of appropriate quality must be used.

Tanks with a volume of 300 liters are screwed to a wooden pallet using M12 bolts. After removing the tank from the pallet and before commissioning, install the 3 adjustable feet supplied with the product. Using the three adjustable feet, the vertical position of the reservoir can be ensured within 10 mm.

2.2 Additional Electrical Installation

The water heater can be additionally equipped with an electric heating unit (TJ, TPK, or R) with fixed heating element power. The possibility of installing heating elements is indicated in the table of heating element applicability, see the catalog or www.dzd.cz.

2.3 Plumbing Installation

Water is connected under pressure to pipes with 3/4" thread. Blue indicates cold water inlet, red indicates hot water outlet. To disconnect the tank if necessary, install threaded connections Js 3/4" on the inlets and outlets. The safety valve is installed on the cold water supply, marked with a blue ring.

Every pressurized hot water tank must be equipped with a diaphragm spring safety valve. The nominal passage of safety valves is determined according to the standard. The safety valve must be easily accessible, as close to the tank as possible. The supply pipe must have a minimum passage equal to the passage of the safety valve.

The safety valve should be installed at a height that ensures gravity drainage of overflow water. It is recommended to install the safety valve on the drain pipe. This facilitates replacement without needing to drain the tank. Safety valves with fixed pressure from the manufacturer are used for installation.

The safety valve's activation pressure must correspond to the maximum permissible pressure in the reservoir and be at least 20% higher than the maximum pressure in the water supply network (Table 10). If the pressure in the water supply network exceeds this value, a pressure reducing valve must be installed in the system. There should be no shut-off valves between the reservoir and the safety valve. Follow the manufacturer's instructions for the safety device during installation.

Before commissioning the safety valve, it must be tested. The test is performed by manually lifting the diaphragm from its seat using the lever on the release device, always in the direction of the arrow. After turning, the knob should lock into the groove. Correct operation of the release device is indicated by water flowing through the safety valve's drain tube. This check should be performed at least once a month and after any tank shutdown exceeding 5 days. Water may drip from the safety valve's drain tube; the tube must be open to the atmosphere, oriented vertically downwards, and located in a room where the temperature does not drop below freezing. When draining the reservoir, use the recommended drain valve. First, shut off the water supply to the reservoir.

Required pressures are listed in Table 10. For correct operation of the safety valve, a non-return valve must be installed on the supply pipe to prevent spontaneous emptying of the tank and backflow of hot water into the water supply. It is recommended to keep the distance from the tank to the hot water distribution point as short as possible to reduce heat loss. At least one quick-disconnect coupling must be installed between the tank and each supply pipe.

Appropriate pipes and fittings with sufficiently calculated maximum temperature and pressure ratings must be used.

The tank must be equipped with a drain valve on the cold water inlet for possible disassembly or repair.

2.4 Pressures

Table 10: Pressure Specifications

Figure 8: Pressure Loss Diagram

Graph showing pressure loss (in mbar) versus heating water flow rate (in m³/h) for different heat exchanger areas (1 m², 1.4 m², 1.5 m², 2 m²).

Table 11: Pressure Loss (mbar) for Heating Water Flow Rate at tHV = 60°C

2.5 Tank Connection Examples

The reservoir is installed on the floor next to or in close proximity to the heat source. The heating circuit is connected to the designated inlets and outlets of the heat exchanger, and an air vent valve is installed at the highest point. To protect pumps, the three-way valve, shut-off valves, and the heat exchanger from contamination, a filter must be installed in the circuit. It is recommended to flush the heating circuit before installation. All connecting pipes should be thoroughly insulated.

If the system is to operate with priority GVS heating (domestic hot water) using a three-way valve, always follow the three-way valve manufacturer's instructions during installation.

Connecting the Tank to the GVS Distribution

Cold water is connected to the inlet marked with a blue ring or the label "COLD WATER INLET". Hot water is connected to the outlet marked with a red ring or the label "HOT WATER OUTLET". If the GVS distribution has a circulation circuit, it is connected to the outlet marked "CIRCULATION". For possible reservoir draining, a T-fitting with a drain valve must be installed on the GVS inlet. Each separately closable reservoir must be equipped with a shut-off device, a control tap, a safety valve with a non-return valve, and a manometer on the cold water inlet.

Figure 9: Group Connection of Reservoirs using the Tichelmann Method for Uniform GVS Consumption from All Reservoirs

Diagram shows three water heaters connected in parallel using the Tichelmann method. It illustrates connections for heating water (OV), cold water (SV), circulation (C), and hot water (GVS), along with components like pumps (2) and check valves (1).

2.6 First Commissioning

After connecting the tank to the water supply, electrical network, and after checking the safety valve (according to the instructions supplied with the valve), the tank can be put into operation. The tank must be filled with water before connecting to the electrical network. The first heating must be carried out and controlled by an authorized specialist. The drain pipe and parts of the safety device may be hot.

Procedure:

1. Check the water supply and electrical installation. Verify the correct placement of the operating thermostat sensors. 1) Sensors should be inserted as deep as possible, preferably with capillaries, in the order of the working thermostat first, then the safety thermostat.
2. Open the hot water valve of the mixing tank.
3. Open the cold water supply valve to the tank.
4. When water starts to flow from the hot water valve, the tank filling is complete, and the valve should be closed.
5. If leaks are detected at the flange cover, tighten the flange cover screws. Tighten screws crosswise. Tightening torque: 15 Nm.
6. Attach the electrical installation cover.
7. When heating domestic water with electricity, connect the power supply (in combined tanks, the valve on the heating water inlet to the heating element must be closed).
8. When heating domestic water with thermal energy from the heating system, disconnect the electricity and open the heating water inlet and outlet valves. If necessary, vent the heat exchanger.
9. Flush the accumulator until the water is clear before commissioning.
10. Fill out the warranty card thoroughly.

2.7 Tank Cleaning and Anode Replacement

With repeated water heating, scale forms on the walls of the enameled reservoir, especially on the flange cover. Scale formation depends on the hardness of the heated water, its temperature, and the amount of hot water consumed.

It is recommended to check and, if necessary, clean the tank from scale and replace the anode rod every two years of operation. The theoretical service life of the anode is two years, but it depends on the water hardness and chemical composition at the place of use. Based on this inspection, the next anode replacement interval can be determined. Entrust the cleaning and replacement of the anode to a company that provides service. When draining water from the tank, the hot water mixer should be open to prevent pressure buildup in the tank, which would hinder water outflow.

To prevent bacteria formation (e.g., Legionella pneumophila), it is recommended to periodically increase the GVS temperature to at least 70°C. Another method for GVS disinfection is also possible.

Procedure for Replacing the Anode Rod in the Upper Part of the Heater:

1. Disconnect the reservoir power supply.
2. Drain 1/5 of the reservoir.
3. Procedure: Close the valve on the water inlet to the tank. Open the hot water valve at the mixer tap. Open the tank drain valve.
4. The anode is screwed under the plastic cover in the upper tank lid.
5. Unscrew the anode using a suitable wrench.
6. Remove the anode and perform reverse steps for installing a new anode.
7. When installing, pay attention to the correct connection of the grounding cable (300-500 L), as this is a condition for correct anode operation.
8. Fill the reservoir with water.

Procedure for Replacing the Anode Rod in the Side Flange:

1. Disconnect the reservoir power supply.
2. Drain the reservoir.
3. Procedure: Close the valve on the water inlet to the reservoir. Open the hot water valve at the mixer tap. Open the tank drain valve.
4. One anode is screwed under the plastic cover in the upper tank lid, and the second anode is screwed into the side flange.
5. Unscrew the anode using a suitable wrench.
6. Remove the anode and perform reverse steps for installing a new anode.
7. Fill the tank with water.

List of heaters with an anode in the side flange:

• OKC 200 NTR/BP
• OKC 200 NTRR/BP
• OKC 300 NTR/BP
• OKC 300 NTRR/BP
• OKC 500 NTR/BP
• OKC 500 NTRR/BP

2.8 Spare Parts

• Flange cover - flange cover seal
• Magnesium anode
• Insulation jacket
• Thermostat and thermal protection - thermostat handle
• Control lamps with wires - temperature indicator - set of screws M12 (or M10)

When ordering spare parts, specify the part name, type, and model number from the reservoir label.

3. Important Warnings

3.1 Installation Rules

[Warning Icon] The warranty is void without confirmation from a specialized company regarding the electrical and plumbing installation.

The magnesium anode must be regularly checked and replaced if necessary.

No shut-off valves should be installed between the reservoir and the safety valve.

If the water supply network pressure exceeds 0.48 MPa, a pressure reducing valve must be installed before the safety valve.

All hot water outlets must be equipped with a mixer tap.

Before the first filling with water, it is recommended to tighten the flange connection nuts of the tank. Tighten the screws alternately. Tightening torque: 15 Nm.

Any manipulation with the thermostat, other than adjusting the temperature using the control knob, is prohibited.

Any manipulation with the electrical installation, adjustment, and replacement of regulating elements must be performed only by the service department.

The thermal fuse must not be put out of operation! The thermal fuse, in case of thermostat malfunction, interrupts the power supply to the heating element if the water temperature in the tank rises above approximately 95°C.

In exceptional cases, the thermal fuse may shut down the device due to overheating of water resulting from boiler overheating in the heating system (in a combined accumulator tank).

It is recommended to operate the tank using only one type of energy.

If the heater (hot water tank) is not used for more than 24 hours or if the room with the heater is left unattended, shut off the cold water supply to the heater.

The heater (hot water tank) must be used exclusively in accordance with the conditions specified on the rating plate and in the electrical connection instructions.

3.2 Transport and Storage Instructions

The appliance must be transported and stored in a dry place, protected from weather conditions, at temperatures from -15 to +50°C. When loading and unloading, follow the instructions indicated on the packaging.

[Information Icon] As a result of transport and thermal expansion, slight enamel detachment may occur on the tank bottom. This phenomenon is normal and does not affect the quality or service life of the heater. The decisive factor is the layer of enamel remaining on the tank. DZD company has many years of experience with this phenomenon, and it is not a basis for a claim.

Electrical and plumbing installations must comply with the requirements and norms of the country of use!

3.3 Disposal of Packaging Material and Defective Product

A service fee has been paid for the packaging in which the product was delivered, to ensure the return and disposal of packaging material. The service fee was paid in accordance with Law No. 477/2001 Coll., as amended. Company's client number: F06020274. Dispose of the packaging from the water reservoir in a place designated by the municipality for waste disposal. Dispose of the decommissioned and unusable product after its service life by dismantling it and taking it to a recycling center (collection point) or contacting the manufacturer.

13-8-2025