Connecting A Two-Circuit Gas Boiler To The Heating System: Rules And Installation Instructions

Gas equipment of boiler+water heater type is a suitable solution for owners of apartments and private houses: heat is provided, hot water is available, it is economical. And the connection of a two-circuit gas boiler to the heating system is not as complicated as it seems. But before embarking on the implementation of such a project, it is not superfluous to get acquainted with the theory, agree?

In this publication we will talk about the features of the connection process: what requirements of service organizations should be considered and what technical nuances of installation of wall and floor models should be paid special attention to. The presented material is complemented by clear photos and videos, which will help to perform all the work as quickly and correctly as possible.

Content of the article:

  • Equipment installation rules
    • General requirements at the design stage
    • Documentation preparation process
  • Features of wall-mounted model piping
    • Step #1 - connection to heating system
    • Step #2 - connecting the boiler to the electric grid
    • Step #3 - connecting the unit to the chimney
  • Installation of the floor standing appliance
  • Boiler circuit variations
  • Additional recommendations for installation
  • Conclusions and useful video on the subject

Installation rules

The boiler must be installed and connected to the system after passing the planning stage, when a place in the house has been prepared for the unit. If you install it improperly, the specialists of the gas distribution company will not connect the equipment to the gas mains.

General requirements at the design stage

The basic rules for installing gas equipment are prescribed in SNiP 42-01-2002. Supporting information is also contained in the now invalid but useful SNiP 2.04.08-87.

All rules are usually taken into account by the design engineer, but it is useful to know them for yourself. The room for the location of the boiler can be a kitchen if the capacity of the device ranges up to 60 kW. A separate or attached furnace room is relevant for units with a capacity up to 150 kW.

Connecting a two-circuit gas boiler to the heating system: rules and installation instructions

Additional regulations for the installation of gas appliances are given in the SNiP about boiler systems as well as about heating, ventilation and air conditioning

The requirements for the room are following:

  1. The minimum room height is 2 m, the volume is 7.5 m3. If there are two or more gas appliances, the values are changed to 2.5 m and 13.5 m3 respectively.
  2. Not suitable: cellars, balconies, bathrooms, corridors, rooms without vents.
  3. The walls of the room must be covered with nonflammable materials or protected by special panels.
  4. Lighting: for 10 m3 rooms there are at least 0.3 m2 windows. In case of a gas explosion, the windows are a light-removable construction increasing the operational safety of the equipment.
  5. Ensure there is a ground connection and a cold water pipe.
  6. The size of the chimney corresponds to the capacity of the installed equipment.
  7. Leaving space around the appliance: from 1.25 m at the front and from 0.7 m at the sides (if maintenance is necessary).
  8. The distance from the vertical chimney to the unit must be no more than 3 m.

Must also be provided for ventilation. Natural ventilation is calculated at the rate of 3 room volumes per hour. When organizing air supply, to this value is added combustion air (the parameter is specified in the boiler certificate).

Requirements do not apply only to the rooms. The distance from the hinged appliance to the nearest structures is also regulated. This information is indicated by the manufacturer in the instructions of the appliance.

Connecting a two-circuit gas boiler to the heating system: rules and installation instructions

If the double circuit boiler is installed on a wooden wall, a sheet of roofing steel (0,8 - 1 mm) or minerite board shall be fixed to it. If the equipment is not located in the kitchen, asbestos is also possible

Floor models of boilers are installed on non-combustible bases. If the surface is wooden, a metal carpet pad is compulsory.

It is recommended to place the appliance as close as possible to the gas pipe. The use of special hoses is allowed, but they must not be too long. Bellows hoses of up to 5 m are commercially available and are approved for installation, but European standards limit the length to two meters.

Documentation preparation process

After a general familiarity with how to technically connect two-circuit gas boilers, you can begin to prepare the documentation. The first stage is receipt of TU. It is necessary to apply to the regional gas service with a statement indicating the expected volume of blue fuel consumption per hour

Technical conditions are issued in 1-2 weeks. The document is a permission to connect the house to the gas mains.

Second stage - according to the specifications a project of installation is developed. The third stage -approval of the prepared documentation by engineers of the gas distribution company.

Connecting a two-circuit gas boiler to the heating system: rules and installation instructions

The project includes both the scheme of the boiler itself and the laying of a gas pipeline from the connection point to the gas pipeline. If it is a private house, a drawing of the communications across the plot is added

The boiler technical certificate, operating instructions, certificates, expert opinion on the compliance of the device with all norms are submitted to the supervisory authority. The necessary papers are provided by the manufacturer of the two-circuit boiler.

Approval of documentation can take a week or last up to 3 months, all depending on the complexity of the project. In the case of refusal, the inspection must provide a list of amendments to correct deficiencies. If all the requirements are met, they are stamped and the equipment can be connected.

Peculiarities of wall-mounted model wiring

First the heating, water and power connections must be made if the appliance has control and regulation elements. The connection to the gas mains is made by an employee of the relevant service or by a licensed firm. The homeowner only needs to buy a meter and a gas filter.

Connecting a two-circuit gas boiler to the heating system: rules and installation instructions

The appliance has 5 connection pipes: heating system supply and return, cold water inlet and hot water outlet plus gas supply. All fittings are conveniently screwed on before the appliance is hung on the wall. Handles that interfere with rotation can be removed by unscrewing the nut on the stem. Installation of the gas valve does not require a dielectric gasket

What products and materials will be needed during the work:

  • 3 ball valves with 1/2″ American size and 4 of the same size 3/4″;
  • 2 dirt traps (mechanical or self flushing) - installed on the cold water supply and heating pipe return;
  • gas filter;
  • expansion vessel (if there is not enough capacity for a large piping network, a membrane tank is also required);
  • pipe fittings - elbows, tees;
  • three-wire cable (VVG brand, 2.5mm diameter2);
  • a 20A double pole, automatic switch.

This list is suitable for simple heat generators with an open combustion chamber. The more expensive models are equipped with an expansion tank and a gas filter.

If the water pressure is less than 1 atm, it is worth installing a pressure booster station. It is useless as long as the water pressure is constant within 2-3 atm.

Connecting a two-circuit gas boiler to the heating system: rules and installation instructions

Additional to the system may be included: a third cartridge fine filter, pressure gauges to monitor the pressure in different places of the circuit, automatic air vent, circulation pump, voltage regulator

Connecting a two-circuit gas boiler to the heating system: rules and installation instructions

In the case of a separate boiler room, a heating radiator will be needed, which will ensure a normal temperature regime for boiler operation and protect it from condensate formation

Further hang the boiler on the wall, determining the optimal height. It is not advisable to hang it under the ceiling - it is important to use it comfortably. The minimum distance from the ceiling to the outlet spigot shall be 15 cm, from the floor 80 cm and from the wall 20 cm.

Fitting the appliance requires two special brackets supplied with the kit. They are fixed to the wall with plastic dowels and self-tapping screws. To position them correctly it is recommended to use a level and a plumb line.

Step #1 - connection to the heating system

All shut-off ball valves are installed more for system maintenance than for possible shut-off and dismantling during operation. Heating equipment is characterized by reliability. Example: The shut-off valve in the heating return is designed for cleaning the filter without draining the heating medium.

Connecting a two-circuit gas boiler to the heating system: rules and installation instructions

The standard connection diagram is in the data sheet of any two-circuit boiler. This is the guide to follow when fitting the appliance

Commutations for connection:

  1. Half-inch cocks are mounted on the water fittings and the gas inlet. And DN20 are mounted on the heating water connections.
  2. Fittings should be screwed downwards.
  3. Filters are connected horizontally with the \"spouts\" turned to the floor. In this position they are easy to clean.
  4. The external expansion tank is connected to the return with an additional fitting.
  5. The drainage pipe is installed at the lowest point of the system.

If non-freeze antifreeze is to be introduced into the system as heat transfer fluid, additional flow and return cocks should be added to the scheme as a precaution. This allows for removing the boiler without draining the antifreeze.

Step #2 - connecting the boiler to the mains

There is usually no problem with connecting the power as it is enough to plug the device into the socket. But there are also rules and safety requirements.

Connecting a two-circuit gas boiler to the heating system: rules and installation instructions

If the boiler is strongly dependent on electricity and its supply is often cut off in the region of installation, the circuit is supplemented by an uninterruptible power supply

The main requirement when connecting the appliance to the mains is earthing and the presence of a circuit breaker. The latter is positioned so that it will not be exposed to water in case of emergency.

Basic requirements:

  • Need a cord connected to an earthing circuit. If no such cord is found in the kit, the conductor is connected to the body of the appliance itself.
  • The steel pipes of the DHW system must not be used as earthing switches.
  • The cable is laid in a protective \"corrugation\".

When connecting turbine boilers from European manufacturers it is important that the phase and zero are not confused. Otherwise the electronic unit will not start the system.

Step #3 - connecting the unit to the chimney

In 95% of modern houses wall hung boilers with closed combustion chambers and coaxial chimney are installed. It is led horizontally through the wall with a 3-5% slope towards the street for condensate escape.

Connecting a two-circuit gas boiler to the heating system: rules and installation instructions

Parts of the pipe of several elements are mounted into each other in the direction of combustion products flow. In a vertical duct, the joints must be sealed

For a high power unit, only a vertical design that can handle a large volume of combustion products is suitable. It should have as few turns as possible and protrude beyond the roof boundaries by at least 0.5 m.

Installation of the floor unit

If the dual circuit heat generator requires power, then it is connected in the same way as its wall-mounted \"counterpart\". An energy-independent device has a built-in copper or stainless steel coil for water heating. Such equipment is not supplied with a burner, automatics and heat exchanger.

For the installation of the energy-independent unit the set from the previous list plus the following system elements are required:

  • safety group with a safety valve designed for the boiler operating pressure (data is in the certificate);
  • expansion tank with 10% volume of the total heat carrier;
  • circulation pump.

Safety group is always installed on the supply pipe next to the heater to protect the most expensive part of the system from being destroyed by a pressure surge.

Connecting a two-circuit gas boiler to the heating system: rules and installation instructions

The distance from the boiler to the unit should be no more than 50 cm. No taps or tees may be installed in the pipe section between the heater and the element, the line shall be left clean

If the floor unit is connected to a gravity flow system, only an open-type expansion tank with overflow shall be installed. A pump and a safety group are excluded.

In this situation pipes with a diameter of 40 mm or more are needed which are laid with a slope of 5 mm per linear metre of line. The heat generator remains at the lowest point, the tank is placed at the highest point.

Connecting a two-circuit gas boiler to the heating system: rules and installation instructions

If electricity is connected, the forced circulation by means of a pump is acceptable. In this case it is installed by means of a bypass

Most modern systems include a circulation pump, which is efficient but electricity-dependent. When lights out, heating and water heating are shut off. It is reasonable to organize an alternative natural circulation method for force majeure.

Schemes with boiler

When the standard 9-13 l boiler capacity is not sufficient to cover the needs of the residents (example: there is a bath in the bathroom), the system is completed with a boiler. If an indirect heated boiler is selected, it is not possible to simulate the flow by an additional circulation pump that is started and stopped by the thermostat signal.

If the scheme is not correct, the problem is the long heating of the boiler. For this time (up to 2 hours) the heating of the house does not happen, the rooms get cold. Plus it reduces the resource of the boiler because of the effect of \"clocking\" and the flow into the second circuit of hot water, rather than cold water. In the same boiler the bacteria multiply.

Connecting a two-circuit gas boiler to the heating system: rules and installation instructions

The correct scheme is to connect the indirect boiler to the heating circuit. The thermostat is connected to the boiler automatics. The DHW outlets are simply plugged

In such a scheme, the heating between the circuits is ensured by a three-way valve. The boiler is loaded in 20-25 minutes. Plug valves do not affect the service life of the heat generator.

More practical options - installation of a layer-by-layer heated boiler (there are models for two-circuit) or an electric storage tank. The first has no heat exchanger, which reduces the cost of the system. The second significantly improves the comfort of using hot water.

Connecting a two-circuit gas boiler to the heating system: rules and installation instructions

In the scheme with an electric boiler, a check valve and a safety valve are mounted on the supply pipe. The latter sometimes leaks water which must be disposed of. The safety valve requires a manual check twice a month

In the case of an electric boiler it is recommended to install an additional expansion tank. And if the system pressure is higher than 6-8 bar, a pressure reducing valve is necessary to reduce this pressure.

Advanced installation recommendations

Categorically avoiddecreasing the inner diameter of the pipes to be connected. The optimum value for a boiler up to 28 kW is at least 20 mm for heating and at least 15 mm for water supply.

If the boiler is not in the scheme, it is wise to install the appliance close to the hot water tap, which is frequently used.

If floor heating is connected, the system is supplemented by a separate branch with a manifold and circulation pump.

Conclusions and useful video on the topic

Principle of operation of a two-circuit boiler. Advantages and limitations of the model.

Disassembly of the connection diagram of a two-circuit heat generator with recommendations on the nuances of installation.

Connecting the boiler to the system - consequences of improper installation.

After collecting and preparing the documentation, you must connect the two circuit boiler to the heating, electricity and chimney. The devices are different, but the requirements for their installation are the same. Features of a particular model are specified in the operating instructions.

The first start-up of the unit is wise to entrust the specialist of the gas service. He will pressurize the dual circuit boiler, check all the blocks, set the modes and instruct the owner on the operation of the equipment.

Would you like to share your own experience of installation and connection of a domestic dual circuit boiler? Tell us about the difficulties you encountered in the process - leave your comments in the block under the article.

If you have questions about the rules of connection or installation, ask them to our experts and other visitors of the site - the feedback form is located below.


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