Gas boiler with built-in cylinder – components
Gas boiler with built-in cylinder – components
A standard-output domestic boiler comes with a wall-mounting kit, an expansion vessel and a circulation pump. A thermostat or other controller is never included. The diagram shows all the other components you add to the boiler. Click a number to open the matching product.
A number in the diagram takes you to the matching item in the list below.
Step 1: gas connection
Step 2: boiler and system protection
Step 3: pipework, radiators and underfloor circuits
Step 4: temperature control
Step 5: hot water production
Accessories for a boiler with a built-in cylinder
A boiler with a built-in cylinder combines the comfort of stored hot water with space saving – the customer does not need a separate cylinder, and hot water is available even when it is drawn at several outlets simultaneously. The overview is intended for heating engineers preparing the complete materials for both the heating side and the water side of the customer's boiler. ATRIA Europe does not supply the boiler itself. The gas, flue and electrical connections may only be made by a qualified person.
Installation procedure
- Check the installation location. A boiler with a cylinder is heavier than a combi boiler, so check the load-bearing capacity of the wall or floor and leave space for servicing the cylinder according to the manufacturer's instructions.
- When connecting to existing pipework, flush the system and remove the sludge from the radiators.
- Fit ball valves on the heating flow and return. Place the heating filter in the return before the boiler.
- Decide on the radiator pipework layout. With a star layout, a separate flow and return run from the manifold to each radiator, which makes both balancing and later modifications easier.
- Join multilayer pipework with screw fittings. Calibrate and chamfer the pipe before assembly so that the O-rings are not damaged.
- If the system volume requires it, connect an additional expansion vessel and a safety valve with a discharge to the drain.
- On the cold water supply, fit a shut-off valve, a drinking water filter and the cylinder safety equipment to the extent specified by the boiler manufacturer. If the mains water pressure is high, also add a pressure reducing valve.
- The gas, flue and electrical supply are connected by a qualified technician; the gas connection ends with a ball valve and a safety hose.
- Connect the room thermostat and fit thermostatic heads on the radiators.
Choosing the right parts
The radiator manifold should have as many outlets as there are radiators, plus a small reserve for future extension. Place it centrally so that the connections to the individual radiators are of similar length.
The pipe for connecting individual radiators is most often sized at 16 × 2 mm for typical outputs. Main branches with a higher flow need a larger size – what matters is the total output of the connected radiators and the flow velocity, which should not cause noise.
Screw fittings must match both the type and the size of the pipe. Fittings designed for multilayer pipe are not automatically suitable for PE-Xa or PB pipe.
Water treatment. The cylinder in the boiler is sensitive to limescale. Where the water is hard, recommend a filter and suitable water treatment – this extends the service life of both the cylinder and the taps.
Thermostatic heads should be checked against the connection thread of the valve. The most common thread is M30 × 1.5, but older or less common valves may have a different connection.
Most common installation mistakes
- Missing safety equipment on the cold water supply, even though the boiler manufacturer specifies it.
- No pressure reducing valve despite high mains pressure – the safety valve then drips unnecessarily.
- A screw fitting on uncalibrated pipe, or a fitting unsuitable for the type of pipe.
- Manifold positioned at the edge of the floor plan, so that the connections differ greatly in length.
- Boiler put into operation without flushing the existing pipework.
Commissioning and maintenance
First fill and bleed the cylinder on the drinking water side, and only then the heating side. Entrust the start-up and setting of the boiler to an authorised service engineer. During regular maintenance, check the condition of the cylinder according to the manufacturer's instructions, including the anode if the cylinder has one, clean the filters and check both the system pressure and the expansion vessel pre-charge.
Frequently asked questions
What is the advantage over a combi boiler?
The store of heated water covers simultaneous draw-off in the bathroom and the kitchen, and the outlet temperature is more stable. The boiler also starts less often for short draw-offs, such as hand washing.
Do I have to use steel pipe for the gas installation?
Not always. Multilayer pipe designed and certified for gas is also used for internal gas installations. Its use is governed by local regulations, and the installation is carried out by a qualified person.
Is a star layout for radiators better than branching via tees?
A star layout is easier to balance, and each radiator can be isolated separately. However, it requires more pipe and space for a manifold. Branching saves material but is more demanding to size correctly.
Why is a filter needed on the drinking water too?
Sand and dirt from the mains settle in the cylinder, damage tap seals and impair heat transfer. A filter on the inlet is simple protection for all the equipment downstream.
What to order for the customer's boiler
For the pipework, prepare radiator manifolds and PEX/AL/PEX screw fittings; for the water side, parts from the water filtration and treatment category; and for the internal gas installation, the alpex - gas pipe for gas range. Registered partners can see wholesale prices after logging in. We dispatch goods from our warehouse in Žilina and ship them throughout the EU.