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System Design

When fitting a hydronic (wet) central heating system you have to consider how the warm air will permiate your living space. Here Alde UK give our advice on designing your bespoke Alde central heating system.

1. Siting the heating circuit
2. Plumbing
3. Convector/radiator output
4. Commissioning

Siting the heating circuit

The correct siting of the heating circuit, the pipes, convectors and radiators, is fundamental to the performance and efficiency of the central heating system. It should be your main design consideration.

• Fit convectors/radiators around exterior walls, this creates an even temperature without hot and cold zones.
• Fit convectors/radiators under each window. This will reduce heat loss, cold draughts and condensation.
• Fit at least the minimum amount of convector/radiator for your living space. This will greatly improve responsiveness (how quickly and adequately the living space is heated) and economy (an overall reduction in fuel consumption).

If your boiler produces 6 kW of power but you only have 3 kW of convector/radiator, the boiler must run for longer to permiate the living space with 6 kW of heat.

• Fit ventilation in furniture. Air must be able to flow freely around convectors and radiators, wherever they're sited. Vents should be located in the bottom-front and top-rear of bunks, luton seats, cupboards, etc., so cool air can be drawn under the furniture across the convector/radiator and then rise up the wall behind. The gap between floor and furniture (cool air in) should be at least 50 mm high, and between wall and furniture (warm air out) at least 25 mm wide.

Likewise, vents should be located in the bottom-rear and top-front of overhead louvres to avoid cold and damp pockets along the ceiling.

• Fit ventilation in the floor. The regulations governing floor vent area vary according to country and depend on the type of vehicle and number of occupants it is designed for. Consider locating vents under convector/radiator wherever possible.
• A correctly fitted Alde aluminium convector output ≈400 W per metre.

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Plumbing

It's easy to get too focused on convectors and radiators, or the connectors and pipework running between them, and to forget that the plumbing will all be part of one heating circuit, with a boiler and possibly other inline devices.

• DO use a one-pipe heating circuit. This keeps the system simple, simpler to design, simpler to fit, whilst cutting down on weight and cost.

A one-pipe heating circuit allows a direct flow of heating fluid around the circuit with minimal pressure resistance, greatly improving responsiveness and economy.

• DO ensure all plumbing is clean and undamaged before fitting.
• DO locate air bleeds at high points in the heating circuit immediately before the drop-off.
• DO locate a drain at the lowest point in the heating circuit, preferably near to the Alde boiler.
• DO locate the expansion tank 400 mm above the highest point in the heating circuit.
• DO NOT store pipework on the floor where it may intake corrosive particles or be damaged.
• DO NOT cut pipework with a hacksaw, use a pipe-cutter.
• DO NOT use copper parts. There are aluminium contact surfaces in the boiler, and copper parts will cause corrosive galvanic action in any aluminium parts of the system.

When using an Alde Compact expansion tank specifically, ensure it's fitted so that the circulation pump impeller sits above the in pipe.

Alde 22 mm aluminium tube should be lodged 30 mm into Alde rubber connectors and squarely fastened with spring clips 10-15 mm onto the connector.

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Convector/radiator output

Without convectors or radiators, how will heat transfer from the heating circuit into the living space? Using Alde aluminium convector as a standard, we can produce a rough guide* to the minimum amount needed to adequately heat your living space.

*This is only a rough guide, based off of area rather than volume (so ceiling height is assumed). It is also assuming good insulation. Any central heating system should be tested in a cold chamber if possible.

Alde UK recommend that you fit an amount of convector/radiator to equal the output of your boiler, regardless of the size of the living space.

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Commissioning

There are no more important tests you can make of a central heating system than a pressure test. The test should maintain 1 bar of pressure for at least 30 seconds. Remember, your intention should not be to use pressure testing to identify flaws in your working practices. It will be twice the work to correct mistakes at this late stage.

When recommissioning a system, ensure it is purged with a suitable cleaning agent to remove bacteria, corrosive particles and other detrius.

To fill or purge a system, an Alde service pump should be used to avoid trapped air. Trapped air is a nuissance, and furthermore if trapped in the 230 V heating chamber of an Alde 3010 Compact boiler may cause serious damage to the boiler.

After the heating circuit is filled with a 50/50 mix of ethylene glycol antifreeze and clean water, performance testing can be carried out in a cold chamber. Alde International Systems AB offer free of charge cold chamber testing, by appointment, at their facility in Sweden.

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