SEALED SYSTEMS
ALTECNIC HEAD OF OEM SALES UK AND ROI MARK MOGEY TALKS THROUGH SOME OF THE COMMON QUESTIONS AND TROUBLESHOOTING ISSUES RELATED TO SEALED SYSTEMS… Knowing the facts – Sealed systems
Mark Mogey, Altecnic Head of OEM Sales UK and ROI.
WHAT ARE SEALED SYSTEMS FOR? Sealed systems are designed for central heating and are widely used in Europe and other parts of the world. They are popular because they simplify installation by eliminating the need for feed and vent tanks in the system. WHAT ARE THE ESSENTIAL COMPONENTS OF A SEALED SYSTEM KIT? • Diaphragm expansion vessel (complying with BS EN 13831) • Safety relief valve • Pressure gauge • Filling loop WHERE SHOULD KEY COMPONENTS BE INSTALLED? • Safety relief valve: Should be fitted on or close to the boiler on the flow pipe. • Pressure gauge: Preferably close to the expansion vessel and/or the boiler, in a position that is easily readable from the filling point. • Filling point: Should be near key components, particularly the pressure gauge, and should be a temporary connection allowing filling from the water mains, incorporating a double check valve and isolating valves.
WHAT IS THE PRINCIPLE OF OPERATION OF A SEALED SYSTEM?
HOW SHOULD THE SIZE OF THE EXPANSION VESSEL BE DETERMINED? The expansion vessel should have an acceptance volume sufficient to accommodate the volume change of the system water when heated from 10˚C up to full operational temperature or beyond under fault conditions. WHERE SHOULD THE EXPANSION VESSEL BE LOCATED IN THE SYSTEM? The expansion vessel should be connected to the system at a point close to the pump inlet to maintain positive pressures throughout the system.
In a sealed system, water cannot be compressed. When water heats up and expands, the increased volume is accommodated by the expansion vessel. The diaphragm inside the vessel is pushed by the expanded water, creating additional volume. When the water cools down, the pre-charge pressure forces the water back into the main system, maintaining constant pressure and reducing energy consumption. WHAT ARE THE ADVANTAGES OF SEALED SYSTEMS? • System flexibility: Components can be installed in various locations. • Cost savings: Reduced installation time lowers overall costs. • No feed and expansion tank: Eliminates issues like ‘pumping over’ and the risk of freezing. • Longer life: Reduced corrosion problems extend the system’s lifespan. • Noise reduction: Higher system pressure reduces or eliminates boiler noise. • Low maintenance costs: Requires only periodic operational checks, making the system virtually maintenance-free.
TROUBLESHOOTING
WHY IS MY SEALED SYSTEM LOSING PRESSURE? Potential causes for a sealed system losing pressure include: • A leak in the system, such as from radiators, pipes or connections. • Issues with the expansion vessel, such as a loss of air charge or a damaged diaphragm. • Air trapped in the system that needs to be vented.
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80 | PLUMBING & HEATING MAGAZINE
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