Burning issue
Resolving the issue of magnetite
Dan Wild explores the role that circulator pumps have in the fight against system inefficiency and magnetite build-up
Carbon Trust, heating and hot water account for 60 per cent of a building’s total energy use. Understanding how and where to make savings therefore as well as the potential problems that can occur, should be a priority. With energy bills continuing to rise, property owners in both the domestic and commercial sectors are looking for ways to save money every day. While simple measures such as turning the thermostat down by one degree and installing Thermostatic Radiator Valves are well docu- mented – there are a number of other ways that installers can help building owners achieve greater system efficiencies. Needless to say, sludge build- up in heating systems is a com- mon cause of heating deficiency with radiators not reaching tem- perature and causing potential damage to boiler components. Helping building owners to iden- tify this issue, as well as propos- ing a potential remedy, should be a priority during service and maintenance visits.
Magnetite or ‘black sludge’, as it is commonly known, is a prod- uct of natural corrosion within heating systems. If you consider that a heating system comprises a number of different metals such as copper pipes, steel radiators and aluminum heat exchangers it may come as no surprise that the addition of water is the perfect recipe for rust.
In truth, it is actually the intro- duction of oxygen that causes the metals to corrode – through a process of oxidation which forms aluminum hydroxide and iron oxide. As the minerals are deposited out of the water they form crystalline like structures that, due to their weight, sink and then build-up throughout the sys- tem. As water flows past the debris, it circulates the dirt
around the system – depositing it in pipework and radiators which, over time builds to a black sludge.
On the surface, the biggest problem is that the scale blocks pipework and, because it acts like a thermal conductor, absorbs the heat rather than passing it on. As a result, the boiler has to work much harder but actually produces less – meaning that the boiler is less efficient.
If a system is designed, installed and maintained correct- ly the issue of sludge build-up will be less of a problem but, if there is any form of leak – and a system refill required – air can enter the system, exacerbating the problem. The key therefore, in the event of system leaks and failures, is for the heating engi- neer to introduce a corrosion inhibitor on installation as well as when re-filling it.
In fact, a system flush has been proven to increase the life of the whole system, helping to keep bills and maintenance costs down as well as safeguarding the qual- ity and efficiency of the pump. And so, despite the time it may take to complete and the respec- tive cost to the customer; a system flush is necessary in order to safeguard the future system. One of the biggest challenges
affecting the market however is the introduction of new circulator pumps, under ErP. The directive requires all new boilers from 26 September 2015, 400kW or less, to be compliant with the stan- dards and therefore benefit from the new energy savings. However, the majority of the new pumps actually use permanent magnetic motors, meaning that they attract magnetite from within the heating system. In reality, this means whenever a magnetic field is present i.e. when the system is operational, the motors are more susceptible to magnetite build-up;
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Magnetite build-up on a circulator pump
therefore increasing energy costs as a result of the pump working harder to achieve the desired flow. In fact, there is growing evi- dence that magnetite can actually increase the power consumption of the pump by between 10 and 20 per cent, with some estimates as high as 50 per cent.
The solution therefore is to install pumps with ‘anti-block technology’, such as the Lowara ecocirc range, offering the ability to separate the main flow of water from the magnetic parts of the pump and thus avoiding con- tact with the magnetite. We would also recommend fitting magnetic dirt separators within the heating system. All-in-all, this prevents the build-up of sludge and therefore increases system
efficiency as a matter of course. Needless to say, the issue of magnetite is a key concern and while awareness of flushing con- tinues to rise, the issues around the circulator pump and perma- nent magnetic motors are less well known. System inefficiency does not have to be the norm. Solutions are available within the marketplace that can ensure a boiler system operates to its best possible standard and energy savings maximised. We now must realise their true potential. For more information visit
http://www.lowara.co.uk/heat- ing-air-conditioning-and-hot- water-circulation-pumps/ecocirc/ // The author is the building services consultant for speciality industries at Xylem //
HVR | October 2014 | 9
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