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CONDENSING BOILERS & ENERGY EFFICIENCY Four ways to maximise value and performance

It is now mandatory for a new commercial boiler with an output between 70 and 400 kW to be a condensing model. As a result, older units are being phased out to conform with ErP Direcve requirements. Steven Evans, Sales Director at Poerton Commercial, explains how best pracce must consider a number of factors to achieve the most energyecient and highperforming soluon.

he ErP Directive for space heaters in commercial premises has drastically changed the market for boilers in the last couple of years. Since September 2015, if a non-condensing commercial boiler under 400kW needs to be replaced, a high- efficiency condensing boiler needs to be installed.


New changes to ErP are set to hit this month (September), which further tighten the regulations as the EU aims to make products more energy- efficient and more environmentally friendly. All gas-fired appliances must have NOx emissions under 56 mg/kWh. The legislation will prompt more organisations to replace aging boilers with condensing models. The good news for the building services sector is that manufacturers are forced to design and build their heating products to the new specification, resulting in better performance and reduced energy consumption.

For example, Potterton Commercial’s forthcoming Sirius Three range offers one of the lowest NOx ratings on the market. All models are ErP compliant, highly efficient and offer a maximum modulation ratio of 9:1. With outputs of up to 250kW and cascade options, there’s an efficient boiler for every type of building and usage.

However, it is important to remember that there are profound differences in the way condensing boilers should be installed, used and maintained. To help building managers and contractors navigate this process, we have outlined our tips for a hassle-free transition.

1. Accurate system design

Condensing boilers are capable of achieving over 90 per cent thermal efficiency compared with 70 to 80 per cent with non-condensing models. They achieve this by using exhaust gases normally dispersed via the flue into the atmosphere.

These gases are sent through a heat exchanger, which cools and condenses them back into liquid form or condensate which contains much of the heat otherwise lost.

Replacing a non-condensing boiler and updating controls can save up to 25 per cent of energy costs, depending on consumption. But getting the system design right is critical to ensure the boiler performs effectively.

For example, accurate sizing needs to take into account factors such as the building’s heat gains from people, lighting and equipment, and system

design should also take account of what is expected in terms of performance.

2. Where to fiue

Another factor to consider when designing a system for condensing boilers is the siting of the new flue that is required if a non-condensing boiler is being replaced.

Careful consideration must be given to where the flue is sited because the gases discharged from the flue terminal are cooler and less buoyant than those of a non-condensing boiler, and usually form a visible plume of water vapour. This needs to be carefully managed, as it might cause wetting of surfaces too close to the terminal, which could lead to water ingress and damp issues. The pluming can also be a nuisance to neighbouring properties and passers-by. Plume displacement and defector kits can also be used. These extend the flue terminal in order to essentially move the pluming to a point where it will be less noticeable and won’t cause a problem to neighbours or the general public.

3. Water separaon

When fitting a new condensing boiler into an older system, there can be a temptation for engineers to use the existing water rather than drain the entire system. However, high performance condensing models need to be installed as part of a sealed system in order to work effectively. The challenge is that converting an open vented system to a sealed system can be tricky, with leaks from old pipework fittings to consider and potential corrosion if water from an old system gets into the brand new condensing boiler.

A solution to this problem is to leave the existing system open vented and separate the boiler primary circuit using a stainless steel plate heat exchanger. Adding a plate heat exchanger to the mix ensures a safe and protected primary circuit for the new condensing boiler and reduces the risk of corrosion to the existing system at the same time.

4. Water treatment

Chemical water treatment is an important aspect of any commercial heating system, whether a replacement boiler is installed into an existing system or an entirely new system is fitted. Although there are numerous benefits to ensuring adequate treatment is in place, ongoing maintenance and whole-life costing often are often overlooked – either due to lack of awareness or budget constraints.

Water treatment should always be incorporated into both the commissioning and ongoing maintenance of a heating system. Failing to do so can result in corrosion and the build-up of lime scale – leading to inefficiencies, poor performance and potential boiler failure. Installing a new condensing heating system provides the perfect opportunity to overhaul the quality of water circulating within it. If a new boiler is being installed on an old system, we recommend a gentle neutral-pH clean four to six weeks prior to the installation, followed by a more aggressive (though still neutral-pH) chemical clean over one to two days, along with power flushing. Following this, an initial dose, and ongoing use, of a high-quality inhibitor will prevent corrosion and any further build-up of limescale, helping to maintain boiler efficiency and extend the life of the system.

The deployment of magnetic filters that help collect sludge is also a good option. Much of the sludge is made up of rust particles that have corroded and come away from inside pipes or radiators. A magnetic filter is made up of a large magnet that attracts these particles, and then filters them out of the system.

The ErP Directive has paved the way for condensing boilers to deliver more energy savings for commercial building occupiers, but following best practice is critical. Whether installing a new system or replacing an older unit, these benefits can only be maximised through careful system design and ongoing maintenance. VISIT OUR WEBSITE: BUILDING SERVICES & ENVIRONMENTAL ENGINEER SEPTEMBER 2018 19

When fing a new condensing boiler into an older system, there can be a temptaon for engineers to use the exisng water rather than drain the enre system. However, high performance condensing models need to be installed as part of a sealed system in order to work eecvely.

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