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THE ‘ON‐DEMAND’ ALTERNATIVE Heating efficiency served up on a plate

Paul Sands, Director of Stokvis Energy Systems, puts forward the case for modulating low water content gas boilers combined with compact modulating low water content plate heat exchangers, to meet hot water demands reliably, safely and economically.

the models which dominated plant rooms in offices, schools, shops, offices, hospitals and other premises in the second half of the last century. Indeed they have been transformed in terms of not merely their efficiency, but their environmental impact, scale, reliability and safety implications. In tandem with what have mainly been mechanical improvements in such components as burners, gas valves, pumps, flues and, of course, heat exchangers there has also been a technological revolution in terms of the control systems, sensors and other electronics which optimise their performance throughout a long working life.


By contrast, modern high efficiency boilers are fully modulating and feature an automatically controlled premix to match output to demand. In addition to extracting the maximum energy from the gas burnt, it also results in very low NOx and carbon dioxide generation. They further feature a much lower water content than conventional boilers, with a far larger heat exchanger surface area. Modern condensing boilers are often installed in a cascade arrangement, where the duty is shared between units: ramping up and down to meet demand, and when no hot water or heating output is required, they will modulate right down and turn off; simply maintaining temperature in their own primary circuits.

In fact, to look around a modern plant room – especially one of the custom- built, modularised versions which can be completely pre-fitted and craned into position – is to view a clean, compact and contemporary building services solution. But what may escape the untrained eye is the even more radical change in size and form in the means by which hot water is delivered. Demand for hot water varies greatly


uJo Harris, BSRIA’s Sustainable Construction Group Manager.

SRIA advises that in a critical environment it is key to ensure that all assets deliver their optimal level of performance. This requires a management strategy that reflects the importance of key assets. By having good quality, reliable asset information, implementing standard and emergency operation procedures and assessing asset maintenance needs for condition, functional resilience and criticality, BSRIA members can ensure their asset management effort can reduce operating costs and increase their resilience to engineering risk.

BSRIA’s top 10 tips for running an efficient critical environment are: 1. Develop effective operational management strategies. 2. Ensure there is a continuous improvement culture.

ontemporary commercial gas boilers bear little resemblance to either their early ancestors or even

depending on the purpose of a property – a hotel for instance being subject to different peaks compared to offices or a school – though in the past the only means of satisfying such requirements was to vary the size of the storage vessels.

Stokvis Energy Systems has been involved on many contracts over the past two decades to replace cumbersome, wasteful and potentially dangerous hot water storage vessels with technically superior packaged plate heat exchangers.

Where maintaining the temperature in large volumes of stored hot water requires constant energy input, which then causes constant cycling of the boilers – even when insulated to a good standard – plate heat exchangers represent the ‘on demand’ alternative. They themselves feature very low water content and comprise a series of corrugated, corrosion resistant stainless steel plates which are able to optimize the transfer of heat between the boiler’s primary circuit and the domestic hot water feed, or secondary circuit. Plate heat exchangers therefore instantaneously generate hot water at the required temperature, with flow rates measured in hundreds of litres per minute. This means that in places like large hotels and conference centres, where there may be hundreds of people deciding to take showers or baths over a very short time-span, there will still be sufficient supply. Even in industrial applications, plate heat exchangers successfully meet very high expectations for the provision of process water.

Stokvis Econoplate plate heat exchangers feature factory fitted primary pumps and fast responding, three or four-port valves on the primary circuit. Then there is a bespoke PID controller which monitors the secondary water temperature and regulates the motorised valves, while the equipment can be readily linked into the main Building Management System. Despite the depth of knowledge regarding the Legionella virus in water – whether for air conditioning systems or that intended to reach the taps – there

remains a considerable risk to health when storing hot water. Therefore, choosing instead to utilise plate heat exchangers to generate instantaneous hot water also negates the danger associated with storage vessels that have a temperature gradient from the bottom to the top of the vessel. The focus on the use of alternative energy sources, and the introduction of the Renewable Heat Incentive payments, as well as previous government grant schemes, has seen the popularity of solar thermal installations gain momentum in recent years. On a domestic scale, the solar gain is normally delivered to a twin coil cylinder. For commercial applications, however, Stokvis would generally recommend employing the output from the collectors as a solar pre-heat arrangement, preheating the water in a vessel from where the water at whatever temperature is fed through a plate heat exchanger in order to ‘top up’ the temperature to the required level for delivery.

Essentially, whatever type of building is being considered, or the nature of the occupant’s business activity, modern modulating low water content gas boilers combined with compact modulating low water content plate heat exchangers, can meet the hot water demand reliably, safely and economically. ‘ Plate heat exchangers instantaneously

generate hot water at the required temperature, with flow rates measured in hundreds of litres per minute. In places like large hotels and conference centres, where there may be hundreds of people showering or bathing over a very short time‐span, there will still be sufficient supply.

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BSRIA releases top 10 tips for efficient data centre management B

up as heat: match power input to load.

9. Measure your static floor pressure to ensure ventilation is getting to the heat load: think of warm air as a pollutant.

3. Ensure you capture performance data.

4. Benchmark and use the data to drive improvements.

5. Embrace new technologies that provide performance improvements.

6. Ensure engineers are suitably trained and competent.

7. Test critical assets and operating procedures regularly.

8. Non useful electrical power ends 18 BUILDING SERVICES & ENVIRONMENTAL ENGINEER JUNE 2017

10. Review your maintenance tasks to ensure the activities address the likely causes of failure. Jo Harris, BSRIA’s Sustainable Construction Group Manager, said: “For efficient critical environment management – there’s the trusted mantra: Plan, Do, Check, Act. “You must have a management strategy in place that enables you to undertake the management and maintenance of the assets. Then the

key is to check that what you had planned is actually giving you the results you wanted.

“Measures that reduce risk in a business with a critical environment are key for operators and should be of interest to BSRIA members. These salient tips will hopefully get organisations on to the path of success.

“It cannot be underestimated the impact that management can have on engineering risks in a critical environment. And of course – good management will also help reduce operating costs.” uBSRIA is a non-profit distributing, member-based association,


uStokvis Econoplate plate heat exchangers feature factory fitted primary pumps and fast responding, three or four‐port valves on the primary circuit.

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