Essex college enjoys the benefits of boiler replacement
Faced with the need to replace three cast-iron sectional boilers with ages from 12 to 30 years, Bryan Yates, site manager with Braintree College in Essex, embarked on a feasibility study with consulting engineers Atkins Management Professional Services. The aim was to identify new boilers that would achieve efficient performance with low emissions, ease of maintenance, responsiveness ot varying space-heating requirements and the ability to be easily retrofitted to existing pipework. Adrian Sharp of Atkins says, ‘Having carried out the feasibility study, we decided there were significant advantages to the Hoval Ultragas condensing boiler, and this was obviously the best boiler for the job. We also visited a school that was already using these boilers, and their experience confirmed that decision. With net efficiencies of up to 109.5%, we estimated that the new boiler plant would achieve savings on fuel bills in the order of 40%.’ The three existing boilers were replaced with three 500 kW Ultragas boilers, which have a much smaller footprint than the original sectional boilers. The pipework is also simpler, so the college could reduce the amount of pipework and the number of circuit pumps, freeing a considerable amount of space in the boiler room, making maintenance much easier. NOx levels are 20 mg/kWh, with carbon-monoxide levels of 10 mg/kWh. The project also involved replacing existing hot-water calorifiers with direct-fired water heaters, so the new boilers only provide space heating. ‘I wanted to ensure there was extra capacity so that we can accommodate any future changes in the heating requirements for the college,’ explains Bryan Yates. ‘Before, we were using one of the boilers for water heating; now all three are used for space heating, mainly through conventional radiator systems throughout the campus.’ This further-education college is located on a 13 acre site and comprises several buildings. Because the occupancy of each space can vary greatly during the day, the college is divided into a number of heating zones, and the boilers modulate in response to demand. An energy-management system also controls boiler sequencing to rotate the lead boiler each month. Bryan Yates also has the capability of monitoring the performance of the boilers from his office PC, and reports that it is already clear that the plant is much more efficient. The efficiency of Ultragas condensing boilers is the result of several design factors. A pre-mix down-firing burner is combined with a stainless-steel combustion chamber with a single pass heat exchanger comprising stainless-steel tubes with aluminium-alloy internal fins to provide a large surface area for heat exchange.