BSEE BOILERS & HOT WATER
Phil Pett, Technical Sales Manager at EOGB Energy Products Ltd, takes a detailed look at ‘add‐on’ trim systems and how they work to reduce harmful emissions and increase heating efficiency.
Oxygen Trim (O2 trim) is widely acknowledged as an essential element of burner control that allows reduction in both energy costs and associated emissions. Since its inception in the 1980s, O2 trim has evolved from basic systems that adjusted mechanical linkages using Bowden cables through to today’s sophisticated microprocessor- controlled burner management systems that employ highly accurate and repeatable servo motors to position air dampers and fuel drives. Efficient and safe combustion requires a precise mixture of fuel and air. Too much air results in energy being wasted up the flue; too little air results in incomplete combustion. Incomplete combustion is particularly undesirable and results in the formation of Carbon
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wo of the most well-known energy efficiency controls designed for commercial and industrial burners are CO and O2 trim systems.
Advertising: 01622 699116 Editorial: 01354 461430 Combating emissions with combustion control
Monoxide (CO), Hydrocarbons (HC) and Hydrogen in the form of H2. To avoid sub-stoichiometric combustion, burners are always commissioned with an element of ‘excess air’. Combustion is complex and there are many variables such as air temperature, humidity, barometric pressure and fuel quality that affect the whole process. Excess air ensures that, even if the combustion variables change, the combustion process remains safe.
Combustion variables
O2 trim works in a fairly simple way in that it adds or reduces either fuel or air (depending on the system used) to compensate for changes in these combustion variables. For each point on the combustion profile there is an O2 setpoint. If the O2 reading for any point increases, then air is reduced, or fuel added, to bring the process variable back to the setpoint, if the O2 decreases the opposite happens.
Most systems work by adding or subtracting air as this has less effect on the power output.
CO Control takes a more empirical approach than Oxygen Trim, enabling combustion systems to get closer to stoichiometric conditions whilst remaining safe. A self-adapting algorithm optimises the fuel/air ratio over the entire firing range. It ‘learns’ each point on the programmed combustion curve by reducing air to the point where CO is detected and then ‘backing-off’ to a safe setpoint. Each ’learned’ point has a lifetime of eight hours after which it is ‘learned’ again. This ensures that if external conditions have improved then the CO Control will readapt to compensate for this and increase efficiency. A combustion analyser and combination 02/COe probe provide a failsafe solution for CO Control when used with a burner management controller. For example, the Lamtec LT3-F combustion gas analyser uses two separate processors to cross-check the zirconia probe’s outputs with the advantage of using a single probe in the flue.
CO Control also promotes increased safety as CO and other unburnt hydrocarbons are only produced as a result of incomplete combustion which cannot be detected by probes measuring only oxygen. It is not uncommon for systems employing CO Control to run as low as 1% O2 and as a rule of thumb, CO Control can generate an additional saving of up to 50% over conventional O2 trim systems.
uCombustion control systems can play a big part in increasing heating efficiency.
The controls are easily retrofitted to all types of burners on most heating systems and the payback is typically less than two years.
www.eogb.co.uk CASE STUDY
The first Remeha Gas 220 Ace has been installed in the UK at Samuel Whitbread Academy in Shefford, as part of best practice asset management. The new, high‐efficiency floor‐standing condensing boiler replaces an existing 13‐year‐old Gas 210 Eco Pro. Currently operating alongside a Gas 210 Eco Pro, it serves the Arts & Drama block that houses the school’s Main Hall, Theatre and Activities Hall.
Remeha Gas 220 Ace scores top marks at school
The ease of installation certainly impressed heating engineer Ashley Jones of Spa Gas. “A lot of thought has obviously gone into the packaging and pallet design to simplify and speed up installation,” he said. “Disconnecting the old Gas 210 Eco Pro, unpacking the new Gas 220 Ace and then positioning it in the plant room took just an hour and a half.”
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Key to the Gas 220 Ace’s exceptionally high output to physical size ratio is its innovative new monobloc heat exchanger. Designed for maximum performance and durability, at the top end output (300kW), it is almost half the size of previous models.
The reduced footprint and lighter weight are winning features for Ashley. He commented: “The Gas 220 Ace is a nice size – it’s light and extra-compact which makes it easy to handle as well as providing more working space. I also like the integrated wheels which make it easier to manoeuvre the boiler into final position.”
The Gas 220 Ace features a new ‘click and go’ condensate drain positioned underneath, rather than inside, the boiler. “This is really easy to connect and access,” continued Ashley, “which
24 BUILDING SERVICES & ENVIRONMENTAL ENGINEER SEPTEMBER 2017
he Gas 220 Ace builds on proven Remeha condensing technology to offer an even higher output to physical size ratio, optimum design simplicity and flexibility, and outstanding performance.
means there’s no need to dismantle the boiler to get to it when servicing.”
The heart of the Gas 220 Ace is its pioneering control platform with time and temperature controls supplied as standard. The enhanced, back-lit panel simplifies input and control for end- users while new parameter codes provide heating engineers with access to greater technical detail for rapid, straightforward servicing and diagnostics.
“First impressions? It’s so compact!” commented Tristan Mitchell, Facilities Manager at Galliford Try, facilities management provider for Samuel Whitbread Academy PFI, on first seeing the new Gas 220 Ace.
“The smaller footprint gives us greater accessibility within our plant rooms and we also like the enhanced control platform. Small, simple and accessible – can’t go wrong.” Now fully operational, the performance of the Gas 220 Ace continues to impress. Tristan Mitchell adds: “There’s not one fault we can list – it has exceeded our expectations. We have instructed our installer to proceed with the Gas 220 Ace for the remaining four boilers to be installed this year. This is mainly down to the accessibility the smaller unit gives us within our plant rooms but also the fact that the new interface allows for faster, clearer and simpler user control.”
Perfect for large-scale, high end projects, the Gas 220 Ace is a premium Class 6 NOx boiler,
uRemeha’s new Gas 220 Ace is compact, simple and accessible.
available in 160, 200, 250 and 300kW models. All connections and pipework are at the top of the Gas 220 Ace, enabling side-by-side or back-to- back positioning and flexible modular configuration options. With cascade options available for up to eight boilers, the Gas 220 Ace makes it possible to install a high heat output in a small area.
gas220ace.co.uk VISIT OUR WEBSITE:
www.bsee.co.uk ‘
Combustion is complex and there are many variables such as air temperature, humidity, barometric pressure and fuel quality that affect the whole process. Excess air ensures that, even if the combustion variables change, the combustion process remains safe.
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