Jet power
Charlie Mowbray, Senior Product Manager at Ideal Heating – Commercial, explains the advantages of using commercial condensing pressure jet boilers for heating large loads, as well as the important things to consider to ensure their effective installation and operation.
Boilers that operate with a pressure jet burner are common in industrial applications but over recent years have been largely removed from the domestic and commercial heating spheres. Several regulatory changes have been responsible for this, including the Energy related Product (ErP) Directive, the Medium Combustion Plant Directive (MCPD) and, most recently, the uplift to Building Regulations Part L.
These changes are necessary to reduce emissions and improve overall energy efficiency of the buildings and the systems within. Many pressure jet boilers designed to work in commercial applications have been unable to comply and have been withdrawn from the market. But not all. Those that can be operated in condensing mode are able to achieve the new, more demanding efficiencies and emission limits when matched to a suitable burner.
What is a condensing pressure jet boiler?
The description of a boiler as a ‘pressure jet’ appliance would most accurately be applied to a boiler being fuelled with oil. However, the term ‘pressure jet’ has become synonymous with large shell and tube boilers where a fanned burner with associated fuel controls is mounted to the combustion chamber. For a pressure jet boiler fuelled with gas this fuel is mixed with air that is blown through the burner by a fan and ignited at the combustion head of the burner.
Burner controls ensure proper fuel/air ratio and mixing across the range of operation for efficient and complete combustion. It also determines the shape and direction of the flame.
All commercial pressure jet burners used on gas or oil boilers work in this way, but only those that are fully able to operate in condensing mode are compliant. Condensing pressure jet boilers, such as our Evojet range, feature a double return condensing system (connections for high or low temperature return water) which enables them to keep the temperature difference between the heat exchanger wall and the return water high, thus maximising the formation of condensation. This design, plus the three-pass layout for the combustion gases, the titanium stabilised stainless steel internal components and extensive insulation combine to provide a high level of efficiency and reliability.
Not all pressure jet boilers can be operated in condensing mode. Those that are constructed from standard steel or iron, as opposed to high grade stainless steel, will, in time, corrode from the condensate which can be mildly acidic.
Why opt for a condensing pressure jet boiler?
In commercial settings, pressure jet boilers are rarely the first option to turn to as high-efficiency condensing boilers can achieve several megawatts. Plus, you have the option to cascade boilers.
The problem with this approach comes when plant room space is limited as cascades can, in some instances, take up quite a large floor area and present challenges installing all the flues and pipework to each boiler. This is where it is worth considering a condensing pressure jet boiler, which can deliver several megawatts from a single unit. Our latest Evojet models have outputs up to 3,000kW.
With a reduced number of pressure jet boilers overall, due to the high capacity of each individual boiler the system design and installation work for a pressure jet boiler can be considerably less complex in terms of the number of connections and the pipeline you have to put in, and the number of pieces of equipment you’ve got to deal with.
In the commercial sector, condensing pressure jet boilers are therefore most frequently suited to leisure facilities, hotels, healthcare facilities and the increasingly popular heat networks.
Important considerations
Condensing pressure jet boilers need to be considered carefully as they are not the ‘easy’ option when it comes to commercial heating.
Firstly, specialist installers and commissioning engineers are required who have the appropriate training for this type of equipment. The people who operate and maintain them also need suitable training, especially on the health and safety aspects such as Pressure Systems Safety Regulations; these are far more complex than your typical commercial boiler.
A robust water treatment and ongoing maintenance regime is essential to ensure safe and reliable operation. Inadequate water treatment will result in scale and corrosion, reducing the efficiency of the installation and potentially reducing the working life. Furthermore, the condition of the water supply used to initially fill the system can directly impact the quality of the overall heating system if the water treatment is not correct.
Revaluate your options
Where there is high demand for heating and hot water, delivered efficiently with minimum emissions, don’t exclude pressure jet boilers from your considerations when weighing up the best option for your application. Pressure jet boilers may have been around for some time, but modern commercial condensing pressure jet boilers and burners might well surprise you yet!
