When installing condensing commercial boilers, it is vital to think in terms of the whole system and ensuring you get the most out of it. After all, high efficiency boilers are only as good as the system they are installed within. For example, it is counterproductive to install new boilers onto an old system that is contaminated with debris and dirt. So-called dirty water is an inevitable consequence of an aging system but if it is circulated through a new boiler it could affect its ability to run efficiently and can lead to boiler breakdowns and even early failure.
Why is protection or separation needed?
To overcome this, we encourage building service professionals to consider water treatment and system separation. This will ensure the longevity and performance of the boiler, and the system generally, by protecting internal parts from corrosion and the build-up of scale over time. The whole aim is to prevent unscheduled interruption of essential services provided by the boiler.
Within the UK’s commercial heating industry, due to the maturity of the market, older open vented systems are relatively common. This can mean that there are pollutants in that system that present a risk to the new boilers. When retrofitting new boilers onto older buildings the main threat can be caused by the sludge and dirt that has accumulated in the system often as a result of oxygenation.
Within the boiler heat exchanger waterways any contamination such as limescale, system dirt and magnetite can result in hard residue on the heat exchange surfaces. This can reduce the heat exchange capacity and affect the output of the boiler and therefore the system. Any reduction in the cross section of the boiler heat exchanger waterways, including potential blockages as a result of debris in the system, will present more resistance to system flow and can again affect the performance of the boiler and system. If the water is left untreated and the system circuit flows without treatment into the boiler circuit this can have a direct effect on the heat exchanger’s efficiency and lifespan.
Protection or separation can sometimes be taken out of tender proposals to reduce on initial installation cost. This is a potentially risky move when considering the long-term operation of the system. Protection is the key to boilers achieving their full potential, and by advising on the potential long-term savings to an end user via system protection you add value to your services.
Protection and Separation methods
To ensure that a boilers longevity is maintained we encourage installers to consider system protection and separation. Doing this helps add protection to the internal parts from corrosion and built-up of scale over time. There are a number of methods that can be used to address this such as; filters or strainers, air and dirt separators, Low Loss Headers, Magnetic Low Loss Headers and Plate Heat Exchangers.
Low Loss Header
By hydraulically separating the boiler from a secondary system a Low Loss Header adds a huge benefit to an installation. The boiler can operate independently to a system where the load is likely to be variable and the operating range for the system may not be ideally suited to the boiler. For the boiler, if it was installed directly to the system pipework, a variable flow rate may lead to minimum flow rates for the boiler not being maintained. By keeping both systems separate, each side of the system can operate without disturbing the other. The boiler can provide as little or as much heat input as is required, and the system load can vary over a very wide range without affecting the boiler.
Not only can Low Loss Headers help the boiler and system to work well together, Low Loss Headers can help to preserve the working life of the boilers. As the flow rate through the Low Loss Header is very slow it allows entrained dirt or other particles to fall out of the flow and they collect at the bottom of the low loss header for safe removal via a drain valve. In order to prevent any of the debris that settles out being carried back through the boiler Low Loss Headers are normally mounted vertically. Another approach would be the use of a Magnetic Low Loss Header which combines the benefits of a Low Loss Header with the addition of a magnet inside it, capturing the magnetite particles as well.
Plate Heat Exchangers
A Plate Heat Exchanger is another popular option for system separation. This method of separation works by transferring heat from the boiler circuit to the system circuit without the two circuits coming in direct contact; they are hydraulically separated by a pressure break with no mixing of the fluids in the different systems. The heat is transferred through a series of parallel plates with channels between them which the water can flow through independently of the other system.
The advantage of installing a Plate Heat Exchanger onto a system is that they do more than simply protect the boilers from potentially poor in quality water. The boiler circuit and secondary circuit can operate at different temperature profiles provided the plate heat exchanger is specified correctly, the two systems can operate at different pressures, or the fluid within the secondary system could be a process or food grade fluid that could not be heated directly by a boiler.
Something to take into consideration when looking to install a Plate Heat Exchanger would be the heat transfer capacity and the temperature profiles on each side of the plate. These parameters will have a direct impact on how effectively the Plate Heat Exchanger will function, therefore the plate will need to be accurately sized prior to installation to achieve and maintain these parameters.
Plate Heat Exchangers are typically offered in two types, Gasketed and Brazed. Gasketed Plate Heat Exchangers comprise a series of plates fitted with elastomeric gasket which are retained in a frame whereas Brazed Plate Heat Exchangers eliminates the gasketed joints, allowing for higher design pressures and temperatures.
The importance of water treatment
While protection for boilers in any installation is considered to be good practice the importance of maintaining water quality in the boiler circuit or the system circuit should not be forgotten.
While protecting and separating the installation mechanically will help the boilers to reach their full potential it makes sense to treat the water within the systems to ensure all parts of the installation are chemically protected as well. Protection and separation are crucial with retrofit installations in commercial settings; however they could be redundant if the water is left untreated.
The Water Treatment and Conditioning of Commercial Heating Systems Guide published by ICOM (Industrial and Commercial Energy Association), outlines the objectives of water treatment and pre-treatment to minimise the corrosion of system materials, to prevent the formation of mineral scale and prevent growth of microbiological organisms. Aimed at specifiers to maintenance contractors, it helps to identify best practice in water treatment.
Fresh untreated water used to initially fill a system can contain oxygen and other compounds that if left untreated would present a risk to the longevity and efficiency of the system. Cleansing the system prior to installation and suitable post installation water treatment is considered as good practice. The ICOM guidance recommends the use of dosing pots which provide a means to introduce liquid chemicals such corrosion inhibitors or biocides into closed systems. The guidance highlights that water treatment is needed across both circuits in the installation.
Obviously modern boilers and systems can comprise a number of different materials, so always seek the advice of a competent water treatment specialist to ensure that the appropriate chemicals in the correct concentrations are used.
The key thing to remember when planning and preparing any boiler installation is maximising the lifetime and efficiency of the boilers. System protection and separation using equipment such as Low Loss Headers, Magnetic Low Loss Headers and Plate Heat Exchangers will ensure that the boilers will work to their full potential along with ongoing water treatment. While it’s easy to win business on price, reputation lasts much longer.
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