Air bubbles and dirt particles are a fact of life when it comes to hot water and chilled water plants. They will be introduced at the installation stage but also can accumulate further throughout the life of the system. They cause corrosion, deposit build-ups and generally lead to a decreased life span of components and efficiencies of a system if not handled correctly.
These days there are many options to eradicate this issue and ensure you have a healthy, efficient system that will perform for many years. Air has many ways of entering a system which makes it very hard to avoid. Prior to being filled with water, new components within a system will contain air which will latch onto anything it can once the system starts circulating. In existing systems, older components with even the smallest weep are a weak point which allows the entry of air. Even water has dissolved air particles throughout it.
Any amount of air can cause issues with heat transfer and result in nuisance noises. Your main concern with air is the possible corrosion as a result of oxidising metal. Corrosion is one of the leading causes of a reduced lifespan of any components within a hot or cold water HVAC system – from the boiler or heat pump to tanks, pipework, and radiators. Knowing the different types of air bubbles within a system and the products available to combat each of them will give you a clear indication of which direction to head in to alleviate the possible issues and protect your system.
Macro bubbles or free gases are the largest kind and therefore, the easiest to get rid of. They tend to float up to the highest point possible where they can be vented out with a basic float style valve. Modern boilers and heat pumps are fitted with automatic air vents which vent macro bubbles when air tries to pass by. These vents must always be on the highest point so the air will gather and be vented out. Terminal products such as radiator panels are always installed with an air vent fitted, although it is often a manual air vent which needs to be operated when necessary.
Microbubbles are smaller than macro bubbles and therefore behave in different ways meaning they require different products to combat them. Some microbubbles can float throughout the system but tend to latch themselves onto objects rather than float upwards by themselves. These bubbles are generally dealt with via the Coalescence technique – that is, forcing them to join together until they are large enough to float upwards and be vented out. Many air separators contain PALL rings to assist with this process.
The final step, if required, in complete de-aeration of dissolved gasses within the water is the use of a vacuum degasser. This unit is the ultimate solution for any sized water-based HVAC system. The most popular style incorporates a VSD pump, a water column and an interface with full controls and monitoring. The unit creates a vacuum effect inside the water column, which forces the de-aeration of the water which it subsequently vents out. Vacuum degassers also include makeup water connections, ensuring fresh water introduced into the system is de-gassed prior to mixing with the system water.
Dirt is also very hard to avoid. With new products, it is common for them to contain particles like metal fragments, sand, or splatter from welds during the production process. If these particles aren’t flushed out completely. Magnetite can also generate throughout the life of the system after a reaction between oxygen and iron. Dirt has obvious repercussions on the system, including reduced flow, reduced heat transfer, and blockages. Many modern heat sources have quite small waterways in order to get such high efficiencies, so it is vital to ensure these waterways remain clear and unobstructed.
Due to the ongoing risk of dirt, it is crucial to install a permanent and serviceable dirt filter/separator. These can range from basic inline strainers to magnetic filters, or a complete dirt separation unit. In line strainers come in a few different variations including the simple ‘Y’ Strainer. Other inline filters have a vertical cylindrical body with PALL rings. The rings cause the dirt particles to collide with them, then sink to the bottom of the cylinder where they can be easily drained out with a valve. This solution helps with maintaining the flow of the system as the particles are removed from the water flow rather than collecting on a mesh that sits in line.
Magnetic filters are a great solution for removing magnetite and any other odd bits of magnetic fragments within the water should there be any. These filters make service and maintenance very straight forward. They consist of magnets either submerged in or placed on a small vessel which is generally plumbed into the return line of the system. Simply isolate the filter, remove the magnet and clean/drain the filter of anything that it has caught.
A complete dirt separation unit is the optimal solution and the best protection for the system. Specialised dirt separators can combine filters, magnets, and specially designed flow deflection methods to optimise the separation of even the most minuscule dirt particles. The top Flamco range of separators deflect only a small amount of water into the chamber for filtering/separation then returns it into the main flow via a small injection point – the Venturi principle ensures the loss of flow is kept to an absolute minimum.
By only separating around 10% of the water flow, the separator can remove up to 40% of dirt particles in every cycle. The majority of these dirt separators also combine air separation capabilities as well to combat both.
Your new solution from Hunt Heating
Proper filtration of both air and dirt is vital to prolong the life of a hot or chilled water HVAC system and to ensure it continues to run at the highest possible efficiency for many years. For new installations it is paramount. For older or existing systems without air and dirt separation, it’s a small investment to make to ensure you continue to get the most out of the components within.
With a large catalogue of strainers, filters and complete air and/or dirt separation units, contact Hunt Heating Commercial to discuss how we can help with your project or system.