VDI2035 is becoming more and more recognised in the UK heating industry, I have been banging on about this method for about 8 years, so it’s good to finally see it been used more in the UK, both in the Domestic and Commercial side of our industry, but what are the requirements of VDI2035? I will try and explain these using methods used by my preferred brand Elysator, other products are available.
VDI2035 identifies 3 key parameters required to cause corrosion in heating and cooling systems
1. Dissolved Oxygen
2. System water with high conductivity
3. Low pH
Elysator products work with how metals are naturally inclined to react, not against them, harnessing the effects of these natural reactions and applying them to the benefit of system protection
The Science: let us delve a little into the science of corrosion, A typical heating system can be made up of a variety of materials, copper, brass, various forms of steel, composite and even plastics.
All metals contain negatively charged particles called electrons, the number of electrons in a metal define how stable that metal is, many metals in their refined state, do not have a stable number of electrons, instead they have a surplus of electrons and will readily give up these electrons to become stable, conversely, Oxygen requires additional electrons for it to become stable, so metals and oxygen exchange electrons to achieve greater stability.
Chemists refer to these processes as Oxidation (loss of electrons) and Reduction (gain of electrons) the more common term for this process within metals at least is corrosion and for iron and steel it is better known as rusting, the presence of oxygen in the water of a heating system therefore creates a favourable environment for corrosion to occur
let’s look at ways we can address this naturally occurring process.
Oxygen is and always has been the enemy of a heating system, so it’s always something we should deal with, in my opinion on installation the best way to do this is good design, using good quality materials, correct expansion vessel sizing and correct pre-charge of the vessel as well as a good maintenance regime, if dissolved oxygen is a problem within the system, there are ways to address this using Elysator products, I will go into this in further detail a bit later
System water with high conductivity: a lot of the UK has hard to very hard water, water has minerals and salts in them, it is these that create the conductivity, different areas in the UK have different water hardness, so each area will have different needs, but whatever the water, if we remove these minerals and salts on filling, we lower the conductivity, basically restricting the path that is needed for the chemical reaction that is needed between metals, water and oxygen for the corrosion process to take place, so rather than adding a chemical to try and stop the natural process of chemical reaction that creates corrosion, we just remove the pathway, the best way to treat heating water on filling is using a demineralisation unit, basically a mobile cartridge that you just connect inline with the mains water fill point and the filling connection to the heating system (as in image below)
Filling the heating system with the Elysator Purotap Leader using the Nexion cartridge has the additional benefit of raising the pH of the initial fill water to around 8.4, the salts and minerals are removed from the water through an ion exchange with the resin, the Nexion cartridge has a surplus of anion resin and it removes free carbon dioxide which raises the pH of the water, this give you water suited to a heating system, with all the potentials to allow corrosion removed, so lowering the risk of system corrosion massively, without the addition of any chemicals