Your boiler is integral to the smooth running of your home, providing hot water on demand and central heating when you need it. It’s often not until it stops working properly that you give a second thought to its health.
CORROSION WITHIN THE SYSTEM
We all think of water as pretty innocuous stuff, but when the wrong conditions come together as they can inside a central heating system, corrosion can occur rapidly. The process of corrosion is a chemical reaction and is likely to occur when a metal surface is in contact with water. As with most chemical reactions, heating the water accelerates the process, making your central heating the perfect place for corrosion to thrive if it hasn’t been properly prepared and protected.
INDICATIONS OF BUILD UP OF SLUDGE WITHIN THE SYSTEM
Boiler noises which gradually get worse over time
Pin holes developing in radiators
Radiators having a cold area at the bottom
Wearing of pumps and valves
BLOCKED PLATE HEAT EXCHANGERS
Plate heat exchangers in combi boilers are classed as secondary heat exchangers. Plate heat exchangers are a major cause of problems in combi boilers and since most combi boilers use them it’s important to know how they work and the how to protect them.
In central heating mode, the boilers heats the water in the main heat exchanger and then pumps it around the central heating circuit, When a hot water tap is turned on the boiler operates a diverter valve and the boiler switches into hot water mode. In hot water mode the diverter valve in the boiler diverts the heating water from the radiator pipework, sending it instead through the plate heat exchanger. There are two sections in the plate heat exchanger, one for central heating water and one for hot water. The two lots of water don’t mix but the waterways are tightly interleaved, separated by a series of plates. As the hot water travels through the plate heat exchanger it picks up heat from the central heating section of the plate and therefore straight to the hot taps. The main issue with the plate heat exchangers is that the plates are fitted as close together as possible and they can get easily blocked and this can happen in 2 ways.
Limescale is not really a issue within the heating section of the plate heat exchanger, This only becomes a issue if your plate heat exchanger has a split inside which is noticeable as your boiler pressure constantly raises. The hot water is basically fresh water being heated up which if your in a hard water area its very important to fit a limescale inhibitor.
Signs of a block hot water section is slow water flow at hot taps (cold water should flow fine) and in turn makes the hot water become very hot, its important to mention that sometimes the limescale coats the inside of the plate heat exchanger therefore the hot water is likely to come out cool as it wont be able to pick up enough heat
The most common way for the plate heat exchanger to block up is for the heating section to be blocked with black oxide sludge and debris.
Combination boiler manufacturers are very clear in that they insist that any existing heating system must be cleaned prior to installing a new boiler. The recommendation from most boiler manufacturers is to chemically flush and install Magnetic filters, Personally a powerflush if done correctly can be very beneficial to the heating system and energy bills (this will be covered on a future post) If your system is known to be contaminated with sludge and debris then this option is a must as chemically cleaning and installing a filter just wont do the job, it can be expensive especially if you have a big system but still cheaper than constant maintenance on your new boiler and the potential of voiding your warranty with the manufactures.
Worcester Bosch is our preferred Magnetic filter https://www.worcester-bosch.co.uk/professional/support/troubleshooting/videos/system-filters
Sentinel is our preferred chemical cleaners https://www.boilerfixltd.co.uk/product/sentinel-x100-inhibitor/
Guides on how to power flush https://www.sentinelprotects.com/uk/support/guides/how-to-powerflush-central-heating-system