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POWER-FLUSHING FOR MAXIMUM PERFORMANCE
Power-flushing is suitable for both new and existing heating system and It is important that when installing a new boiler into an existing system that all system debris is removed or this could accumulate into lime scale sludge and corrosion deposits eventually leading to system breakdown. It is also a prerequisite of Boiler manufacturer’s warranty that systems should be free and clean of debris as well as a requirement of Building regulations Part L.
Power-flushing helps to eliminate these problems on existing boilers by restoring the system back to optimum condition! New systems can also benefit from power-flushing by removing corrosion debris such as flux which if left can lead to cold spots in radiators.
Stage 1 – Equipment
Power-flushing is the most efficient and effective method of cleaning a central heating system prior to installing a new boiler. Cleaning works on the principle of creating a powerful flow of fresh water, under controlled conditions, to remove debris from the system, boiler, hot water cylinder and each radiator is cleaned individually to ensure that no scale or debris remains. A power-flushing machine can push high levels of water per minute around a system and uses a reversible flow to dislodge debris. When used in conjunction with water treatment products a typical powerflush can take around 8 hours based on a 10 radiator system.
Stage 2 – Preparation
To start, electrically isolate the system pump and make sure all of the radiator wheel heads or TRV’s are open. The TRV’s must be set to maximum or the heads removed and all zone and three port valves should be locked open. On open vented systems you will need to cap off the cold feed supply and open vent – or join them together. Sealed pressurised systems can be left as they are. It’s advisable to protect carpets by putting plastic sheets under the Powerflush machine and dustsheets on the other areas where you will be walking.
Stage 3 – Connecting
Position the Power flushing machine to the nearest suitable drain and cold mains water tap, ensuring there is a continuous fall along the length of both the drain and discharge hose. When connecting the Power-flushing machine to the system, connect across the pump connections. If this isn’t possible connect across the flow and return pipes of the boiler or, if there is no other connection point available, connect across a radiator. Connect the supply, overflow and discharge tubes and check for leaks before turning the machine on.
Stage 4 – Purging
Purging is the process of pumping fresh water through the system, purging the debris and replacing with fresh water. To achieve this all valves should be fully open and the waste pipe discharging to the foul water drain. Turn the Power flushing machine on and fully open the mains inlet. Adjust the dump valve on the machine to keep the level of water in the tank constant. If the water level keeps rising turn down the mains supply. Reverse the flow direction every five minutes and once the discharge water runs clear the system is fully purged. To check the cleanliness of the system water, a TDS (Total Dissolved Solids) meter will give an accurate on-site analysis.
Stage 5 – Power flushing
Add a cleaner into the power flushing machine and bring up to temperature. Adding a chemical cleaner can increase the amount of sludge removed by up to 50% and is ideal for heavily contaminated systems.
With all the radiator valves closed, clean the central heating and hot water circuits for ten minutes in each direction, then open the valves for each individual radiator in turn – flushing each one for up to 15 minutes in both directions before closing the valves and moving onto the next radiator. after this process is completed you return to the first radiator and then pass clean water through the radiator for up to 15 minutes, check the discharge water from each radiator with the TDS meter to ensure they are properly cleaned and water matches the total dissolved solids of tap water.
Stage 6 – Finishing off
When all the radiators have been flushed and are now clean, it is advisable to flush the system through one more time with clean water. Refill the system and add a suitable Build cert approved corrosion and lime scale inhibitor. Dosing the system with an inhibitor provides long-term protection against the formation of lime scale and corrosion, and will ensure the system continues to perform at optimum efficiency. Finally set all the valves back to their original positions, turn the system pump back on and re-commission the system. Job done.
For a Standard Heating System with 10 radiators, the cost of a Powerflush starts at £450.00 including Chemicals (Plus Vat) and will take around 6-8 hours to complete.
Reasons to undertake Power Flushing of your Heating System:
Cause: Sediment of iron oxide sludge accumulating at the bottom of radiators restricts the flow pattern. The objective is to restore systems with circulation and boiler noise problems (caused by sludge and corrosion deposits) to optimum operation. Power flushing removes these deposits and the problems that they cause.
Power flushing is also an excellent way to pre-commission clean new heating systems, to remove excess flux, swarfe and other debris, and the grease and oil used to prevent rusting of components before use.
Cause: Assuming no other faults exist, the insulating effect of accumulated deposits of sludge and scale can restrict the transfer of heat to such an extent that the boiler overheats and fractures.
Cause: In untreated heating systems, corrosion debris accumulates in the boiler and, in hard water areas lime scale will form. The insulating effect of these deposits reduces heat transfer to the circulating water. 3mm of lime scale deposit on the heat exchanger will add 18% to your fuel bill. It is in the current British Standards requirements that prior to boiler change, the system must be cleaned, power flushing is the best way to achieve a proper well done job.
Pump Seizure & Failure
Cause: Black Oxide sludge, being abrasive and magnetisable, increases shaft and bearing wear which is the most common cause of sticking pumps and pump failures.
Frequent Venting, Cold Spots Near Top of the Radiator
Cause: Hydrogen, sometimes mistaken for air, is a by-product of electrolytic corrosion. It is flammable and can be identified easily.
Cause: Black Oxide sludge forms continuously in all unprotected central heating systems as a result of corrosion. It will also harden into scale on the hottest surfaces of a system. (i.e. the boiler heat exchanger causing it to make knocking and kettling noises). This prohibits efficient heat transfer. Boiler Manufactures will not guarantee your new boiler installation if the system is not chemically cleaned. The British Standards and the Benchmark demand that the system should be thoroughly cleaned.
Red Iron Oxide
Red or brown rust is only formed in heating systems when they are aerating. Aeration faults must be cured when replacing failed components to prevent further failures.
Hydrogen Gas (highly flammable)
Hydrogen is a by-product of corrosion processes and may necessitate frequent venting. Hydrogen is often mistaken for air. It can be detected by igniting it at a radiator vent and it burns with a yellow flame. Gas accumulations depress the water level, disturbing the flow pattern in the radiators and thus causing cold radiators.
Galvanic corrosion is well known and contributes significantly to the deterioration of central heating systems. In the presence of copper, steel and aluminium become “sacrificial”, just as in a consumable battery.
Some of the ways in which galvanic corrosion occurs are:
1. Copper pipe in electrical contact with a radiator
2. Brass fittings
3. Pieces of copper swarfe in radiators
4. Sediments of ferrous oxide (magnetite)
5. Folds in steel radiators – stressed areas sacrificial
Impurities in the water can play a very big part in central heating corrosion processes. Corrosion rates are increased by soldering fluxes containing chlorides. New systems should be pre-commission cleansed in accordance with BS7593 and Benchmark to avoid such problems.
Pin-holed or Perforated Radiators
Radiator leaks occur due to localised pitting corrosion, which is a result of a combination of the above circumstances.
Localised boiling can develop where there is sludge or scale in the heat exchanger. This causes very high internal skin temperatures, which result in steam bubbles forming in the heat exchanger.