CENWAT Inhibitor & Water Treatment 3 — Questions and Answers
Question 1: What is a magnetic system filter and how does it work?
- It uses powerful magnets to capture ferrous particles (magnetite) circulating in the system water (Correct answer)
- It filters gas using magnetic fields
- It uses an electrostatic charge to remove scale
- It filters only non-ferrous particles
Correct answer: It uses powerful magnets to capture ferrous particles (magnetite) circulating in the system water
A magnetic filter contains a strong magnet that attracts and retains magnetite and other ferrous particles circulating in the system water, preventing them from reaching and damaging the boiler heat exchanger.
Question 2: How often should a magnetic system filter be cleaned?
- Annually during boiler service, or more frequently in heavily contaminated systems (Correct answer)
- Only when the boiler fault code indicates a flow problem
- Every 5 years
- Filters are self-cleaning and never require maintenance
Correct answer: Annually during boiler service, or more frequently in heavily contaminated systems
Magnetic filters should be cleaned annually (typically during the annual boiler service) and the collected debris inspected to assess the rate of system corrosion. High debris volume suggests more frequent cleaning may be needed.
Question 3: What does 'system volume' information do for correct inhibitor dosing?
- It tells the engineer how much inhibitor is required to achieve the correct concentration throughout the system (Correct answer)
- It tells the engineer the system pressure
- It is needed to size the expansion vessel only
- It is irrelevant to inhibitor dosing
Correct answer: It tells the engineer how much inhibitor is required to achieve the correct concentration throughout the system
Knowing the system volume (total litres of water) is essential for calculating the correct dose of inhibitor, cleaner or antifreeze to achieve the specified concentration recommended by the manufacturer.
Question 4: What is the consequence of operating a central heating system without corrosion inhibitor?
- Accelerated corrosion of ferrous components, magnetite sludge formation, reduced efficiency, pump failure and potential boiler warranty invalidation (Correct answer)
- No consequence — inhibitor is optional
- Increased NOx emissions from the boiler
- Reduced system pressure over time
Correct answer: Accelerated corrosion of ferrous components, magnetite sludge formation, reduced efficiency, pump failure and potential boiler warranty invalidation
Without inhibitor, electrochemical corrosion attacks ferrous pipework and radiators, producing magnetite sludge that blocks system components, reduces heat transfer efficiency, and can invalidate the boiler manufacturer's warranty.
Question 5: What is a dosing pot (chemical pot) in a central heating system?
- A small vessel fitted inline in the system pipework that allows chemicals to be easily introduced without draining the system (Correct answer)
- A pot used to store spare inhibitor chemicals
- A pressurised vessel for antifreeze storage
- An expansion vessel for the inhibitor circuit
Correct answer: A small vessel fitted inline in the system pipework that allows chemicals to be easily introduced without draining the system
A dosing pot (or chemical pot) is a small inline vessel with isolation valves and a removable cap; it allows inhibitor, cleaner or antifreeze to be introduced into the system quickly without significant water loss.
Question 6: What should be done with the old system water after a power flush?
- It must be disposed of responsibly — it may not be discharged to surface water drains and must go to foul drainage or an appropriate disposal route (Correct answer)
- It can be discharged to the garden as plant fertiliser
- It can be discharged to any drain
- It can be recycled back into the system
Correct answer: It must be disposed of responsibly — it may not be discharged to surface water drains and must go to foul drainage or an appropriate disposal route
Power flush water contains heavy metals, biocides and corrosion products and must be discharged to the foul sewer (not surface water drain), following local sewerage provider guidance on acceptable limits.
CENWAT Inhibitor & Water Treatment 3
What is a magnetic system filter and how does it work?