Moffat Heating & Plumbing
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Tackling cold or luke warm radiators on Oil-fired heating systems

The first thing to determine is where the radiator is cold. This will help to identify where the problem is…

Radiator cold at the top

The top being cold indicates that air has been trapped in the radiator. This can be remedied by bleeding the radiator. (See my other home help). Note, air in the system can be a symptom of an underlying problem which may need to be addressed.

Radiator cold at the bottom

If the radiator is cold at the bottom, then the likely cause is ‘sludge’. This would require the radiator and more than likely the heating system to be cleaned. This can be done chemically and/or manually. A cleanser is added to the system for between 2 hours and 2 weeks and the system rinsed through. Occasionally, the radiator may need to be taken off and flushed through manually with mains pressure water.

If the sludge build up is particularly bad, then the heating system will need to be ‘power-flushed’. Note, whenever water is drained from the heating system, it will need a suitable amount of system inhibitor added to ‘top up’.

Radiator completely cold

If the radiator is completely cold, then then the valves may be turned off or stuck or you may have an air lock somewhere in the system. This may warrant inspection by a qualified professional.