How do cast iron radiators work?

Modern bathroom with pair of cast iron radiators beneath windowscredit

***Article supplied by AEL Heating Limited***

If you’re considering installing cast iron radiators in your home, and deliberating the pros and cons of old and new systems, then you may be interested to get the low down on how cast iron radiators work.

If they’re installed and functioning properly, cast iron radiators can be incredibly effective for heating areas, even large rooms. The downside is that they can be bigger in size than their modern radiator counterparts, so you should always bear this in mind. However, that doesn’t negate from the fact that they’re stylish, efficient and affordable too.

Industrial loft apartment with wall of under-window radiatorscredit

The power of steam

Having been around since the mid-1800s, cast iron radiators have played a vital role in heating homes and businesses throughout the world and come in a variety of different styles and designs. But despite their shape, size or style, the principles behind the way they work are the same – steam power.

By converting water into steam, cast iron radiators will then transfer this heat into the atmosphere through radiation and convection. Although, despite the name ‘radiator’, more of the heat is transferred through convection – where warm air rises and cold air sinks – than through radiation.

The steam system requires a hot water boiler that will be the heart of your heating system; continuously heating the water to convert it into steam. The water boiler uses a heating element inside that brings the water to boiling point to generate steam. This steam is then forced up through the pipes into the radiators by sheer pressure, to transmit heat without the need of a pump.

As the steam passes through the radiators and pipes, it will naturally cool down and turn back into water condensation. But this is all put to good use, as the condensation from the cooled steam travels back down to the water boiler, where it is reheated to create more steam to recirculate through the pipes and radiators.

Small cast iron radiator under circular windowcredit

The technical side

Of course, the steam process sounds relatively simple, particularly when you consider the modern day radiator designs, with their water filled radiators that heat the water, and use a pump to circulate it through the system. However, underneath the exterior of these sturdy cast iron radiators are a series of individual sections that are connected by valves and seals that allow the steam to pass into the radiators, pressurise to retain the heat so it can be emitted into the air in the room, and then allow the cooled condensation to flow back down to the central water boiler.

These valves play a vital role in ensuring the cast iron radiator heating system functions efficiently, as small holes in the seals, or cracks in the metalwork can cause leaks and loss of pressure. This results in steam will escaping into the atmosphere, rather than heating the system.

Detail of gold coloured cast iron radiatorcredit

The reality of cast iron radiators

Having been used in homes and businesses for well over 150 years, there is a lot to be said for the effectiveness and efficiency of using cast iron radiators to heat areas. Although, you should be aware that these steam systems takes longer to heat than a more modern water baseboard system as they need to reach boiling point to create steam, rather than just reaching an optimal water temperature. Thus they may consume more energy in the water heating process, but that being said, the amount of heat that is passed through convection into the atmosphere is often much greater and lasts much longer too.

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