Choosing A Radiator Is A Simple Process. Right?

When purchasing a radiator, it’s important to get the most heat from the most economical model available within your budget. However, it’s also important the style suits your décor. So, whether you want a traditional style, a cast-iron style or something contemporary, how do you differentiate the performance of one radiator from another? This is where delta rings come into play. 

Please Be Aware! Confusion Around T50/ T60/ T70s

A Delta rating of T50 when measuring the BTU output of radiators is UK/EU standard; all of our manufacturers are based upon this reading apart from Reina. Meaning most gas safe engineers and plumbers in the UK would normally read radiators at T50

In the UK and EU, most radiators are manufactured and measured at a Delta T50 rating. However, Reina products get measured at a delta rating of T70.

If you measure up at T50 when a radiator is a T70 then your readings will be wrong and your rooms will be under heated. Please see the example below.

Delta Ratings Explained

What Is A Delta Rating?

Delta (Δ) is the fourth letter of the Greek alphabet.

Anyone who has taken studious notes may recall using the "Δ" symbol to denote the word "change" and doctors use it to indicate an alteration to treatment.

Historians credit the ancient Greeks with inventing central heating. Temples were even heated by underground flues with heat circulated from a fire. In maths, Delta refers to “a change in figure or amount”.

So, add together those clever cozy warm Grecians, a measurement of the rate of temperature change and it equals Delta T or Δt. Delta T is simply the difference between the heat circulating in the radiator and the desired temperature of the room.

How A Delta Rating Is Calculated

Different radiators produce different outputs from different temperatures flowing into them. So, basic maths time. Delta T = (Room temperature) - (Average radiator water temperature).

What is average radiator water temperature? Well, if you have an input of 80 degrees and an output of 60 degrees, then this means that the average radiator water temperature would be 70 degrees. Still with us?

Slightly more complex maths time. When you look at a radiator’s specifications, you’ll find the heat output figure quoted is the unit’s Delta T at a specific room temperature. The standard room temperature desired is usually quoted as 20 degrees C. 

So, if the average water temperature across the radiator is 70 degrees C, the Delta T is 50 degrees C. A radiator’s power output is most often expressed in watts. 

The wattage of a radiator is based on the system’s likely operating temperature. That output will usually either be expressed as a measurement taken either at Delta 60 (Δ T60) or Delta 50 (Δ T50). Delta 50 is now the UK standard for all domestic gas boiler systems. Prior to 2013, the UK used Delta 60 until it opted to come into line with the rest of Europe.

Under BS EN 442, to calculate a Delta rating, radiators must be tested with a flow water temperature of 75°C and a return temperature of 65°C in a test room with a consistent air temperature of 20°C. In addition, the flow and return connections should be connected at the same end, normally referred to as ‘top bottom same end’. Add in another acronym - the BTU The BTU (British Thermal Unit) calculation is an important figure to determine the right size of a radiator for a room.

 A higher BTU rating indicates that more power will be required for the radiator to reach its heating potential. BTU is an imperial unit of energy. It is simply the amount of energy required to heat or cool one pound of water by 1 Fahrenheit. 

The higher the BTU rating, the more power is required for the radiator to reach its potential. The BTU system was first used by industry in the 19th century and originally applied to steam-powered engines, locomotives and ships. It was later used by engineers to relate to domestic heating systems. It’s easy to calculate the BTU that you will require for any room using our BTU calculator



Which Delta Rating Should I Look For?

It is very important to understand your heating system and know what it requires.

If you purchase and install radiators using Delta T60 output figures, you will find they lack power on a Delta T50 system. This could be a costly mistake that requires the replacement of the radiators or you’ll be left with an underheated house. This will cost you more to keep it warm.

Plumbing systems powered by modern condensing boilers typically operate at Delta 50. This will be the normal specification assumed for most radiator buyers. However, Newer and more efficient heating systems may use radiators with a lower-level output. Delta 30 and Delta 40 work well for lower water temperature systems.

These options are best for well-insulated modern properties built with eco-friendly heating in mind. Without sufficient insulation and other energy-saving features built-in, most properties will not be sufficiently heated by a Delta 30 or 40 system. Delta 70 radiators are available, such as the Reina range, which offers high output levels.

How Delta Ratings & BTU Link

Delta and BTU ratings are different units measuring different things. If you’re buying a radiator, always check the BTU rating. You will want to make sure it’s accurate.

This depends on the Delta rating at which it was calculated. If you are checking BTUs on different radiators, you need to know or specify whether the figure is calculated at Delta 50 or 60.

You might also find heating engineers who continue to quote figures based on Delta 60 rather than Delta 50. It’s best to check with them which one they’re using.

You can easily convert between Delta 50, 60 and 70, for example: If a radiator has a heat output of 5000 BTU at ΔT=60, to find the heat output at ΔT=50, you simply multiply the BTU by 0.789. If you have a radiator with a heat output of 5000 BTU at ΔT=60, to find the heat output at ΔT=70, you multiply the BTU by 1.223. If you have a radiator with a heat output of 5000 BTU at ΔT=50, to find the heat output at ΔT=60, you need to multiply the BTU by 1.264

Still Stumped By Delta Ratings

If maths and plumbing make your head bubble, then check out our Advice Centre for easily understood guides. Check out our free BTU calculator to accurately work out the heat output required to heat your home

Or, simply contact us for expert advice.

Here at Just Radiators, we have a huge range of radiators on sale. With beautiful stock options from anthracite, white, and black. Made from premium materials such as aluminium or mild steel. Make sure you visit our radiator sale, it's not to be missed. If you're looking for a greener option, check out our huge range of electric radiators.