What is a Delta Heat Output?

What is a Delta Heat Output?

With a variety of heating systems and radiators out there, it's important that you purchase the right product for your home. This quick guide explains what a Delta heat output is and which Delta may apply to your home, so that you can make sure you are purchasing the correct size/type of radiator for each room in your home.

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Delta heat output values represent the heat output of each radiator under different operating conditions, or boiler temperatures as they are otherwise known.

Radiators are made from metal and heated by the hot water from your boiler. So, as you would expect, the hotter the water from the boiler, the higher the heat output from the radiator, and vice versa. This is why a single radiator will have multiple delta ratings - so that you can see the heat output of that radiator when the boiler temperature is different. 

The higher the delta number, the higher the boiler temperature. While these big heat output values look impressive when shopping, having a higher boiler temperature is not a good thing! It will cost you more to run, damage the environment and shorten the life of your boiler. 

Modern boilers and Heat Pumps run at lower temperatures by design, which means they are cheaper to run and have less impact on the environment, but you will require slightly bigger radiators to produce the heat required for your room. 

So, in order to buy a radiator that will actually heat your room, you need to make sure that your looking at the heat output value that represents your boiler temperature.

We currently provide 3 delta ratings (Δ30/Δ40/Δ50) for all of our central heating/gas and dual fuel radiators. The delta rating you need to look at when purchasing our radiators depends on the type and age of boiler you have.

The below will help you to know which delta you should be browsing by:

• Delta 50 = Non-Condensing Boilers installed before April 2005 with a standard configuration, with a flow temperature of around 75-85 degrees.
• Delta 40 = Condensing boiler operating in condensing mode, making it efficient. Any Gas boiler installed after 2005 is a condensing boiler.
• Delta 30 = (Recommended) Low temperature systems such as heat pumps, with a flow temperature of around 55 degrees (you should have this).

If you are unsure of what you have, and to future proof your purchase, buy your radiator based on the Delta 30 heat output. You can then manage the room temperature using Thermostatic Radiator Valves in rooms that are not the reference room (the one with the main boiler thermostat), which will stop the room and radiator from producing too much heat on a higher boiler temperature, but should allow your radiator purchase to be used on newer lower temperature systems when replacing in the future.

How do I compare Heat Outputs with different suppliers?

As part of BS EN 442 and the Construction Products Regulations (law), all radiator suppliers must show the Delta 30 and the Delta 50 heat outputs on their products and catalogues (including website catalogues).

These are the values that should be compared between different suppliers and websites to see what heat output you will get for your boiler type & age.

If you go to purchase a radiator from a supplier where these two values are not visibly clear and marked as Delta 30 (Δ30) and Delta 50 (Δ50), then those radiator listings do not comply with BS EN 442, and you should not purchase the radiator from that website/supplier.

Simple steps to purchase a radiator:

Smart Way  

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Manual Way

1. You need to know the heat requirements of the room in BTU or Watts.
2. Purchase a radiator where the Delta 30 heat output value is higher than the heat requirement of the room to ensure it will work suitably on your current system and future systems.
3. If the radiator is going in a room where the main boiler thermostat* is not present, purchase a Thermostatic Radiator Valve.

*Little box on the wall to control the temperature, this will only be in one room of your house.

Now that you know these simple steps you can start browsing our full range of radiators and heated towel rails.