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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. Struggling with all the Jargon? Try our RadSizer® App which will take care of all of this for you!

RadSizer® App
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 (like those retailers showing Delta 70 values), 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 you're looking at the heat output value that represents your boiler temperature. We currently provide 2 delta ratings (Δ30/Δ50), in line with BS EN 442, 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 heating system you have:
  • Delta 50 = Gas or oil boiler with a flow temperature of around 75°C and a return temperature of around 65°C.
  • Delta 30 = Low temperature systems e.g heat pumps.

    Column Radiator

    If you currently have a gas or oil boiler but are likely to change to a low temperature system in the future, you can buy your radiators based on the Delta 30 heat output, this should mean that you dont need to buy new radiators when you change the system as they will be big enough to heat the rooms with the lower water temperature. While still using the gas or oil boiler, you can use Thermostatic Radiator Valves to control the temperature of the radiators and stop your rooms from getting too hot.

    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. 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  

    Try our RadSizer® App which will take care of all of this for you! RadSizer® App Manual Way
    1. You need to know the heat requirements of the room in BTU or Watts. Your heating engineer can tell you this, or you can use RadSizer® to work it out.

    2. Find a radiator with a heat output that matches (preferably exceeds) the rooms heat requirements at the right Delta:

      • Gas or oil boiler - Delta 50 (Δ50)

      • Low temperature system - Delta 30 (Δ30)

    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.

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