How do I convert BTUs to Watts

* Divide by 3.412 

How do I convert Watts to BTUs

* Multipy by 3.412 

What is a BTU

*A British Thermal Unit (BTU) is the amount of heat energy needed to raise the temperature of one pound of water by one degree F. This is the standard measurement used to state the amount of energy that a fuel has as well as the amount of output of any heat generating device.  


Some outputs listed are calculated in line with the European BSEN442 Testing Standard at ∆t50� (the latest standards for modern boiler systems). Sometime they may be listed outputs at ∆t60� to allow for the older boiler systems. To convert Δt50� to Δt60� simply multiply x 1.264. 

If you use a BTU calculator, make sure you know if it is calculating at Delta 50 or 60.  This also applies if your heating engineer has quoted you a BTU figure - ask him if it is calculated at Delta 50 or Delta 60.

If our boiler is a modern boiler and you cannot control the temperature of hot water for the central heating, we recommend you use the Delta 50 figure.  If you are unsure it is better to use the Delta 50 figure.

What is Delta 50.

Delta 50 (75/65/20) - with Delta T of 50C, means 75C inlet water temperature, 65C outlet water temperature and 20C of room temperature.

The mean average water temperature is 70C (i.e. 75 plus 65 divide by 2).  If we then take the 20C room temperature we are left with a temperature differential of 50C or Delta T of 50.


What is Delta 60.

Delta 60 (90/70/20) - with Delta T of 60C, means 90C inlet water temperature, 70C outlet water temperature and 20C of room temperature.

The mean average water temperature is 80C (i.e. 90 plus 70 divide by 2).  If we then take the 20C room temperature we are left with a temperature differential of 60C or Delta T of 60.  

Delta T 50 to Delta T 30 = .515

Delta T 60 to Delta T 30 = .424


  • Installation

  • Who will install my radiators?
    Radiators can be installed by any competent plumber / installer (electrician for electric models) who is preferably Gas Safe registered.
  • What should I use to secure the radiator to the wall?
    Radiators are heavy items and should be securely fastened to the wall. Specific care should be taken to identify the construction of the wall and use the appropriate fasteners to secure the radiator bracket. 
  • How do I fit valves?
    Wrap at least five turns of PTFE tape around the threaded tails of the valves and screw them into the radiator. Make sure the PTFE tape stays on the thread rather than just running along it as you tighten. If it does run, undo the valve and roughen the thread slightly with a hacksaw blade then re-tape the thread. Some of our valves have parallel threads which means that they never tighten against a stop like traditional valves so more PTFE than usual is required we recommend the use of gas type PTFE which is much thicker than the standard. The advantage of parallel threads is that they fit the same depth on all radiators so giving pipe centres is more accurate and also the threads are completely hidden inside the end of the radiator.
  • Should I prepare my pipe work before my radiators arrive?
    We endeavour to ensure all pipe centres are correct, however manufacturing tolerances must be considered; therefore we strongly recommend that pipe work is not altered or adjusted until your new radiator or towel rail is delivered. We will not accept any responsibility for claims resulting from incorrect pipe centres.
  • Can I use microbore pipework?
    Yes, but on really big cast iron radiators (over 3500 watts) it can prove problematic on balancing the central heating system. If in doubt, ask your plumber / installer.
  • Can I remove and refit my radiators for decoration purposes?
    This can be easily achieved on most traditional open vented systems, however it can be more complex for sealed systems. An open vented system has a feed and expansion tank, with a ball valve and overflow located at high level in the property. A sealed system should have a pressure gauge located in or near the boiler. For open vented systems switch the heating system totally off and allow it to cool. Close the radiator valves at each side of the radiator, making a note of how many turns each valve is open. Place a receptacle under one radiator connection (not the valve to pipe connection) and loosen it until water slowly drains. Some radiator valves have an integral drain point that makes this task easier. Once the water has drained from the radiator, loosen the other radiator connection and remove it. To refit, replace the radiator, re-attach the radiator valves and open the valves to their previous settings. The air vent at the top of the radiator will need to be opened until the radiator is full of water.
  • Valves
  • What is the difference between a TRV (Thermostatic Radiator Valve) and a manual valve?
    The TRV controls the radiators temperature by sensing the room air temperature and automatically opening and closing the flow to the radiator to maintain a preset temperature. A manual valve controls the temperature of the radiator regardless of how warm the room already is. TRVs are now a requirement as part of Building regulations, check with your installer to make sure you have the correct valves.
  • Valves are sold in pairs, what is the other valve for?
    The wheelhead valve is the temperature control; the other is called a lockshield valve and is used to balance the radiators in the system so that they all heat up at roughly the same rate. Simply put, the radiator closest to the boiler if left unchecked would heat quicker than the one sited at the other end of the house, so the lockshield valves should be set opened at increasing amounts the further away from the boiler the radiator is.
  • Should I install my valves on the flow or return pipe?
    Even though some of our valves are bi-directional, we recommend they are fitted on the flow pipe rather than the return pipe in order to avoid noises that may naturally occur if they are fitted on the return. 
  • Control valve

A valve that is installed on the 'flow' side of the radiator, to control the flow of water coming from the boiler.

a) Manual – a valve which is turned on and off by hand

b) Thermostatic – a thermostatic radiator valve (or TRV) is used to control the heat output from a radiator by controlling the water flow into it with a self-activating air temperature sensor. TRVs provide individual room control and shut off the radiator when there are other sources of heat such as the sun, people and electrical appliances.

  • Lockshield valve

A valve that is installed on the 'return' side of the radiator to control the flow of water returning to the boiler and to 'balance' the heating system.

If all the valves in a system are fully open, the temperature of the radiators will vary throughout the system as the hot water will tend to follow the path of least resistance and flow through the radiators closest to the boiler. The radiators farthest from the boiler will not reach the same temperature. Your plumber should 'balance' your system after installing new radiators.

  • Air vent (or bleed valve)

This is a small valve which enables air that has accumulated at the top of a radiator to be let out or 'bled' from the radiator using a special air vent key.


  • Radiator Positioning

  • Where should I position my radiators?
    In modern homes, radiator positioning is less important however please feel free to ask for advice. In traditional homes, most radiators are best placed in the coldest part of the room - usually found under a window. Large spaces are more effectively heated with 2 or more, smaller radiators rather than one large one. A rule of the thumb often used in the trade is to have one radiator every four metres (about 15 feet) or so in the room. An alternative could be two tall thin radiators either side of the window or a long low radiator along the wall.
  • Should I choose horizontal or vertical?  Many of our designs are available in horizontal or vertical options, which means you can maximize the use of ceiling heights and long low spaces without losing heat output.
  • What clearances do I need above and below my radiator to ensure maximum efficiency?
    We recommend that clearances of 50mm above and 100mm below should be left clear so heat from the radiator can be effectively distributed.
  • What is the difference between Cast Iron, Steel and Aluminium radiators?
    Traditional cast iron radiators have been the staple material in period homes and schools since the Victorian age. Their dense heavy structure takes time to reach optimal temperature but remains hot long after the central heating is turned off - perfect for cold drafty period homes.
    For more control and a range of traditional and modern designs, steel radiators may be the better choice. Comprised from a lighter less dense material, steel radiators will heat up and cool down quickly providing manageable control. 
    Aluminum is a highly efficient conductive material that will heat up instantly after the central heating is turned on, giving you total control over your central heating system.
  • Technical Information

  • What is the difference between indirect and direct system?
    An indirect system is filled with water that remains in the system and is circulated through the boiler and radiators. A direct system uses mains water that is continually replaced within the system -this causes an influx of oxygen and bacteria in the water, meaning Stainless Steel or Brass radiators should be used to avoid rusting of the radiators or contamination of the water supply.
  • I want to install aluminium radiators, is there anything I need to know?
    Aluminium radiators are installed in exactly the same way as steel or cast iron ones, as with all central heating systems a suitable quality and quantity of inhibitor must be used to avoid corrosion. Mixed metal inhibitors are now easily available from most plumbers merchants. Your installer will know all about this.
  • Are the cast iron radiators compatible with my system?
    All of our Cast Iron radiators are compatible with normal central heating systems and have British Standard fittings. On an existing system you can replace all the radiators or just the ones you want. Confirm with your installer that your pipe work and system set up is suitable for additional radiators.
  • Do cast iron radiators take longer to warm up than standard radiators?
    Yes, however, because there is a lot of mass with cast iron, the radiators have the advantage of staying warm long after the central heating has been turned off. This means that the changes in temperature in a room heated with radiators made of cast iron are gentler than those in a room heated with regular radiators. Most people tend to run their central heating twice per day, once in the morning and then again at night, if a third short period is added into the middle of these two times then the warm up time is greatly reduced and the house will remain warm all day and night. When mixing standard radiators with cast iron we find that if the central heating thermostat is sited near a standard radiator the heating may close down before the cast iron radiators sited elsewhere have reached full temperature. The solution is to slow down the standard radiator influencing the thermostat by part closing the lockshield valve on that radiator (the usually covered end valve opposite the temperature control valve on the radiator used to balance the central heating system). Heating a home is partly about heating the fabric of the building. Cast iron radiators are again becoming popular amongst heating engineers and architects (particularly for older buildings) as they tend to retain the warmth in the fabric of the building which in turn counteracts damp and condensation


  • Do my radiators need venting?
    Pockets of oxygen naturally build up in central heating systems due to the amount of fresh water running through it - this in turn causes radiators to become less efficient. Radiators require venting to alleviate the built up of air, which in most cases is a manual process. 
    If you already own a radiator that is cold at the top and hot at the bottom, it is likely that your radiator needs venting (bleeding). Venting is best carried out when the system is cold - simply turn off the heating system and slightly open the air vent (some radiators will require a radiator vent key, others may need a small screwdriver) until water is noted at the air vent. Take care to protect decorated surfaces with a cloth prior to opening the air vent. Gently close the vent and switch the system back on. If the radiators need venting frequently, there may be a fault with the system and a heating engineer should be called. 
  • Why are my radiators hot at the top and cold at the bottom?
    This indicates that the radiator may be receiving an insufficient flow of water; typically large radiators need a higher water flow than small radiators. There may be several reasons for this, such as incorrect balancing, incorrect pipe size or an under-performing or under-sized pump; there may also simply be a blockage in the radiator. A heating engineer should be called to carry out further investigations.
  • Open vented system

A central heating system with a separate feed and expansion tank that accommodates the expansion of the central heating water volume as its temperature rises. This tank is located at the highest point of the system, usually in the loft space.

  • Sealed system

A central heating system that incorporates an expansion vessel which replaces the separate feed and expansion tank. Systems of this type remove the need to install pipework in the loft space.

  • Combination or 'Combi' boiler

A boiler that provides both heating and domestic hot water from one unit. It produces domestic hot water instantaneously on demand, eliminating the need for roof tanks or a hot water cylinder to store domestic hot water.

  • Condensing boiler

A more efficient, modern boiler incorporating an extra heat exchanger which extracts most of the heat from the exhaust gases. This heat is used in the heating process rather than being vented outside and wasted.

  • Flushing and chemical cleaning

On installation of a new system and after installing a new radiator, the entire system should be flushed and chemically cleansed. A chemical inhibitor such as that supplied by Fernox must be added to the water in the system by your plumber in order to minimise possible corrosion in the radiators and pipework. Failure to observe this will invalidate the warranty.

  • IP rating details

  • Zone details

Mainland UK (Definition - Courier purposes)

UK mainland courier services do not include parcel delivery to places that are not on the main island, like the Isle of Man and the Isle of Wight. This also means the Channel Islands: Geurnsey and Jersey.

Guernsey postcards are GY; Jersey is JE.

PO is the Isle of Wight, and IM and TR the Isle of Man.

The restriction includes Northern Ireland, which is separate from the UK mainland. Postcodes there are BT.

Please also call before ordering if you live in the Scottish Highlands as additional costs will apply.

These postcodes are KW, IV,  FK, AB, DD, PH, PA and ZE.

Our website may show FREE delivery to mainland UK - this refers to the above definition.  Please also refer to the actual product - this will show exceptions which may differ from the above.  Eg The Agia radiator includes delivery to Mainland England & Wales.  However a delivery charge will apply to ALL Scottish postcodes.