Adding a radiator to your Aga hot water circuit
22 February 2011
Many people find that their Aga, Rayburn or heat storage cooker can generate too much hot water. Often the water in the hot water cylinder boils and consequently the water coming out of the taps is far too hot. When this happens, you may need to find a way to “lose” heat from the hot water circuit and the most effective way of doing this is to install a radiator to act as a “heat sink”. This article tells you how to install a radiator on an Aga hot water circuit
Many people find that their Aga, Rayburn or heat storage cooker can generate too much hot water. Often the water in the hot water cylinder boils and consequently the water coming out of the taps is far too hot. When this happens, you may need to find a way to “lose” heat from the hot water circuit and the most effective way of doing this is to install a radiator to act as a “heat sink”. The information below tells you how to install a radiator on an Aga hot water circuit. The key is to maximise the flow of water through the system wherever possible. Hot water circuits on Agas are gravity fed. In other words, they rely solely on natural convection to circulate the hot water, without the need for a pump. For this reason, it is important to maximise the flow of water both in and out of the radiator. This is done through both the design of the system and choosing a suitable design of radiator. There are many different ways in which you can maximise the flow of water around the circuit. 1. Maximize the vertical length of flow pipe from the Aga to the radiator Your radiator should be piped from a joint that is sited as close as possible to the Aga. This maximises the “thermal lift” effect which results in a stronger water flow to the radiator. 2. Minimise the horizontal distance the water needs to travel The ideal position for the radiator would be directly above the Aga, so choose a spot that is as close to this as possible. 3. Minimise the number of restrictions in the water’s flow Minimising the number of angled joints between the flow and return will help the flow of water. If you need the pipe to turn, then opt for pipes that have been curved using pipe benders instead of angled joints so any “corners” are not as angular. 4. Maximise the size of the bore on the pipe and valves Always use the maximum diameter or “bore” of pipe to and from the radiator. Your hot water circuit up to the hot water tank and back down to the Aga is normally fed by 28mm pipe and, where possible, try to continue the 28mm pipe. Valves are usually put on a radiator as standard to control the flow of water, but if a direct connection to the radiator without valves can be achieved, then this is preferable. However, where valves are to be used it’s always better (but not mandatory) to use full-bore lever arm ball valves. Regular radiator valves usually have a much smaller diameter bore, sometimes as small as 5mm. Also radiators that have ¾ inch connections are better than radiators that have ½ inch connections. 5. Maximise the radiator output The radiator should be connected with the flow at the top of the radiator and return at the bottom of the radiator, at the opposite side. This will ensure that the whole radiator becomes hot and that there are no cold areas, which could occur if you pipe the flow in at the bottom. 6. Maximise the size of the radiator’s interconnecting tubes The best radiators to use on Aga hot water circuits are those with interconnecting tubes that have a large diameter. Examples include “tube in tube” style towel radiators and tubular steel column radiators such as our Bordo. The Bordo is a fantastic option in this type of situation, as it is classically styled to suit many interiors, it comes in a variety of finishes including textured and traditional options, it comes in many sizes including both vertical and horizontal models and it can be fitted with a towel hanging rail. The Bordo can also be fitted with ¾ inch connections. Many radiators have interconnecting waterways that are small, such as “tube on tube” style towel rails or panel radiators. This means they are not ideal for use in this type of application. 7. Minimise the amount of air in the system A certain amount of air may build up in radiators over time so utilising an automatic bleed vent will ensure the radiator is kept free from air building up and maximise the water flowing through the radiator. For more information on this topic or any other radiator related subjects, then speak to an expert such as Feature Radiators. You can contact them on 01274 567789, via their website www.featureradiators.co.uk, or visit them at their showroom in West Yorkshire.
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