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CylindersThis is a indirect combination cylinder which has the header tank built in on the top of an indirect cylinder, it is has foam lagging for insulation

Most modern cylinders come with foam lagging bonded on to the outside of the cylinder. This is an extremely efficient insulator and will keep the water hot for a long time. There are a lot of different shapes and sizes to suit the space available, but the capacity of the cylinder is important.

There are lots of different types of cylinder available, all of which basically store and supply hot water, but in different ways.

The 5 main types of cylinder are: -


Direct which are only for use with Circulators and immersion heaters because the water is heated directly.


An indirect cylinder showing the indirect coil of copper pipe inside which conducts the heat from the C/H system in to the hot water cylinder

Indirect  which are for use with any type of central heating system. This is because the water from the central heating goes through a coil of pipe within the cylinder (giving its heat up to the water in the cylinder) but doesn't mix with the water in the cylinder. This type of cylinder usually has an air bleed on a pipe at the side, often the pump and motorised valves are located in the same cupboard


Primatic (self priming) only for use with gravity systems because the water for the central heating is taken from within the cylinder, and is only separated by an air lock (system additives must not be used with this type of cylinder as this will come out through the hot taps)


Thermal Storage a large type of cylinder were the main cold water is passed through a coil of pipe within the cylinder taking its heat from the thermal storage and supplying the hot taps. The central heating circuit is also taken from the cylinder. these are ideal for working in conjunction with solar panels as the heat generated from the sun can be use for both hot water & heating




Unvented Cylinder    an Early Unvented cylinder which shows the red expansion vessel, the pressure reducing valve on the left and the back up electrical immersion heater at the bottom lefta modern unvented cylinder with all the pipes entering from the top under a plastic cover, above is the system boiler that feed the CH system and this unvented cylinder

     An unvented cylinder is the same as an indirect cylinder except there isn't a header tank which is at a relatively low water pressure, and its connected directly to the main water supply giving mains (high) water pressure to the hot taps and showers 

This is probably the future standard because of the reliability and true mains water pressure and when fitted with a low water content boiler are very cheap to run 

These come in various sizes and are ideal for the lager home  Diagram so these can fed hot water to more that one bathroom and more than one shower, these too can be used in conjunction with solar panels





There is a large choice of radiator styles like Ladder radiators, Hospital radiators, Towel warmers, Kick space radiators, Skirting heaters and Fan assisted radiators. It doesn't matter which type you choose providing the heat output of the radiator(s) meets the needs of the room.

BeforeLadder type Towel Rail that is secured to the floor & wall with the pipe connection on the inside of the bottom legs choosing your radiators you must determine how much heat each room requires. This is done by using one of the radiator manufacturer’s heat loss calculations (usually your installer will do this when quoting). The best calculations take every measurement of every room and especially the window sizes and outside wall sizes.  They can work on a specific temperature required and even take in to consideration the type of materials used in the building (to calculate “U” values) to get an accurate radiator size. Too big and the system will overshoot its temperature and be less economical to run, too small and it won't reach its desired temperature. (Some of the poorer installers get round this complex step by putting in radiators that are to big, and then fitting thermostatic radiator valves to every radiator to cut the heat down.) This calculation produces a Heat loss figure in watts, of how much heat you need to warm that room up to the design temperature from -3 deg C in one hour,

Choosing & Positioning

The best place for every radiator is in the coldest part of the room, which is usually under a window. (I recommend this) With the heat loss figure consult a radiator size chart (available at the suppliers) and consider the wall space available.

Most manufacturers supply several types of radiator, like a single panel radiator, or a single panel radiator with convector (an extra fin on the back), or a double panel radiator, or a double panel radiator with convector. When looking on the size charts there will be several radiators giving a similar heat output, but the ideal one is a single panel with a convector as long as possible, but as low as possible. If the length is too long for the space, then one smaller in length but higher should be chosen. Only choose a double panel radiator if the wall space available is really small, if there still isn't enough room then it is possible to get a fanned convector radiator. These have a fan unit that blows warm air out, a small version of this is designed to fit in the kick space of kitchen units.

Radiators do not burn gas, therefore turning radiators off will not save money. In fact it will probably put your fuel cost up as this creates cold drafts in the house because cold air is heavy and hot air is light. If an upstairs room is not heated then the cold air will fall down the stairs and in to the warmest room. (Cold Feet) In an unused room do not set the TRV (if fitted) below 1.

How to Bleed Radiators

1. Make sure that the CH (Central Heating) is in the off position

2. Place your bleed key on the bleed nipple (this will be at the top, at one side only and could even be at the back, but usually is at one end)

3. Turn the bleed key 1/2 a turn anti clockwise to open (you should here the air hissing)

4. When water starts to dribble out turn the key 1/2 a turn clockwise to shut it off (Do Not Over Tighten)

If you have a sealed system then the pressure will probably need topping up to 1 bar (If there isn't a gauge on or near the boiler then this instruction will not apply)


  Faulty Radiators

If a central heating system has been fitted correctly, flushed out, inhibitor added at the time of installation and topped up if the system has been drained down, then the radiators should never go faulty. A radiator has no working parts, but it is made of steel and so can be damaged (rusted) by the corrosive effects of untreated water within it.

If you have got damage to the radiators, then often the first sign is when a radiator leaks. Cold spots or constantly having to bleed the radiators. If you’ve bled the radiators and the water is black then you have a slight problem, but if the water is brown or orange then you have a major problem. This needs sorting out properly before you get to the stage where a different radiator starts leaking every few months

The Main Causes of Radiator problems are: -

·        TRV sticking, this is usually when left at the off position all summer

·        The system’s cold feed and expansion are not configured correctly (Open systems only)

·        The system had not been properly flushed out when new

·        No corrosion inhibitor has been added to system



·        Leave all TRV's on Max all summer and turn the heating off at the clock

·        Firstly, make sure that the system has been installed correctly, or correct if necessary

·        Secondly, add a cleaning agent to the system

·        Thirdly, flush out the system several times with clean water

·        Finally add a good quality system inhibitor

·        Or you can have the system “Power Flushed” which is the same as above, except a powerful pump is used to force in the clean water and flush out the dirty water.

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