What are the benefits of having a combination boiler?

The Combination Boiler. Was a unit designed to save the cost’s on installation. The Combination Boiler has now upgraded to a Condensing Boiler. The Condensing Boiler is still a Combi. But better. As the need for a hot water cylinder is not a requirement. Neither is the header tank. Associated with the old fashioned back boiler. It works direct from the Water Mains. The combination boiler is small and compact.  This only heats the domestic hot water. As you need it. It also serves your Central Heating System. Some other advantages in fitting a combination boiler are listed below.

  • Saves you money on the running costs. (As you are not heating Water you do not use).
  • Saves Space. (Good for loft conversions and no longer requiring airing cupboards).
  • Saves on time. (Great for if you are in a rush for work.
  • Installation costs. (Save paying our for a Hot Water Cylinder and Hot Water Tank).

The dis-advantages of having a Combi Boiler is:

  • Boiler going faulty and no back up of Hot Water Storage.
  • Unable to have a Power Shower Installed.
Combination Boiler Panel & Timer

Combination Boiler Panel & Timer

Why should I choose a combination boiler. As apposed to a traditional back boiler?

The building concept has changed. From the early 1960’s Designers. The Government. Manufactures and the general public.  Have become more environmentally friendly. Some do it but do not realise that they are doing it. May I say firstly the Government helped. By getting the ball rolling. Thus by introducing the Smoke Control Areas. This saw a massive change towards gas fires. Many were fitted with a back boiler. This  basically was swapping what was there. For a modern equivalent. But fuelled by gas. Things progressed and for the better. As more modern trends evolved. The introduction of guidelines and regulations. Within the construction of the structure. Meant materials being used had to meet standards. These where a great deal higher.The Designers not only now have to take into consideration. The materials to be used for example. They must prove that the timber comes from known resources, graded and stamped. The modern building must be insulated to a minimum standard. The building must be serviceable, ie; you must be able to maintain the property. This brings into play the combination boiler or more commonly known as the Combi Boiler. As we have said earlier the combination boiler. Dose not require a Hot Water Storage Cylinder or Hot Water Header Tank. Saving you money on a new installation. But it gives you pound for pound more value. As apposed to the conventional gas fire and back boiler. The gas fire only heats the room it is in. The back boiler keeps a cylinder of hot water hot. The cylinder must be kept hot. In order to service your domestic hot water & central heating needs. The Combi boiler however only fires up when you want hot water or Central Heating.

When considering whether or not to install a combination boiler, the question’s one needs to ask yourself are:-

  1. Is the building Modern & Energy Efficient? as the demands on the boiler would be less.
  2. There is a limit both to the volume of water and the speed in which it can heat the water. A combination boiler in a domestic property can cope with the demand,example: Someone running a bath and another person say opening the hot or cold tap in the kitchen. Providing the cold water is adequate in the first place. Then there will be little to no effect on the performance of the Combi Boiler. However this would not be so in a Hotel as the demands for numerous outlets (taps) to be opened or the  boiler would be unable to cope. Even the cold water may be supplied from a storage tank. This also helps in order to cope with the demands. Please look up Circulating Pumps for Hotels.
  3. Do you have an adequate water supply? You need to have a good constant water supply. The incoming mains must be able to cope with several taps being turned on at the same time. As this will effect the performance of the combination boiler and safety.

What are the different types of Combination Boilers?

In the current market there are many variations, makes and models of combination boilers. They all work on different design concepts, some examples are as follows:

1)  If the central heating system calls for heat, the motorised valve is energised by a signal from the thermostatic switch. This allows the water to pass through the Venturi. Then a pressure differential occurs in the deficiency valve, (see diagram od Combi Boiler) causing the gas valve to open.

2) The gas then flows through the burner and is ignited.

3) The water which is now being pumped is rapidly heated in the Low Content Heat Exchanger, and can only then circulate around the combination boiler. Then through the domestic hot water heat exchanger. The expansion of the water is taken up into the sealed expansion vessel.

4) When the water temperature in the Combi Boiler reaches (55-60 degrees C) the thermostatic element within the boiler expands. Causing the hot water system valve to close. Then the central heating system valve to open. Thus allowing the hot water to flow around the heating circuit.

5) The closing of the hot water system valve. Also causes a rod to rise. Which operates a micro switch. In so doing notifies the combi boiler  control box. That a higher temperature of water can be achieved. Built into the combination boiler there is a manually operated switch. This will allow you to turn up or down the heat of the water. Usually the heat range is between 60-90 degrees C.

Can I still get hot water if the heating is on?

Yes the following, automatically happens within the workings of the combination boiler:-

a. When one or more of the hot water taps is opened. In the household. The water is drawn through the different pressure valves. This then causes the diaphragm to lift. Which in turn will operate the micro switch controlling the central heating pump. The pump will energise and take the hot water to the tap/taps.

b. The main burner ignites as discussed in 1,2 & 3 above. and is repeated each time the demands for hot water is required.

c. Within the combination boiler, as the cold water passes over the thermostatic element, it keeps it cool, ensuring that the element dose not expand. Which would cause the heated water to flow out of the heating circuit. This means the central heating hot water only circulates through the domestic hot water heat exchanger, and around the boiler.

d. As the mains cold water passes over the domestic hot water heat exchanger, the water is rapidly heated, before being discharged through to the hot tap. (please refer to diagram).

Combination Boiler Diagram

Combination Boiler Diagram


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