What boiler do I need

There is nothing worse than not knowing what you have got or what the problem is. This is really frustrating when you need a boiler or central heating system and this is where Mr. Central Heating can help. For the last 40 years we have been advising homeowners on what is the best system for them. Please feel free to call any of our depots and give them as much information as you can find and we will definitely get you the best deal on central heating products in the UK supplied directly to your door by our own dedicated transport. The diagrams below are to help with what you have and are freely available at Worcester Bosch.

Combination boilers

The most popular boiler on the market with over 80% of all boilers sold are combination boilers. They offer really good flow rates on the hot water and do not need to store water, so do not run out. These work directly on the cold mains and heat the incoming water and supply it directly to the hot water taps. The heating circuit is heated via a heat-exchanger in the boiler and is a sealed circuit.

 how does a combi boiler work

System boilers complete with Un-vented cylinders

These are becoming increasingly more popular as houses get bigger with loft extensions and general extensions.The system uses the incoming main so there is no water storage in the loft except in the heating circuit which is sealed, and the hot water cylinder which is pressurised by the incoming main. The boiler will heat the water circuit in the radiators directly through a heat exchanger and a motorised valve will be used to divert the heat to either the rads or the hot water cylinder. The hot water is indirectly heated via a coil in the cylinder and the water in the cylinder for the taps is under pressure from the mains. This is classed as a sealed system and does not rely on a break tank in the loft to store hot water to create a head. Standard copper cylinders in traditional systems cannot except mains pressure and un-vented stainless cylinders like the uniSTOR from Vaillant has a 25 years guarantee and a fantastic re-heat time so you never run out of hot water. A system boiler has a expansion vessel and pump inside allowing for a neat installation and is fully controllable by room stats and programmers.

how does a system boiler work

Conventional boilers or systems

These are what maybe you are replacing and cold be up to 40 years old. If this is the case then you could save ££ on your gas bills by updating your boiler. The existing boiler could be as little as 40% efficient and your new boiler will not only be more reliable but over 90% efficient.
Traditional systems or open vented ones rely on storage tanks in the loft. One for the heating circuit that allow any expansion in the system to blow off into a tank but also as a feed for evaporation of water loss. Water when it is heated expands and in a circuit of radiators which are closed it needs to go somewhere, so hence the name feed and expansion tank. Conventional boilers cannot produce hot water so have to use a cylinder indirectly to heat the hot water. The cylinder generally copper and hopefully lagged but not always stores water and then it is heated indirectly by the boiler. The cylinder cannot accept mains pressure so relies on stored water in the loft which creates a head and generally your pressure in the hot water taps. If there is no head or distance between the cylinder and water storage tank then you will require a shower pump. A complicated system with lots of components and water storage that is really no longer required if you choose the right system.

what is a conventional boiler