Having Calculated the boiler size, there remains the questions of What type of boiler should be chosen and where should it be located.
There are various types of domestic boilers available and the type best suited to any application must depend on the particular circumstances involved. The choices available are as follows:-
Gas boilers are available in either room sealed or open flue form. Normally a room sealed boiler is preferable, but in extreme cases, there may not be a position for a room sealed terminal. With the open flue type, the flue system is "open" to the room at the boiler and the air for combustion is taken from within the room. Additional air is also entrained from the room into the draught diverter to dilute and cool the products of combustion coming from the room. In a room sealed boiler, the flue is sealed from the room, and all air for combustion is taken from the terminal position outside the property. It should be noted, that open flued boilers are becoming more difficult to obtain, as modern designs of boiler can accommodate almost all domestic circumstances.
There are several important factors to be considered when deciding where to site a boiler. Proper fluing arrangements to dispose of the products of combustion are crucial to the safety of gas and oil appliances. The manufacturers installation instructions and british standards 5440 must be studied and followed.
In general, room sealed flue systems are to be preferred. If A Balanced Flue appliance is chosen, then the boiler must be positioned on an outside wall, so the flue can be taken directly through the wall. Nowadays, however, the varied flue configurations possible with modern fan assisted flues mean that this restraint is no longer valid, invariably, a boiler with a fan assisted flue system can be positioned almost anywhere within the property.
There are also various restraints on the position of room sealed flue terminals with respect to building features, eg. Distance from openable windows, ventilators, doors corners etc. Some guidance on the siting of terminals are given in Figure 5.
It should be noted, that the type of boiler selected and it's siting are not wholly independent considerations, since a decision on one may affect the other. Even though room sealed boilers draw their air for combustion form outside, they may still require ventilation for cooling purposes if sited in a cupboard or compartment.
Open flued boilers have so many restrictions on siting, and ventilation requirements. If You have one to replace, then for safety considerations, it should be replaced with a room sealed model.
Other considerations when siting a boiler include.