What is a Combi Boiler?
A combi boiler, or combination boiler, is a compact heating system that heats water on demand. The boiler provides two functions; it can supply hot water and central heating via one compact unit. Water supply comes direct from the mains and is heated within the unit on demand.
There is no need for a cold-water supply tank or hot water cylinder, the water is supplied directly to the boiler and diverted to the tap or central heating. This offers space saving efficiency but can also hinder its ability to handle multiple requests for hot water throughout a house.
The boiler functions with valves that operate in different directions. As a result, water can either flow into the central heating system or to a tap. It is not equipped for demands from both. Multiple running taps and showers can also cause a drop in pressure/flow rate preventing hot water from being efficiently delivered. Generally, the combi boiler can only deal with one request for hot water at a time. Therefore, the best applications for combination boilers tend to be within smaller houses with less consistent demand for hot water.
The size of the combi is very important and looking at the incoming flow rates into the property must always be checked
Some manufacturers also make more powerful boilers and storage combis for use with multiple taps
What is a Conventional Boiler?
Conventional Boilers are typically found in older or larger houses. This is due to the extra space that is required for separate components of the system. As part of the conventional boiler, two cold-water tanks typically need to be fitted into a loft space and an airing cupboard is required for hot water storage.
Unlike the combi boiler which heats water on demand, a conventional boiler will heat many litres at once and store it within a hot water cylinder. As hot water is requested throughout the house or within the central heating, there is a supply to meet all demand.
This method is much more effective for properties that contain multiple bathrooms, require constant heating and supplies of hot water. Of course, after a certain amount, the hot water supply will run out and the system will need to refill to heat more water. If water is not heated in advance, you could be facing a thirty minute or hour wait for a supply of hot water.(dependent upon the amount required and the boiler’s specification) Interested in a conventional or combination boiler?