A Combination Boiler typically requires no storage tanks. It provides hot water to your taps ‘on demand’ by heating cold water supplied to it directly from the incoming cold water main as required. It also provides a circuit of hot water to heat the household radiator system which can be programmed. Combi’s only heat what you require.
Offering the advantage of space saving, Combi Boilers are popular.
They can however have the disadvantage of lower hot water flow rates – more often noticed when filling a bath or when simultaneous supply is called for at more than one outlet.
Not particularly suitable for properties with more than one bathroom or shower.
Boilers with bigger and better flow rates are being achieved but performance is still a little lacking.
Positives: Compact unit requiring no external tanks – good for space saving. Perform well with showers. Endless amounts of hot water on demand albeit slowly.
Negatives: Typically lower flow rates than other systems. Baths can take a long time to fill. Will not support simultaneous demand from several outlets. You cannot install a shower pump to increase performance if you discover your are less than happy.
Economy: You only heat what you need. No storage equates to no standing losses.
Typical System Requirements: Combination Boiler Only – (No external tanks) – Rads.