Oil Fired Combi Boiler

Combination boiler system in home




A combi boiler is similar to a conventional boiler with a second heating circuit which instantaneously produces hot water.  

Often overlooked is the fact that the operating / engineering differences between gas and oil fired combi boilers is significantly different.


Oil fired combi’s, unlike gas, do not have modulating burners to cope with additional heating demand when a hot tap is opened.


This problem is addressed in two ways:

  • an integral water store making them physically big.
  • a larger boiler output than is actually required to satisfy central
  • heating demand; you might end up with a 30kW boiler where
  • a 20kW conventional boiler would suffice and also be more
  • efficient.


When the heat store is exhausted, hot water flow of 10-13ltrs / minute @ 35oC rise above mains temperature is around the norm. To fill a bath (112ltrs) will take about ten minutes, provided no other taps are opened.



Second heating circuit
 Second heating circuit for hot water


High life-time costs...unlike a gas combi, water is stored in the boiler at circa 80oC, components subjected to this constant residual temperature will fail. Oil fired combi boilers are complex, have bespoke components; they will be more expensive to maintain than a conventional system. Good business for boiler manufacturers, not necessarily the best option for the homeowner!


So what's the solution?

Keep it simple! In so many cases a conventional boiler with a pressurised domestic hot water cylinder such as a Megaflow is a far better option.


The benefits:

  • loads of hot water at mains pressure - up to 72 litres per minute
  • back up immersion heater
  • industry standard components


For more information on our Hounsfield Tuscan boilers, or to find an installer near you, visit our contact page, or call us on 0845 680 8153.