Combi Boilers - It's All About Flow Rate For anyone considering combi boilers when choosing a new heating device, it all comes down to the words, flow rate. Or, to be more precise, with combi boilers, it's all about hot water flow rate.
You need a flow rate of 13 li/min absolute minimum whilst leaving a residual pressure in the pipes of say 0.5 Bar as there is a pressure loss within the boiler. An open tap flow of 13 li/min will possibly reduce to 5-10 li/min dynamic flow rate at 0.5 Bar.
Hot water flow rates and combi boiler power This is another calculation on heating water, this time relating hot water flow rates and boiler power. It too ends with a handy rule which can be applied without reference to a manufacturer's manual.
The boilers suggest are from two different makes and have DHW flow rates of 12.4 and 15.2 at 35C. I wont go into which is best make but the 15.2 is £400+ more than the 12.4 (some of this is down the the make and some down to the specification).
Gas Combination boiler - Flow Rate and Water Pressure by BBC Rogue Traders Expert Ian Puddick ... How to get hotter water from your Combi boiler - Duration: 4:48. dereton33 45,115 views.
Two weeks ago the hot water flow rate (at all taps) from my combi boiler (Worcester Bosch 24Cdi) dropped from it's usual 9L/min to less than 4L/min. Suspecting the boiler I called Worcester Bosch for one of their fixed price call outs. The enigineer came and replaced the water-water heat exchanger, diverter valve, and pressure relief valve.