Boiler flow rate is much lower than stated

EnglandFalls

I have a Worester Bosch 28i Junior. It is supposed to deliver water around 11.4 litres per minute at 35 degrees temperature rise. Mine only delivers 8 litres per minute on the lowest heat setting and it's brand new.

I called WB and they said this was normal because the boiler has to move water in the pipe, and the rating of 11.4 is if there's no water to move. They said 8 was very good. It doesn't seem good to me.

I would have thought a combi boiler would use the mains pressure to handle that kind of problem and the boiler would deliver hot water at the stated speed?

macman

It should deliver the rated flow at the boiler. Obviously if the pipework between boiler and hot tap is restricting it then the flow will be reduced.
Is your mains pressure and flow suitable for a combi-did not your RGI do a site survey before install to establish this?

Cardew

I suppose the only way to test the flow would be to disconnect the outlet pipe at the boiler.

I am always surprised how much the pipework can restrict flow. Re-fitting my bathroom with new taps for bath and basin in my en-suite meant there was virtually no Hot water flow.(gravity fed from a tank). I had to get a pump fitted.