The rate of hot water delivery is unusually poor. Measuring the water flows will help find the reason. I suspect you have a half-inch incoming water main, and some other restriction.
Boiler kw advice
- Thread starter mole81
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- boiler hearoutput
If the boiler is going in the same place the delay will nearly always be the same unless you use Smart preheat, not standard preheat. (smart preheat is available in the winter and uses heat when the boiler turns off from radiators to pre-warm the hot water. This is using heat you've already paid for, standard preheat has a 24/7 operation and cost).
If you're happy with hot water supply at the moment stick with 25, if you have a good flow and pressure, your engineer seems to indicate you do, then go 30. The only reason to go more power than your cold water supply is if you require very hot water.
It's very unlikely you will require more than 8-10kW for heating and that's in extreme weather which lasts 2 weeks usually. The majority of the heating season will be made up of minimal or near minimal heating output so check modulation of the boiler, if it doesn't drop below 2-3 kW it'll cycle which will impact efficiency. Choose a boiler that drops output below these figures.
If you're happy with hot water supply at the moment stick with 25, if you have a good flow and pressure, your engineer seems to indicate you do, then go 30. The only reason to go more power than your cold water supply is if you require very hot water.
It's very unlikely you will require more than 8-10kW for heating and that's in extreme weather which lasts 2 weeks usually. The majority of the heating season will be made up of minimal or near minimal heating output so check modulation of the boiler, if it doesn't drop below 2-3 kW it'll cycle which will impact efficiency. Choose a boiler that drops output below these figures.
My mains temperature is 11C just now so a 31kw combi should give a flowrate of, 31*860/60/(50-11), 11.39LPM @ 50C, so, 100/11.39, 8.8, say 10 minutes max to fill a bath with 100L at 50C, if its taking 20 minutes, then either the boiler is only delivering ~ 15kW, or the flowrate is only 5.7LPM at 50C, or 4.4LPM if set to 60C, very unlikely to be this low?.
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Probably on a Vokéra as he works for them
Probably on a Vokéra as he works for them
All Vokera combi models
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