Help please - boiler boil off

[barry44]

Hi,

i recently bought beersmith and following on from this i decided to test all of my kit to create a profile.

I have just boiled 10 litres of water in my boiler for an hour and i lost 4 litres!!

40%!!!

Surely there is something wrong with the test i carried out which has left me with such a boil off?

Was it the volume, should i have carried it out at full volume rather than the 10 litres?

Under normal operation, i.e. brewing, i appear to lose 3 litres, which ties in with the estimation in beersmith but i cant see why i would lose more with lesser boils.

Was it the fact that it is water and not wort that has increased the boil off?

Any assistance would be greatly received.

[Eric]

Sounds right.
Total heat input can be thought of as constant at the rating of the element.
Heat loss will be in some way proportional to the surface area of the liquid, the larger the surface area the greater the the amount of heat that will be lost to the surroundings.
Heat retained in the liquid will be the heat input minus the heat loss.
So the larger the volume in a given container, the greater the heat loss, the slower it heats such that when boiling point is reached, less will evaporate.

Think this, using a 2.5 kW element will quickly boil a 2 litre kettle, more slowly boil a 30 litre boiler and never has the power to overcome the losses and boil a 10 barrel beer plant.

[Brotherton Lad]

Wot Eric said.

Try with a big pan on the stove top. You'll boil a half pint dry in no time. 100% loss. But with a gallon you might lose just 5 or 10%.

[barry44]

Phew, thanks lads. I'll try it with a full volume boil next time