losses in boiler

[eddy b]

hi all i am fairly new to all grain after only doing 4 brews so far but each time i have trouble getting the correct volume in the fermenter i have been using daabs batch sparge calculator and always get the correct pre boil volume but never get the required amount after the boil i am always around 3 litres short .I have the hop and grape 10 gal boiler and there always seems to be quite a lot of liquid left at the bottom ,when brewing yesterday i collected all this liquid and strained all the hops out and there was 3 liters , I always put 3l in the hops and trub losses box so i dont really know whats going on i could try upping the losses to 6 litres but surely i would be diluting the wort to much, as it is im not reaching the expected og please help edd.

[tomU]

It sound like you're losing a lot to evaporation - is it the 2 element boiler? if so perhaps turning one off once you hit the boil is a good idea.
If you're not reaching your expected OGs then you need to work out your efficiency then up the grain bill accordingly. Then add 3 litres to the pre-boil volume and you should be ok