Grainfather water calculation

[meirion658]

Good afternoon all,

Decided to do a 19L california common today and used the grainfather app to build the recipie.

Mash 16L
Sparge 12.5

On transferring to the FV I was around 3 liters short!!!

I decided to have a look at the grainfather water calculator on their website which gave a totally different water volumes!!

Mash 20L
Sparge 13.5

Why would the website give a totally different readings to the app.

 

[Horners]

33.5 total liquor sounds toppy for 19L. How many kg of grist? How long did you boil? Most of my hour boils on GF I reckon about 31L total for 21L in FV for standard gravity beers/ hop bills.

 

[meirion658]

33.5 total liquor sounds toppy for 19L. How many kg of grist? How long did you boil? Most of my hour boils on GF I reckon about 31L total for 21L in FV for standard gravity beers/ hop bills.

I had 5kg of grist and a boil time of 70min.

 

[strange-steve]

I had 5kg of grist and a boil time of 70min.

The app and the website both give me the same volumes for those values, 17L mash and 11.5L sparge

 

[meirion658]

The app and the website both give me the same volumes for those values, 17L mash and 11.5L sparge

Same total volume just different ratio!

How have you set the profile of the grainfather up Steve?

 

[strange-steve]

Same total volume just different ratio!

How have you set the profile of the grainfather up Steve?

I think it's just the default settings, I don't remember changing anything.

 

[Zephyr259]

Yeah, I just did it manually and get Steve's numbers, except I forgot you boiled 70 mins which adds an extra half litre. Something that gets me is the fact that wort at 20c is 96% the volume of it at 100c, doesn't sound like much but it's basically a litre when you've got +/- 20 L post-boil.

2.7 L/kg x 5 kg + 3.5 L = 17 L mash
19L + 2 L (DV) + 3.5 L (boil) = 24.5 L pre-boil
24.5 L - 17 L + (0.8 x 5) L (grain absorption) = 11.5 L sparge

 

[Spanners]

I had 5kg of grist and a boil time of 70min.

In case you need a breakdown of the water calcs for a G30 Grainfather here they are, it's nice to know where the figures come from .......

Mash volume = (Grain Weight in KG * 2.7) + 3.5
Sparg volume = (preboil volume - mash volume) + (grain bill in KG x 0.8)
Boil off loss = 3L per hour (0.05L per minute) for a 230V Grainfather
Preboil volume = (0.05 * boil time in minutes)) + trub loss(2L) + batch size


An example **** 5KG grain bill, 19L batch size, 70min boil time ****

The preboil volume for a 70min boil is 19L + (0.05 * 70mins)) + trub loss(2L) = 24.5L

Mash volume = (Grain Weight in KG * 2.7) + 3.5
mash volume = (5 * 2.7) + 3.5 = 17L

Sparge volume = (preboil volume - mash volume) + (grain bill in KG x 0.8)
Sparge volume = (24.5 - 17) + (5 * 0.8) = 11.5L

total water volume = mash volume + sparge volume
total water volume = 17L + 11.5L = 28.5L


As has been already said you can always use the grainfather calculater on their site to check that you are getting the figures correct when creating a recipe. If there is a descrepancy then I would check your equipment profile. You can always genarate a new default equipment profile, there is a nice little wizard on the grainfather site to do that.