Boil off rates

[DonT]

Hello All... I'm 3 brews in on my Kal-clone-ish system and I have questions about my boil-off rate...
First of all, I'll describe my system for you. I have 15g Spike+ kettles with a 5500w heating element controlled by a Auber Brew Buddy II wired to 240v, the amp meter displays 22.1a at full power.
I've been fine tuning my system, my process and Beersmith. I'm getting close to getting it dialed in but I still had concerns about my boil off rate. I've done a boil-off test twice before but I feel I screwed it up due to still learning the auber. So I did it again...
This time I kept the lid on until it started to boil at about 210*, I then removed the lid and let it go. At first I used 90% power but it seemed more like a simmer so I upped it to 100% because Kal has stated he likes a hard boil so why not? After 15 min. I turned off the power and slapped the lid on. That was Sunday... I lifted the lid this morning and it's down to around 5.25g. I started at 6g. I still need to drain and measure for an accurate reading but 3/4g seems like a lot in 15min. So 3g an hour?
What's your boil off rate?

 

[michaeltrego]

I think you just need to measure the results on your next couple of real batches to determine how your system is performing. The water test you described seems like an apples to oranges comparison - ie. do you keep your lid on when you are actually boiling wort? I have a 15 gallon kettle with a 5500w element driven by an Auber PID and I typically do 10 gallon batches running the boil at 55% power, which is a good churning boil (any higher and it would be a volcano), and I see about 1.5 gal of boil off per hour.

 

[MaxStout]

A 15 minute boil may not be a long enough sample duration, perhaps some non-linearity in that, especially given you bumped up the power part of the way along. See what it does over the course of a full-length boil. It might take a few brews for you to determine some kind of average. Nothing like real world empirical testing.

 

[doug293cz]

... At first I used 90% power but it seemed more like a simmer so I upped it to 100% because Kal has stated he likes a hard boil so why not? ...

90% of 5500W should be a raging boil. If you are just getting a simmer, something is off. Did you check you ammeter during this time?

Also "boiling hard" is not considered good practice by most knowledgeable brewers.

Brew on

 

[DonT]

I think you just need to measure the results on your next couple of real batches to determine how your system is performing. The water test you described seems like an apples to oranges comparison - ie. do you keep your lid on when you are actually boiling wort? I have a 15 gallon kettle with a 5500w element driven by an Auber PID and I typically do 10 gallon batches running the boil at 55% power, which is a good churning boil (any higher and it would be a volcano), and I see about 1.5 gal of boil off per hour.

I leave the lid off completely when brewing. I only had the lid on for the warm-up period, then I took it off for the 15min boil, then put it back on.
55%? Somethings wrong here... (my end, not yours)

A 15 minute boil may not be a long enough sample duration, perhaps some non-linearity in that, especially given you bumped up the power part of the way along. See what it does over the course of a full-length boil. It might take a few brews for you to determine some kind of average. Nothing like real world empirical testing.

The three brew I've done so far I've used a 1.625 rate and the end volume into the fermenter was about right...

 

[DonT]

90% of 5500W should be a raging boil. If you are just getting a simmer, something is off. Did you check you ammeter during this time?

Also "boiling hard" is not considered good practice by most knowledgeable brewers.

Brew on

Hmmm... interesting. I need to read the whole thread. But I also think I need to do some more experimenting. I can't remember what the ammeter read during the 90% phase...

 

[marc1]

I use a 5500W element with a Still Dragon controller to boil ~12.5 gallons. Once it gets boiling, I run it around 50% with the lid on (using a condenser to eliminate steam) for a gentle boil.

 

[Falstaff]

I lose about a gallon an hour with my system.

 

[Genuine]

I'm using a 20 gallon kettle with 5500w element and I also boil with the power around 55%. I boil off a gallon over the course of an hour.

 

[faithie999]

Also "boiling hard" is not considered good practice by most knowledgeable brewers.

Brew on

what is a good description of the correct boiling rate?
thanks

 

[jerrylotto]

what is a good description of the correct boiling rate?
thanks

Rolling - and unless you want to trap DMS, leave it uncovered.

 

[faithie999]

Rolling - and unless you want to trap DMS, leave it uncovered.

thanks!

 

[jerrylotto]

Quoting "Off-Flavor of the Week: DMS"
Get a nice rolling boil, and don’t cover the pot until it’s cool.
Chill wort rapidly. The longer it stays hot, the more SMM (S-methylmethionine - a component of malted barley produced during germination) is converted to DMS.

 

[odie]

asking us what our boil off rates are is not going to help you in any way. All that matters is what your system does in the manner that you use it. All you can do is measure your boil off during a few beers and average the results.

 

[DonT]

asking us what our boil off rates are is not going to help you in any way. All that matters is what your system does in the manner that you use it. All you can do is measure your boil off during a few beers and average the results.

Well, it tells me how out of whack I am... but yeah...

 

[doug293cz]

Rolling - and unless you want to trap DMS, leave it uncovered.

°°
Quoting "Off-Flavor of the Week: DMS"
Get a nice rolling boil, and don’t cover the pot until it’s cool.
Chill wort rapidly. The longer it stays hot, the more SMM (S-methylmethionine - a component of malted barley produced during germination) is converted to DMS.

Doesn't even need to be a heavily rolling boil, a a light roll, with visible convection currents, is all that is required. DMS boils at around 100°F (38°C), so it dissipates rapidly as long as you have convection currents to carry the DMS formed in the bulk to the surface.

You don't need to leave the BK uncovered. As long as there is enough of an opening for steam to escape, the DMS will escape with it. Commercial BK's typically have a relatively small vent compared to the cross sectional area of the BK. The low boiling point of DMS means that it will not condense on the hot surfaces, so there will be no drip-back into the wort.

Quick cooling is desirable when the wort is undisturbed (no whirlpool, etc.) during cooling, as you loose the convection currents that were bringing the DMS to the surface during the boil. SMM continues to break down into DMS down to around about 170°F (77°C), so it needs a way to escape from the bulk. The slower the cooling of "still" wort, the more DMS can build up in it before it gets down to 170°F. The amount of SMM in the cooling wort will depend on how much of the original SMM was converted to DMS during the boil.



Brew on

 

[doug293cz]

what is a good description of the correct boiling rate?
thanks

According to the link in my post that you quoted: "A lightly rolling boil that you can see is circulating particles in the kettle, is sufficient."

Brew on

 

[Mad Mann]

If your boil is off, you might want to calibrate your PIDs temp readings, especially if it is a new set up.

 

[DonT]

If your boil is off, you might want to calibrate your PIDs temp readings, especially if it is a new set up.

This fixed it... I had my settings all screwed up.