How much reduction in boil off with lid on?

[DawgPen Brewing]

How much of a reduction in boil off (everyone states it is approximately 1 gallon/hour) should I expect if I keep the lid on with constant recirculation during the boil? Anyone got any numbers they have observed from their system?

 

[Electric Brewer]

How much of a reduction in boil off (everyone states it is approximately 1 gallon/hour) should I expect if I keep the lid on with constant recirculation during the boil? Anyone got any numbers they have observed from their system?

Why would you need to recirculate during a boil? The boil is enough to recirculate. Are you sure your pump and hoses can tolerate boiling water?

Why would you keep the lid on? Where would the steam go? Seems like it will re-condensate and fall back in. Also you'll have a massive boil-off to manage.

Are you are trying to get a better boil? Then you can look into a kettle jacket.

 

[jtratcliff]

https://brulosophy.com/2016/10/31/the-boil-lid-on-vs-lid-off-exbeeriment-results/
tldr;
about the same...

 

[DawgPen Brewing]

Why would you need to recirculate during a boil? The boil is enough to recirculate. Are you sure your pump and hoses can tolerate boiling water?

Why would you keep the lid on? Where would the steam go? Seems like it will re-condensate and fall back in. Also you'll have a massive boil-off to manage.

Are you are trying to get a better boil? Then you can look into a kettle jacket.

I guess I was planning on doing it because that is the way I have seen it to this point similar to what I have seen in the Clawhammer system setup and videos. I do think it would do a good job at preventing boil-overs and was generally a good plan but it may not be. If it is a bad plan please help to educate me because I am blindly following what I have seen. I guess my question now is "would it hurt to recirculate during a boil?"

My system will be a 240V system with a 5500 W element so heat should not be a problem or should negate the need for a kettle jacket or insulation. My hoses are silicon which are rated to 500 degrees per the spike website so I don't believe I will be hurting anything from that standpoint.

 

[jtratcliff]

The recirculation can be useful during the mash... or after the boil for whirlpool and/or chilling...
Not really needed during the boil ...

 

[Spartan1979]

I have an electric system with a steam condenser. I went from boiling off 1-1/2 gallons per hour to about a half gallon per hour.

 

[Beermeister32]

I run a 7 gallon rigorous open boil using propane. Evaporation rate is 1 gallon per hour bringing it down to 6 gallons finished.

If I’m running a 90 minute boil, I add about a half gallon pre-heated hot liquor at the 60-minute point to re-establish the 7 gallons. This way the boil keeps going without stalling from the water addition.

I prefer doing full volume boils!

 

[BigDave1303]

I wouldn't recirculate whilst boiling. As previously mentioned by Electric Brewer "The boil is enough to recirculate"
Also, If any gasses/air get into the pipe, pump, tubing (it does happen) it could rapidly expand resulting in boiling liquid & air being forced out under pressure (dangerous & messy)

 

[Spivey24]

Boiling with the lid fully on is just asking for a boil over. Especially with recipes with plenty of boil hops. I always keep it partially on and have no issues.
Boil off rate can also depend on temp and humidity of air. I did a batch last week when it was super dry and had almost 2 gallons boiled off in 60 minutes making a 5 gallon batch in a 15 gallon kettle running at 4200 watts on induction. More than I calculated.

 

[Spartan1979]

Boiling with the lid fully on is just asking for a boil over. Especially with recipes with plenty of boil hops. I always keep it partially on and have no issues.
Boil off rate can also depend on temp and humidity of air. I did a batch last week when it was super dry and had almost 2 gallons boiled off in 60 minutes making a 5 gallon batch in a 15 gallon kettle running at 4200 watts on induction. More than I calculated.

If you're applying enough heat to be boiling off 2 gallons per hour, sure, having the lid on may be asking for a boilover.

 

[Vale71]

How much of a reduction in boil off (everyone states it is approximately 1 gallon/hour) should I expect if I keep the lid on with constant recirculation during the boil? Anyone got any numbers they have observed from their system?

Boiling with the lid on if you don't change the output of your element will actually increase the boil rate which depending on circumstances might lead to boilovers.
Besides recirculation being unnecessary as others have already pointed out if you pump boiling liquid you could get massive cavitation in your pump amd that is a very bad thing.

 

[jerrylotto]

Not to mention that one of the key purposes of a boil is to remove nasty volitiles like dms. Open boil! I only use a lid AFTER the boil is done for kettle hopping.

 

[DGW]

While it's true Clawhammer do have their lid down, they always have their hop spider hanging inside the pot. This keeps the lid from sealing completely down and lets steam escape.

 

[Vale71]

While it's true Clawhammer do have their lid down, they always have their hop spider hanging inside the pot. This keeps the lid from sealing completely down and lets steam escape.

Steam will always escape with or without a lid. Just placing a lid on a pot does not a pressure cooker make.

 

[DGW]

How true, but I believe more escapes if there is inch or two gap available, how about you?

 

[DawgPen Brewing]

Steam will always escape with or without a lid. Just placing a lid on a pot does not a pressure cooker make.

I love the wording of your statement and I guess that was my thought also because I am expecting some to leave since it is not a sealed lid. I don't have to run the lid but was just thinking that others have been doing it in their videos so I would do the same. It seems that the consensus would be to take the lid off after the mash is complete. Will try both and see what works for my system. Will report if either seems to work significantly better.

 

[jddevinn]

People that are boiling with the lid on probably have a steam condenser. Unless you have one of those do not boil with the lid on

 

[DawgPen Brewing]

People that are boiling with the lid on probably have a steam condenser. Unless you have one of those do not boil with the lid on

I understand that the reason people boil with a steam condenser when trying to limit the amount of condensation in a residence but doesn't that limit the amount of DMS removal? I understand that the consensus is that you should not boil with the lid on but it seems like this is one of those many instances where I don't understand the science behind it. It seems like a steam condenser would not allow DMS to be removed any more than leaving the lid on but maybe that has been disproved.

 

[Vale71]

You probably have an incorrect mental picture of how a steam condenser works. A steam condenser will condense steam while at the same time removing it from the pot via a side port. A steam condenser actually causes suction in the pot (Venturi effect) making steam removal even more effective than the same pot without a lid.

 

[Vale71]

How true, but I believe more escapes if there is inch or two gap available, how about you?

It's a misconception. Exactly the same amount will escape and that will be all the steam that cannot condense before escaping. A lid has a very small surface which makes it very ineffective at dissipating heat. For every gram of steam that is turned back into water 2.12 kJ of energy is released as heat and that must all be dissipated for condensation of said gram of steam to be possible. Also every molecule of steam that cannot condense will have to escape the pot very quickly or pressure will quickly build up and the lid will raise itself until pressure is relieved. That's the reason why pressure cookers are quite sturdier in construction as they need to withstand higher pressures. The amount of heat per unit of time that the lid as a whole can dissipate is only a function of its surface area and its material and thickness and also the ambient temperature. Raising or lowering the lid by a small crack is not going to change any of those parameters.
Some things in physics (even everyday physics like in this case) are really counter-intuitive but that's what makes it so intriguing, at least for me.

 

[jtratcliff]

Read the brulosphy link... he actually measures the boil-off with and without a lid...

I believe I saw a youtube vid of Bamforth saying much the same as @Vale71 ... the steam escapes regardless...


Yup... here's the thread: to lid or not to lid .... a boiling question.

edit to add direct link to Bamforth video:

 

[Vale71]

Just to get things into perspective you should not expect a huge increase in boil off rate if you just put a simple lid on a pot but a small increase will happen nonetheless. Now if you went to the trouble of insulating the pot and used an insulated steam hood instead of a simple lid, just like in a large commercial system, the increase would be quite significant.

 

[marc1]

I understand that the reason people boil with a steam condenser when trying to limit the amount of condensation in a residence but doesn't that limit the amount of DMS removal? I understand that the consensus is that you should not boil with the lid on but it seems like this is one of those many instances where I don't understand the science behind it. It seems like a steam condenser would not allow DMS to be removed any more than leaving the lid on but maybe that has been disproved.

I use a steam condenser. The wastewater is stinky. DMS is removed.

 

[tracer bullet]

Something sure the heck is. That water does not smell good.