Direct fired RIMS question

[johnnysoj]

Hello all!

I've been all grain brewing for about 2 years now, primarily single infusion mashes. I recently created/converted a 15.5 gallon keggle to use for mashing 10 gallon batches, but figured I had everything I need to do a direct fired RIMS setup.

The keggle has a false bottom, so my grain isn't sitting directly on the bottom. I've heated my strike water in my BK as usual, and pump it into the keggle/MT.

The particular recipe I was going for called for step infusion going from 122 to 152 in supposedly 15 minutes.

Once I mix up the grain, I start recirculating, and when everything is flowing good, I gently apply the heat. It seems to take a long time to get from 122f to 155f, much longer then 15 minutes.

I just kept the heat on probably medium/medium low. anything lower would blow the flame out of the darkstar burner. (This year santa's going to bring me a second burner for my top tier)

What ends up happening is basically around 144ish the wort seems to stop flowing, so I kill the flame, and get it pumping again, then apply the heat again. as soon as the heat runs again for a minute or so, it stops again.

I ended up abandoning the recirculation, and just stirring until I got to 155. Same with the issue with the mashout.

My grist was just 14lbs maris otter...20 quarts of strike water.
Should I have used a thinner mash? Or just be more patient?

I did find the darkstar burner was a bit irritating because even in the slightest wind it would blow out, so maybe the flame could've been lower, im not sure. I was heating up my sparge/cleaning water in my main bk, so I didn't want to shuffle things around.

Any idea why it would do this? Or how I could stop it from doing this next batch?

Thanks!

 

[helibrewer]

You're going to have an issue heating under a false bottom. Any air trapped under there from heating will disrupt you recirculation. Your options are to 1) Separate your mash and lauter tuns so that there is no false bottom in the MT, or 2) Use a small grant so that you are just heating liquid that gets returned to the mash.

 

[Keating]

You're going to have an issue heating under a false bottom. Any air trapped under there from heating will disrupt you recirculation. Your options are to 1) Separate your mash and lauter tuns so that there is no false bottom in the MT, or 2) Use a small grant so that you are just heating liquid that gets returned to the mash.

There shouldn't really be any trapped air in there, unless your recirc gets stuck, or maybe if the wort under the FB starts to boil.

I dough in and wait about 10 min, then start recirculating.
Once the grainbed is set, I run the recirc at nearly full speed with my March 809 pump, and fire up my 23 jet NG burner at full power to correct temp, or to step up, through to mashout temps.

 

[rekoob]

I have pretty much the same setup, thee keggle system all direct fired.

I heat my water, about a 1.5 quart to a pound, set the PID at what I want and get my HLT PID set to the temp I want for mashout.

I dough in and slow my pump flow so it doesn't slow when the grain bed starts to set. I guess it's about a 1/4 or 1/3 flow rate or there about. Again, a little more water then I used to use in the cooler setup I had prior.

I then stir the mash about every 10-15 minutes just to mix the grain bed up a little more, with the slowed flow rate it stays steady.

The PID keeps temps good, with both HLT and MLT burners going I'm running them about half or just over half. When I want to step or mashout I just adjust the PID, again, maybe give it s stir and the temp reading on the PID climbs with no issues. I have never timed it but it has never been slow enough for me to even think about it so it must be a pretty good rate.

I would try more water in your mash and see how that goes. I suppose I might just try a few gallons of water first to see what the rate is and then try more water for your next batch. I can't see why you would have any issues changing temps.

 

[dcbc]

Maybe I missed it, but from where are you reading the temperature? I have a direct fired RIMS with a false bottom and take the temperature after the pump (so basically just after the point where heat is being applied). I have a lot of room under my false bottom. So my liquor to grist ratio is often 2:1 (qts/lb) or higher. But sometimes I'll be at 1.75:1 (I used constant volumes on all beers below a certain gravity. Like the man said, let it settle for 10 minutes after doughing in, start the recirculation slowly, and open it up until you're getting a nice steady flow (I'm usually about half way open on a March 815). Apply moderate heat to move from step to step. To hold temperature, it's going to be a lot of work without a PID controller. I use a Blichmann TOP.

 

[johnnysoj]

dcbc, I have a thermometer inside the keggle/mt, and It's read from there. When I'm only doing a small batch, and it doesn't reach the thermometer (at approx the 6 gallon level in a 15.5 keg) I use a thermapen that I measure various points around the mash. What seems to be happening I believe is the wort on the bottom begins to boil, and those air bubbles are what seems to be getting into the pump and stopping it from flowing. I'll try a higher h20/grist ratio next time, and a high flow on the pump (a chugger w/ polysulfonate impeller)

 

[jbaysurfer]

Maybe I missed it, but from where are you reading the temperature? I have a direct fired RIMS with a false bottom and take the temperature after the pump (so basically just after the point where heat is being applied). I have a lot of room under my false bottom. So my liquor to grist ratio is often 2:1 (qts/lb) or higher. But sometimes I'll be at 1.75:1 (I used constant volumes on all beers below a certain gravity. Like the man said, let it settle for 10 minutes after doughing in, start the recirculation slowly, and open it up until you're getting a nice steady flow (I'm usually about half way open on a March 815). Apply moderate heat to move from step to step. To hold temperature, it's going to be a lot of work without a PID controller. I use a Blichmann TOP.

This is a key question. I was doing the same thing for a few batches using the mash tun kettle thermometer only to find out after purchasing a thermapen I was overshooting my wort temp by 7F or more when relying on that thermometer. I put a thermometer inline with my pump outlet and it helped me dial it in. I suspect your "it took a long time" has to do with this. There's a latency effect for some reason between when your wort gets to the temp you want it and when the thermometer on the mash tun reads the temp you're aiming for.

Not sure about the pump failing to flow though. Could be a narrow pickup tube in conjunction with a slowing/sticking mash?

Helibrewer one of the most knowledgeable posters on this board IMO, but I've never had any problem with air being stuck under my mash/false bottom. I just stir it well on dough in and there is no air in the whole mash tun (beyond headspace of course) that I know of. Maybe he's speaking to something specific with Keggles?

 

[jbaysurfer]

dcbc, I have a thermometer inside the keggle/mt, and It's read from there. When I'm only doing a small batch, and it doesn't reach the thermometer (at approx the 6 gallon level in a 15.5 keg) I use a thermapen that I measure various points around the mash. What seems to be happening I believe is the wort on the bottom begins to boil, and those air bubbles are what seems to be getting into the pump and stopping it from flowing. I'll try a higher h20/grist ratio next time, and a high flow on the pump (a chugger w/ polysulfonate impeller)

Yeah, you don't want your mash wort boiling IMO. If you're trying to bump up temp you are denaturing the enzymes and ending conversion. If you're mashing out it's less consequential, but a cavitating pump IS a consequence.