Fermentation Chamber Heating in Overdrive

I built a 4 compartment fermentation cabinet last year using the popular ST1000 controllers, 4" muffin fans and mating 'equipment heaters'. The wiring on the heaters and fans was setup so the fan and heater both come one at the same time. I knew this was not ideal as you can get major temperature variation from top to bottom, but was OK with it till I completed the housing for the controllers, and updated the fans to run at slow speed when the heat was off, and full speed when the heat was on.

I finally got the housing done to the point where I could mount the controllers properly, and get it wired up for this winters brewing season. During the summer/fall my basement is pretty stable in the mid 60's so no need for heating then.

I do not have the motor controls done yet, so I decided to just let the fans run full speed all the time, and have the heater cycle on and off. Got that wired up earlier tonight, and left it to settle for a couple hours. When I went and checked on it, all three active chambers were well above the set points, and rising with no heat on. As I stood there all 3 increased by .1C. Huh? Well it seems my chamber is so well insulated that the 24 watts the fans produce is enough to run the heat cycle!

I know there are a lot of people running various controllers, but has anyone found that you can get away with this little amount of heat to maintain the temps? My concern is that when the temp outside goes back to winter and my basement drops to around 50 the fans may not be enough and I'll need real heat, but that requires a re-wire again.

I'm still going to do the fan speed control (I'm building my own scr controllers) for 1 as soon as I can, and reconnect the heater to see if the lower power on the fan will give me the control I need with the 2 working together.

I've got extensive electronics and heating controller background, so I don't need any feedback on this part, but I'd love to hear from anyone that's encountered any similar issues with too much heat just from fans!

And the pics, cause everyone wants pics! The white board would normally have the brew specs on it, but since I just got them in the carboy tags are hanging on the knobs for now. The extra 2 spaces in the white board are for my lager cooler. The switches on the controller are to control heat/off/cool mode. Eventually I want to incorporate some amount of cooling for summer brews when I need it, as my plan to cool to lager temps in this cabinet has hit a snag, but that's another story.
John

I have no idea how you reached the conclusion that the fans were creating the heat in your chambers. You say that the ambient temp is 19° C in your ferment room, the same as inside the chamber.you don't mention the temp you pitched at and I don't see where you are accounting for the active fermentation temp increase. The fans may throw off some heat. I don't know, but to describe the heat increase from the fans is not proven. Turn on the fan in your empty box and monitor the temperature in that one otherwise you have too may variables.

Yeah, it's not the fans...
Do you have the temp probe taped to the fermenting vessel and covered with insulation?
Do you have the cooling hooked up?

If the fans are truly 24 watt I can believe a temperature change in the air of an insulated box. I use a 100 watt light bulb to keep my well's pump house above freezing during the winter, with temperatures reaching below 0 F.

What I have a hard time believing is a 4" fan drawing 24 watts as the 10" oscillating fan in my office draws only 42 watts.

Disconnect the fans and see where the temperature settles out to. Then connect only 1 fan and see what happens to that chamber, and look for an effect in the other chambers. While doing this, also look for fans that draw less than 1 watt each.

FWIW. I have a fermentation chamber consisting of a commercial beverage cooler with a Willhi single stage controller. The cooler has a continuous 9watt rated evaporator fan that provides enough heat to slowly raise temperatures with no additional active heat control. The chamber is in an unheated garage that has reached high 30s during a fermentation and held ale temperatures throughout. I monitor temperature with the probe attached to the carboy under a layer of insulation.

The fans ARE making the difference. The cabinet is in my basement with an ambient of about 55F (13C) right now. This morning all 3 were still at the correct temps, 1 cycled while I was checking, with the heaters disconnected.

After I set them up to run the fans continuously last night (and heaters cycling) the temp in all 3 active chambers was up over 24C after about 2 hours. The heaters ran for 1 cycle initially and the temp was still rising 2 hrs later. After I disconnected the heaters, and had the controllers only running the fans, the temps came down to the proper level and the fans started cycling.

The carboys are all long past active fermentation. The Lager is on a Drest, and the 2 Ales are both secondaries. With no heat or fan the temps drop below the set point within a few minutes.

I verified the specs and the fans are 25 watts. It's more a factor of CFM then size.

When I was running them previously with fan and heater they would come on and run for about 15 seconds with a temp diff of 1.0C. But, they would typically overshoot by about 2C, due to the delay in the sensor picking up the change. They (fans) now run about a minute, with the differential set to 0.4C, and 0 overshoot.

No, the sensors are not taped to the carboys, and insulating them makes no sense since they're in an insulated chamber. That sounds more like a setup for direct heating the carboys, not the chamber they are in. The sensors are located about 1/3 up from the bottom and about a half inch from the carboy. The 'fermometers' on the carboys are within 1F of the chamber temp. Probably a calibration error in the controllers (I don't have a thermometer accurate enough to set them closer), or error in the fermometers. The whole reason for wanting the fans to run all the time was to ensure no temp variation in the chamber.

After what I saw this morning, it's clear the 24 watt fans are sufficient to maintain the temps at the current ambient. I'll have to bring my temperature strip chart recorder home and set it up to monitor for a 24 hr period to see exactly what the temperature swing is in the chamber, and of the carboys.

As I noted, the cooling is not setup yet. I had planned to use my cooler (technically a small chest freezer, although branded for Redi Whip) glycol, diaphram pumps and little mini radiators (made to fit 4" fans like I have), but after following another post on glycol, it turns out that the glycol turns to slush well above zero, and then you can't pump it without a substantial pump. I may go back to my original thought to use fans and small flexible ducting, but the cooler is still set up for lagering right now (and storage for yeast & hops), so I'll just move the carboy to it until I decide how to go in the chambers. My long range plan is to have the cooler back to a freezer for long term yeast & hop storage. But that's yet another project....
John

jleiii said:

.....No, the sensors are not taped to the carboys, and insulating them makes no sense since they're in an insulated chamber. That sounds more like a setup for direct heating the carboys, not the chamber they are in. The sensors are located about 1/3 up from the bottom and about a half inch from the carboy. The 'fermometers' on the carboys are within 1F of the chamber temp......

Click to expand...

Here on HBT, relative to STC1000 type controllers, it's likely to be over 90% support for monitoring fermentation temperature by placing the probe in direct contact with the carboy under a layer of insulation. It makes sense to monitor and control the wort temperature rather than just hope the wort remains at the correct temperature while controlling the air temperature around it. It does work.

I'm not surprised that the fermometers are reading within one deg of the air temperature because that's what they are measuring, unless you insulate over them. What they are likely NOT doing is providing an accurate temperature of the wort, especially during active fermentation.

raouliii said:

Here on HBT, relative to STC1000 type controllers, it's likely to be over 90% support for monitoring fermentation temperature by placing the probe in direct contact with the carboy under a layer of insulation.

Click to expand...

Certainly monitoring the carboy directly gives better wort temperature monitoring, but the latency between heating the chamber and the wort catching up has got to be HUGE. What kind temperature differential does it take to heat 5 gallons of water by 1/2 degree in a reasonable time frame? (rhetorical question) Actually it's not really about temperature as it is the number of watts/hr you add to the space. It takes about 12 watts for 1 hour to raise the temp of 5 gallons of water by 1 degree, assuming no loss. What are the chances of overheating some of the wort while the insulated probe catches up?

I own a heating element manufacturing business (30 yr old family business) and work with customers all the time on understanding their temperature control systems, although 'we don't do controls' so to speak. When working with ovens (effectively what the fermentation chamber is) the oven temperature is almost exclusively what is monitored and controlled when the target is heated fully (vs heating a coating, or the surface). During the initial heating phase the heat is absorbed by the target until it reaches steady state, then the oven maintains it there. I'm having trouble understanding how monitoring the wort temp in an indirect heating situation does not result in super heating the chamber until that temp is reached, up to the limit of the heat source, or taking hours to come back to temp if the source is low power. I definitely want to do some tests with my chart recorder. Could be interesting.

I suspect that once you reach steady state temp on the wort the difference between maintaining the ambient temp vs maintaining wort temp is minimal (post fermenting) and the point of monitoring makes no difference. The real difference will be cycle time and ambient fluctuation. I'll set up my 4th chamber with 5 gal of water and do some tests. I'm intrigued by this now. Sure wish I had a multi channel recorder.

I'll bet that maintaining ambient gives a nearly flat temperature reading on the wort, although a slower ramp up to that temp initially (again assuming fermentation is done). In the case of fermentation, setting the temperature lower initially would give you a stable wort temp, although higher, as well.

I'll report my findings in a few days.

John

I would disagree that the fermentation chamber functions as an oven and much more as a chiller. Of course, a chamber in cold ambient conditions would need heat much more often then one in conditioned space.

I cool my wort down to 70-80F with a counter-flow chiller as it enters the carboy. I then chill to a few degrees below the lower end of the recommended fermentation temperature. I pitch yeast, inject oxygen and shake. It goes into the chamber with a set temperature at the lower recommended temperature. So far, none of this has required any actual heating.

The critical, first few days of fermentation is exothermic and if the wort temperature is not being monitored, it's not really being controlled at this point. At some point the fermentation stops generating heat and the system reaches a steady state temperature which includes the effects of ambient external and internal temperature and any inherent heat generation.

Due to its thermal mass, the wort resists temperature change while the air in the chamber doesn't. The layer of insulation over a probe on the surface of the carboy seems to dampen the system such that the compressor doesn't short cycle with quick air temperature changes but doesn't undershoot the set temperature the way a thermowell probed configuration might.

Other than the 9watt, always on, evaporator fan, I have not had to add any heat to my chamber, lager or ale. This allowed me to swap my Celsius two stage controller for a Farhenheit single stage controller.

It's great that you want to experiment with probe placement. I just wanted to let you know that MANY here have already experimented.

You are measuring air temp... not fermentor temp. Of course the cycles will be wild... there is no buffering action.
Those temp controllers will hold the temp easily to withing +/- .1C IF you monitor the actual fermentor AND have both the heat and cooling working. If you do this, I guaranty you'll need to connect the heaters (the fans won't be enough).

raouliii said:

I would disagree that the fermentation chamber functions as an oven and much more as a chiller.

Click to expand...

There is no difference. You have a chamber, you add heat, or you take heat away. The word 'oven' infers that you are only adding heat. The actions inside are identical except the direction of transfer. It's a temperature controlled chamber to be less specific. The name (oven, chiller, etc) was never meant to be a point. In my case it's more about adding heat. My basement rarely gets to 70F even in a heat wave, so cooling is minimal.

The fact that your chamber stays above ambient with the 9 watt fan means you are adding heat, and your situation clearly calls for very little, so you don't need to add any otherwise. I'm finding the same result as well. If I was ready with my chilling side, I could run the fans 100% as I'd like to, and chill as needed to keep the temp down, also needing only a cooling control. Almost bought 4 by accident as the "F" range was clouding my thought patterns. I just can't think in "C" yet. Adding the cooling requires cutting/drilling the back of the cabinet, so I want to 100% sure of my cooling solution before I breakout the tools. I suppose I could make a temporary door for testing before I commit.

The reference to the short cycling of the compressor is a critical point. Controlling a compressor with chamber air monitoring would be the death of the compressor in no time if it were not for the built in delay of the controller. This was never my intention for cooling. I would be drawing cool air (or chilled liquid as I had previously planned) into the chamber and it would be cycling similarly to the fans now. My cooler has the Cool only version (but in C, Argh), and has been working great for about 18 mo now.

I'd like to think I'm looking at more than experimentation since I have the experience with controllers, temperature monitoring, infrared 'heat' transfer, and such, and am simply applying that knowledge to beer brewing. Can't wait to get home and get set up. The recorder is at my shop, and I won't be there till tomorrow to get it, so testing won't start till tomorrow night assuming something more important comes up to distract me. It usually does. Case in point since I started this post.... just got a 'do you want to go out to dinner' text. Priorities. Gotta keep my wife before beer, especially since she does not drink it.

I just last night hunted down my 'cheap' step/ramp controller to ponder using it to control the entire fermentation duration. You set the start, ramp, steps and go. For example on a lager: Start at 65, ramp down to 55, hold x days, ramp up to 68 for x days, then ramp down to 35 for the lager phase. Won't transfer to the secondary for you, but that's about it. Hmmmmm, I just might have consider this more......it's ideal for lagering. For ales you can add a cold crash as the last step. It controls heat and cool as well, plus is externally programmable. Shame it won't fit in the same cut out as the ST-1000.

acidrain said:

You are measuring air temp... not fermentor temp. Of course the cycles will be wild... there is no buffering action.
Those temp controllers will hold the temp easily to withing +/- .1C IF you monitor the actual fermentor AND have both the heat and cooling working. If you do this, I guaranty you'll need to connect the heaters (the fans won't be enough).

Click to expand...

I ran them with fan & heat cycling all winter last season (9 brew sessions), and used the cooler for 3 lagers. Monitoring the fermentor temp will assuredly give a much wilder air temp in the chamber.
It was only when I ran the fans 100% and attempted to cycle the heaters that I found the 24 watts of fan alone were enough to push the temp up, by 5C in 2 hours. I never expected that. It takes about 1 minute to raise .4C with fans only.

jleiii said:

I ran them with fan & heat cycling all winter last season (9 brew sessions), and used the cooler for 3 lagers. Monitoring the fermentor temp will assuredly give a much wilder air temp in the chamber.
It was only when I ran the fans 100% and attempted to cycle the heaters that I found the 24 watts of fan alone were enough to push the temp up, by 5C in 2 hours. I never expected that. It takes about 1 minute to raise .4C with fans only.

Click to expand...

Dude...
respectfully...
You are completely missing the point.
You are not fermenting air. Who cares what the air is doing.

acidrain said:

Dude...
respectfully...
You are completely missing the point.
You are not fermenting air. Who cares what the air is doing.

Click to expand...

No he's not missing the point. He understands this quite well. These systems are built to create and hold an ambient air temperature. Attaching the probe to a large object and insulating it would cause extreme over heating or cooling and lead to much more extreme fluctuations in wort temperature.



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Conman13 said:

No he's not missing the point. He understands this quite well. These systems are built to create and hold an ambient air temperature. Attaching the probe to a large object and insulating it would cause extreme over heating or cooling and lead to much more extreme fluctuations in wort temperature.

Click to expand...

Thanks for the support. The level of 'extreme over heating or cooling' is very much dependent on the heat produced during the heating cycle. My 24 watt fans will produce little overheating, whereas the 250 watt heaters I have will reach oven temps (if I dare say oven again!) before the wort heats up enough to end the heating cycle, then possibly overshoot. The difference in thermal mass of the chamber vs the wort is easily hundreds to 1, as it's Masonite and foam.

Regarding fermenting air - The air surrounding the carboy is what is keeping the carboy at temp.
If direct heating the carboy, monitoring the carboy is mandatory, ie wrap heater, glycol jacket and such. ANY other method (heaters such as I have, or the bulb in a can for example) heats/cools the air and that conducts to the carboy there by changing it's temp. The point of monitoring is the only real variable. Technically the 'bulb in a can' can also heat the wort by infrared absorption, but I doubt that is measurable without very expensive equipment.

This thread seems to have gone off on quite a tangent from my original post where I was wondering if anyone else had experienced incidental heating from the fans alone. 1 confirmation of that.

After an unexpected dinner out, and 3 hours of dealer pricing updates on the heaters we manufacture, and I see that the 3 chambers are dead on the set points with nothing but fans, with the basement at 10F lower. Clearly the heat from the fans is enough as seemed the case last night. Hopefully I can get the 4th chamber set up for testing tomorrow and see what the real difference is when monitoring air vs carboy. The one point that can't be disputed is the fact that the wort CAN be warmer than the chamber air if any active fermenting is going on. In that case the carboy heats the air, and could require cooling to keep it at the desired temp. For my circumstances that's a summer issue only. It will be interesting to see if the fan heat can keep up when the really cold weather comes back. That will be about 15F difference from chamber to basement, vs 10 now.

Conman13 said:

.....Attaching the probe to a large object and insulating it would cause extreme over heating or cooling and lead to much more extreme fluctuations in wort temperature.....

Click to expand...

Shared experiences by many here on HBT has shown this NOT to be the case. The insulation does not completely isolate it from the chamber, but acts as a thermal buffer from the quick temperature changes of the chamber air and strongly couples the probe to wort temperature.

Overshoot/undershoot of set temperature can certainly be a factor but experience shows that it is usually less than 1deg. It can be mitigated by monitoring and taking steps like reducing the heating element power rating or improving air movement and then setting the controller differential just outside the greater of the two. Building/designing with too much cooling or heating capacity will exacerbate this issue. Gentle, slow, cooling and heating is the preferred method as yeast do not respond well to quick temperature changes.

Consideration must also be made to the type of chamber being implemented. All will function differently, residential fridge, residential freezer, mini-fridge, commercial cooler, window a/c unit, glycol cooled, etc. and require tweaking once it is up and running.