ATC 800+

[therebelmc]

Hi after a disasterous effort to brew during the hard frosts in December i have decided to invest in the ATC 800+ controller set up. does anyone know the link for wiring up and is it best to have the probe in the FV or not ?

[Blackaddler]

Hi after a disasterous effort to brew during the hard frosts in December i have decided to invest in the ATC 800+ controller set up. does anyone know the link for wiring up and is it best to have the probe in the FV or not ?

ATC800+ wiring diagram

Put the probe in the FV for more accuracy.

[EoinMag]

If you have the plastic probe then just be sure to wash and star san it well, use the stopper to stick it to the side of your FV and feed the probe down into the fermenting wort, not an issue.

[richc]

Put the probe in the FV for more accuracy.

I have heard that simply taping the probe to the outside of the vessel (perhaps with some insulation over it) is pretty much as good as sticking it in the wort. I haven't tried this yet but it would save a bit of cleaning work.

[boingy]

Where you put the probe will depend on how you will be heating the wort. If you are heating it directly with a brew belt, heat pad or submerged aquarium heater then put the probe in the wort. If you are heating indirectly, say by heating the air in an insulated cupboard/fridge, then put the probe in the air.

[Bobba]

I got both probes with my ATC 800+ so compared both methods. I was keen to use the one in the wort initially as I thought it would be more accurate, but found that the temperature was identical to that of the probe taped to the side of the FV. I cut out a few sections of insulating foam stuff from some packaging and placed it on top of the probe and duck-taped it all to the outside of the FV - this should keep the probe temp closer to the beer temp than to the air temperature. Works a treat, you don't need to sterilse it, and I've been using the same ducktape for the past 7 brews. I would definitely attach it to the FV rather than measuring the ambient air temperature in the fridge however, otherwise you will find the fridge/heater will come on much more often for shorter periods of time.

[richc]

Where you put the probe will depend on how you will be heating the wort. If you are heating it directly with a brew belt, heat pad or submerged aquarium heater then put the probe in the wort. If you are heating indirectly, say by heating the air in an insulated cupboard/fridge, then put the probe in the air.

I think this isn't actually correct, fermentation produces heat therefore the temperature of the wort can be significantly higher than the temperature of the surrounding air.

[boingy]

Where you put the probe will depend on how you will be heating the wort. If you are heating it directly with a brew belt, heat pad or submerged aquarium heater then put the probe in the wort. If you are heating indirectly, say by heating the air in an insulated cupboard/fridge, then put the probe in the air.

I think this isn't actually correct, fermentation produces heat therefore the temperature of the wort can be significantly higher than the temperature of the surrounding air.

That is true to some extent but if you put the sensor in the wort and heat the air you will get massive overshoots in the air temperature, because of the huge thermal mass of the wort. If you are lucky, the heater you are using will hit its thermal trip and shutdown safely. If you are unlucky you will melt the lining of the fridge. If you are really, really unlucky, and a Monty Python fan, then the fridge will burn down, fall over and sink into the swamp.

So it is the lesser of two evils. I set an air temperature of 18C and get a fermentation temperature of about 20C. A better solution would be to use a PID controller.

To be honest, unless you are somehow circulating the wort round the FV then it is a fairly moot point. There will be significant temperature gradients across the wort throughout the fermentation period and the temperature controller will only be measuring at one point.

[EoinMag]

If you pitch close to the fermentation temp then the placement of the probe will be a relatively moot point as the temperature fluctuation will be slow and always stay in or about the same with the fridge and the heater never doing too much work.

[Kev888]

Where you put the probe will depend on how you will be heating the wort. If you are heating it directly with a brew belt, heat pad or submerged aquarium heater then put the probe in the wort. If you are heating indirectly, say by heating the air in an insulated cupboard/fridge, then put the probe in the air.

I think this isn't actually correct, fermentation produces heat therefore the temperature of the wort can be significantly higher than the temperature of the surrounding air.

I completely agree with Boingy on this one, though I also agree that its a bit counter intuitive. Essentially if you're heating or cooling the air then you really need also to be measuring the air (maybe with at most some slight added thermal damping from some copper or small pot of liquid around the sensor) to get proper responsiveness from the control system, otherwise things can get out of hand without the sensor ever realising it (It takes ages to change the temperature of all that wort so the heater/fridge will be on solidly for ages too). Only if you're heating/cooling the wort itself (or as near as damn it) is the link between cause and effect close enough that its it really safe (in my opinion) to measure the wort directly, and then (see the next point) I'd probably want a higher resolution controller than the ATC.

Also I think its worth distinguishing between consistancy and accuracy. If your sensor is in the wort then the wort will change measurably before the ATC takes action, which isn't very consistant with a 'relatively' low resolution controller like the ATC. But if you instead control/measure the air, then the air changes measurably not the wort, which (being much slower to respond) barely moves - so the air approach gives more consistant wort temperature (for a given resolution of controller) - and yeast likes consistancy. The absolute accuracy is the trade-off, as has been mentioned the wort is a little warmer as fermentation generates (some) heat, but I find setting the desired temperature 1c less than I want the wort to be (or 2c for bigger 45l batches) gives pretty much what I'm after - particularly given the variation within the FV that Boingy mentioned. My understanding is that consistancy is more important to yeast than hitting an exact temperature - provided of course that its consistant at a temperature it is happy at and that we like the tase results of.

Cheers
kev

[richc]

I'm still not convinced this that measuring the air is the right thing to do, unless your heater is going to get the fridge temperature really high or the fridge to get it really low then measuring the temperature of the wort is still, IMO, the right thing to do. The heat capacity of the air in the fridge is pretty low compared to that of the wort so I don't think over shooting the temperature is very likely. Also measuring the air temperature will not give a more consistent temperature as the wort temp will change as the fermentation produces more or less heat.
Actually this topic was a discussion on one of the recent US brewing podcasts (Brew Strong IIRC) and they concluded that in contact with the outside of the fermenting vessel was the right place for the temperature probe. I don't always agree with out American friends but this time they sounded correct from what I know of thermal physics and control electronics.

Hmmm, reading about this more I find myself disagreeing with myself, of course with something like an at800+ you will oscillate over the control range of that device. I think I need to think about this a bit more.....

[richc]

ok aftere more thought, measuring the wort temp will give a variation of one degree as the comtroller switches on and off. Measuring the air will give a slower, but possibly larger variation as the fermentation progresses.

Edit: sorry about the typos, posting from my phone

[Kev888]

Heh heh, yes tricky isn't it, and it seems so simple.

Yes I agree: measuring the wort will let it oscilate within the set perameters - say for example +/-1c = a 2c range. Measuring the air will mostly eliminate that inconsistancy - due to the wort's far slower response it will average it out nicely. There is a difference between the air temperature and the wort temperature with this method, which I also agree isn't ideal; its 'reasonably' consistant over time (compared to the wort oscillating within the range of the controller) and can be offset manually to at least an approximate degree so can be mitigated but not completely. So I guess the choice comes down to your priorities; for myself I'm far more concerned about my fermentation being consistant, and not oscillating often/quickly, than I am about hitting say 18c instead of 19c which doesn't concern me much at all.

The other issue though is the safe control of the heater - I think we largely get away with either method in practice because people tend to use fairly modestly powered heaters. But the wort has such a big thermal intertia that if the sensor is in it and if the heater is heating the air rather than the wort then the cause/effect link is flawed and there is the potential for a heater to be doing pretty much anything to the air for ages without the sensor in the wort noticing anything at all, and having a lower heat capacity the air is easy to get quite hot compared to the wort.

The only issue I've been aware of is with a small volume (like a starter) providing little regulation (or I believe with cold lager) - then an air probe can sometimes react too quickly/sensitively and oscillate heating and cooling devices without a generous dead band being set, hence the pots of water/copper thing, or probably taping it to the side of the FV - at least that would hedge the bets I suppose; I've not actuallt tested that but I'd imagine if the air got really hot at least part of the sensor would register it.

Cheers
Kev

[richc]

Only one minor point, in any particular conditions you are likely to get only just over 1 degree of variation unless the air is holding a lot more heat energy than I think it can. Say it is cold outside, the wort cools down below the switch on temperature for the heater, this heats the wort up until it hits the required temperature (not the same as the switch on temperature for the cooling) then switches the heat off.

[Kev888]

Yes, if its a cold day thats definately true, and if its a hot day the same would apply but in the other direction for the cooling.

However, if the daytime is warmer than the set temperature and is then followed by a night temperature that is cooler than the set temperature (for example) then it will be able to go over and then later under the set temperature by about 1 degree, or to have changed by up to 2degreesC in a relatively short period. I even had that happen within the daytime last year; mid day was warmer than I'd set the controller for whereas either side of it the early AM and later PM were cooler - the ATC worked its magic and overcame the variation but I'm intending to insulate the garage roof this spring to help reduce energy use.

Cheers,
Kev