HERMS temp probe placement? Help!

[Kazi the Younger]

I've built a HERMS system- pics to come eventually, and I did my first batch last weekend. The temp is controlled with a Ranco etc. I have the probe in a thermowell @ the exit end of my heat-exchange coil, but I'm thinking that isn't the best placement in my setup. I'm thinking it belongs somewhere near the wort-return manifold so it's controlling the temp of the liquid being dumped directly on top of the grain bed. I have about 7 feet of uninsulated tubing/material between the heat exchange coil exit and the wort return manifold, so by the time it gets there it has cooled down several degrees. So if I set the RANCO for 152, by the time the wort is returned to the grainbed, it is 147, so I need to compensate--set the RANCO to 157 in order to get 152 on top of grain bed. This seems a little inelegant to me.

Also dumb question, but do you guys set your temp differential to +/- One degree?

BTW mylo, your pics look awesome--where is your temp control probe placed?

[Mylo]

That's a tough question. I don't have any empirical data one way or the other. I was initially thinking that I would put mine in a thermowell in the middle of the mash, but now I think I will just put one in a stainless T off of the output. I also think that I will not ever run a larger than a 5-6 degree differential. All my copper will be insulated. I might just put some inline thermometers on both sides of the coil - just for kicks.

I will have two probes, one on the HLT and one on the mash. The HLT will control the burner. I will wire my mash pump so that I can either constantly recirc, or switch it to temp based. Once I get the mash up to temp, I can choose to continue to circulate, and bypass the coil - or just knock it off.

Unfortunately, all the probes and PIDs won't come until the v2.0 control panel. In the meantime, I can still do a mashout - although it will be all manual.


Mylo

[Herms]

The place to stick it is right at the output of your wort return manifold.

That way you compensate for any heat loss between your heat exchanger and your manifold. The wort returned to your mash should be exactly at your setpoint temp. I have a thermometer in the middle of my mashtun, so if I want I can bump up my setpoint a little, to compensate for any heat loss as the wort moves thru the mashtun.

You may want to agitate the water around your herms coil. I just use an aquarium pump to pump bubbles around the herms coil. This prevents stratification (I think that's what it's called). I always had trouble hitting my setpoint until I added the the aquarium pump, the temp would always be a few degrees low.

Mark

[Kazi the Younger]

thanks guys--that's what I'm thinking--probe @ wort return manifold.

I am agitating the water around my herms coil with a paint stirrer attached to a drill running @ low RPM--this has worked well and prevents the "thermal blanket" that will occur around the coils if the water isn't flowing.

I agree it's nice to have multiple thermometers--I have one that sits midway through the mash itself, so I can see the temp in the grain and another one that sits just beneath the wort-return manifold, so I can see the temp of the liquid coming directly on top of the mash. Now I am going to do what you suggest and put the RANCO probe right @ the wort return manifold, so that the setpoint IS EXACTLY the temp of the wort that hits the top of the grain. I will keep that additional digital probe there as both a second check to see if the ranco is on target (I notice it is actually 1 degree off of my other digital thermometers) and also I think it's good to have it there so more importantly, I can know exactly what the temp of the sparge water is when it hits the top of the grain, since my sparge water temp is not being controlled by a ranco.

Another thing to note: When I did my last mash, I direct-fired the mash tun because the temp wasn't ramping up to mash-out fast enough and in the process caramelized some of the grain in the tun. This happened because I am using a manifold in my mash keggle rather then a false bottom. I am going to convert to a false bottom now because this happened--you guys were right. I guess my effeciency will get worse, but oh well. Goodbye 92% effeciency in Gott cooler, Hello 80% in keggle!

[Kazi the Younger]

another thing to add: there seems to be no substitute for having the probe placed directly in flowing liquid.

There seems to be a bit of heat loss in thermowells--and they react slower, even when made with copper. I don't think they are meant for super precise temp measurements

I think I will rig up something so I put the thermowell in some compression fitting with rubber stopper so I can slide it in and out for cleaning, but the point is the end of the probe is directly in the path of flowing liquid

[foomench]

There seems to be a bit of heat loss in thermowells--and they react slower, even when made with copper. I don't think they are meant for super precise temp measurements

I was planning on getting a temperature probe that could go right into my brewing vessels, no thermowells. At that point the decision is grounded or ungrounded, with grounded reacting faster, but subject to electrical noise. I've been led to believe that thermowells are much more important in a continuously running industrial setting as they allow the probe to be replaced easily and without emptying the vessel. For my homebrew setting, this isn't so important.

[aleguy]

You might want to take a look at these.
http://auberins.com/index.php?main_page ... ucts_id=96

[3G_]

My HERMS had its maiden voyage a few nights ago. The temp. probe is mounted at the exit point of the HE.
When i dialed in 66 celcius to raise the wort from 50 degrees the wort exiting the HE came up to 66 quite rapidly, about 15 minutes. However the temp probe in the centre of the mash tun was much slower to come up in temp.
I am led to believe it is the wort temp which is crucial not thetemp in the mash tun.
If i mount the temp probe at the sparge arm i would get the temp correct there but i am worried about denaturing the enzimes in the HE.
Where are most of the HERMS brewers mounting their sensors in the US.

Cheers