Where best to place the PID thermostat?

[RoomWithABrew]

R u sure!

 

[Galena]

Just for interest I've just mashed in and started recirculating for a 65º mash (using my diy HERMS).

Why is the yellow line (kettle) so high and what is it measuring?

 

[peebee]

Why is the yellow line (kettle) so high and what is it measuring?

I think I can make a stab at that?

Kettle is seconding as "HLT" 'cos what else listed is heating the HERMS coil?

I'm quite impressed with what the graph is showing. I could only assume when I chose to sample temperature at the exit from the coil, but the graph shows I would be seriously exaggerating to think the entry to the coil would significantly lag behind.

The exit might be the best place if attempting to step up the temperature (exit temperature would be best at controlling the temperature), but the entry temperature would be best to confirm temperature has stabilised (entry temperature would be best for monitoring the temperature). Taking the temperature direct from the stodgy mash is likely to be somewhat random.

I remember when you started this project (last year). I think I'm being consistent with my response now as back then?

 

[Galena]

The exit might be the best place if attempting to step up the temperature (exit temperature would be best at controlling the temperature), but the entry temperature would be best to confirm temperature has stabilised (entry temperature would be best for monitoring the temperature). Taking the temperature direct from the stodgy mash is likely to be somewhat random.

Good points, it should be easy to try both and see which gives the best result.

I remember when you started this project (last year). I think I'm being consistent with my response now as back then?

Yes I have had some time away from brewing but got the bug again now, I have not been able to locate that old thread to check what was decided, though I guess I haven't spent sufficient time searching.

 

[Buffers brewery]

Why is the yellow line (kettle) so high and what is it measuring?

If you checkout TETBs brewday thread and his latest post (#202) you can see his HERMS set up (that I’ve copied). Right at the back you’ll see a “kettle”. That is used to heat the water circulating in the counterflow heat exchange. The reheated wort temperature is taken as it returns to the mash tun (wortometer).
Why the grain bottom should be 0.1C hotter than the top where the reheated wort is returning, is not clear. Could be just a tolerance/calibration thing? Still 0.1C between bottom and top is impressive

 

[Galena]

If you checkout TETBs brewday thread and his latest post (#202)

Thanks, much clearer now, and yes I agree 0.1C is very impressive.

 

[The-Engineer-That-Brews]

Why is the yellow line (kettle) so high and what is it measuring?

Yes @Buffers brewery described it correctly: the kettle temp is the temperature of the water entering the jacket of the counterflow...

The photo of the kit is a bit confusing so it might be easier to see what's going on from a system diagram:

During the mash taps A, B and D are closed.
For the sparge I close tap C, open tap A and then balance taps B and D (runoff)

 

[peebee]

I have not been able to locate that old thread to check what was decided, though I guess I haven't spent sufficient time searching.

It just so happens ...

https://www.thehomebrewforum.co.uk/...id-thermometer-in-electric-mash-kettle.97278/

 

[Galena]

It just so happens

Thank you :)

 

[Galena]

If the PID thermostat is placed inside a thermowell I seem to recall that you need some sort of thermal grease to make it work efficiently, is that correct?

 

[The-Engineer-That-Brews]

If the PID thermostat is placed inside a thermowell I seem to recall that you need some sort of thermal grease to make it work efficiently, is that correct?

It's not essential but it makes it react faster to changes in temp and can also help stop it falling out accidentally

This is the sort of stuff to use - you don't need to use much

https://www.amazon.co.uk/HY-510-25g-Thermal-Paste-Heatsink-Conductivity-510-25g/dp/B07NRG8KJK

 

[Galena]

This is the sort of stuff to use

Thanks, ordered some

 

[user 47834]

It's not essential but it makes it react faster to changes in temp and can also help stop it falling out accidentally

This is the sort of stuff to use - you don't need to use much

https://www.amazon.co.uk/HY-510-25g-Thermal-Paste-Heatsink-Conductivity-510-25g/dp/B07NRG8KJK

View attachment 86491

Does that stuff not dry up and stick? Could make removing the probe a bit tricky if so.

 

[Agentgonzo]

It's not essential but it makes it react faster to changes in temp and can also help stop it falling out accidentally

This is the sort of stuff to use - you don't need to use much

Amazon.co.uk

View attachment 86491

thermal pastes like that are normally used for CPU coolers where you want to really maximise the heat transfer. For just having a temperature probe, I'm sure any grease/paste will be just as quick (I have just dribbled water into mine as it's more conductive than air) but a cheap poor man's solution is to get any powdered metal (aluminium) and mix it into vaseline or any other grease you have

 

[Agentgonzo]

Does that stuff not dry up and stick? Could make removing the probe a bit tricky if so.

from using the ones designed for CPU cooling etc, no, they don't dry up much, even over many years. Easy to clean with tissue and a bit of solvent.

 

[user 47834]

from using the ones designed for CPU cooling etc, no, they don't dry up much, even over many years. Easy to clean with tissue and a bit of solvent.

Thanks. Always wondered if people "cemented" on their CPU to their motherboard and therefore married them together forever.

 

[The-Engineer-That-Brews]

thermal pastes like that are normally used for CPU coolers where you want to really maximise the heat transfer. For just having a temperature probe, I'm sure any grease/paste will be just as quick (I have just dribbled water into mine as it's more conductive than air) but a cheap poor man's solution is to get any powdered metal (aluminium) and mix it into vaseline or any other grease you have

Heh I have loads of old tubes of heatsink paste in my toolbox, but no powdered aluminium!

 

[user 47834]

For guitars, we make nut sauce*. Grind a lead pencil into vaseline and smear it in the nut groove for the string to move around in easily.

Would any kind of metal filings work?

*heh

 

[Agentgonzo]

Heh I have loads of old tubes of heatsink paste in my toolbox, but no powdered aluminium!

I used to have a half pound bag of it from the days where I was 'experimenting' with how you could light a campfire with thermite. Long since got 'disposed' of (safely)

 

[Agentgonzo]

For guitars, we make nut sauce*. Grind a lead pencil into vaseline and smear it in the nut groove for the string to move around in easily.

Would any kind of metal filings work?

*heh

As long as they are thermally conductive, I'm sure it would.