Where to stick it?

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Troutman47
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Where to stick it?

Post by Troutman47 » Thu Nov 09, 2017 6:46 pm

Hi Guys, just wondering where the best place to have the PT100 probe on the HERMS?
I’ve got hold of a couple of kegs and want to convert one in to a mash tun, so is it best to have the temp probe as the wort returns in to the mash tun or what if the probe was in a thermowell so it sits in the mash?

Thanks guys!

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GrizzlyBrews
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Re: Where to stick it?

Post by GrizzlyBrews » Sun Dec 10, 2017 5:08 pm

I would say with HERMS that you are pretty safe placing the probe in a thermowell in the mash tun. As you're not applying heat directly to the wort.

In a RIMS system a lot of folks place the sensor in a T piece just before the wort re-enters the tun. This is because it will have the fastest thermal response and reduce the chance of scorching the wort.

If the sensor was in the grain bed the thermal response would be a lot slower, because of the large thermal mass of the grain bed. Theoretically this then causes the element to be going hell for leather, scorching your wort. Something that can't happen in a HERMS system.

Hope this helps.

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PeeBee
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Re: Where to stick it?

Post by PeeBee » Sun Dec 10, 2017 6:10 pm

You can put temperature probes in the mash, in the wort outlet to the HERMS coil and in the wort inlet from the HERMS coil. But all these placements are only informational so you can check what's going on.

If the probe is controlling the temperature of the mash it MUST be in the HLT or whatever else is heating the water around the HERMS coil (some folk have a small pot for housing, and heating the water around, the HERMS coil so as to react more quickly - there's 101 ways to <harm> a cat and I don't hold with this "small pot" idea). Placing the probe anywhere else will react too slowly and cause wild fluctuations in mash temperature before it settles down.

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Re: Where to stick it?

Post by RobP » Sun Dec 10, 2017 7:40 pm

As ever there are people that differ from that view.

"You want to be able to take the temperatures of the water and wort as it flows. If you just stick it in the kettle you will only get a stratified temperature, in your mash if you don't have good flow you will get a miss reading of temperature and miss your target temperatures. It also helps you notice if your having flow problems with pumps of a stuck sparge by displaying temperature swings. Remember this system is designed to control the process/temperatures. This is a very important placement of the probes and should not be minimized. Keep them in the flow.

Castermmt"

http://www.theelectricbrewery.com/forum ... p?p=290893

It's one of those contentious questions that will never have definitive answer.

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PeeBee
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Re: Where to stick it?

Post by PeeBee » Mon Dec 11, 2017 12:43 am

RobP wrote:
Sun Dec 10, 2017 7:40 pm
As ever there are people that differ from that view.
"... If you just stick it in the kettle you will only get a stratified temperature, ...Castermmt"
http://www.theelectricbrewery.com/forum ... p?p=290893...
That's probably true; it is easy for me to forget the water does not stay stationary in my HLT and I get none of that "stratified temperature" business, and that's probably very relevant.

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Re: Where to stick it?

Post by RobP » Mon Dec 11, 2017 11:40 am

PeeBee wrote:
Mon Dec 11, 2017 12:43 am
RobP wrote:
Sun Dec 10, 2017 7:40 pm
As ever there are people that differ from that view.
"... If you just stick it in the kettle you will only get a stratified temperature, ...Castermmt"
http://www.theelectricbrewery.com/forum ... p?p=290893...
That's probably true; it is easy for me to forget the water does not stay stationary in my HLT and I get none of that "stratified temperature" business, and that's probably very relevant.
I don't understand how "stratification" happens. I'd expect the heating from the element to make convection currents in the water. Hey-ho.

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Re: Where to stick it?

Post by jaroporter » Mon Dec 11, 2017 12:46 pm

it will create convection currents but it's not perfect. in a system where you need accuracy to within a degree or so a gradient spanning a few degrees i guess would be an issue. i don't use HERMS though, are you controlling the temperature of the HLT to control the wort?
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PeeBee
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Re: Where to stick it?

Post by PeeBee » Mon Dec 11, 2017 2:21 pm

jaroporter wrote:
Mon Dec 11, 2017 12:46 pm
it will create convection currents but it's not perfect. in a system where you need accuracy to within a degree or so a gradient spanning a few degrees i guess would be an issue. i don't use HERMS though, are you controlling the temperature of the HLT to control the wort?
Yes the HLT (or special "small" vessel) is being heated in HERMS systems to indirectly heat the mash. Hence the temperature probe is in the HLT to control the HLT heater. The mash temperature is just following the temperature in the HLT via the HERMS coil.

My HLT is constantly pumped hence the temperature in the HLT is reasonably uniform.

It is important to agitate the HLT as you not only get the (doubtful) stratification of heat in the HLT but also a gradient of heat as you get further from the HERMS coil. (As my HERMS coil is outside the HLT, jacketed, and the HLT water continually pumped around the jacket I don't get that heat gradient either).

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Re: Where to stick it?

Post by RobP » Tue Dec 12, 2017 11:50 pm

jaroporter wrote:
Mon Dec 11, 2017 12:46 pm
it will create convection currents but it's not perfect. in a system where you need accuracy to within a degree or so a gradient spanning a few degrees i guess would be an issue. i don't use HERMS though, are you controlling the temperature of the HLT to control the wort?
I am, yes. It seems to work fine but I'll implement a way to agitate the water in the HLT. Shouldn't be hard.

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johnmac
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Re: Where to stick it?

Post by johnmac » Fri Feb 09, 2018 6:42 pm

Does it matter if you have uneven temps in the HLT? The wort will pick up an average HLT temp and if some of the HLT is above mash temp, some below - so what. The HLT is a heat source for warming your mash, just like the element in a RIMS, which is obviously much hotter than the mash.

Please tell me if I'm wrong - I'm still working on my first HERMS!

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