HERMS rig - best place for the thermostat sensor?

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brewbrew
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HERMS rig - best place for the thermostat sensor?

Post by brewbrew » Mon May 25, 2020 2:20 pm

Just done my first HERMS run - 15 litres of mash liquor (6kg malt) - heated and controlled via a 30 litre kettle (2.4kW) and heat exchanger (both circulation pumps running at approx 12 litres per minute). The thermosensor (Inkbird controller) in the kettle - positioned in the flow of the return pipe at the base of the heat source kettle.

I did a trial run and established that if the kettle ran at 69.5 dec C, I got roughly 66.5 deg C in the mash tun top outlet onto the grain bed - however, I did see a 1 deg C variation in this as the kettle cycled on the thermostat (Inkbird temp bandwith set to minimum ie 0.3 deg C).

I'm thinking about moving the sensor to the mash re-circulation circuit - probably in the outflow at the top of the grain bed.

Does anyone have any advice on the best configuration? - I'm no chemical engineer and this seems to need some deep knowledge if I'm to improve on what I have got. Whilst the mash circuit seems logical, I wonder if there will be a lag and some sort of over-run or bull-whip effect on the temp profile if the control is one step away from the heat kettle.

What do others do with HERMS rigs?

Thanks for any advice anyone has.

Rankin_leigh
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Re: HERMS rig - best place for the thermostat sensor?

Post by Rankin_leigh » Mon May 25, 2020 2:50 pm

I'm still in planning phase for upgrading to herms so no real life experience.
But I know Peebee did a pretty extensive thread month or 2 on the positioning options of the probe.

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HERMS rig - best place for the thermostat sensor?

Post by LeeH » Tue May 26, 2020 12:42 pm

My RIMS controls on the return leg, and it controls well. However, I ultimately use the temp indication in the grain bed and tweak the RIMS control temp to suit my target as that is the real mash temp.

Hope that makes sense.


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Re: HERMS rig - best place for the thermostat sensor?

Post by billygoat » Mon Dec 06, 2021 12:32 pm

Usually the temperature sensor is placed at the exit of the HERMS coil where the wort temperature is at its highest.

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Re: HERMS rig - best place for the thermostat sensor?

Post by PeeBee » Mon Dec 06, 2021 2:20 pm

Rankin_leigh wrote:
Mon May 25, 2020 2:50 pm
I'm still in planning phase for upgrading to herms so no real life experience.
But I know Peebee did a pretty extensive thread month or 2 on the positioning options of the probe.
Eee ... thanks for that!


The thread in question is : viewtopic.php?f=60&t=80501



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Re: HERMS rig - best place for the thermostat sensor?

Post by barneey » Tue Dec 07, 2021 5:42 pm

I have played around with HERMS & RIMS systems in the distant past temp sensors in the HLTs, Mash Tun inlets and outlets and the Mash itself, mostly controlled with PIDS, it can lead you down a rabbit hole if you are not careful.

My only piece of advice if you don't need a multi temp mash profile, just go for a single mash temp in a highly insulated mash tun.

I am very much for the KISS approach these days :)
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