HERMS rig - best place for the thermostat sensor?

[brewbrew]

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]

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.

[LeeH]

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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[billygoat]

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

[PeeBee]

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



[EDIT: The "month or two ago" in reality started several years ago. Scary isn't it!]

[barneey]

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