HERMS coil

[bobsbeer]

I am going to change my plastic bucket and tesco element HLT to a 38lt thermobox. Being insulated it should be more efficient. I am also thinking of putting a herms coil in the HLT. Has anyone done this? Any reason why not? I know I would be heating a lot of water, but I would be doing this anyway for the sparge, so why not use the heat for the mash? The MT is also a 38lt thermobox. And it would only mean one pid type controller rather than two. I have also seen smaller thermoboxes on ebay, 4lt, although they are not much less expensive than 38lt ones. What about the internal coil? Can that be copper 10mm or is it better to have stainless steel?

 

[Fil]

I'm doubtful, you may need big elements to heat up the volume of water quickly enough to be reactive to the mash temp, AND hit your sparge temp quickly after maintaining the volume at mash temps. Most diy herms use smaller vessels so the heat input can react quicker to need. might be worth seeing how quickly the element/s? can heat up your volume before you commit, if it takes 1/2 an hour or more to hit sparge temp after maintaining mash temp, it may not be such a winning plan. and a immersion coil chiller can make a makeshift coil for testing the systems reactivity to changes in temps. I'd test before you commit tho.

 

[bobsbeer]

That is a consideration. I've not done step mashes before so have no idea on the mechanics of it. But my thinking was that a larger coil in the HLT was going to change the temp in the MT fairly quickly, if the HLT was already at the higher temp before recirc started. My understanding of step mashes is that the temp gets raised in stages, or steps rather than incremental increases. With rests at the specified temperature. So if the HLT is at say 45c initially for dough in, rests 30 mins. During this period the HLT can move on up to the next step ie 61c or so before the pump kicks in while the mash it at rest at the specified temp. Then say 68c for another 30 mins. With an insulated HLT the temp will increase fairly rapidly and a decent coil will heat the MT fairly quickly. The size of the coil may need a bit of calculating to get the optimum heat exchange and temp lift in a reasonable time. Say 5 minutes to move 10c? I'm not sure what smaller but more powerful exchangers take to raise 10c. But also this way must be less aggressive on the mash liquor. There is no need to heat the liquor higher than the desired temp to average out the whole mash at the higher temp. Or am I misunderstanding the mechanics of the smaller heat exchangers.

 

[mixale]

Plenty of evidence on here and JBK to NOT go down the HLT/Herms path.

Almost like you need the heating power of an electric shower to get the temp back up.
I've just removed the herms coil from my HTL and gone done the 4lt pot with kettle element route.

 

[Aleman]

I am going to change my plastic bucket and tesco element HLT to a 38lt thermobox. Being insulated it should be more efficient. I am also thinking of putting a herms coil in the HLT. Has anyone done this? Any reason why not?

I know several people who have done this . . .and then got very upset frustrated and angry when it does not work as expected. . . . In order to get a rapid rise in temperature you need the smallest volume of water in the water batch you can get away with (and still allow convection currents to get a 'stable' temp in the water bath).

It can be done very successfully IF you use a massive heat source to your HLT . . .think something like a 12-13KW burner under it . . . obviously not a viable solution in a Thermobox.

If you consider that the HERMS approach came about due to the 'limitation' in RIMS where the heater is in direct contact with a small qty of wort, and the potential of caramelising the wort and denaturing enzymes is quite high (apparently), then you can see that big volume water baths are great for stable temperatures, but not for rapid changes in temp . .. i.e step mashes.

 

[bobsbeer]

Thanks for your replies. I think given the evidence that putting the heat exchange coil in the HLT is not a good idea, so back to the drawing board on the HERMS tank. The HLT is going to be fitted with a 2.4kw burco element which can be fitted in the bottom. As I am restricted to 10 amps, 3kw elements are out. The HERMS will just have to wait until phase 2 of the new build.

 

[Kevin Wood]

Is it vital to have your HERMS and HLT working simultaneously, though?

I use a supermarket kettle with a copper coil inside for my HERMS.

The small volume of water makes it respond very quickly and it keeps a very stable mash temperature. Once the temperature is stable it's only occasionally "tickling" the element on and off, so whilst the peak current is 10A the average is very low.

 

[Fil]

I think that a hlt mounted h/e coil in the established breweries is more about energy saving and heating the next batch of mash liquor while cooling the boil of the last brew first, and then was used for herms as a secondary use, since it was there ...

 

[Kevin Wood]

I think the other thing to consider is that you might be able to make this approach work by accepting that the HLT is going to be at a constant temperature (probably a bit higher than your mash, as you're preparing liquor for the sparge) and control the mash temperature by some other means, such as controlling how much wort passes through the exchanger as opposed to bypassing it. I've seen setups where the PID is controlling a servo valve which does exactly that.

 

[bobsbeer]

This is a question for current HERMS users. How long does it take to increase the temp in the mash from one steep to the next? I.e how long does it take to increase 5 or 10 degrees with a kettle type heat exchanger?

 

[Aleman]

Depends on the size of the mash . . . but even with my 50L mash I can get around 1C/min

Insulation is your friend

 

[bobsbeer]

I am just trying to get my head around the science and mechanics of this. So with your system Tony you will change the mash step say from 50 to 68 in about 18 mins before the full mash is at the higher temp. Obviously the rise will be linear over the time period. Presumably the faster the change can be achieved the better. And all this depends on the volume required to be changed.

 

[Kevin Wood]

I haven't got any times for mine, unfortunately.

You can look at it another way..

I know that, with my kettle HERMS, the full output of the kettle element is transferred to the wort when heating the mash, i.e. the water in the kettle never boils. It gets to about 10-15 degrees above the mash temperature and sits there. I think it's a 2.2kW element, and obviously a bit of heat is lost to the environment, depending on how well insulated everything is, but that can be minimised with care. That tells me that unless I can put more heat into it, the HERMS is as good as it's going to be and I can't make it heat any faster.

The only advantage I can think of in having the heat exchanger in the HLT, is that you could store thermal energy in the HLT and use it for a step mash. I.e. let the HLT reach boiling point, then start circulating through it. You have a large amount of water at maybe 40 C above the mash temperature, and, with an effective enough heat exchanger, you might be able to dump that heat in quicker than an element could otherwise heat it with a smaller HERMS vessel. In theory. The price you pay is that it won't hold a constant mash temperature well due to the inertia of the large HLT, as already said.

 

[Aleman]

Problem with your approach Kevin is that the initial wort through the HEX would be denatured . . .the whole point is to have the water bath only as high a temp as it needs to be to get the returning wort at the next step temp . . .that way less of the enzymes are denatured.

 

[Kevin Wood]

Problem with your approach Kevin is that the initial wort through the HEX would be denatured . . .the whole point is to have the water bath only as high a temp as it needs to be to get the returning wort at the next step temp . . .that way less of the enzymes are denatured.

Ah.. Yes, that's true, of course. Was just thinking aloud.

 

[bobsbeer]

But if the HLT is up to temp with a 10m coil in the HLT the larger amount of stored heat in the HLT due to it's volume is going to heat the circulating wort faster that a small coil in a small vessel. What size the element in the HLT would need to be to keep up with the rapid loss of heat in the HLT I don't know, but there must be a way of working it out. But if a 2.2kw can only keep up heating say 2-3 lt of water, it follows that a 2.5kw would struggle to maintain 25lt, given the extra heat exchange capacity of the 10m coil. No doubt more costly as well, as more water is being heated to maintain the temp.

 

[tazuk]

tesco kettle +1 here is mine use a wine botttle to make coil :thumb:

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[Aleman]

Remember that you don't have to have a massively long coil a couple of metres is more than enough

 

[bobsbeer]

I have decided to not go down the HERMES in the HLT and add it later to the system. So it's back to the drawing board.