Pot for HERMs

[Vossy1]

:mrgreen:

 

[MacKiwi]

A big thank-you to Awolphotography, who saved me the trouble of making one of these myself. Here's some piccies of my newly acquired HERMs (ironically, delivered by a courier company called MyHermes)...

 

[Vossy1]

She is a thing of beauty :mrgreen: fab work awol :clap: :hat:
Are you making to order awol or just one offs :hmm:
Let us know how you get on with it MK :thumb:

 

[MacKiwi]

First question for folks who have done this before - this element looks a lot like what is called a "burco boiler element". Am I right?

If so, I believe it has a thermal cut-out switch in it. Should I bypass this, or will it not be an issue when heating a HERMS heater exchanger (as I guess it won't be getting up to boiling)?

 

[evanvine]

I don't think you need do the by-pass surgery, mine only ever gets up to 85C.

 

[Cyclops]

looks brilliant, a lot better than my Herms pot :)

 

[djcorbetto]

what size pot is that? and kw of element?

 

[MacKiwi]

It's a 6 litre pot (you can get them from Bergland). I don't know for sure the wattage, but I suspect it is 3kW

 

[djcorbetto]

Thanks, I have a 6litre thermopot on order. and now a 3kw element

 

[evanvine]

It's a 6 litre pot (you can get them from Bergland). I don't know for sure the wattage, but I suspect it is 3kW

'Tis a thing of beauty MK, but at 6ltrs you only have 0.5 kW per litre!
My scruffy thing

is 2 litres and 1.1 kW per litre which will give a more rapid response time.
Will be very interested to hear how you fare with yours.

 

[djcorbetto]

I guess there could be ways to increase the amount of stainless pipe in it to increase the efficiency?

 

[MacKiwi]

Yep, 'tis a good point Evanvine. I'm new to this, so I'm interested to see how I fare too!

With 3kW of grunt I'm hoping it can shift the mash temperature at a reasonable rate. What the low Watts-per-litre will get me is a sluggish response (frequency response) to step-changes in the mash temperature (for example, if I dropped some cold water in it). Since most of the time it will be targetting a stable temperature, I hope this won't be an issue.

The other area where a slow frequency response might be an issue is, if it is too slow, the PID control algorithm might fail to lock, or wander around. I'm planning on building my own PID using a microprocesser and a digital temperature probe, so if I have to slug it, or hack the algorithm to make it work, I will.

I think your HERMs pot is a thing of beauty too, in a rustic, well-used sort of way

 

[MacKiwi]

Djcorbetto - if the watts-per-litre does turn out to be an issue, I don't think that more stainless pipe in the coil is the answer.

Essentially, if the controller decides the wort needs heating and switches on the element, this will take longer to have an effect on the output wort temperature in my system than in Evanvines, since his/hers will heat the heat-exchange medium (the water) quicker, due to the higher watts-per-litre. Once the element switch-on starts to take effect, it may well have more of an effect in my system due to the higher overall wattage, but it will take longer for this to be apparant.

All of this might mater because the PID algorithm won't work with very long response times, although I'm pretty hopeful that in my case it still will. :)

Anyway, I'm just wittering away really. I'm yet to even make a working HERMs...

 

[MacKiwi]

And I've just realised - I can probably trade response-time against rate-of-change, simply by not filling the pot completely. If I put 3 litres in, I have 1kW/litre, although only half of the coil is immersed...

 

[evanvine]

I use a PID for my HLT, it seems to have no problems!

 

[MacKiwi]

I use a PID for my HLT, it seems to have no problems!

Another excellent point!

 

[Vossy1]

And I've just realised - I can probably trade response-time against rate-of-change, simply by not filling the pot completely.

You could reduce the volume of your pot buy immersing something in it to take volume away whilst still using the full coil. Naturally a big block of steel would negate any benefits due to it's heating time but if the object were hollow and held in place by the lid (those pots have secure lids) you could just jam it in

 

[evanvine]

but if the object were hollow and held in place by the lid (those pots have secure lids) you could just jam it in

All the best ideas are the simple ones! :clap:

 

[MacKiwi]

Doing some leak testing and running water through the coil. My pump seems to push 8 litres per minute through the system. At what rate do you guys recirculate wort through your HERMs?

 

[Vossy1]

At what rate do you guys recirculate wort through your HERMs?

It really depends on the open surface area of your false bottom and the diameter of your mash tun. I played with flow rates until I achieved what I thought was a good compromise between the possibility of a stuck mash, and the best flow rate for quick heat exchange, which for me is between 2.75 and 3ltr/min and 1 deg/min IIRC. Faster isn't always better as it if the pump is sucking on the mash too hard you may extract tannins.

EDIT, due to the way my HERMS pipework is set up it happens to pump at this flow rate ( I only discovered that after removing a flow restricting ball valve ) , so before you think of restricting the flow see what your system does 'real time'....if 8ltrs is as per final set up ignore above :thumb: