Dedicated Herms Guide, Problems And Solution Thread

[Tex N Oz]

I believe the secret to success here is getting the volume of your HLT water as low as controllably possible, having as much flow through the HEX as possible and as much HEX surface area as possible.
If you get all these ducks in a row, you can focus step temperature control on your HLT and everything will fall in place. Unlike a RIMS you'd never exceed the step temperature in any part of the system.

I'm designing my system around a cylindrical filter (like a water filter), as they are much more efficient with a greater surface area than a bottom filter like we see most often in drip coffee filters. They have several times more surface area for the volume and the mash thickness is much less. I've always thought the current mash tun design was a bit archaic.

 

[Adr_0]

Unlike a RIMS you'd never exceed the step temperature in any part of the system.

Uh-huh...

 

[fraser_john]

So I have been a HERMSer for years now, before that a RIMs user for years (thought I was going to say RIMer did'nt you!), but, on my current configuration, I have really been struggling with attenuation. I'd set my PID to mash through 63c to 65c for 90 minutes to try get a drier finish, a wort of OG 1.053 finishes at 1.020, it was getting pretty frustrating.

So Saturday making a weizen and I test the mash bed temp when the PID says it as mashing out at 78c, temp looks all settled and the mash bed is sitting at 83c! I calibrate the RTD probe at least once a year and it is always smack on 0c, so calibration is not the issue. If this happens at say mash temp of 64c, then it is actually at 69c, would certainly account for my attenuation problems.

What I don't get, is how can the bed be at 83c when the outlet of the HERMS is 78c, just does not seem possible.

The only thing I "think" it could be is that the probe is not fully immersed in the wort as it comes out of the HERMS, maybe there is an air pocket in the T-fitting or something, or maybe the probe is actually touching the T-fitting on the far side and therefore not picking up the true temperature, dunno.

But, I am moving my temp probe into the mash tun when a bulkhead I ordered arrives, just to see what difference it makes.

Any one else have such odd results?

 

[Yob]

you tested that probe against another trusted thermometer?

Doesn't seem possible that the mash can be higher than the HEX temp :blink:

 

[MastersBrewery]

Always always always calibrate any temp probe within the temp range it will be used, if you aren't going to be cold crashing in the mash tun then there is no need for the probe to be accurate at those temps. Find a trusted thermo and re calibrate in the mid 60's. I note that this may not be the issue but a probe drifting 5 or 6c over 60 or 70 wouldn't be unheard of.

 

[Adr_0]

The only thing I "think" it could be is that the probe is not fully immersed in the wort as it comes out of the HERMS, maybe there is an air pocket in the T-fitting or something, or maybe the probe is actually touching the T-fitting on the far side and therefore not picking up the true temperature, dunno.

That sounds plausible actually. I was very careful to solder my probe in such that the tip would be in the stream leaving my RIMS tube, and works a treat.

You might want to check the thermometer with the RTD in 60-70°C water. If there is a genuine gap in accuracy, are all three wires properly connected? It might be that you've bridged or lost connection on one of the bias connections or you have a loose/dirty connection.

 

[TheWiggman]

Agree with you fraser, there is 0% chance the wort can be a higher temp than the HERMS outlet. I think your suggestion as Adr_0 has backed up is likely. *cue harp music...*

With my HERMs I have a type K thermocouple which I insert into my coil each brewday. One day I accidentally didn't insert it all the way to the bottom of the thermowell and ended up with a few °C difference between mash temp and measured temp on the PID. I stuck it down further and bam, temp reading increased to match the mash temp.

Due to my [inaccurate] type K thermocouple I measure the mash temp independently of the HERMS temp, which I suggest you do for now as this will identify the differences. I rely on my thermapen only.

1. Set PID to 58°C for mash-in
2. At about 55°C, measure temp of liquid going into the mash tun coming out the the HERMS return
3. Note difference and set PID accordingly (i.e. if return temp is 56°C but PID is reading 57°C, I'll drop PID by 1°C)
4. Leave for another 30 mins, check MT temp and when ok mash in

I'll then check again when I'm reaching sacc rest temp to make sure the difference is linear, which is typically is over 50 - 80°C. I have had it out by about 2°C at the worst.

Do this and I think you'll be cheering

Ed: best to check return flow temp under high flow conditions. If it's trickling out you'll lose some heat between your thermowell and MT, and end up compensating for that.

 

[fraser_john]

That sounds plausible actually. I was very careful to solder my probe in such that the tip would be in the stream leaving my RIMS tube, and works a treat.

You might want to check the thermometer with the RTD in 60-70°C water. If there is a genuine gap in accuracy, are all three wires properly connected? It might be that you've bridged or lost connection on one of the bias connections or you have a loose/dirty connection.

I have a two wire RTD and use thermocouple plugs/sockets on my system, so they are clamped well and truly in place, so should not be an issue there.

I think I'll pull the t-piece, ball valve section of the HERMS return tonight and have a good look what is going on, might be time to modify the layout just a little.

Plugs/sockets are panel mount like this.

 

[MastersBrewery]

Genuine RTD PT100's are a 3 wire device and the most accurate, so makes me wonder what thermocouple your using, this may go some way to explaining your issue.

 

[fraser_john]

Genuine RTD PT100's are a 3 wire device and the most accurate, so makes me wonder what thermocouple your using, this may go some way to explaining your issue.

http://www.auberins.com/index.php?main_page=product_info&cPath=20_15&products_id=96

RTD probes come in both two and three wire versions, two wire versions use the same set of wires for both excitation and measurement.

<edit> hmmm I note the following line in one of the Auberins manuals "for two wire RTD the wires should be connected to terminals 8 & 9. Jump a wire between terminals 9 & 10."

Makes me wonder if I missed that on my install?

 

[Adr_0]

An easy way to check accuracy (as Yob suggested) is to compare side-by-side in the same liquid. It will at least give you information: it is either comparable (within 1°C) or is not.

TheAuber controllers have different configurations for the type of probe you are using.

If the above all checks out you should look into correcting air pockets.

 

[Adr_0]

http://www.auberins.com/index.php?main_page=product_info&cPath=20_15&products_id=96

RTD probes come in both two and three wire versions, two wire versions use the same set of wires for both excitation and measurement.

<edit> hmmm I note the following line in one of the Auberins manuals "for two wire RTD the wires should be connected to terminals 8 & 9. Jump a wire between terminals 9 & 10."

Makes me wonder if I missed that on my install?

That would do it.

 

[fraser_john]

That would do it.

Yeah, I'll do a tear down tonight on the t-piece and investigate the wiring of the PIDs (both HLT & HERMS), just in case!

 

[fraser_john]

Heheh, don't I feel the fool..... been so long since I built this thing I forgot it was really K-type thermocouples I had, d'oh.

But that does not change a lot, pulled the T-piece off and definitely scope there for the probe to maybe not being in the full flow, it was entering at 45 degrees from vertical, so rotated the fitting an extra 45 degrees to make it parallel to the horizon, should not be an issue there.

Rechecked all wiring connections, all tight.

Rechecked sensor setting, Sn correctly set to 0.

Recalibrated, no issue.

Ran a new auto tune, with just water.

Right now PID says sensor 66.1c, process temp, water coming out of tube where it enters mash tun is 65.8, allowing for a little cooling in the line I guess and mash tun is at 65c.

Now, I know I have not done a fresh auto tune in a long time and I had reconfigured the system slightly, same HEX, but lines might be longer leading into the HEX intake, so maybe the PID values were screwed up and resulting in overshoot?

To be safe, ordered two 50mm three wire RTD probes off evil bay and will swap them all out when they arrive and retune, retest.

Looks ok for now though! Course, water is different to a full mash, might hit the auto tune again when I next dough in, just to be sure!

So note to all HERMS owners, make a small mod, don't forget to use the At setting to auto tune again!

 

[Adr_0]

Cool, good to hear!

Regarding the tuning, which probe is the element driven off, the return from the HERMS? If this is set to 64°C (but actual temperature is 69°C) it will continue to drive until the temperature leaving the HERMS coil is a solid ""64°C"". This would have explained why another thermometer saw 5-6°C higher. So it was controlling OK but there was a measurement error. As we all know it's not possible to 'heat' a 69°C mash tun with 64°C wort coming in.

Minor plumbing changes shouldn't need a re-tune. Theoretically, any time your water level in the HEX changes you need a re-tune; possibly the same with changes in pump flowrate; and changes in your mash tun volume (total grain + water). However if your system is inherantly pretty good, the numbers won't change much.

 

[Adr_0]

I believe the secret to success here is getting the volume of your HLT water as low as controllably possible, having as much flow through the HEX as possible and as much HEX surface area as possible.
If you get all these ducks in a row, you can focus step temperature control on your HLT and everything will fall in place. Unlike a RIMS you'd never exceed the step temperature in any part of the system.

I'm designing my system around a cylindrical filter (like a water filter), as they are much more efficient with a greater surface area than a bottom filter like we see most often in drip coffee filters. They have several times more surface area for the volume and the mash thickness is much less. I've always thought the current mash tun design was a bit archaic.

While I like what you're doing with your design principles, it's absolutely false to say temperatures exceed your step temperature in a RIMS setup. If you control off mash tun temperature, your temps will exceed step temperature whether you use RIMS or HERMS, and conversely, you won't get temps exceeding your step temperature if you control as close to the wort outlet (from whichever heat source you have). This is totally independent of RIMS vs HERMS vs BIAB/1V, and totally dependent on system layout.

 

[TheWiggman]

I'm assuming he's saying that the temp on the surface of the element in a RIMS will exceed the control temp. This is the case if you aren't careful but generally not a concern with a well-designed system.
I'm not sure I'd be super-keen on the filter design Tex. I think it would be hard to design an appropriate filter that would be adequately submerged to provide the surface area you're after. It's doable, for sure, but industrially filter elements consume the majority of the volume in the housing (hence exceptional surface area, what with the voids and all) which would be awkward with a decent grain bill. The base of a pot is a decent enough amount of surface area in practice for mashing and considering how simple it is and there isn't a void that can be sucked dry, it's a tried and true concept.
HOWEVER...
Prove me wrong and make something out of the box.

Ed: I should also reiterate that it's the grains that do most of the filtering, not the false bottom.

 

[Rosscoe]

Hi all. A quick question if I can do so without provoking a flame war...

I was planning to use 1/2" S/S tube for my HEX. I've been reading a lot of pages of this thread though (massive as it is) with many suggesting copper is a much better conductor. I could be well and truly wrong, but I assumed that once the steel was up to temp it would behave the same after that, although maybe take a bit longer to get up to it. S/S has other obvious benefits as well, which is why I was leaning that way.

My question is, have some of you tried one material, then replaced it with the other and can comment on the difference you noticed?

Rosscoe

 

[MastersBrewery]

On a home brew scale it beggars belief that the SS v Copper argument should continually raise it's head.

If your getting the copper cheap ie free go for it

nuff said

 

[dent]

I've run both under near identical conditions. Copper is better, but not so you'd notice. Stick with whatever is easiest as suggested above, the whole heat conduction thing is a non issue.