Dedicated Herms Guide, Problems And Solution Thread

[matho]

Very true dent, maybe when Ostojic said he measured across the output of the SSR he was measuring across the SSR and not the load. I looked up the specs on the fotek SSR and it states a max leakage current of 3mA, so to achieve 24v across the SSR 'output' terminals the internal resistance of the SSR in the off state would be about 8K.

I just want to say this isn't right as it doesn't follow Kirchoff's voltage law, so i don't know whats going on but it doesn't sound right whatever it is

cheers matho

 

[mateostojic]

Very true dent, maybe when Ostojic said he measured across the output of the SSR he was measuring across the SSR and not the load. I looked up the specs on the fotek SSR and it states a max leakage current of 3mA, so to achieve 24v across the SSR 'output' terminals the internal resistance of the SSR in the off state would be about 8K. It's hard to say without testing it for myself.

edit: also maybe the led glows at a very small current which it would have to if its connected across the load

cheers matho

Yes i did measure across the SSR rather than across the load. The SSR makes the connection between the two ends of the live wire. So if I see 24V across the SSR and if the SSR leaks 3mA, then as you say matho the resistance of the SSR is 8000k. I dont really know what to make of this, i read the pdf you posed but i have to say i couldnt understand 95% of it. I think i have to sit down and learn a bit more about his before i post any more questions.

Also, a correction: While i was testing my control box, i didnt actually have the element plugged in, rather my desk lamp, which has a much lower wattage. Sorry for misleading you dent and matho. I am sure that this now makes sense to you guys, however its still over my head. Oh and the element plug and the indicator light are definitely in parallel.

I will try and nut this out now that you guys have pointed me in the right direction.

Thanks for your help.

 

[mateostojic]

Ok so i understand my previous problem, but now i am faced with a new one.

This time its my HERMS heat exchanger, its tripping the RCD in my house.
It seems that the insulation inside the heating element is not working properly, and as a result i get a resistance between the conducting rod inside the element and the casing of the element.
The strange thing is that the resistance reading is between 300k ohms and 1000k ohms, which corresponds to a current of 0.8mA. The current required to trip the RCD is 30mA, correct?

Also i have measured this resistance at least 10 times and i never get the same value, but its always in the 300k - 1000k range. Oh and when i take the reading, the resistance climbs (or falls) until it finally settles on a value (this takes about 10 minutes!)

I am hoping that someone can help me make sense of this.

Thanks,
Mate

 

[matho]

mateOstojic,

if that resistance was measured with a multimeter then the reading is too low, to measure insulation you need a device called an Insulation resistance tester which puts out a dc voltage at levels of 250v,500v, 1000v. The insulation needs to be tested at 2 times normal voltage and the reading for all wiring must be over 1M ohm (heating elements are allowed to be lower).

Most immersion heating elements are made up of the sheath , insulating material (magnesium oxide) and resistance wire (nichrome), now magnesium oxide is a great insulating material when dry but not if its wet. Unfortunately magnesium oxide is hydroscopic so even exposure to the atmosphere will cause it to draw in moisture.

what i would do is to check the sheath for any cracks, if that all ok then check the ends (by the look of the photo the one on the right doesn't look that crash hot). Now get a heat source like a blowtorch and start heating up the element from the center and work you way out to both sides, check to see if the resistance has gone up with your multimeter, repeat and see if it goes up more, then seal the ends with heatproof material, i would think silicon sealant would be ok.

cheers matho

 

[mateostojic]

Thanks for that matho,

Just to make sure i understand, are you saying that the multimeter is not appropriate for measuring the resistance between the wire and the sheath? Therefore, the values that i was getting (300k - 1000k ohms) are not correct and are in fact probably lower than that. Therefore the residual current is probably greater than 30mA?

I tried to evaporate some of the moisture out by running the element in water for 15 minutes at a time and measuring the resistance (as per photo). I did this 5 times but the resistance reading was all over the place.

I will try burning it like you say.

Thanks

 

[matho]

Just to make sure i understand, are you saying that the multimeter is not appropriate for measuring the resistance between the wire and the sheath? Therefore, the values that i was getting (300k - 1000k ohms) are not correct and are in fact probably lower than that. Therefore the residual current is probably greater than 30mA?

thats what i find, the multimeter doesn't have enough oomph to get thru, probably explains why the reading is all over the place. A blowtorch is the way to improve insulation resistance readings on 'pyro' which has the same magnesium oxide in it, so hopefully it helps with the element

cheers matho

 

[NickB]

aka Meggermeter. Puts out 500V or 1000V. As mentioned, used to test insulation resistance.

Cheers

 

[booargy]

This time its my HERMS heat exchanger, its tripping the RCD in my house.

A stove is not wired with RCD due to nuisance tripping, could be your problem. the element can have a megger reading as low as 10K ohm. Although by the look of it your element could have had the Richard.

 

[zxhoon]

unless my math is really bad tonight that would put your insulation resistance under 1kOhm which is very dangerous, I'd bin it and get a new one, don't use it on a non RCD protected supply, asking to get a belt otherwise...

 

[NickB]

+1, go the safe option for sure. A 240V kick is not much fun, believe me!

Cheers

 

[booargy]

zxhoon and NickB are right. trust the RCD it is telling you the element is rooted and needs replacing.

 

[mateostojic]

zxhoon and NickB are right. trust the RCD it is telling you the element is rooted and needs replacing.

Yeah i am definitely taking the safe option here.

Also, i tried heating the element on the gas stove in an attempt to evaporate the moisture but that was a big fail. Ended up burning the insulation and it oozed out one of the ends all black and sticky.

The supplier has been really good and is sending me a new element all the way from Vietnam.

Thanks for the advice brewers.

Mate

 

[prongs_386]

I had my first brew with my herms yesterday. Some things went well and some things didn't.

I started off by getting my mash water up to 50 degrees for a protein rest which went well. There ended up being a wide degree difference between the pid and mash tun so I set my pid a bit higher. I then added my grain and the temp leveled out at 50 after a few minutes which was good. After a few more minutes the flow out of my mash tun stopped so I figured it was a stuck mash and started stirring but even with stirring the flow didn't come straight back. Often I would have to stir and then let it settle before the flow would start again. I have a washing machine hose as my grain filter so thought maybe some grains got stuck inside but it just seemed to randomly correct itself. I felt like there was some plumbing mystery of pipe pressures which I don't understand.

We seemed to get through this problem by luck but ran into another one. I set my pid up to 70 degrees for the mash but the temp sat at 60 so I stirred the mash which then showed 64 but even after setting my pid higher it never got hotter than 65. Is it possible id reached some kind of limit with my hex?

Any insights would be much appreciated!

 

[mxd]

I had my first brew with my herms yesterday. Some things went well and some things didn't.

I started off by getting my mash water up to 50 degrees for a protein rest which went well. There ended up being a wide degree difference between the pid and mash tun so I set my pid a bit higher. I then added my grain and the temp leveled out at 50 after a few minutes which was good. After a few more minutes the flow out of my mash tun stopped so I figured it was a stuck mash and started stirring but even with stirring the flow didn't come straight back. Often I would have to stir and then let it settle before the flow would start again. I have a washing machine hose as my grain filter so thought maybe some grains got stuck inside but it just seemed to randomly correct itself. I felt like there was some plumbing mystery of pipe pressures which I don't understand.

We seemed to get through this problem by luck but ran into another one. I set my pid up to 70 degrees for the mash but the temp sat at 60 so I stirred the mash which then showed 64 but even after setting my pid higher it never got hotter than 65. Is it possible id reached some kind of limit with my hex?

Any insights would be much appreciated!

need more info, pics, description, element size, etc..

 

[prongs_386]

need more info, pics, description, element size, etc..

OK ill provide some more info.
The heat exchanger is an 8l pot with 2400watt element. Not sure how much you copper I got in there but my ramp time was a bit less than 2 degrees a minute.
The temp controller is dei106h and the pump isn't a march but it has the same specs as a 809 march pump but with an extra 1/2foot of head.
And a couple of pics.

 

[Tim F]

From that pic you have a fair length of hose connecting the HEX to the MT on each end, that might explain a lot of your heat loss? Can you try getting the connections as short as possible? What type of false bottom/manifold are you using in the tun?

 

[mxd]

OK ill provide some more info.
The heat exchanger is an 8l pot with 2400watt element. Not sure how much you copper I got in there but my ramp time was a bit less than 2 degrees a minute.
The temp controller is dei106h and the pump isn't a march but it has the same specs as a 809 march pump but with an extra 1/2foot of head.
And a couple of pics.

sorry still more questions, you mention 2 temps, are these readings off the PID or are you looking at a thermometer in the mlt ?

I don't feel there is anything wrong with your HX as such it feels more like a "setup" issue.

I (who is still trying to figure it out) believe the high level theory of HERMS is along the following.


1) Measure you temp of the Mash (that is controlling the PID) where the wort returns to the MLT, don't look at your MLT gauge.
2) Run a loose Mash
3) recirculate quickly (to get the Mash to temp)

 

[prongs_386]

sorry still more questions, you mention 2 temps, are these readings off the PID or are you looking at a thermometer in the mlt ?

I don't feel there is anything wrong with your HX as such it feels more like a "setup" issue.

I (who is still trying to figure it out) believe the high level theory of HERMS is along the following.


1) Measure you temp of the Mash (that is controlling the PID) where the wort returns to the MLT, don't look at your MLT gauge.
2) Run a loose Mash
3) recirculate quickly (to get the Mash to temp)

Thanks for the reply.

I was talking about a temp gauge in the mash tun which does sit in the opposite corner to where the return is. So if the temp out of the hex is say 70 I can say that my mash was at 70? Even though the temperature throughout the mash tun was 65.

How do I run a loose mash without stirring a lot? Maybe my understanding of that term is incorrect.

 

[mxd]

Thanks for the reply.

I was talking about a temp gauge in the mash tun which does sit in the opposite corner to where the return is. So if the temp out of the hex is say 70 I can say that my mash was at 70? Even though the temperature throughout the mash tun was 65.

How do I run a loose mash without stirring a lot? Maybe my understanding of that term is incorrect.

what do you use for you false bottom ?

For a loose mash you could do a 3 to 3.5 ltr to kg ratio, you could add some rice hulls.

for me, the wort return is at the top of the tun, I have a "pipe" that I ensure is in the fluid (and bouncing off the side of the tun) to try and avoid channeling. If I wat to mash at 65 I set the pid at 65 and recirc as quick as possable, the MLT thermometer is probably 2 degrees lower but I try to ignore that


I think the theory is if your recirculating at 65 degrees at some stage it will be at 65 degrees.

I only stir at Mash in, the "fill" the tun via the "out" valve (this helps to loosing up the grist on the false bottom and gets a quick flow going).

The following you can see where I measure the temp.


And this is what the PID sesor connector looks like.



For your return you could look at doing a sparge arm, would should minimize the risk of channeling.

 

[hsb]

I think the theory is that out of the H/Ex is going to be the warmest part of the system, so measure here. Wort comes in at say 66C, it might drop slightly but by constantly recirculating, every part of the mash will be 66C. I found my dial thermo in the body of the mash quickly settling at 66C also. If liquid is regularly cycling through the H/Ex, you can be sure it is hitting 66C.

For my setup, 4:1 seems to be about perfect for the ratio, very loose by more traditional Cooler MLT standards but works for me. My return is just some coiled silicone tube sitting on top, no way is any grain missing out on a nice warm bath. my probe is at the MLT return in a T piece, as above.

Does everyone recirculate for the full mash, or pause and restart throughout? I've been recirculating for 90 minutes but wondering if I really need to?