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Burnt Element Again

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iralosavic

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On my last brew, my keg king element charred so badly that the wort was undrinkable. I had to use a brass coated wire brush bit for a drill in order to clean back the charring and then pickle the element again. After that I soaked it in sodium percarbonate and it was looking as good as new again.

So for the next batch I skipped the protein rest and mashed in 64c for an hour, followed by a 10 minute rest at 72c and mash-out at 76c. I also used the hop spider to reduce hop sediment.

Well none of these changes helped at all. The burning wasn't AS BAD this time, but I'd put that down to the 60 minute boil vs 90+mins in the last brew.

Needless to say, this is all rather disheartening and I'm hesitant to spend any more money on grain just to waste it. Another couple of burnt batches and I could've bought a gas burner/reg/bottle instead.


Any ideas as to what's going on and how I could prevent it? I have put brewing on hold for now, as I can't financially justify the risk.



Cheers
 

Steve@PMF82

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On my last brew, my keg king element charred so badly that the wort was undrinkable. I had to use a brass coated wire brush bit for a drill in order to clean back the charring and then pickle the element again. After that I soaked it in sodium percarbonate and it was looking as good as new again.

So for the next batch I skipped the protein rest and mashed in 64c for an hour, followed by a 10 minute rest at 72c and mash-out at 76c. I also used the hop spider to reduce hop sediment.

Well none of these changes helped at all. The burning wasn't AS BAD this time, but I'd put that down to the 60 minute boil vs 90+mins in the last brew.

Needless to say, this is all rather disheartening and I'm hesitant to spend any more money on grain just to waste it. Another couple of burnt batches and I could've bought a gas burner/reg/bottle instead.


Any ideas as to what's going on and how I could prevent it? I have put brewing on hold for now, as I can't financially justify the risk.



Cheers
From your previous thread, i am just thinking?? that it is a problem with the turbid wort from biab and your element may be a slighlty hotter one than the un - clarified wort can handle?

Different kettle of fish, but in my thin big W pot on electric portable stove element with biab i always had a slighlty burnt ring on the bottom.
When i switched to SS braid and now copper manifold and boiling clear wort there is pretty much nothing on the bottom of the pot except for break and hops and its a lot easier to clean.

So maybe look into some other kind of lauter, mash in bag, drain and then transfer grain only to pap zap bucket in bucket system and volauf for a while to get things a bit clearer.

Just my thoughts
 

MHB

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You arent going to like it but here is my answer
The element is too Hot, by that I mean the surface temperature of the element is so high that its causing charring of wort constituents.
When we are sizing elements or other heating mechanisms there are a bunch of factors to take into account but what they all come down to is energy/area, in the old days to heat a 20% sugar solution we would have said 1 Watt/inch^2 which is 1.55 kW/M^2. Now thats an ideal and very rarely obtained Heat Density.
Taking a quick look at a Keg King element its 20mm in Diameter and the heated zone is about 250 mm Long giving a surface area of .0157m^2 at 2200 Watts that is a Heat Density of 140056 W/M^2 or 140 kW/M^2 about 100 times the ideal.
Now there are going to be a bunch of people saying I use one and its fine... and I have no doubt thats the case (with some reservations). As above there are a bunch of factors that come into play, the main ones being: -
Wort Concentration the sweeter (more concentrated) the wort the worse it conducts heat and the easier it is to scorch.
Protein Content Higher protein in the wort makes it stick to the element, if you are a BIAB brewer who squeezes his bag you are adding a bunch of protein that is just making the problem worse.
Agitation a wort that isnt moving spends more time near the element and you get more localised heating.

Personally I wouldnt even think of using one of these elements to boil a wort, nor would I use a cheap jug element or an over the side bath heater all for the same reasons they are just too dam hot to do the wort any good.

Given that you dont want to rip out the existing element and spend a bomb on new longer ones, things you can do to reduce the charring problem are to, dilute the wort as far as you can given the pot size, take all practical steps to reduce protein in the wort and stir especially while the wort is heating from mash out to boil.
Once you are at a boil natural convection should keep the wort moving but as you are ramping you are building up a coating of protein on the element, this bakes on further reducing the ability of heat to escape from the metal surface of the element, so you get more localised heating, causing more accretion to build-up on the element... a bit of a vicious circle round about here it all really goes to shit.
As an aside, elements are rarely exactly the stated wattage, bit like buying resistors, there is a range of wattages that are nominally 2200W, get your element metered the resistance should be close to 26 Ohms if its significantly lower you are running even hotter than normal.
Mark
 

black_labb

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Plenty of people use the kk elements with biab, myself included. It hasn't been an issue. It's possible that the element has a partial short making it hotter in a specific spot. It won't last long like this. if you have a multimeter at home check the resistance on the lowest setting. from memory a 2200w element should be reading around 20 ohms or so.

edit: missed the post above which mentions the resistance. I'd expect the resistance to be lower than the 26ohms mark posted as resistance goes up when things heat. From memory I measured a 2.2 or 2.4kw element with its lead at 19 or 22 ohms when cold. when it is on it heats up increasing the resistance a bit and draws the correct current.
 

Wolfy

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The element is too Hot, by that I mean the surface temperature of the element is so high that its causing charring of wort constituents.
...
Given that you dont want to rip out the existing element and spend a bomb on new longer ones, things you can do to reduce the charring problem
If that is the case, couldn't you also add a controlling mechanism so the power output can be adjusted, something like this: http://www.ebay.com.au/itm/270945091419?ss...984.m1423.l2649 or a PID/SSR with manual control.
 

punkin

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Much better off with a low density element. Mark has it all correct as usual. ;)
 

iralosavic

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Thanks for the detailed explanation, Mark.

From a positive standpoint, at least I have a functional HLT... or I could try to find a more suitable element. The problem here is the installation. Most all other elements require wiring and mounting in a die-cast box etc. A task that I understand how to do, but Murphy's law and 240v don't mix well as far as staying alive is concerned.

I have been toying with the idea of adding a HERMS heat exchanger to the single vessle and continue BIABing, but it seems that switching to a lower density element would still be required. It may be an opportunity to switch to gas and use the original Keggle as a HLT and just BIAB in the gas fired Keggle until I can afford to add a separate Mash tun.

Either way I am at an impass concerning the brewing of beer in the immediate future.


Cheers, gentlemen.
 

black_labb

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I agree that low density is ideal but I doubt that this is the issue. It sounds like he was using the element successfully for a while and then suddenly he started burning his wort. It's just silly to suggest that the heat density suddenly became an issue when it wasn't before.

I had a similar thing happen with a cheap urn. There was a sudden boiling over that happened near the end of the boil and a bit of burning flavour but I stirred alot to prevent boilovers and burning before shutting the heat off. Next time I turned it on to heat up the water for mash in it heated most of the way then the element blew. I wouldn't be surprised if this is what is happening.
 

booargy

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If that is the case, couldn't you also add a controlling mechanism so the power output can be adjusted, something like this: http://www.ebay.com.au/itm/270945091419?ss...984.m1423.l2649 or a PID/SSR with manual control.
Did some tests on those dimmers this week. the current is reduced therefore reducing heat density. PID control is % of time on over a set period. so this doesn't reduce heat density.

iraslovaic maybe you should try draining the wort to a buckett and clean the element before the boil.
 

punkin

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I understand, but the answer you seem to be leading to is to buy another bodgy element.
 

black_labb

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I understand, but the answer you seem to be leading to is to buy another bodgy element.

I was just saying that the element sounds fucked, not that he should get the same one again, though it is a pretty easy fix. The issues people are commonly having with the element is related to the wiring assembly, not burning out.
 

iralosavic

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I agree that low density is ideal but I doubt that this is the issue. It sounds like he was using the element successfully for a while and then suddenly he started burning his wort. It's just silly to suggest that the heat density suddenly became an issue when it wasn't before.

I had a similar thing happen with a cheap urn. There was a sudden boiling over that happened near the end of the boil and a bit of burning flavour but I stirred alot to prevent boilovers and burning before shutting the heat off. Next time I turned it on to heat up the water for mash in it heated most of the way then the element blew. I wouldn't be surprised if this is what is happening.

The first paragraph is true. I did brew a few batches without any charring. The first beer I brewed with a protein rest is where the charring began and now, even though I avoided a protein rest, the burning continues. It has never boiled over or boiled dry or anything.

So what about the element is stuffed? I mean it powers on and boils like the day I got it and there is no loose wiring as far as I can tell.

Draining the wort and cleaning the element before the boil may help, but the wort would really need to be lautered and cleared up before being returned - and this amount of work makes BIAB a redundant idea. I'd rather have a dedicated 3v setup if that were the only solution.
 

bum

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I'd rather have a dedicated 3v setup if that were the only solution.
No reason you couldn't continue happily BIAB-ing (aka - brewing in a baging) with the burner and keggle you suggested previously.

Good luck with it.
 

bigfridge

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I agree that low density is ideal but I doubt that this is the issue. It sounds like he was using the element successfully for a while and then suddenly he started burning his wort. It's just silly to suggest that the heat density suddenly became an issue when it wasn't before.
It is just silly to suggest that things can never change - particularly if it was only 'just' avoiding problems before and now the current circumstances make the charring noticable. The thing with burnt wort is that once it starts, it becomes a run-away process as the charing acts as an insulator making the hot-spot even hotter.

Now for the perhaps the most surprising factor - stainless steel is the worst material to use for boiling wort due to surface tension. :eek:

Let me explain - think about how water 'balls' on a polished car. Here the wax increases the surface tension in the bubble of water to the point where the tension in the skin of the water droplet can overcome gravity and allow it to form the ball above the car surface.

This is exactly how heated wort behaves on stainless - with the bubble of water being the bubble of steam formed by the hot stainless surface. Water boils at 100 Deg C (at sea level) and no steam can form until the liquid water reaches 100 Deg C. You can turn this around to say that the temperature cannot increase above 100 while there is still liquid water present. Once all the water has been converted to steam, adding extra heat can then heat the steam above 100.

The trouble with wort comes from the steam bubble allowing a tiny part of the stainless surface to heat above 100 Deg (because there is no liquid present) and then when the bubble collapses (or more correctly detaches and rises to the top) the wort rushes in and is momentarily overheated before it can cool the stainless back to the wort temperature. This overheating doesn't cause any problems for heating water, but the sugars in wort can caramelise and burn - the amount depends on the heat density - as MHB has explained.

If you are lucky you will get a darkening of the wort (which is fine for a Wee Heavy but not so good in a golden pilsner) - in extreme cases you get the burnt flavours.

So if stainless is so bad, what should you use for heating elements ? Copper is the best as it is fully wetted by wort (which is why the kettles in a jam factory are always copper) and has the other advantage that it reacts with Sulphur to remove it from the wort as the black powder you will often see in your copper fittings. The black incalloy elements are also better than stainless steel.

HTH,
Dave
 

QldKev

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Something I've though about before, why not just weld/solder on some cooling fins to the element. A bit like the 2 stroke cooling fins. Then could we just extent these cooling fins to touch the pot and transfer heat so it too becomes an extension of the heat distribution?


QldKev
 

iralosavic

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Something I've though about before, why not just weld/solder on some cooling fins to the element. A bit like the 2 stroke cooling fins. Then could we just extent these cooling fins to touch the pot and transfer heat so it too becomes an extension of the heat distribution?


QldKev

A bit of fun for someone of your skill; a bit extreme for someone of mine!
 

bigfridge

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*Like*

Your post and MHB's should go in the Wiki. Thanks for the writeup!

Thanks Clint (or should that be Mr Gadgets)

You're very welcome - Polite individuals such as your self make it a pleasure to contribute to AHB.
 

seravitae

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Did some tests on those dimmers this week. the current is reduced therefore reducing heat density. PID control is % of time on over a set period. so this doesn't reduce heat density.

iraslovaic maybe you should try draining the wort to a buckett and clean the element before the boil.
PID controls power over time, so PID can reduce heat density. so long as the PID period setting is short enough. it will work just as well as a dimmer. in fact most dimmers (TRIAC based ones) use partial cycle cutout, and voltage/current of an AC waveform changes throughout the cycle. A PID usually acts as a number of full cycles, but given the thermal mass of the wort, it doesnt really make a difference.

I have done some tests with grain and a bare incoloy 1.35kW element and recieved no scortching with a PID (all the way up to a boiling slurry), so it can be done
 

Lionman

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Necro!

Started having issues with my KK element. Seemed to go ok first 10 or so brews but has started to get blackened. Has been a pain to clean and the Vienna Saaz smash I did last night was next level. I noticed during the boil a smell of burntness and after emptying the pot I noticed the element was a about 1mm charcoal crust all over it. Hopefully the beer doesn't taste like the smell.

Short of not letting the element tough wort, which is probably the best solution, are there any other options? I am considering clamping something to the element to help spread the heat out over a greater surface area.

Maybe some copper fins held on with stainless hose clamps? Is this a ludicrous idea?

Or get a 50L Guten and use my pot for heating sparge water...
 

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