Is a pulsing electric boil really such a bad thing?

I have read in several threads that folks seem to be concerned about the pulsing nature of the boil in their electric systems.

I use an Auber Instruments 2352 PID to control a 3800 watt element in my system. I have my PID set to a 2 second cycle time. I bring my wort up to 200* in auto mode at which point an alarm sounds. I then switch to manual mode to bring the wort up to a boil and prevent a boil over. Once the 6.? gallons of wort is boiling and the foam has settled back, I dial the power level back to somewhere between 65% and 75%, set my timer and go about my other activities. The rolling boil in my kettle pulses in step with the 2 second cycle.

I guess I don't understand the concern about the pulsing. Is this a bad thing? Will it harm my beer? I don't see how it can. I have read a few posts about how to prevent the pulsing. I do not recall seeing anything explaining why one should go to the trouble to prevent pulsing much less care about it.

What am I missing?
Anybody?

I guess the thought would be that you want to keep the boil rolling the whole time to maximize the extraction of alpha acids and boil off of DMS, etc.. At 65% I can't tell when my element is on or off, just a solid rolling boil the whole time. I suspect my cycle time is probably faster than 2 seconds, but I never paid much attention.

My thoughts on the pulsing would be that it might shorten the life of electrical components. Don't know the stats on that however. Can't imagine it would effect the quality of the beer.

samc said:

My thoughts on the pulsing would be that it might shorten the life of electrical components. Don't know the stats on that however. Can't imagine it would effect the quality of the beer.

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These components were all designed specifically with this type of pulsing in mind. ie. A PID will switch much much faster than this 2 second cycle time if you let it. We use a SSR over a mechanical relay specifically because we want to be able to switch on and off frequently.

So you are saying that 2 - 40 million hour lifetimes on these SSR's are enough. LOL, no worries, pulse on!

Pulsing a resistor (element) wont damage it, and like already said SSR's are designed to be used like we are using them, just make sure to not get them hot, so buy over rated and heat sink and you'll have a long healthy SSR life span.


As far as pulsing... If my system doesnt pulse then no ones will. I have 11,000 watts in the kettle and I do 5 gallon batches. I put so much in because.... I hate waiting, it will boil 5 gallons from 130 deg F in under 5 minutes.

Once boil is achieved the PWM power output is set to 30%. This gives a nice rolling boil, no pulsing what so ever.

I will however warn you about your period. When talking PWM you have your duty cycle and your period. The period is how long the entire waveform is. If you have a 4 second period and a 25% duty cycle that means you're on for 1 second, off for 3. If you have a one second duty cycle and you're at 25% power you're on for .25 of a second off for .75.

So if you're running a long period you can get a pulsing boil, especially at high power. On my system I run a 1 second duty cycle, and with 11,000 watts (2x 5500 ULWD) elements it does not pulse.

The trick, just like any PWM controlled system, is to make sure that the system is enough of a low pass filter to make your square wave turn into an average DC output. And because water is a great low pass filter for heat we can run as slow as 1 second (I'm used to talking nano and mico seconds), but if you get too long, like say 10 seconds, you'll run into issues as the frequency is just too low for the water (your low pass filter) to turn it into something smooth and flat.

So if you ever have pulsing issues just reduce your period.

There's a second problem though, if you get much under 1 second in your period your SSR becomes a problem because it does not shut off until the zero crossing of the sine wave coming out of the wall. So if you turn it on, and then try to turn it off before the zero crossing it will not turn off until the zero crossing comes, and that's at 60 hz. At 60hz you have a zero crossing every 120th of a second, so that's the best resolution you can get. So you have to make sure that the smallest change in your output duty cycle represents greater than or equal to 1 120th of a second or else it will last longer than you wanted it too.

At 1 second you're slightly under this with 100 steps (1 - 100%) and so you're good, but you go much under 1 second and you cant switch fast enough with the SSR for a 1% duty cycle change.

skipper1953 said:

I have read in several threads that folks seem to be concerned about the pulsing nature of the boil in their electric systems.

I use an Auber Instruments 2352 PID to control a 3800 watt element in my system. I have my PID set to a 2 second cycle time. I bring my wort up to 200* in auto mode at which point an alarm sounds. I then switch to manual mode to bring the wort up to a boil and prevent a boil over. Once the 6.? gallons of wort is boiling and the foam has settled back, I dial the power level back to somewhere between 65% and 75%, set my timer and go about my other activities. The rolling boil in my kettle pulses in step with the 2 second cycle.

I guess I don't understand the concern about the pulsing. Is this a bad thing? Will it harm my beer? I don't see how it can. I have read a few posts about how to prevent the pulsing. I do not recall seeing anything explaining why one should go to the trouble to prevent pulsing much less care about it.

What am I missing?
Anybody?

Click to expand...

Have you measured the cycle time? I had my PID set to t=2, yet the cycle time was over four seconds. Someone here on HBT showed me that the P setting impacts the minimum cycle time. Once I reduced P to 1 I had a two second cycle time.

The reason I want a constant rolling boil is that I can then control how hard it is boiling. I think a hard boil increases the maillard reaction, for example, which I would like to keep to a minimum in a pale beer. If the boil pulses then it is unavoidable to have a harder boil then intended for part of the time.

At the risk of sounding overly technical, it's kind of creepy sounding.

I guess I don't understand what is happening. Even with a PID, my boil never stops. It's still a rolling boil. You want to set it so that you maintain a rolling boil all the time. I can't even tell when my element is on or off- the boil is steady. I dial it down to maintain a rolling boil, usually 70% or so (it's a 4500w element).

Yooper said:

I guess I don't understand what is happening. Even with a PID, my boil never stops. It's still a rolling boil. You want to set it so that you maintain a rolling boil all the time. I can't even tell when my element is on or off- the boil is steady. I dial it down to maintain a rolling boil, usually 70% or so (it's a 4500w element).

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I get a very distinct on-off rhythm. Ferocious bubbling boil ... then calm and quiet. I would love to get it somewhere in the middle. I have a 5500 watt high density coil with 5 gallon batches.

GRHunter said:

I get a very distinct on-off rhythm. Ferocious bubbling boil ... then calm and quiet. I would love to get it somewhere in the middle. I have a 5500 watt high density coil with 5 gallon batches.

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Definitely try adjusting the period/cycle time as Quaffer and Shushi point out.
My boil is like Yooper's, I can't tell when the element is on or off.. 5500W ULWD.

Thanks for the responses. Curiosity satisfied.

"Creepy sounding". That's a good one.

Quaffer said:

Have you measured the cycle time? I had my PID set to t=2, yet the cycle time was over four seconds. Someone here on HBT showed me that the P setting impacts the minimum cycle time. Once I reduced P to 1 I had a two second cycle time.

Click to expand...

I should give credit where credit is due. This helpful post by bbognerks is what showed me the way.

Thanks for the props Quaffer. But really, my info simply points to The Pol's resolution to the problem, heh.

Just thinking out loud here. No scientific backing what-so-ever. In regards to the pulsing, I'm thinking really it's all visual. I don't really see how going from a vigorous boil to a lull really makes much difference. We all boil at different temperatures anyways. I suppose if the lull was long enough, say 10 seconds lull and 5 seconds boiling, then you might have a dms problem. But who knows?

As for the increase in maillard reaction. Is it possible for it to significantly change with 1 degree temp swings? The lulls I would think at most would decrease your temp from boiling to boiling -1. I read up about the maillard reacion briefly on Wikipedia. Basically I got that it was what makes bread brown in the oven and causes similar reactions in other food types when heated.

My thinking is that since we are boiling, we can't go over a set temperature and we can't "overcook" the wort really because it's a liquid. If we were reducing wort down to really concentrate the sugars, such as in making a sugary sauce reduction, then I could see the pulsing being a problem and causing too much of a Maillard reaction if you didn't know how to control it or judge it. But even in conventional cooking, you don't get a Maillard reaction in sauce until it is significantly reduced down by boiling off liquid and highly concentrating the solids. I would love to read more about it as it relates to brewing if you have some resources. I hadn't heard of it until today.

Quaffer said:

Have you measured the cycle time? I had my PID set to t=2, yet the cycle time was over four seconds. Someone here on HBT showed me that the P setting impacts the minimum cycle time. Once I reduced P to 1 I had a two second cycle time.

The reason I want a constant rolling boil is that I can then control how hard it is boiling. I think a hard boil increases the maillard reaction, for example, which I would like to keep to a minimum in a pale beer. If the boil pulses then it is unavoidable to have a harder boil then intended for part of the time.

Click to expand...

THAT DID IT!!!!! I changed "P" from the default 500 to 1 and now my boil is almost identical to a propane boil. Thanks Quaffer.

bbognerks said:

Thanks for the props Quaffer. But really, my info simply points to The Pol's resolution to the problem, heh.

Just thinking out loud here. No scientific backing what-so-ever. In regards to the pulsing, I'm thinking really it's all visual. I don't really see how going from a vigorous boil to a lull really makes much difference. We all boil at different temperatures anyways. I suppose if the lull was long enough, say 10 seconds lull and 5 seconds boiling, then you might have a dms problem. But who knows?

As for the increase in maillard reaction. Is it possible for it to significantly change with 1 degree temp swings? The lulls I would think at most would decrease your temp from boiling to boiling -1. I read up about the maillard reacion briefly on Wikipedia. Basically I got that it was what makes bread brown in the oven and causes similar reactions in other food types when heated.

My thinking is that since we are boiling, we can't go over a set temperature and we can't "overcook" the wort really because it's a liquid. If we were reducing wort down to really concentrate the sugars, such as in making a sugary sauce reduction, then I could see the pulsing being a problem and causing too much of a Maillard reaction if you didn't know how to control it or judge it. But even in conventional cooking, you don't get a Maillard reaction in sauce until it is significantly reduced down by boiling off liquid and highly concentrating the solids. I would love to read more about it as it relates to brewing if you have some resources. I hadn't heard of it until today.

Click to expand...

I have no hard evidence that shows that the maillard reaction is picking up with a stronger boil. It does however increase with higher temperature since it is the browning that we are familiar with from baking and cooking. Here's my thinking about this. As the wort goes from the liquid state to gas state, the temperature at the surface of the heater can go beyond 212°F for a short moment. Then as liquid again touches the hot spot it is violently pushed into the gaseous state and the pressure increases locally. I believe this is what we can hear and feel as vibrations during the boil. As the pressure increases the temperature can go beyond 212°F in that local spot and singe the wort. A stronger boil will exacerbate the singing. It's a theory anyway.

Then again, DMS is perhaps a more likely problem if the boil is pulsating, not giving the precursor to DMS enough time to boil off.