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Home Brew Forums > Home Brewing Beer > Electric Brewing > PWM for new EBIAB
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Old 09-22-2011, 03:57 PM   #1
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Default PWM for new EBIAB

I am in the final stages for building my BIAB system.
Right now I have 2 30 amp relays being controlled by my a love controller.
The love controller will run 2 5500 W - 240v elements independently.
After I built my relay box I stumbled onto the threads about SSR and PWM to have better temp control.
How bad will my current set up be trying to maintain temperatures. Should I scrap my current relay setup and just do the PWM and SSR setup?
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Old 09-22-2011, 04:19 PM   #2
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As I see it, PWM is great for adjusting the heat on a boil kettle. Not so good for maintaining temps in a mash. All the PWM does is adjust the amount of time the element is hot, on a very fast rate, so there is no sense and feedback to the controller.

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Old 09-23-2011, 02:38 PM   #3
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Ok so I was thinking about making up another box to connect in line with one of my elements that will have the SSR and the PWM circuit in it. Then if I need finer control for the boil I can just plug it in and turn the dial to the power I want.
After looking around, I can't tell if these are DPDT relays. So my question is do you guys run 2 of them for one element? That could get pretty expensive.
You need to switch both hot legs and it looks like these only would switch one.
http://www.auberins.com/index.php?ma...products_id=30

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Old 09-23-2011, 03:56 PM   #4
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How big is your system? I single 5500W element should be sufficient for 10 gallons I think.

I'm concerned with trying to maintain mash temps with a 5500W element in a BIAB system. Will you have sufficient stirring action to prevent scorching? Frankly, I've never pictured an electric BIAB system. Interesting.

If I were to do it, I'd probably have a smaller 120V mash element, and then the biggest boil element you could get. Elements are pretty cheap. Having a Low Density 120V element for mash might work better. Then I'd put them both on separate control circuits, and tap the 120V from the 220V coming in.

With a 3-way switch, you could place the Love controller on one side, and the PWM boil circuit on the other, and make the center dead (OFF).

With PWM for boil, you won't need finer control. You just turn it up a bit for more boil, and down a little bit for slower. You should have all the control you'd need with a simple twist of the knob, from Zero current to full power.

The Love controller will cycle on and off at a much slower pace, turning itself on and off as needed to keep the thermocouple at the temp you set it at. Too much heat at a time and the area around the element will get very hot before the sensor can detect it.

If you don't mind, can you describe the way your grain and bag will be arranged in the vessel with the element?

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Old 09-23-2011, 04:22 PM   #5
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Quote:
Originally Posted by Homercidal View Post
How big is your system? I single 5500W element should be sufficient for 10 gallons I think.

I'm concerned with trying to maintain mash temps with a 5500W element in a BIAB system. Will you have sufficient stirring action to prevent scorching? Frankly, I've never pictured an electric BIAB system. Interesting.

If I were to do it, I'd probably have a smaller 120V mash element, and then the biggest boil element you could get. Elements are pretty cheap. Having a Low Density 120V element for mash might work better. Then I'd put them both on separate control circuits, and tap the 120V from the 220V coming in.

With a 3-way switch, you could place the Love controller on one side, and the PWM boil circuit on the other, and make the center dead (OFF).

With PWM for boil, you won't need finer control. You just turn it up a bit for more boil, and down a little bit for slower. You should have all the control you'd need with a simple twist of the knob, from Zero current to full power.

The Love controller will cycle on and off at a much slower pace, turning itself on and off as needed to keep the thermocouple at the temp you set it at. Too much heat at a time and the area around the element will get very hot before the sensor can detect it.

If you don't mind, can you describe the way your grain and bag will be arranged in the vessel with the element?
My system is based on a 15.5 Sankey keg. I have a half coupler at the bottom with a 5500 W Ultra low density element. Everything I have read about the element it will not scorch. Your bag can even be touching the element and it won't burn it. I haven't tested this tho.
I made a large brew bag out of Voile material as recommended in the BIAB forum. The bag basically lines the entire inside of the keg and stops short about an inch above the element. Full of grains it might actually touch or sag around the element a bit. I will have to wait and see if that happens or not. The bag is reinforced with strapping and is basically a copy of the BIAB bags that a couple people are selling on the internet for $35.

I plan on running my march pump for continuous re circulation to try and keep the heat even. If that doesn't work I was going to take my second Sankey and use the second element to heat water and use my Chiller plate as a HERMS system to hold the temps during mashing as the WORT and Water circulate thru the plates. These are just ideas and I haven't tested these options yet. But it seems like it would work.
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Old 09-23-2011, 05:01 PM   #6
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Ok, that sounds fine then. The only concern is having too much heat in one place for any length of time. If you recirc then probably no problem.

I wonder if the love controller would be able to control the PWM directly, as opposed to cycling an SSR, effectively replacing the control knob on the PWM circuit... That way you could use it to vary the amount of heat the element creates, as opposed to the amount of time the element stays on.

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Old 09-23-2011, 05:53 PM   #7
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Quote:
Originally Posted by Homercidal View Post
Ok, that sounds fine then. The only concern is having too much heat in one place for any length of time. If you recirc then probably no problem.

I wonder if the love controller would be able to control the PWM directly, as opposed to cycling an SSR, effectively replacing the control knob on the PWM circuit... That way you could use it to vary the amount of heat the element creates, as opposed to the amount of time the element stays on.
The PWM is DC voltage and low current based using a 555 timer. I am pretty sure you would need the relay to control the high current AC load of the element.
But my thought was to just add the PWM and SSR to the existing relay circuit being controlled by the Love Controller. That way when the Love turns on the element is not full power. That might give me more control in not over shooting temps. Again this is all ideas and I won't know for sure until I actually try it.
It might just be less trouble on brew day to turn a knob for more heat or turn it down for less. Just like my gas regulator now. Little more user friendly.
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Old 09-23-2011, 06:35 PM   #8
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I think this plan is definitely worth a try. I have a HERMS arrangement, with 5500W elements, and right now, just by dropping the duty cycle of the element in the HLT, I am able to hold my mash temperature relatively easy. It may take you a bunch of trial and error to get there, but it'll work. Once everything is up to temp it takes about 10% duty cycle on the element to hold the temp at ~155 (that's with 10 gallons in the HLT). If you kept the Love controller, and put the duty to say 20%, you should get nice holding with little overshoot. Good luck.

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Old 09-23-2011, 07:10 PM   #9
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Quote:
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I think this plan is definitely worth a try. I have a HERMS arrangement, with 5500W elements, and right now, just by dropping the duty cycle of the element in the HLT, I am able to hold my mash temperature relatively easy. It may take you a bunch of trial and error to get there, but it'll work. Once everything is up to temp it takes about 10% duty cycle on the element to hold the temp at ~155 (that's with 10 gallons in the HLT). If you kept the Love controller, and put the duty to say 20%, you should get nice holding with little overshoot. Good luck.
Very cool. Makes me want to hurry up and get it all working.
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Old 09-23-2011, 08:02 PM   #10
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I see what you are saying now, and I think using a PWM to lower the output of the element would work well with a Love controller. The controller doesn't really care how much heat is coming out, it's only turning it on and off to help maintain the temp.

So you'd wire the one lead to the SSR, and the other to the PWM. The PWM would be turned on using the output from the Love to turn on the PWM connected to it via 12VDC wall wart hooked up to the 120V output from the Love (unless your love is a 12VDC model, then connect it directly).

Then whenever the Love says to heat the mash, the PWM fires the element at, say 25% power, reducing the amount of heat it puts out at a time. Sounds right to me.

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