Gonna build an Electric Boiler...how to control?

I'm gonna get supplies to build an electric boiler this weekend.....it is wayyy to hard to boil 6.5 gallons on my stovetop. And I don't really wanna go propane. I can run an extra 240 outlet off my breakerbox... so

I think I'm gonna buy one of these 4500 or 5500 watt 240v elements
Product Information Error Page


Drill a hole into my AHB Economy 7 gallon SS brewpot, and install that badboy.


My question is, I don't really wanna spend alot of money on a high dollar temp controller. So lets rule that out.
BUT, do I need some sorta potentiometer or rheostat to control it?

You will need something to control it...

I researched many different things while building mine, and could not get away from the PID and SSR combo. A rheostat for that much amperage/wattage is going to cost you.

look into honeywell, they have some great burner controllers at a resonable price. If your going electric you gotta do GFI, fuses/breakers, and like apol said you gottta control it. You could try to fin an Rstat but it aint cheap. A POT on the otherhand, well for that kinda amperage is just not gonna happen on any budget (unless your an AIG exec). Look at commercial oven parts also.

OH yeah, i forgot. I recommend to everybody, (Get a damn turkey fryer and use it with your stainless brewpot). I get like 12 batches out of a tank. I use a CO3(carbon monoxide) detector and have no problems. Electric is just not cost effective unless your brewing more than 10 batches a month(if you are you are a god!)

There is nothing cost effective about brewing in my mind. Electric is cheaper to operate than propane... but costs you to build. I have less $$ into my rig than many do in thier gas heated rigs...

A 5500 watt rheostat, if they exist, would be hundreds of dollars and HUGE.

so whats the cheapest way out for a controller or rheostat?

Can you give me a link to something?

Pol,

Would it be possible to not use a controller and just let the element run at 100% if it was sized properly...just guessing here, say 3500w for a 6 - 6.5 gallon boil?

I realize this will be kind of crude and take a bit longer to reach boil.

Mike

PID $45
SSR $20
Heat sink $20

$85 is about as cheap as you are going to get controlling that much power... 240VAC at 23 amps and 5500W is not a trivial ammount of power, it takes some serious equipment.

wilserbrewer said:

Pol,

Would it be possible to not use a controller and just let the element run at 100% if it was sized properly...just guessing here, say 3500w for a 6 - 6.5 gallon boil?

I realize this will be kind of crude and take a bit longer to reach boil.

Mike

Click to expand...

3500W is sized about right for a 6.5-7.5 gallopn boil. I run my 5500W element at 3500W to maintain the boil, after I get it boiling. You CAN do it that way, crude, but doable.

Thanks Pol,

While I admire your work and am a bit jealous, not all of us are cut out for such high tech rigs.

wilserbrewer said:

Thanks Pol,

While I admire your work and am a bit jealous, not all of us are cut out for such high tech rigs.

Click to expand...

Several months ago, I swore that I could not build this thing either. I learned how to wire the whole thing up via the interweb!

It isnt for everyone, but you have options.

I've been thinking about doing this for a long time as well. I've always wondered why a simple ordinary light dimmer switch couldn't be used to control an SSR which in turn controls the heater element? At the end of the day, if you use the SSR then don't you just need a simple way to control duty cycle in order to regulate the boil? Doesn't a simple wall dimmer do just that?

Does anybody know why this wouldn't work? How 'bout it Pol? Any input on this?

DNisich said:

I've been thinking about doing this for a long time as well. I've always wondered why a simple ordinary light dimmer switch couldn't be used to control an SSR which in turn controls the heater element? At the end of the day, if you use the SSR then don't you just need a simple way to control duty cycle in order to regulate the boil? Doesn't a simple wall dimmer do just that?

Does anybody know why this wouldn't work? How 'bout it Pol? Any input on this?

Click to expand...

It wont work...

The SSR is merely a switch, on and off. Its purpose is to switch large loads that normal switches cannot, and do it quickly, without mechanical relays.

A dimmer is a resistance switch that has an infinitely variable output. The SSR needs a ON and OFF input, not a variable constant input. Dimmers dont control duty cycle, if they did, your lights would turn on and off constantly, that is duty cycle. Dimmers are always ON, or off... they have no duty cycle.

The input voltage for most SSRs is about 3-10 volts DC... this is what causes the SSR to switch on and off.

Dimmer + SSR will not work, they are not compatible.

maybe even go more ghetto.... use two 3500watt elements, and just turn one off when ya get up to boiling.


....btw, I don't understand SSR, PID. Links? Where do I get this stuff?

Auberins.com

PID is a temp controller that switches the SSR ON and OFF. The SSR is just a fancy non mechanical relay capabe of switching power many times per second!

The PID is 120VAC, has a temp probe in the vessel. The power to the heating element is routed through the SSR, it is he switch. The PID controls the duty cycle.

65% equals 65% on, 35% off...

It is simple once you see it and understand that it is just a temp controller connected to a simple relay that has an input and an output

The Pol said:

It wont work...

The SSR is merely a switch, on and off. Its purpose is to switch large loads that normal switches cannot, and do it quickly, without mechanical relays.

A dimmer is a resistance switch that has an infinitely variable output. The SSR needs a ON and OFF input, not a variable constant input. Dimmers dont control duty cycle, if they did, your lights would turn on and off constantly, that is duty cycle. Dimmers are always ON, or off... they have no duty cycle.

The input voltage for most SSRs is about 3-10 volts DC... this is what causes the SSR to switch on and off.

Dimmer + SSR will not work, they are not compatible.

Click to expand...

I'm not yet convinced. I read at How Stuff Works that the old way that dimmers worked was with a variable resistor but the modern dimmers use a triac to vary the on-off time (duty cycle). Check out the article here:

HowStuffWorks "How Dimmer Switches Work"

Additionally, I've found a slew of A/C input SSRs at Grainger.com. So, just pull from one of the hot wires to power the dimmer and I would think you'd be in business.

Admittedly, I've haven't yet tried this. But the plan was to buy a dimmer, SSR and heatsink. Then use it with a simple light socket to see if I can control a light bulb. If it works for the bulb, I'm pretty sure it will work for the heater element too.

Not as sexy as PID but man, I still think this would work.

The point is, an SSR (relay) is an on/off state device that doesn't know what the hell a variable voltage (analog) input means. They have a voltage threshold at which the device goes from off to on.

I think one cheap way was already mentioned. Run two elements to heat quickly then kill one to maintain. Another way would be to run a 5500w element on 240v to ramp up quickly then cut it to 120v which would run about 1300 watts. I don't know if 1300 is enough to maintain boil though.

I am also a SSR user. You can pick up a 40A ssr on ebay for less than 15 bucks. My setup uses an AVR microprocessor (tiny2313) hooked to my laptop's serial port. I type a number into a hyperterminal window and it adjusts the PWM that controls the SSR. All my parts are < 10$ and it works great. I use serial because I plan to do more automation and logging, otherwise id use a 10$ lcd and some buttons to make a self contained unit.

If you don't have much microcontroller experience, i recommend an arduino board. They are about 35 bucks and are very easy to work with.

Calculating how much energy input is required to maintain a 6.5 gallon boil isn't too hard depending on the accuracy required. Energy input = conductive heat loss + boil off.

My boil off rate in my somewhat squat boiler is 0.97 gallons/hour or 1.02 mL/second. It takes 2,260 Joules/gram to vaporize water. A mL of water at 212F weighs 0.9584 grams (don't use the common approximation of 1 mL = 1 gram since we are far from 4C in a boiler) so the power required to maintain the boil rate is P = (1.02mL/s)(0.9584g/mL)(2,260J/g) = 2,209J/s = 2,209 watts.

To this we need to add the heat lost through coduction and radiation which is somewhat less trivial and requires a few assumptions. If anyone were seriously interested in this additional step I could probably swing the bat but it wouldn't be much more than a first-pass approximation of the true number given the number of assumed unknowns.

ChemE said:

Calculating how much energy input is required to maintain a 6.5 gallon boil isn't too hard depending on the accuracy required. Energy input = conductive heat loss + boil off.

My boil off rate in my somewhat squat boiler is 0.97 gallons/hour or 1.02 mL/second. It takes 2,260 Joules/gram to vaporize water. A mL of water at 212F weighs 0.9584 grams (don't use the common approximation of 1 mL = 1 gram since we are far from 4C in a boiler) so the power required to maintain the boil rate is P = (1.02mL/s)(0.9584g/mL)(2,260J/g) = 2,209J/s = 2,209 watts.

To this we need to add the heat lost through coduction and radiation which is somewhat less trivial and requires a few assumptions. If anyone were seriously interested in this additional step I could probably swing the bat but it wouldn't be much more than a first-pass approximation of the true number given the number of assumed unknowns.

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Cool calcualtions, but from practical testing in my garage on my system, 2,200 watts is going to give you a very anemic boil, if it boils at all. I require 3,500 watts in my keggle in a 60F ambient environment. If you have a well insulated vessel, this may change significantly, but that is my $.02

Well if you are determined to use a dimmer, then do it. Let us know how it goes. No one has any experience here with that sort of thing.

If the SSR does recognize it, I am not sure it will be able to switch that quickly. In a normal system the SSR will be running a 1 second duty cycle... since you dont see your lights flicker in your house with a dimmer, it must be running hundreds of duty cycles per second, not sure what that will do to an SSR.

Id recommend getting an oversized SSR and heat sink, switching 100's of cycles per second is definately going to create some heat and wear on the SSR.

Do it, let us know how it works.

Thanks! 3,500 watts is a very believable number since conduction and radiation losses over such a large area and thermal gradient are not going to be negligible. If I get some free time this evening I might make a first pass approximation to see if these values calculate out to be around 1,500 watts.

On a side note, when I switch my boiler to electric this fall I'm going to use some sweet heat blankets from McMaster Carr and some serious insulation in order to try to minimize the heat loss through conduction and radiation. The goal is to do it all for 2,500 watts as it is very easy to place this much heat around my boil kettle. Plus, why pay for the electricity if I don't need to? This would drop the cost of fuel for each batch down to less than $0.50. Its always fun to do more with less and it will pay out after around 4,000 batches! Good thing this is a hobby and not a business venture!

So I did a little boning up on heat transfer through radiation and finally got the equations producing reasonable numbers. Below is the radiative heat loss for my boiler based on a 70F room, a highly polished aluminum boil kettle, and an assumed skin temperature of 190F. I was very surprised to see that the vast majority of radiated energy is coming from the wort rather than the boil kettle itself.



If anyone truly wanted to minimize heat loss while not risking DMS suspend an inverted shallow cone made of aluminum flashing a few inches over the rim of the boiler. This will allow condensing DMS to drip out but a lot of the radiated energy will bounce back into the boiler.

That really surprised me! I thought that all of these ppl insulating thier SS tanks were mitigating the problems with insulation... you are saying that they are putting a bandaid on a gunshot wound.... ? Wow... cool.

ChemE said:

So I did a little boning up on heat transfer through radiation and finally got the equations producing reasonable numbers. Below is the radiative heat loss for my boiler based on a 70F room, a highly polished aluminum boil kettle, and an assumed skin temperature of 190F. I was very surprised to see that the vast majority of radiated energy is coming from the wort rather than the boil kettle itself.

Click to expand...

Interesting. That seems really low though. I don't know the calculations myself but I think the skin temp (especially in an aluminum kettle) will be rather close to boiling since it is such a good conductor. Still doesn't explain the 1500W difference between the original (just boiling off water) calc and The Pol's experience. I've run my 5500W element as low as 50% but the boil does pulse a little bit. I haven't run enough batches to nail down how much I boil off though so it could be The Pol boils off more water.

The Pol said:

That really surprised me! I thought that all of these ppl insulating thier SS tanks were mitigating the problems with insulation... you are saying that they are putting a bandaid on a gunshot wound.... ? Wow... cool.

Click to expand...

My textbooks claim that at temperatures around boiling radiative heat loss and natural convection are roughly equal so one might expect convection to be good for another 500 watts or so since polished aluminum has an incredibly low emissivity.

Insulating the boil kettle will tremendously reduce convection losses since rather than an outer skin temperature of 190F to 212F you can get a skin temperature very close to room temperature. Then your biggest loss becomes radiation from the surface of the wort itself (well after mass loss through boiling water of course!).

conpewter said:

Interesting. That seems really low though. I don't know the calculations myself but I think the skin temp (especially in an aluminum kettle) will be rather close to boiling since it is such a good conductor. Still doesn't explain the 1500W difference between the original (just boiling off water) calc and The Pol's experience. I've run my 5500W element as low as 50% but the boil does pulse a little bit. I haven't run enough batches to nail down how much I boil off though so it could be The Pol boils off more water.

Click to expand...

I run my 5500W element in the keggle at about 60-65%... 3300W to 3575W.

I get 1.5-1.6 gal/hr boil off

conpewter said:

Interesting. That seems really low though. I don't know the calculations myself but I think the skin temp (especially in an aluminum kettle) will be rather close to boiling since it is such a good conductor. Still doesn't explain the 1500W difference between the original (just boiling off water) calc and The Pol's experience.

Click to expand...

But The Pol doesn't have a means of measuring how many watts are required other than 2,200 isn't enough but 3,300 is. There is a lot of gray area there!

The Pol said:

I run my 5500W element in the keggle at about 60-65%... 3300W to 3575W.

I get 1.5-1.6 gal/hr boil off

Click to expand...

You're boiler is also stainless steel and much larger than mine, so you would produce a decent amount of convective and radiative heat loss compared to me. Just for fun, what is the ID, OD, and height of your boiler? Let me see what I get for you.

EDIT: I missed that 1.5-1.6 gal/hr boil off rate. It takes 3,643.7 watts just to accomplish that rate of mass transfer out of the boiler. I'd say theory and experience are jiving pretty damn well now!

Let me meaure... BRB

OKAY...

15.75 OD
15.5625 ID

20" deep...

I cant measure how many watts it takes, but I DO know that below 60%, the boil is pretty anemic.

To add to the dimmer switch part of this thread: Don't do it. You can however make a diy function generator on the cheap and use it to control the SSR. You would just have to calibrate the frequency/peak to peak voltage fit the SSR you're using.

Very cool math here. So does this mean that insulating my boiler or HLT really won't give me a huge improvement? (SS kegs, not shiny)

The Pol said:

Let me meaure... BRB

OKAY...

15.75 OD
15.5625 ID

20" deep...

I cant measure how many watts it takes, but I DO know that below 60%, the boil is pretty anemic.

Click to expand...

Here is the result from just radiation for your boiler...

ChemE said:

Here is the result from just radiation for your boiler...

Click to expand...

SO what does this mean to me in practical terms?

conpewter said:

Very cool math here. So does this mean that insulating my boiler or HLT really won't give me a huge improvement? (SS kegs, not shiny)

Click to expand...

Not at all. No, I'm still looking around for a decent way of estimating the overall heat transfer coefficient due to convection (any other chemical engineers out there who have a good number speak up) so I haven't calculated convection yet but I'm betting it will be far more significant than radiation. Interestingly, shining up your metallic vessels will significantly reduce the radiative heat loss from them. Still the wort dominates even with stainless rather than aluminum.

Math is always cool and powerful! BWAHAHA!

The Pol said:

SO what does this mean to me in practical terms?

Click to expand...

Very little admittedly. You could save perhaps 20 watts by polishing your boiler but is that view worth the climb? You can save another 60+ watts by suspending a flashing cone above your boiler.

I'm more doing this to prove that I can mathematically predict how much energy is required to run a boiler so I can optimize the design of my upcoming electric boiler. From all this it is very obvious that a tall narrow boiler made of highly polished aluminum is ideal. Also, once I get convection in there I believe I'll have an incredibly accurate estimate for the real world power requirements which gives me great satisfaction.

ChemE, doesn't your idea of a cone above the boiler jive with the professional breweries use of cones with chimneys on top of their coppers? I always wondered if professional breweries use this method, why couldn't a homebrewer do it as well, without the risk of DMS.

Additionally my knowledge of distilling is rather limited, but stills run a similar attached cone/chimney as a beer copper, and my understanding is that the condensate collects on the cone but then essentially is pulled out through the chimney.

So, I guess I am saying, why don't we use an attached cone top w/chimney on our home rigs- from the professional breweries it would seem DMS is not a factor using this method...

ChemE...

That is sweet man... totally sweet. I dont care about saving 60 or 20 watts, but it is cool to see my experience in scientific terms.

I also don't think insulating your Kettle will do much, a simple test would be to place your hand next to your kettle at full boil, lets say 1" from the surface, I bet its much easier to hold there than it is to hold it 1" OVER the boiling liquid. Splashing aside, I always assumes that more heat was lost through the top of the kettle than the sides. Which is usually why we put the lid on a pot to get it boiling faster. We all do that when cooking on the stove, and I actually do it on my turkey fryer. Crank that sucker wide open, put on the lid, and less than 10 minutes later I have 6.5 gallons of wort beginning to boil. Or, about 15-20 with the lid off.

I recently finished my electric kettle conversion using a 5500W RIPP element. I'm using one of these cheap-o SSR / Heatsink combos from ebay:

SSR

And a homebuilt PWM controller based on the design seen HERE.

I have PCB layout files in gerber format that I generated for the controller. If anyone else can make use of these let me know and I can upload them.

I've brewed three batches on the system so far, and it works excellent. The cheap SSR/Heatsink combo does get quite warm, but a little fan should solve that.

I see no reason not to try the wall dimmer. The new wall dimmers are definetely PWM controlled. This matched with an SSR that has a 110V AC input for switching would be a slick setup. As stated earlier, the PWM frequency may be faster then would be ideal, but it's definitively worth a shot.

My E-keggle / HERMS setup.