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

[leboeuf]

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.

 

[conpewter]

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)

 

[ChemE]

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.

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

 

[The Pol]

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

SO what does this mean to me in practical terms?

 

[ChemE]

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)

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!

 

[ChemE]

SO what does this mean to me in practical terms?

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.

 

[cyberbackpacker]

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...

 

[The Pol]

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.

 

[RedIrocZ-28]

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.

 

[bnscherm]

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.

 

[conpewter]

Looks like a dimmer switch will turn on and off 120 times a second. Make sure you have a serious heatsink on your SSR and that you have a fan on it. I'm switching at once a second (as is The Pol I think) and the heat sink gets warm. 120 times faster.... Hey it might work, give it a shot and report back, don't burn down your house.

http://home.howstuffworks.com/dimmer-switch2.htm

 

[RedIrocZ-28]

Also, what I would be more concerned with is the current draw through the dimmer switch. Lights don't draw much current, but a heater element running at full tilt or half would draw quite a lot of current I would think.

 

[conpewter]

Also, what I would be more concerned with is the current draw through the dimmer switch. Lights don't draw much current, but a heater element running at full tilt or half would draw quite a lot of current I would think.

Right a 30 amp dimmer switch is expensive! I think that's why they want to use it in conjunction with an SSR which doesn't require much current at all to control.

 

[kickflip_mj]

Thanks Pol,

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

i just read this so i thought i would post this

you know what i found is the simplest way to get a project done is:
1) tell us what you want to do.
2) Give us a Budget ( Ex. you want it done right and the Cheapest way)
3) I can garrentee you that many of us will put all the suppliers together and im sure you will get complete directions step by step if you need them..

Just ask bc many people on this fourm have got my through some interesting and complicated stuff, and want to spend my money.. so if you want the most complex rig we can help

 

[bnscherm]

Very little current will run through the dimmer switch, since this is only used to trigger the SSR.

The current throught the SSR is what generates the heat. Not the switching on and off. It should not get any hotter if you're switching once per second or 120 times per second.

Switching the heating element at 120 Hz may actually lead to a slight decrease in effective wattage due to the inductive impedance of the heating element. The SSR may actually be cooler, but the heat output may be a little less...

 

[jtucker101]

how about something similar to this:

POWER VOLTAGE SPEED CONTROLLER, Variac - 25Amp - eBay (item 110362559813 end time Apr-10-09 04:00:22 PDT)

 

[bnscherm]

That type of variac would make for a slick setup. That specific unit would burn up with a 5500W load, but if you find one at around 9600VA (40 amps) or even better 12000VA (50 amps) you'd be golden.

 

[ClaudiusB]

but if you find one at around 9600VA (40 amps)

CRYDOM RPC2440 40 AMPS, 240v, $ 154.00

Cheers,
ClaudiusB

 

[The Pol]

CRYDOM RPC2440 40 AMPS, 240v, $ 154.00

Cheers,
ClaudiusB

See, to me an $80 PID/SSR combo at half the price makes more sense. It works, it is easy and it is 1/2 the price?

But, again, I have room for 2 cars to ACTUALLY fit in my garage.

 

[jmilton1987]

Hey ChemE, I am a mech. engineer, and convection will be much higher. Also b/c it is wort and not water that is boiling I would bet that at boiling temp 1g/mL would probably be more accureate due to the increased sugar conten of the mixture, and then once you add hopps even higher. But I will look through my old thermo books to see if I can get a better h value for you. But verry cool to see boltzmans (sp.) equation in action.

 

[ChemE]

...Also b/c it is wort and not water that is boiling I would bet that at boiling temp 1g/mL would probably be more accureate due to the increased sugar conten of the mixture, and then once you add hopps even higher...

While it is true that the specific gravity of a mL of wort is higher than that of pure water the water boils and the sugar doesn't so it doesn't make any difference. We still need to boil 1 gram of pure water to dissipate 2,270J. 1 gram of water (with or without sugar) is going to occupy less than 1 mL of volume at 212F. And thanks, this is definitely the first time I've used the Boltzman constant since P-Chem II.

 

[slouch]

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

For my 7 gallon turkey fryer I have a single 1500w element that works fine. It take about 30-40 minutes to reach boiling and then I just leave it on at full power to maintain the boil.

The element was $8, the switch box ~$5 with the mount, box, gasket, faceplate and switch. The insulation was $12. I used a cord I already had, and the jb weld I already had. The bulkhead fitting and ball valve were about $10-13.

When I use it as an hlt it holds enough strike water for the mash, and will heat enough for the sparge by the time the mash is done.

It runs fine on a 15 amp circut. No upgrade required.

 

[ScubaSteve]

Great thread, hate to dig it up...but something occured to me about the radiative heat loss.....I'm no mathematician, but you need to take into account the evaporative and conductive heat losses....convection and radiation ARE occuring but all these processes are happening at the same time. My bet is that the majority of heat is being lost through the steam (wort/water changing phase and leaving the kettle...taking heat with it into the atmosphere) and by putting a cowl over the top you're actually slowing this process down. Sure, the cowl reflects heat back, but I think the steam leaving has a greater effect. Conductive heat loss is easy....just put something under the electric kettle to stop the stand from acting like a heat sink.

 

[dmfa200]

Didn't want to read through all these pages, but has anyone suggested using an electric stove burner controller.
That's what I use. I have a 4500 watt element to heat my water. The connections to the element and stove controller are housed in a Radio Shack project box attached to the side of my keggle.
Of course I maintain my heat manually but I have a thermometer installed.
So I just watch my temp when it gets close to target I start to turn in down.

 

[rod734]

Didn't want to read through all these pages, but has anyone suggested using an electric stove burner controller.
That's what I use. I have a 4500 watt element to heat my water. The connections to the element and stove controller are housed in a Radio Shack project box attached to the side of my keggle.
Of course I maintain my heat manually but I have a thermometer installed.
So I just watch my temp when it gets close to target I start to turn in down.

Iv been searching the forums for days to find someone that has tried an electric stove burner controller on their element. This is what I thought about doing. How is it working out. Do you use it for a boil or just to heat your mash water. I even thought about using an oven temp controller to heat and keep my mash and sparg water at desired temp.

 

[dmfa200]

Right now I'm using my keggle as a boil kettle as well as a mlt.
I heat my water for the mash. Then I transfer to my cooler and mix with grain.
When the mash is done I transfer the wort back into the keggle for the boil.
I use a couple of buckets with spigots to for the collection and transfer.
It works pretty good for me.

I have a link somewhere on my computer with info on how to build a infinite switch controlled hot water element.

I'll try to find it.

 

[hootowl]

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.

$22 https://www.amazon.com/gp/product/B015IFX4M2/?tag=skimlinks_replacement-20

 

[brewman !]

First off, you generally want to boil liquid off during the boil. So it isn't a matter of keeping the pot at 212F, it is matter of boiling off some liquid, which means you generally need a lot of power.

Most simple PID controllers can be tuned to keep a boil going but prevent a boil over. A PID plus a SSR solves that problem.

If you really need a "rheostat", there are these devices that control AC devices up to 10 Kw. They cost about $12 with a built in heatsink.

Most people have been over specing the heat sink for an on/off SCR. Generally a steel/aluminum enclosure will suffice. scrape off the paint and use heat sink grease.

https://www.ebay.com/p/Ac110-220v-1...-Speed-Controller-Dimmer-Thermostat/692538027