Automated/Electric 5 Gallon Setup... am I missing something?

[OEHokie]

Greetings all! I've been reading a lot from this forum lately and have made the decision to try and make an automated rig, but wanted to get some critiques before I continue.

My friends and I brewed our second batch on last sunday and started talking about automation (we're all engineers). We've been doing extract brewing from kits, which simplifies the equipment need.

Problem is, I live in a 700 sq ft apartment, so I'm rather limited in space and electricity. I've noticed that most rigs are gas powered, and if they are electric they use 3-phase power/several kW heating elements... so I did some basic thermo calculations.

For 5 gallon batches where you boil 3 gallons it requires about 3.7 MJ of energy to bring water up to a boil. My apartment's circuit breakers are rated at 15 Amps. I've read that you can use 80% of that safely (12 Amps). On amazon they have some 300 W immersion heaters... I could use 4 of those and still use only 10 Amps (if they're all on) and (ideally) it would bring room temperature water to boil in about an hour. Comparing this to brewing on my electric stovetop this is an improvement. That doesn't factor in heat loss... but I calculated that at boiling temperature. With some insulation around the boiling pot, the loss would be about 40 W, so that's not a huge concern. Before I do anything I'd buy the heaters/insulation and verify that they will boil the water.

Google Spreadsheet for some basic thermo calculations

The diagram below is the general flow path. The CFC part would probably get added in later but the "inverted" wort chiller would still be there. The pump is a Peristaltic pump, so that it is easy to clean and nothing mechanical touches the wort itself.

The order of operations would be:

1. Load 6 gallons filtered water into prep tank
2. Pump 3 gallons into Heated Tank (steep, boil)
3. Pump enough water from prep tank into Heated tank to make 5 gallons (would involve a volume sensor of some kind)
4. Load Prep tank with ice and cold water
5. Pump Heated Tank through chill system (if temp at the output isn't 70degF then recycle into heated tank and repeat) eventually into Fermenter
6. After 1 week pump fermenter 1 into fermenter 2
7. After 3 weeks bottle/keg and enjoy!

(Sanitizing would just be loading the prep tank with solution and running it through the system)

There would also be some kind of setup for automatically steeping/adding ingredients but I haven't figured that out yet (suggestions welcome).

I'm not sure about the solenoid valves and how they will handle everything (never used them before). I've read that they may not work bi-directionally but I dont know if that's a universal problem or just a particular kind. Have people used them bi-directionally? Or is there something else I should use? 3-port vs 2-port?

What tubing should I use? Clear plastic (like in kegerators) or copper?

Does anyone use flow sensors? Recommendations?

For volume sensors I've read about people using float sensors... how do those interface with the arduino or computer?

Can solid state relays vary voltage/power to the heating elements (so it'd be more variable than on/off... though with 4 I'd have 300W steps)There is something to do that, but it's neither efficient or cost effective, is what I gathered from below.

Pump recommendations other than the PS pump?

Once I get a bigger place I'd expand this to do all-grain, upgrade the heaters/pots for bigger batches, and maybe get a conical fermenter to eliminate the secondary fermenter.

Thanks for the recommendations/criticism/advice

Cheers,

 

[wilserbrewer]

How about a 1500w element? Using four elements seems laborious.

 

[OEHokie]

How about a 1500w element? Using four elements seems laborious.

Only the initial setup would be laborious. The 1500W element would put me over my 12 Amp limit (12.5... so not by a lot). At boiling 1500W would be overkill and I'm not sure how to vary the power of a heating element. Having 4 300W ones allows me to have 0-4 elements on (varying the power in steps if it can't be done with some kind of controller).

 

[buffalobrewer]

Only the initial setup would be laborious. The 1500W element would put me over my 12 Amp limit (12.5... so not by a lot). At boiling 1500W would be overkill and I'm not sure how to vary the power of a heating element. Having 4 300W ones allows me to have 0-4 elements on (varying the power in steps if it can't be done with some kind of controller).

I believe if you do a search for a pid controller with manual mode it will tell you that it can cycle the heating element as needed. I'm working on a brewtroller system (just got the board yesterday) that can also do it.

 

[passedpawn]

(varying the power in steps if it can't be done with some kind of controller).

This is what a PID does. It cycles the power on/off to either

1) achieve a set temperature - this is automatic mode, which all PIDs have, or
2) manual mode, in which you choose the duty cycle. For example, if you chose a duty cycle of 70%, the PID would turn the output (heat) on for 70% of the time - maybe 7 seconds on and 3 off. Engineers refer to this type of cycling as PWM - Pulse Width Modulation.

PIDS are very simple. They have an output which can turn on a relay (solid state or mechanical). They have an input which can be one of a bunch of different types of temperature sensors.

 

[klyph]

Instead of cycling a relay, does anyone set up their electric elements to be regulated by a thermostatically controlled potentiometer?

 

[kladue]

The problem with changing circuit resistance is the heat generated in the voltage dropping resistor, more resistance, more voltage drop, more heat. It is more efficient to tun on/off the power to the element with something that has a low on resistance and low heat build up and vary the on time to control element output. The other alternative for output regulation is a variable transformer but the size and cost for a transformer capable of handling a multi KW element make this approach expensive and space consuming.

 

[OEHokie]

The problem with changing circuit resistance is the heat generated in the voltage dropping resistor, more resistance, more voltage drop, more heat. It is more efficient to tun on/off the power to the element with something that has a low on resistance and low heat build up and vary the on time to control element output. The other alternative for output regulation is a variable transformer but the size and cost for a transformer capable of handling a multi KW element make this approach expensive and space consuming.

Good feedback, so varying the power of the heating element is out. I'll go with an on/off method. I'm still leaning towards 4 - 300W elements but that'll be based on availability. If I can find two 600W elements or one 1200W (etc) I'll do what's cost effective. I'll also have to factor in the price of the SSR's because they probably aren't that cheap (?, haven't researched it yet).

Thanks!

 

[Sawdustguy]

Good feedback, so varying the power of the heating element is out. I'll go with an on/off method. I'm still leaning towards 4 - 300W elements but that'll be based on availability. If I can find two 600W elements or one 1200W (etc) I'll do what's cost effective. I'll also have to factor in the price of the SSR's because they probably aren't that cheap (?, haven't researched it yet).

Thanks!

A 1250 watt element is not hard to find. Check some of the plumbing sites on the web. You guys are engineers. Get a high power triac and build a heavy duty light dimmer like this:

Choose a triac that can handle the current and power and heatsink the crap out of it. This is not a difficult circuit.

What I would really recommend, if you guys don't want to develop your own hardware and software is a brewtroller (www.brewtroller.com). The brewtroller is a Anduino board based on the ATMega644P that has its I/O organized and brought out to some pins. It can control temperature using an SSR, measure pressure for volume measurement and control your valves and pumps for not too much money. If you guys are hell bent on writing code the software is open source.

 

[OEHokie]

A 1250 watt element is not hard to find. Check some of the plumbing sites on the web. You guys are engineers. Get a high power triac and build a heavy duty light dimmer like this:

Choose a triac that can handle the current and power and heatsink the crap out of it. This is not a difficult circuit.

Interesting, we'll have to look into that.

BTW, none of us are Electrical Engineers, so any pointers in the right direction are appreciated.

 

[kladue]

A question for you, do you have a free standing kitchen range that is plugged in?. The reason for the question is that would be a higher amperage power source available for your system than the 15 Amp plug circuits.

 

[paddyfunk]

I would also check to make sure you don't have a 20 amp circuit available, seems a little strange if you have an electric oven on a 15 amp circuit (not impossible but definitely rare). As for the heating elements, you can find 1000 watt water heater elements for about 9 bucks online (plus shipping), combine one of those with a 300 watt element and you are in business (10.8 amps or so full load).

Also, the system you are planning to build is just a few pieces from being a pretty sweet all-grain counter-top system, so why not take the plunge. I know you have heard the sales pitch before.

 

[The Pol]

I didnt think the 80% rule applied to heating elements like it does motors? Youd be at 83% with a 1500W element...

I am fairly certain that the 80% rule applies to continuous loads for 3 hours or more and to motors for example because thier starting amperage will be much higher than thier operating amperage, so 80% is used as a guideline in those cases as well.

 

[The Pol]

I would also check to make sure you don't have a 20 amp circuit available, seems a little strange if you have an electric oven on a 15 amp circuit (not impossible but definitely rare). As for the heating elements, you can find 1000 watt water heater elements for about 9 bucks online (plus shipping), combine one of those with a 300 watt element and you are in business (10.8 amps or so full load).

Also, the system you are planning to build is just a few pieces from being a pretty sweet all-grain counter-top system, so why not take the plunge. I know you have heard the sales pitch before.

His electric oven is probably on a 40-50A circuit that is 240VAC, never seen an oven that ran on 120VAC

Cant tap that circuit for 120VAC

 

[The Pol]

I like this idea, I think you can easily find a SINGLE element that will work, Id just use 1500W

 

[OEHokie]

Actually, taking a look at my circuit breaker again there is a GFCI plug in the kitchen that's on it's own 20A breaker. Problem is, a comically tiny kitchen. The oven is on a 50A and the other big appliances are on 30A or 25A breakers. I don't want to unplug any of them.

Also, the system you are planning to build is just a few pieces from being a pretty sweet all-grain counter-top system, so why not take the plunge. I know you have heard the sales pitch before.

Yeah, that's my long term plan, but I may as well start setting it up in stages.

I didnt think the 80% rule applied to heating elements like it does motors? Youd be at 83% with a 1500W element...

I didn't realize the 80% rule was for motors, I've been reading a lot of forum posts lately so I probably just picked it to be safe.

I may go the 1000W + 300W heating element route. Would only require two SSRs and the 300W should be enough to maintain a boil/steep temperature assuming I insulate everything properly. Lots more research to do.

EDIT: 1 1500W element is still in the running though... like I said... more research/pricing to do.

Thanks for all the help! Cheers,

OEH

 

[OEHokie]

For anyone interested, this is the spreadsheet I used to do thermo calcs. This is a copy of mine so feel free to edit/make changes:

http://spreadsheets.google.com/ccc?key=0AmsvOL3m-H4ndHhIbW04TTR4dmpMSm8teWoyaGZfRnc&hl=en

Anyone have any answers for the bolded questions in the original post?

Thanks,

OEH