My new cheese cooker

[FarmerJd]

Wayne as a physics teacher I have to take off points because you didn't show your work in that equation.  Just kidding but I really didn't follow the math. Here is my math for my tank and pot:

40 gallons of water and milk (24 gallons of milk; 16 of water) = 151 kg liquid with an average specific heat capacity of around 4032 Joules/kg (milk is 3930 and water is 4186) (this doesn't take into consideration the metal in the pot)
raising temp from 31C to 39C (8 degrees Celsius) in 45 min or 2700 seconds

Energy needed =  4032 Joules/kg x 151 kg x 8 degrees Celsius = 4,870,656 Joules
Power needed = 4,870,656 Joules / 2700 seconds
Power = 1804 Joules/ seconds or 1804 Watts

I guess with the steel pot added and the heat lost through convection, radiation, and conduction my setup works out about right because I can turn it on and I don't have to turn it off on a full batch. It takes exactly 45 min to heat it 8 degrees. If I use less milk though I really have to watch it so I really want a thermostat. My problem is that when I have to cool it down I am in trouble.

I figured your setup (wow that's a lot of water!) and got a different answer (but close) than you so I may be figuring wrong.

100 gallons of water and milk  = 378 kg liquid with an average specific heat capacity of around 4125 Joules/kg (milk is 3930 and water is 4186) (this doesn't take into consideration the metal in the pot)
raising temp from 38C to 51C (13 degrees Celsius) in 45 min or 2700 seconds

Energy needed =  4125 Joules/kg x 378 kg x 13 degrees Celsius = 20,270,250 Joules
Power needed = 20,270,250 Joules / 2700 seconds
Power = 7508 Joules/ seconds or 7508 Watts

If this is right, you could take out 1 of the elements and probably let it run wide open and have a perfect cook. I still hate thermodynamics.

I am considering putting my heaters through the walls of my water bath.  What fittings, o-rings, sealants etc. did you all use to penetrate the walls of your water bath vessels?

My solution was pretty simple: I cut a hole and welded a nut the size of my element on the pot and just used Teflon tape to seal it.

[Sailor Con Queso]

The commercial guys use steam and circulating water jackets, so I'm thinking, why not use a water heater to circulate hot water thru your heating vat? Even a smaller mobile home size heater might work. A relatively simple submersible thermostat would control a low flow pump from the water heater to the vat. Inside the vat would be a coil of copper tubing that would transfer the heat to the vat water. When the vat hits operating temp, the pump shuts off. You could probably even use the thermostat from a a cheap commercial steam tray (EBay) to control the pump. Want to raise the temp 10 degrees over 45 minutes? Set the operating temp on the thermostat, but slow the pump down so it doesn't heat too quickly. I'm sure you guys have a formula for this one.

The plumbing would be easy, and the hot water would always be ready to go. Instead of starting with cold tap water, fill the vat with hot water from the heater. Properly filtered, this could also be a source of instant hot water for washed curd cheeses. Just set the water heater to the target temp and "wash" water is always ready to go. Hmmmm.....

[FarmerJd]

Christmas list just got unmanageable! I really wish I could do what you are suggesting sailor because it would be so much easier to control the temp up or down and the washed curd business is a real headache right now. However, I would have to have a separate cheese making room or facility if I was going to add a heater and a pump and all the hoses. I am going to study on it a while and see how feasible it would be. Good ideas.

Oh yea, there is a formula for that too and it also gives me a headache. 

[micah]

I am considering putting my heaters through the walls of my water bath.  What fittings, o-rings, sealants etc. did you all use to penetrate the walls of your water bath vessels?

I had 1" stainless steel threaded half-unions welded on my kettles.  Sound easy?  Not quite.  Hot water heater elements have straight threads and as far as I can tell nobody makes a 1" SS straight threaded half-union; they are all NPT.  So I bought a 1" straight thread tap and converted the NPT to straight thread.  The elements fit the unions perfectly.  I use the washers that come with the elements to finish the seal.  No pipe compound or Teflon tape used.  One kettle has been in service for over 15 years; the other for 8.  I have had no leaks and have not had to replace the elements yet.

Both of these vessels have been employed extensively as brew kettles; that is, they have been used for vigorous boiling of wort.

Unfortunately I don't have my tap on hand to post a picture (or the extra half-unions I bought for future projects) as I've lent them to my brother so that he can craft some brew pots.

[wharris]

This has been my experience.   I was wondering how others solved this....;

[FarmerJd]

My bad Wayne; my heating tank is not stainless so I never thought of it being a challenge; i just coated it in automotive paint and I never get the temp very high like you guys do with brewing. I wish it was stainless though; maybe one day. I said I used a nut but it was actually a threaded coupling with straight threads. I had forgotten that I decided to use that to keep the threads away from the weld. A straight threaded stainless coupling would be hard to find.

[micah]

FarmerJD,

Here is the email thread I had with Ranco.

I'm interested in the ETC Controllers but I don't know which would be best for my needs. I'd like to be able to control both 120 VAC (12.5 amps) and 240 VAC (10.5 amps) devices (though not at the same time). I'm willing to rewire the unit as needed. I read on the "selector" page that external relays can be employed. However, I don't see mentioned in any of the online pdf manuals reference to doing this. It would be nice to use an external solid state relay to control my device(s) this would simplify my switch over task. So basically I'm looking for a single stage controller that could be used for both heating and cooling and 120 vac and 240 vac. Which controller is best for me?

Micah

The ETC-111000-000 controller will run at both 120VAC and 240VAC and will do either heating or cooling.  If you needed automatic switch over from heating to cooling, then the two stage controller (ETC-211000-000) would be recommended, though it has lower amperage ratings and an external relay would be needed to drive the loads you have quoted.   Either model can drive external relays if needed that can in turn drive the load.

Tim (Ranco)

So let me get this right.  The ETC-111000-000 can run at both 120VAC and 240VAC AND can ALSO drive both 120VAC (12.5 amps) and 240VAC (10.5 amps) devices.  It also can drive external relays.

Micah

Yes, it's just a set of dry contacts (a simple relay) so it acts like an on off switch

Tim (Ranco)

Is there documentation for hooking up an external relay?

Micah

There is no specific documentation on connecting an external relay.  In the wiring diagrams for the ETC the coil on the external relay would be considered the load.

Tim (Ranco)

Is the VDC signal selectable (5VDC, 7VDC)?

Micah

No, the 0-10VDC is a output that varies according the current temperature reading.  at -30F it would be 0VDC, and at 220F it would be 10VDC and would read a voltage in between according to the temperature reading.

Tim (Ranco)

[Sailor Con Queso]

Hadn't actually thought of that, but since the milk doesn't actually touch the vat, stainless would be overkill.

[FarmerJd]

Micah,

Ok so I need this controller and a copper thermal well so that it will be submersible in liquid. So what were you suggesting using the external relay for? Was that for controlling the 240v element if the controller would not do it? It sounds to me like Ranco is saying it will work with out one, right? And how did you set up the potentiometer to manipulate the voltage so that you could control the rate of temperature change? And program it too ? And interface with your computer? Wow!
One more question: I don't really understand the analog output. Can you explain?
I saw that Ranco also sells the controller used in the Johnson "freezer to fridge" thermostat I just got. I guess I could have put that together too.

Sorry to bombard you. Just ignore if it's too much. Thanks!

[micah]

Ok so I need this controller and a copper thermal well so that it will be submersible in liquid.

It looks like that will do it.

So what were you suggesting using the external relay for? Was that for controlling the 240v element if the controller would not do it?

Yes.  It was unclear to me from Ranco's product descriptions if 240v devices could be switched.  All the blurbs state "great universal controller for any application where switching 120Volts..." which led me to infer 240v was not supported.  The external relay idea was only for if the controller could not switch 240v at the required amperage.  This is the case for their "two stage" units.

It sounds to me like Ranco is saying it will work with out one, right?

Yes.

And how did you set up the potentiometer to manipulate the voltage so that you could control the rate of temperature change? And program it too ? And interface with your computer? Wow!

My pot actually doesn't regulate the voltage.  I'm cheating and using it to vary how long, over a given period (using a 555 timer chip), the relay is on and off.  So if the knob is turned all the way to the left, the element will be off for the period; all the way to the right, it will be on for the period; in the middle, it will be on for half the period; etc.

This circuit board isn't programmable.  I have a second microprocessor based board that is.

One more question: I don't really understand the analog output. Can you explain?

The vdc output is used to switch on/off the on board relay.  It varies from 0 vdc to 10 vdc based on the temperature sensor's reading.  They are using a thermistor (as opposed to a thermocoupler) and scaling the measured resistance (ohms).  This signal can be used to switch an external relay as well.  It took me a while to figure out why the signal is not merely on/off.  One could also take this signal and given a table or regression formula convert it back to the measured temperature.  So it is much more versatile information than just on/off.  A practical application would be to take the signal and remotely display the temperature reading.  One could also feed the vdc readings taken over time intervals into a computer to monitor/analyze the temperature fluctuation.

It is unfortunate that their two stage units can't handle the amperage we are needing.  They must be using different relays for the two stage model; probably due to space requirements.

I'm going to get one of these pups.

Micah

[FarmerJd]

Thanks for taking the time to talk me through that. Thumbs wayyy upppp!

[Majoofi]

Great idea, Micah
how is it working for you?
I'm thinking about building something like that myself. I was wondering what you used to cut the lid and drill the hole for the heater, also what you used to seal the heater hole so it doesn't leak.

[micah]

Great idea, Micah
how is it working for you?
I'm thinking about building something like that myself. I was wondering what you used to cut the lid and drill the hole for the heater, also what you used to seal the heater hole so it doesn't leak.

The cooker is working out very well.  I picked up a Ranco ETC-11000 controller to throttle the heating element.  I separately monitor the temperature of the milk.  I use an aquarium pump in the water bath to agitate the water in order to avoid stratification.

I used a jig saw to cut the lid and a paddle bit (hole saw also works) to drill the hole for the element.  The heating element has a washer on the exterior which provides the seal but I also used a high heat silicone sealant (available at hardware stores) to ensure water tightness.  A 1" nut from an electrical tension restrainer is on the inside -- those things that you screw into the knock-outs of a J-box and tighten down to keep the electrical wire secure.

When cooking up 4 gallons of milk (5 could easily be done but I haven't done this amount yet) the most difficult task is removing the whey.  The pan is too heavy, using ones finger nails, to remove in order to pour off the whey.  I have successfully used a siphon hose with a small stainless steel "bazooka" screen; eventually the screen clogs but by then enough whey has been removed so I can easily lift out the pan.

The "easy-masher" (EM-1) utilizes the bazooka screen size I use:
http://www.ibrew.com.au/html/equipment/Easymasher/EasyMasher.htm

[Majoofi]

thanks for the quick response.
sounds good. how quickly does the water bath move up in temperature? I was thinking of having a separate  hot water source and pumping in hot water, because I thought that if it works well for me I could build the cookers in series and make double or even triple batches.

[micah]

thanks for the quick response.
sounds good. how quickly does the water bath move up in temperature? I was thinking of having a separate  hot water source and pumping in hot water, because I thought that if it works well for me I could build the cookers in series and make double or even triple batches.

I start with water warmer than my milk's target temperature because the milk needs to come up to temperature.  I'm still experimenting with the system.  The 1500w element seems to be enough to get things done in a timely manner.  It seems to me that you'll either have to employ a pump or use gravity to move all the water from one vessel to another.  I use the heating element to step temperatures when required by a recipe.  I'm not sure you could easily do this with the method I think you are describing.