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Newbie-- Can someone explain the basics

Posted by achilles007 (My Page) on
Tue, Apr 20, 10 at 2:11

Hi guys. the REAL reason why I am here-- I want to create a water bath that would give me TIGHTER control of my cheese-cooking temps. When making cheese, during certain areas of the cooking process you need to control the temp down to the very minute increments. So for example 2 degrees per 5 minutes or 1 degree per one minute, etc. My set-up will consist of one 55 gallon drum, and a heating element installed into it controlled by a PID controller. THIS will be my water bath, and my SS pot of milk will sit in it, thus creating a double-boiler effect.

[B]HOWEVER I have been told that I cant just go out and buy a water heater element and just plug it in otherwise I could be putting myself at serious harm.[/B] [B][I]My question of what brings me here is-- WHY is that?
I'm used to plugging in all kinds of electronic devices with no problems or second-thoughts at all to any harm potentially coming my way. So.. what gives? In my room I could have 5 or 6 different eletronic devices all plugged into the same strip and NEVER have any problems.
[/I][/B]

And secondly if this IS a real issue-- what steps can I take to minimize this? I keep hearing of GFCI and panels, and breaker poles, and 25 amperes but all this stuff is OVER my head-- can someone please help in breaking down this stuff in helping me to understand? Thanks


Follow-Up Postings:

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RE: Newbie-- Can someone explain the basics

This is probably true. The element you are describing is 220 volt based on your 25 amp figure and not 110V which is what you find on everyday small appliances. Therefore the plug on the end wouldn't even fit into your strip. If it is 220 volt, you will need a special 220 volt outlet installed to serve this heating element.


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RE: Newbie-- Can someone explain the basics

Hi,

In general water and electriciy together are dangerours because water, commonly found in a home, is a good conductor. (Pure water does not conduct, but ions and other imputies in typical tap water make it a good conductor). So if you get your wiring wrong your whole water bath could become live.

A GFCI, Ground Fault Circuit Interputer, commonly available at Home Depot, Lowes, is a $US 11 device that you plug your water bath heater into. If senses if there is a leakage or current and switches everything off. It does not stop all possibility of electrical shock, but does reduce the risk alot.

Finally 55 gallons is alot of water to heat. I was just wondering if a smaller gadget would do you. There are micro-processor controlled wather baths which have your accuracy, but they are small, and are typically used in scientific labs. There cost is abot $US 800 to $US 1000, but will give you a +/- 0.2 degree accuracy.

Best, Mike.

P.S. You sound like a real cheese enthusiast and a foodie. I admire your passion!

Here is a link that might be useful: water bath


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RE: Newbie-- Can someone explain the basics

The basics - voltage = current x resistance. Current passing through your heating element is what causes it to get hot. So, if you have an element that is designed to run on 220v and you try to use it on 110v (half the voltage) then you will get half the heat output.

The other half is safety. Water heater elements typically have the element submerged in water and then the electrical connection protected. They don't just put an extension cord on it and toss it in the tank. Electricity takes the path of least resistance. The heating element has less resistance than air but more than water. As soon as the electrical connections from the element go into the water, the path of least resistance will become the water. If you touch the water, of if you touch a metal pan that touches the water, you could be in for a big shock.


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RE: Newbie-- Can someone explain the basics

Jury rigged devices, water, and electricity are a recipe for disaster. Essentially what you want to build is an open top, 55 gallon water heater. Electric water heaters of that size use two elements operating at 240V. At 120V, a single element is going to take quite a while to heat the water, especially in an uninsulated tank.

You need to find a way to weld a suitable flange to your drum, so that the element (or elements) can be permanently mounted. Then the connections can be insulated to protect against electric shock. What ever you rig up, absolutely needs to be GFCI protected.

I can't help but wonder if there isn't a commercial bain maire that would be better suited to your purpose and far safer to use. Obviously it would cost a lot more but probably less than the deductible/co-pay for an emergency room visit.


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RE: Newbie-- Can someone explain the basics

I would suggest a tankless water heater with a pump and loop into the 55 gal drum.


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RE: Newbie-- Can someone explain the basics

"I have been told that I cant just go out and buy a water heater element and just plug it in otherwise I could be putting myself at serious harm."

Water heater elements do not have cords, plugs, or controls.

The water heater has the thermostat to control the heater element.

Tight control is very hard to obtain by directly controlling an immersed heating element.
The element produces the heat, and only heats the liquid in its immediate vicinity.
If high precision is needed the liquid must be circulated, often rather vigorously.
Even a how water heater with two elements (typically an upper and lower) has stratification in the tank.

Tight control of changes in temperature is even harder.
Controllers need to adjust the heat being delivered based on the target temperature profile and the present temperature of the liquid.
PID controllers are normally used for this type of control.


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RE: Newbie-- Can someone explain the basics

It's a smaller scale than probably is practical for you, but this DIY sous vide setup seems to get at the problems of water circulation and exact temperature control. Perhaps it could be scaled up. It might be worth the $75 investment since the controller might be usable in a larger setup.

Here is a link that might be useful: DIY Sous Vide


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RE: Newbie-- Can someone explain the basics

* Posted by scottys (My Page) on
Tue, Apr 20, 10 at 7:16
"This is probably true. The element you are describing is 220 volt based on your 25 amp figure and not 110V which is what you find on everyday small appliances. Therefore the plug on the end wouldn't even fit into your strip. If it is 220 volt, you will need a special 220 volt outlet installed to serve this heating element."
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Ah! Okay--that makes sense. thanks


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excellent post

* Posted by stinkytiger (My Page) on
Tue, Apr 20, 10 at 7:26
"Hi,
In general water and electriciy together are dangerours because water, commonly found in a home, is a good conductor. (Pure water does not conduct, but ions and other imputies in typical tap water make it a good conductor). So if you get your wiring wrong your whole water bath could become live.
A GFCI, Ground Fault Circuit Interputer, commonly available at Home Depot, Lowes, is a $US 11 device that you plug your water bath heater into. If senses if there is a leakage or current and switches everything off. It does not stop all possibility of electrical shock, but does reduce the risk alot.
Finally 55 gallons is alot of water to heat. I was just wondering if a smaller gadget would do you. There are micro-processor controlled wather baths which have your accuracy, but they are small, and are typically used in scientific labs. There cost is abot $US 800 to $US 1000, but will give you a +/- 0.2 degree accuracy.
Best, Mike.
P.S. You sound like a real cheese enthusiast and a foodie. I admire your passion! "
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Ah! This is truly an excellent post. Just the description of the GFCI that I needed.

Unfortunately I cant afford such a microprocessor now and will have to suffice making my own.

No worries though... as home brewers do this ALL the time for making their beer. This example is one of which my model closely follows:
http://www.brewboard.com/index.php?s=e6d653463389b846e5897613b134a38a&showtopic=88163&st=15&p=1063393&#entry1063393

thanks again!


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Makes sense!

* Posted by billl (My Page) on
Tue, Apr 20, 10 at 9:29
"The basics - voltage = current x resistance. Current passing through your heating element is what causes it to get hot. So, if you have an element that is designed to run on 220v and you try to use it on 110v (half the voltage) then you will get half the heat output.
The other half is safety. Water heater elements typically have the element submerged in water and then the electrical connection protected. They don't just put an extension cord on it and toss it in the tank. Electricity takes the path of least resistance. The heating element has less resistance than air but more than water. As soon as the electrical connections from the element go into the water, the path of least resistance will become the water. If you touch the water, of if you touch a metal pan that touches the water, you could be in for a big shock. "
-------------------------------------------------------

Okay great-- now I know what the 220 V is needed for.
I always thought that if I were to plug something that required a 220 V to sustain it into a 110 V outlet that the power would go off out of the whole house or something. What is that called when it does that?

Is it true that certain outlets or houses can nly handle certain elecrtical loads? What happens if you go above that limit?

And are you sure that if one's hand or another metal pan were to go in the water that an electrical shock would ensue? If well sealed and soldered correctly and tight enough to keep away from the electrical wiring-- how can this be?


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Right

* Posted by mike_kaiser (My Page) on
Tue, Apr 20, 10 at 10:29
"Jury rigged devices, water, and electricity are a recipe for disaster. Essentially what you want to build is an open top, 55 gallon water heater. Electric water heaters of that size use two elements operating at 240V. At 120V, a single element is going to take quite a while to heat the water, especially in an uninsulated tank.
You need to find a way to weld a suitable flange to your drum, so that the element (or elements) can be permanently mounted. Then the connections can be insulated to protect against electric shock. What ever you rig up, absolutely needs to be GFCI protected. "
----------------------------------------------------------

Agreed. So are you suggesting to go with two elements instead of one? I was hoping to make the situation a bit less complicated and just install one of them at 240 volts.

As far as the welding part I have a link I gave up aboe that shows how the guy silver-soldered all his material to his keg and operated it from there just fine-- I'll probably be taking that approach too.


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I Agree

* Posted by brickeyee (My Page) on
Tue, Apr 20, 10 at 13:16
"Tight control is very hard to obtain by directly controlling an immersed heating element.
The element produces the heat, and only heats the liquid in its immediate vicinity.
If high precision is needed the liquid must be circulated, often rather vigorously.
Even a how water heater with two elements (typically an upper and lower) has stratification in the tank. "
----------------------------------------------------------

Yeah. I was just thinking about this problem, and figured I could probably use a submersible aquarium/water pump to help circulate the water and avoid stratification. thanks!


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RE: Newbie-- Can someone explain the basics

* Posted by neil_allen (My Page) on
Tue, Apr 20, 10 at 14:30
"It's a smaller scale than probably is practical for you, but this DIY sous vide setup seems to get at the problems of water circulation and exact temperature control. Perhaps it could be scaled up. It might be worth the $75 investment since the controller might be usable in a larger setup."
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Ah! Yes! I had seen that the other day, and decided to go with a little bit of a bigger version of what that was.

I wonder though-- when looking at his site-- he never explained how it was that he circulated the water with to avoid uneven heating and hot spots..


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RE: Newbie-- Can someone explain the basics

Is it true that certain outlets or houses can nly handle certain elecrtical loads? What happens if you go above that limit?

For ordinary, household 120v circuits, 15 or 20 amps is the limit depending on the circuit and receptacle. Beyond that the breaker should trip or things start to melt.

And are you sure that if one's hand or another metal pan were to go in the water that an electrical shock would ensue? If well sealed and soldered correctly and tight enough to keep away from the electrical wiring-- how can this be?

Folks here are going to try to give you suggestions to keep you safe, best practices if you will. Does that mean your jury rigged vessel will be safe 999 out of a 1,000 times? Probably. But you want to be sure because electricity can and will kill.

Make sure whatever pump you pick is designed to handle higher water temperatures. What actually might work is an inline heater combined with a pump like those used in a hot tub. Although I don't know if they're rated at a high enough temperature for cheese making


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RE: Newbie-- Can someone explain the basics

There are some good starting points here. The lab equipment-type baths can be had for considerably less on the used market. There are lots of distributors of used lab equipment, but ebay is a good source as well. I am not sure that they are large enough for the volume the OP wants to work with. How much cheese are we talking about here?

The homebrew solution linked above looks very much like some lab types as well. They are sometimes sold with reservoirs, but you can stick them onto something different. I don't think that type will make enough heat.

An tankless water heater will be expensive and the OP wants to keep costs down. A small tank water heater will cost less and, he might be able to decrease the size of the bath from a 55 gal drum to something smaller.

The other problem with tankless is that the water flow rate will have to be relatively large and the heating rate will be high and more difficult to control as a consequence.


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Almost there!

* Posted by mike_kaiser (My Page) on
Tue, Apr 20, 10 at 17:22
"For ordinary, household 120v circuits, 15 or 20 amps is the limit depending on the circuit and receptacle. Beyond that the breaker should trip or things start to melt. "
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Okay. so what steps can I take to help the house be able to handle a load over that? Just taking out the 120 v circuit and re-wiring a 240 v one would do the job?

do you have any directions into how one can possibly do this?


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RE: Newbie-- Can someone explain the basics

I would probably install a new 240v circuit rather than replacing the 120v circuit, because you might need the latter for something else.

"How" you do it depends on local code and the relationship between your service panel and the where you are going to use your device. You are going to need to calculate the load and then size the wire and breaker appropriately. There are plenty of websites that describe, with pictures, how to install a new circuit but if you are truly clueless, hire an electrician. Made sure you use a GFCI breaker.


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RE: Newbie-- Can someone explain the basics

Bill posted above :

> So, if you have an element that is designed to run on
> 220v and you try to use it on 110v (half the voltage)
> then you will get half the heat output.

The heat output will actually be one-fourth. Ohm's law says that in a pure resistive circuit P = E^2 R => power is proportional to the square of the voltage applied.

So a 5000 watt WH element will produce about 1250 watts' worth of heat on 120 volts. That'll heat your water, but I suspect it won't control the temperature at the delta-T rate you want.

I think if I were going to do this, I might look at ways to control valves releasing cold and hot tap water into the vat. The valves are easy; get 'em from a derelict clothe washer. Maybe you could control them with a Basic Stamp and a couple of relays. (Disclaimer: I've never programmed a Basic Stamp, just read about them.)


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RE: Newbie-- Can someone explain the basics

I'm no cheese expert, but people have been making the stuff for thousands of years. They didn't have fancy electric heaters and electronic controls. Some guy was just in charge of diligently tending a fire. That was part of the "art".

I suspect you could make this process a whole lot simpler with a gas/propane burner along the lines of a super-sized turkey frier. 55 gallons of water is going to change temp pretty slowly, so it should be easy for you to regulate that within a degree.


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