Hot Plate Question

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Hot Plate Question

Postby ammo man » Sun Sep 06, 2009 2:38 pm

If you by pass the thermostat on the average 1500 watt hot plate, how hot will the heating element finally get?

The reason I ask Brewhaus advertises for their 1500w hot plate: "Our tests of this hotplate showed the cycling to be minimized enough that no negative effects on the stability of the distillation column were noticed. A simple adaptation can be performed to eliminate cycling if desired."

I would assume the simple adaptation to eliminate the cycling would be in by passing the thermostat. So back to my question, "how hot will the heating element finally get if you do by pass the thermostat?"

Any comments welcomed. Thank you.

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Re: Hot Plate Question

Postby olddog » Sun Sep 06, 2009 2:52 pm

It will draw a full 1500 watts.
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Re: Hot Plate Question

Postby myles » Sun Sep 06, 2009 2:57 pm

Hot plate temperature controllers are not actually thermostatic. What they are is a timer circuit on quite long cycle. Full power on for 5 seconds then off for 15 seconds for example.

How hot will they get? The same as if you turn it on full and leave it on. They cant get any hotter than their maximum setting. If you left a thick wash on for too long it would burn in the same way as a pan of soup on the same hot plate would burn
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Re: Hot Plate Question

Postby ammo man » Sun Sep 06, 2009 4:03 pm

Thanks. That all makes sense, but I am really more interested at this time in temp. Would that heating element get 98 degrees C, or would it get say 104 degrees C for example if the timing control was by passed. I would venture a guess that it would depend on the element in the hot plate in question. I am sure all hot plates do not have the same heating element, or is there an industry standard?

What I am really getting at was last week I put an 8 or 10 quart pot on my hot plate about half full of water. With the "timing control" completely open kicking in and out the temp would never pass 97 degrees C. That's not good enough for me a 200 feet above sea level. My question really boils down to, "If I by pass the timing control, will the water temp get hotter than 97 degrees C?" I want the water to boil.

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Re: Hot Plate Question

Postby Hawke » Sun Sep 06, 2009 4:35 pm

Yes, it should get hotter. You will be putting constant heat to it. How much hotter? no idea.
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Re: Hot Plate Question

Postby myles » Sun Sep 06, 2009 4:46 pm

If you want to get hotter and stay with electric there is a much more suitable option.

I run an insulated double boiler with a 3kW electric immersion element in the fluid bath. I say fluid bath because some time ago I ditched the water and replaced it with propylene glycol :D

So far I have not taken it higher than 140 degrees centigrade. That is nowhere near full power and at that temperature the glycol is not even close to boiling.

I have not experimented fully yet but how much of a temperature gradient do you wish to have?
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Re: Hot Plate Question

Postby ammo man » Sun Sep 06, 2009 5:23 pm

Not sure what I want myles. I am almost brand new in this most fascinating hobby. Today I hooked up the reflux 3" column still I ordered from Brewhaus. The column was packed with copper mesh and those ceramic things about half and half. With a 1500w hot plate from another dealer it took about 4 hours to get 78.5 degrees C at the top of the column. I had only about 18 L of flake maize wash, but distilled 200mL of 93 to 95 abv (that's not counting the first 50mL we dumped). We never could get the water flow adjusted after that. Finally disconnected the water flow to the top tubes of the column and connected it only to the condenser. I wanted to bring the temperature on up to 95 or 96. We could never get it past 91. And during the whole process we never would get a stream coming out, only drops. My conclusion was that the hot plate was not putting out enough heat.

Give me some of your thoughts.

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Re: Hot Plate Question

Postby cob » Sun Sep 06, 2009 6:31 pm

ammo man i don't have the exact answer to your question but olddog has the right answer. this is why, i put a pyrometer on a 1500 watt. hot plate and covered the probe with a steel plate. i turned the control to 7 which is max. i turned the control off when the pyrometer reached 600 degrees f. at about 2 minutes. your problem is not temp. but power, back to olddog's answer, 1500 watts, i don't know how many btu's that is but it is not enough. put 2 or even 3 hot plates under your boiler (if they will fit) on seperate circuits and you will cut your time or increase output proportionaly. i like propane myself. cob

(edit) myles also has a good solution to the problem. cob
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Re: Hot Plate Question

Postby scotty » Mon Sep 07, 2009 5:53 am

I just by passed my 1500 watt hot plate but havent made a run with it yet. I have a thermo well installed in my boiler and the probe of a remote thermostat with a 1 degree diferential goes into the well. I also heavily insulated my boiler.

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It seems to me that that temp which you were able to achieve would allow you to distill as it is above the boiling temp. of alcohol and below the boiling temp of water--sounds good????????? :D
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Re: Hot Plate Question

Postby cob » Mon Sep 07, 2009 7:57 am

Hawke wrote:Yes, it should get hotter. You will be putting constant heat to it. How much hotter? no idea.


when you bypass the controler and run for extended periods of time the hot plate can reach temps it was not designed to overheating the cord, melting the knob, overheating what is under the hot plate. apply due dilagence to all safety precautions. no smoke on the horizon. cob


(edit) my little experiment only ran 2 minutes and i quit at 600f. an 8-12 hr run ? cob
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Re: Hot Plate Question

Postby ammo man » Mon Sep 07, 2009 8:04 am

I just got through by passing the control on my 1500w hot plate and testing it. I placed a pot with a diameter about three inches larger than the heating pad on the hot plate with about 3 or 4 quarts of water in it. The temperature reached 102 degrees C giving me a good boil. I let it boil about an hour. Last week when I testing the hot plate with the control cycling, I could only get 97 degrees C with no boil. At least an increase of 5 degrees C with the control by passed.

I think if I insulate everything, I can now live with what I have.

Now please tell me the best way to insulate your boiler and distilling column?

Makes sense cob. I will watch it. However, it must be fairly safe when Brewhaus recommends doing it. They do recommend to never operate the hotplate without a product to be heated on the element, as the element may become damaged!


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Re: Hot Plate Question

Postby cob » Mon Sep 07, 2009 8:12 am

the experiment was a pyrometer and steel plate. a boiler or pot absorbes that heat so that kind of temp only happens dry. cob
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Re: Hot Plate Question

Postby Hawke » Mon Sep 07, 2009 8:41 am

As long as you have liquid there to absorb the heat, the burner itself shouldn't overheat. The cord is another weak link on a commercial hotplate. They can overheat, melt plugs, etc. Keep an eye on it.
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