# Hotplate



## acpeacemaker (Oct 23, 2012)

Seeing if anyone could give some advice on this hotplate as I've been pondering on it for a while. I like the space it has as well as the 5ft corded remote. Its pricey I know, about a grand. I also thought about taking that kind of money and buying 4 hotplates with magnetic stirrers at $250 each. Thinking I wouldn't have to worry about all my solutions being heated at once. Does anyone have any suggestions maybe on a remote dial for the four? This will be under an enclosed hood. Any thoughts and suggestions much appreciated.

Take care,
Andrew 

http://www.amazon.com/gp/aw/d/B007HP4WQY?dpm=1&pi=SL75&qid=1351017857&ref_=mp_s_a_1&sr=8-18


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## goldsilverpro (Oct 23, 2012)

http://www.amazon.com/Thermo-Scientific-Controlled-Percentage-Controller/dp/B007HP4WQY/ref=sr_1_1?ie=UTF8&qid=1351026874&sr=8-1&keywords=hotplate+lab+12+x+12

Pretty, but, as a refiner, I just can't imagine spending all that money on a hotplate. 

A good electric skillet is about $30-$50 and works quite well for about anything I could think of doing except boiling something quickly or vigorously. Most are quite controllable. No stirrer but the high dollar one doesn't have one either. 

A beaker on a $60 Pyroceram Corning Wear dish on a $20-$30 kitchen hotplate will boil about anything, fairly quickly.

A stirplate/hotplate is nice but about the only thing I ever used them for was for dissolving certain chemicals that took a long time or for certain titrations. I never remember needing more than one. I've owned several of them but didn't use them that much. They can be sort of a pain.


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## acpeacemaker (Oct 23, 2012)

Thanks GSP. I didn't know if the magnet would be irritating or not I've never used one. But have found several applications where I thought it would be useful. Currently I'm using several cast iron double hotplates. They work ok, but would like to upgrade a little bit in the future. The one thing I would like to change now is being able to control the heat behind glass.

Thanks,
Andrew


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## goldsilverpro (Oct 23, 2012)

acpeacemaker said:


> Thanks GSP. I didn't know if the magnet would be irritating or not I've never used one. But have found several applications where I thought it would be useful. Currently I'm using several cast iron double hotplates. They work ok, but would like to upgrade a little bit in the future. The one thing I would like to change now is being able to control the heat behind glass.
> 
> Thanks,
> Andrew



Get a Variac that's big enough to handle the current on the hotplate. You keep it outside the hood and plug the hotplate into it. It can be used to control all sorts of things. Lots of them used on eBay. I can help you choose one if you like. On eBay, I recently bought a new 20A one, made in China, for $90, to control an electric smoker. Not as good as a $600 equivalent one made in the US, but it works. 

The stirplates can be very handy for certain things. Sometimes, though, especially if you have a lot of solids in the liquid or if you have a thick solution, it can be almost impossible to keep the stirbar centered. It will jump to the side of the beaker and stop turning. You have to keep messing with it to keep it going.

In one of my refineries, we had about a 6' long used restaurant grill with 4 or 5 gas burners. It was great because you could light only 1 or 2 burners at one end and have a wide spectrum of temperatures across the surface. To help cushion the glass containers from breakage, it was covered with fairly heavy asbestos cloth. You can't buy asbestos today but they probably have cloth from the same fabric that furnace gloves are made with. Instead of a fume hood, we used a tall wide tapered plenum, connected to the exhaust, behind and above the back of the grill. This is a tapered box about 4-6" thick with several adjustable exhaust slots on the face of it, running the width of it. Plenums are commonly used in plating shops behind fumey tanks.


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## oldgeek (Oct 23, 2012)

goldsilverpro said:


> Get a Variac that's big enough to handle the current on the hotplate. You keep it outside the hood and plug the hotplate into it. It can be used to control all sorts of things. Lots of them used on eBay. I can help you choose one if you like. On eBay, I recently bought a new 20A one, made in China, for $90, to control an electric smoker. Not as good as a $600 equivalent one made in the US, but it works.
> 
> The stirplates can be very handy for certain things. Sometimes, though, especially if you have a lot solids in the liquid or if you have a thick solution, it can be almost impossible to keep the stirbar centered. It will jump to the side of the beaker and stop turning. You have to keep messing with it to keep it going.
> 
> In one of my refineries, we had about a 6' long used restaurant grill with 4 or 5 gas burners. It was great because you could light only 1 or 2 burners and have a wide spectrum of temperatures across the surface. To cushion the glass containers, it was covered with asbestos cloth. You can't buy asbestos today but they probably have cloth from the same fabric that furnace gloves are made with. Instead of a fume hood, we used a tall wide tapered plenum behind and above the grill. This is a tapered box with several adjustable exhaust slots on the face of it, running the width of it. Plenums are commonly used in plating shops behind fumey tanks.



Would one like this work? I believe the specifications are 120 v 8.5 A 60 Hz


I have 4 of these that need a home. They have a date code of 7720 which I think is 1977, 20th week. They were in an interesting controller I scrapped out about 7 years ago, but I don't think they were ever connected or used.


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## resabed01 (Oct 23, 2012)

That Variac is rated to 8.5A. Most hotplates I've seen have a rating of 1200 or 1500 watts, that equates to 10A or 12A. So the Variac in the picure would be under-rated. Plus you have the problem of finding a suitable enclosure for the beast to keep yourself safe from shock hazards.

A hot plate is a purely resistive load. It wil operate happily connected to a Triac based light dimmer. Of course the dimmer would need to be rated for the load otherwise it would be overheated and burnt out. The small ones you find in your house are usually rated to 600 watts, not enough. They do make heavy duty dimmers that have aluminum heat sinks, those would be the ones to look at.


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## acpeacemaker (Oct 23, 2012)

There are quite a few on eBay for a lot cheaper. The one in this link is 2-3 more times than some of the ones I seen in auction. Would a 20a be a better canidate so its not maxed out while running? 
http://www.officebeyond.com/va-130-2000.html


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## goldsilverpro (Oct 23, 2012)

acpeacemaker said:


> There are quite a few on eBay for a lot cheaper. The one in this link is 2-3 more times than some of the ones I seen in auction. Would a 20a be a better canidate so its not maxed out while running?
> http://www.officebeyond.com/va-130-2000.html



I agree. The ones oldgeek has aren't enough to run a common hotplate. I would want at least 13A.

The one in the link above appears to be identical, even in color, to the one I paid $90 for on eBay.
http://www.ebay.com/itm/20-AMP-110V-VARIAC-AUTOTRANSFORMER-VOLTAGE-REGULATOR-POWERSTAT-0-130V-OUTPUT-NEW-/380453842256?pt=LH_DefaultDomain_0&hash=item5894d0ed50


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## acpeacemaker (Oct 23, 2012)

Thanks for the help, going to make an order tomorrow.  

-Andrew


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## butcher (Oct 23, 2012)

oldgeek, 
Those would work great to make a small silver cell power supply with , or to use for electronic troubleshooting, that variac transformer looks like what they use to use for the old style fluorescent light dimmers.

How much are you asking for one of those variable transformers, and are the carbon brushes on them still in good shape?

A hotplate can be controlled with a thermostat, I would prefer it over using a variac, even if I had to wire one in, or change the existing one.


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## kadriver (Oct 24, 2012)

goldsilverpro said:


> I agree. The ones oldgeek has aren't enough to run a common hotplate. I would want at least 13A.
> 
> The one in the link above appears to be identical, even in color, to the one I paid $90 for on eBay.
> http://www.ebay.com/itm/20-AMP-110V-VARIAC-AUTOTRANSFORMER-VOLTAGE-REGULATOR-POWERSTAT-0-130V-OUTPUT-NEW-/380453842256?pt=LH_DefaultDomain_0&hash=item5894d0ed50



Chris:

I have been looking for something to control the speed of the motor on my fumehood - the blower motor is only 1/10 H.P.

Would you recommend this variac for controlling the motor speed on my fumehood?

Thank you - Kevin


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## mjgraham (Oct 24, 2012)

kadriver said:


> goldsilverpro said:
> 
> 
> > I agree. The ones oldgeek has aren't enough to run a common hotplate. I would want at least 13A.
> ...



Others may know more about it but I'd say a variac is not the best to adjust the speed on an induction motor (just guessing the type of motor) I'd say it would drop the speed some but there is a major hit in torque. Most of those motors you have to adjust the frequency to adjust the speed, I think the RPMs are a function of line frequency and number of motor poles, and voltage to some degree. I guess the drop in voltage would slow it some, may make more heat, I guess I could try it back in the shop here and see, will let you know.

Edit. It did slow it down, worked down to about 20% of line voltage, didn't have much torque but it was adjustable. Used a little 1/16 HP blower fan.


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## goldsilverpro (Oct 24, 2012)

The only motor I've used one on was a small lab stirrer with a shaft and prop. Steve says they will work on non-automatic type battery chargers. I've mainly used them on heating things like hotplates


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## acpeacemaker (Oct 24, 2012)

> A hotplate can be controlled with a thermostat, I would prefer it over using a variac, even if I had to wire one in, or change the existing one.



I'm going to toy around with one since I have 3 hotplates. Would a digital or manuel have any more control over the other? I went ahead and ordered two variacs.

Thanks,
Andrew


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## Geo (Oct 24, 2012)

that the reason ive about switched all my heating to electric skillets. it has an actual temperature on the dial instead of low,medium,high.


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## johnny309 (Oct 31, 2012)

If you are digging in scrap yards you will find cheap(next to nothing) variac controlers....in vaccum cleaners...it is used as a power regulator(what it does is to reduce the voltage applied to the motor)....ussually rated 2000 Watts...
Heatsink must be changed for continuos work(meanning bigger)...but it is simple,low volume and low cost.


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## resabed01 (Oct 31, 2012)

This is a Triac based controller. It's to be used on resistive loads like heaters, incadesent lamps and series wound brush motors. Not useful for inductive loads like transformers, induction motors or floresent lamps.
Cheap and effective.

http://www.ebay.ca/itm/3800W-SCR-Dimming-Dimmers-Speed-Controller-Thermostat-AC-Motor-Voltage-Regulator-/390489657483?pt=LH_DefaultDomain_0&hash=item5aeaff508b


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