I am having issues with my heating mantel jumping way past sp temps. By like 10 to 20°c i have read that you can achieve better temp control using a variac and a kill a volt. What i am unsure of is exactly how to connect these parts to the mantel and what i will use to read the mantel temp.
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You might try the auto-tune feature first.
You need to have an appropriate load in there.
See @Beakers thoughts up on PID for further insight.
Lowering the power to the heat is certainly an appropriate response if you don’t need it to maintain your boil. @LabSociety uses this on their SPD controllers for a reason. It gives better control…
Lowering the voltage you feed your mantle will achieve this, but will also lower the voltage the motor spinning your stirbar sees if all you do is plug into a variac.
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I thought skyhilighter made a controller. I forgot his actual screen name.
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Glas-col also allows you to adjust the power factor. Handy feature
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@Izambard_K_Brunel linked to @SkyHighLer’s thread on the subject.
Here it again with less distractions: Distillation controllers with both temperature and power control
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variacs are normally run on resistance wire.
V=IR voltage = amps x ohms or ohms law comes into play.
you have so much resistance wire that has a resistance of so many ohms
the voltage is the width of the power wave or thickness of the pipe.
this is what you control with a variac.
when you use a pid it turns the power on full and then off full in pulses so its if your in the states
110V on and then off and the timing is how long the resistance wire will heat and how hot it will get.
with the variac it will go to max voltage (unless its step up transformed) which if not steped up
will also be 110V and give the same amount of width to the wire.
the resistance then causes the voltage to drop as it moves through the wire and the current
or amps to go up.
amps + volts = heat.
the other equation one uses is the power rules or P=VA which is watts = voltage x amps
I am sure you are used to normal heaters and when you increase the watts it increases
the amount of power used and the heat produced.
if you have something that turns on and off at 110V it will not have time to reach max temp.
PID
if you reduce the voltage the temp will drop
Variac.
either way lets say you have a 10 ohm wire in the mantle.
110V = 11A x 10 ohms
if the PID is on all the time.
and
110V = 11A x 10 ohms
if the Variac is on max.
so …
1210 watts = 110 volts x 11 amps either way if they are on max.
you have 1210 watts of power and thats all the heat you will get.
so you need to have more volts than the power point is giving or you need to have a
variac that steps/transfroms up as well as down.
so you get a mantle that is rated for your country and put more volts in it than it should have.
what do you think will happen over time.
it is quite possible it will burn out (though most wire can get pretty hot like over 700C some up
too 1600 too 1800C if its kanthal)
but there is more in the mantle than the wire.
on the pid thing.
not sure what beaker has said but being a bee I know what he thinks on this.
you have glass and you max on and off with the temp with a wire that is thin (even though its
in fiberglass shell)
it will make hotspots and over time put fractures in your glass that can lead to implosion when
using vacuum.
as for the reading temp.
variacs and pids give power they dont read resistance.
most mantles that read temp (a lot dont they just have the setting already mapped out)
will have a k type thermocouple.
these can be read with a multimeter that takes k type thermocouples.
so you need a variac that steps up the volts as well as down and if you have a thermocouple
in your mantle a multimeter to read and translate its resistance to temperature.
if you dont have a thermocouple in the mantle what you do is you use an oil and a
thermometer in your flask and slowly turn up the heat till you get an idea of what voltage
correlates to what temperature.
well I was wrong on what beaker wrote.
yes up and down they go on and off so overshoot and undershoot.
still I personally wont use one with something going under hard vac its dangerous over time.
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This is a very bad idea and will lead to a fire or burn out.
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Uhhhhhhb
Purhaps you could articulate your objections more clearly?
I defined plugging the mantle into a variac as sub-optimal, and gave two better ideas.
Is non-trivial to decode, and you’ve aimed it equally at using the auto-tune on the mantel (per the fine manual) & using a temp controller that allows the heating power to be modulated.
The heating band requires x amount of voltage and amps. When you reduce it the band requires more wattage from the source to heat up adequately. It basically cooks and it will also cool any intermediate things hooked up to it in series to the heater. Those components struggle for wattage to opperate under lower voltage or amps.
ok so I hear this idea of heating mantles are not good under reduced voltage.
I have put that they are made form some kind of resistance wire with some insulation
and if your lucky a thermocouple for temp measurements.
then I give you heap of basic math to prove my point.
having pulled a few of these apart and made them from scratch please explain why
you say what you do and don’t say band requires more wattage.
what are you saying the band is made from ?
explains nothing.
now should some one have a control circuit in there mantle like the hard shell sets with the nobs
on them well unless you isolate this circuitry yes you will get interferience from it and yes it will
burn.
that is not a heating mantle that is a mantle with controler.
so can you please explain how low voltage will burn out a nichrome or kenathal wire that is insulated.
or are you thinking of something other than this being a mantle.
I am not a big fan of the I sell shit so I know shit or use the most expensive brand as that way
I know its the best (often not true to be honest)
can you explain the inner workings of the device and how you burn out the device low volt.
now having had a bit to do with electronics and have some understanding pnp and npn transitors
and doped semiconductors.
yes if you have a control circuit and you put reduced voltage in some of them they dont get
enough power to open the circuit through or not enough power for forward drop.
we see this when measuring some diodes and other semi’s with a digital multimeter
and that gives a open circuit for what would have been a closed circuit if there was enough
power to open the device you were testing. this in turn generates heat as the energy turns to work
and generates heat
here we are talking milli watts.
the thought that 300 + watts would go through one of the semiconductors is funny as if that
was the case the semi would have to be huge to deal with the heat generated.
are you calling the controller the mantle as well then ?
calls for the heating mantle ON all the time, connected to a POWERSTATor VARIAC.
straight out of glas coll instructions.
I am more than happy to admit when I am wrong and actually glad when some one gives me
new knowllage (this can be seen in some of my previous posts where I thought one thing and
found it to be wrong latter. I even correct my self if I find the mistake)
I find the attitude that a sales rep with a one liner of its going to cause fire with not proof
or explanation after I have gone to he effort to explain the underlying electronics happening
rather insulting to be honest.
so with some effort as the question this thread was based on was a valid one and does
deserve some kind of effort to answer and educate the asker.
I will not insult your person I will try to endevour to give proofs were I can when I argue against
someone elses comments as I don’t believe what others say I believe in science.
soooo for the sake of being professional and showing knowllage .
EXPLAIN
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and as 1 reference is no way to prove anything
Heating mantles produce their heat by converting AC voltage. The intense energy draw needed to generate the high degree of required heat, can blow fuses or melt socket wiring. For this reason, heating mantles should never be plugged directly into a wall socket. Instead, a transformer, such as a variac, or some form of electronic relay or switch, should be used between the heating mantle and the wall socket.
heating mantle controlled by 250w variac
The flask was heated by a Glas - Col heating mantle controlled with Variac .
so after using variacs with mantles for the last 27 years and having used them as such
in university …
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@squig I don’t know if you have seen this topic. It covers a lot of different mantle control methods.
Maybe you could have a look and comment on the control i found.
I agree with you that a heating element can be controlled by a variac so long as it can provide enough current.
@spdking ( i’m not trying to cause an argument or anything, I don’t have a lot of money so have to be a cheapskate lol )
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that is a uk and australian model.
I am not sure where you are my friend.
dont stress about spdking he posts I suck cock for drugs so as I will not insult him I shall call him
accountable for his statements when it comes to science and tech.
so 220V is its limit so it will give you the total of your volts from the power point though not
good for 110v systems.
if your using a 220/240v system you wish it to go to 260v
if your using 110v I think its about 130 or 140v though as I am using 240v system I am not sure.
most autotransformers (variac is actually a trade name made in the states that stuck for other
products) go to 120% which is what you want but some do not hence me mentioning the over volt
or step up you need.
so look for one that goes to 120% over your voltage.
also what wattage is your mantle.
as for reduced current don’t stress when you turn it off you have the ultimate reduced current 
if its just a resistance element there is nothing other than too much power or reactive environments
like acids etc that will kill it (of course work over time does it too but all things die in time)
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just read your in the uk in another thread so you want one that goes to 260v
simple
light dimmers will never do this as they dont want to burn the lights out.
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I’m waiting for David to send my SPD kit so i have plenty of time for either a variac or some sort of 3rd party digital control as outlined in the other topic.
( I’m not stressed about SPDking, I just want to remain neutral hahah ) 
edit : yes i’m welsh but now live in barcelona
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my mum is from york shire.
you got to lay down some of the welsh lingo for me man I love it.
also light dimmers are normally triacs and as pid’s work turn power on and off.
so you might as well use a pid which will give you temp control for the same price.
this is the reason they are so cheap.
a solenoid/relay hooked to an ic chip requires minimal materials but to actually
convert electricity to another voltage requires a large coil of copper around a ferret core.
as always I am sorry to say we get what we pay for and yep variacs are expensive.
sorry that was not 100% right other things will do this too like resistors but the heat they generate
at such loads is a lot.
I would hate to try and run a heating element of a variable resistor the size of it would be huge.
that is why we use magnetics instead of resistance to convert ac like this
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Yes of course … peanuts in … peanuts out … lolo
I know i need to get a nice variac and a thermometer, it the most important thing after vacuum. The first thing i thought when i started seriously thinking about buying an SPD kit was this.
All my life i have hated electric cookers because they don’t hold a constant temperature like a gas cooker would due to one being a heating element turning on and off and the other being a constant stream of controllable heat.
After reading this site for days lolo I found the post i linked you to from @SkyHighLer. Logic would dictate that a constant variable power source connected directly to the heating element would be far superior to the on/off control of PID.
ALSO !!! A variac would be a far superior for of control for my electric cooker !!!
If the PID control could cycle within 0.5c it wouldnt be a problem but they over shoot by 20c sometimes and this is not acceptable for me trying to learn the art of distillation.
( all for the want of $60 to $120 )
As you said " you get what you pay for "
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