Can you "dim" an electric element with a Variac?

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Jknapp

Jknapp

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Is that possible, to dim an electric element with a Variac - instead of the PID/SSR? Just curious if anyone knows..
 
Absolutely. You could even use a standard light dimmer (sine chopper) if it was rated to the correct current.
 
How large of an element? What size dimmer do you have to have to handle 4500W? 5500W? If it is feasible, why don't people do it?

That may be like a $200 variac.
 
That is almost a BCS, but much easier to set up

But, what is the MAX output of 10A at 250VAC? A 4500W element will draw nearly 19A?
 
The variac in the link has max 10 amp output, despite the 5KVA claim. Not going to work for any reasonably sized element.
 
So, it is $150 and worthless, really?

Yah, a PID and SSR are much cheaper and offer much more control. Or, if you want to spend more, get a BCS and then you have 6 PIDs, web based control for almost the same price as that "dimmer" thingy.
 
I own a couple of 2kw variacs. I recently built 2, 2kw heatsticks.. Sounds like a match.

Needless to say, I'll be using 2 of said variacs for my weekend brew session. Thanks guys!
 
You'll want the SYL-2352 PID if memory serves correctly, and a 40A SSR w/heatsink can be had pretty cheap on eBay.
 
i would imagine you could try the controls from a stove if you can find them at a high enough wattage
 
kezgin said:
i would imagine you could try the controls from a stove if you can find them at a high enough wattage
Click to expand...

The biggest electric range elements are around 2500 watts, so not much help for a BK, unless you used multiple elements.
 
Any "dimmer" type switch will work, IF you can get it at the appropriate wattage/amperage rating. The IF is what causes people to use the PIDs, which are by far cheaper and offer much more control. Not to mention, really easy to wire up
 
An alternative to look into would be speed controls for (woodworking) routers.
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=43060
I believe they are pretty much the same thing as lamp dimmer switches, except made for higher currents. (and if they can handle a 15A motor, then a 15A heating element should be no problem)
They're cheap, you can get 15A or 20A models easily enough, and they just plug inline with a standard AC outlet so you may not have to do any real wiring.

No idea if such a thing exists for 240V circuits though. It may be possible to hack two of them to gang them together on one potentiometer, but that may be getting too ugly.
 
Memorex88 said:
If they have these for 240V it would be GREAT! I like the ideas, keep em coming.
Click to expand...

The problem is, when you start looking at a variac, or dimmer for a 240VAC application that can handle the wattage and amperage that we are looking at here, you are doubling the cost and size for the solution.

I am curious as to what makes this so attractive?

What is the wattage rating of these speed controls? Even at 120VAC and 20A you are limited to 2400W, what does it cost? Can it handle a resistive load of 2400W? Looks like it is made for an inductive load of maybe 10A or so...

Also, does it matter that you are using it for a resistive load instead of an inductive load? Most large "dimmers" or variacs have large heatsinks to dissipate the heat created, this router speed controller does not. I am not sure Id want to wire a $20 speed controller to a 2000W element to test it out, but someone else can ;)
 
Memorex88 said:
To me the attraction is the simpleness of a pot. Just not a fan of relays.
Click to expand...

That is fair, just be careful trying to use an inductive load speed control for a high wattage resistive load. I am not convinced that a $20 speed control is capable of handling the wattages that we deal with. Which is why high wattage variacs are about 10x the size of that speed control (heat sink) and almost 10x the cost.
 
I'm sure if there is a 220V version of that speed control would cost 4X the amount and probably be 4X the size... if one does exist!
I just like people's ideas chiming in here. It's part of our hobby right?
 
djt17 said:
We have a 220v 20A variac at work. It's huge & the thing must weigh 30 lbs.
Click to expand...

That is what we would need... can you get a manufacturer, model #, so we can look one up? The issue is the "shunting" of the current, creates heat, which you need a big heatsink for. They are huge... which makes me fear the tiny router speed controllers that obviously are made to handle only a few watts, there is no real heatsink visible there.

I have found some used ones for $150, they are probably about 30 pounds, 9 x 9 x 9 and will only handle 2.6kW, or about 10A

This one is good to 20A, but the price... gahhhh, that would only control one 4500W element.
http://cgi.ebay.com/NEW-AUTOTRANSFO...emQQptZLH_DefaultDomain_0?hash=item4a9f12e79a

Here is one good to 25A at 240VAC:
http://cgi.ebay.com/STACO-VARIAC-2-...emQQptZLH_DefaultDomain_0?hash=item27afdcf3b5
 
willynilly said:
That is what we would need... can you get a manufacturer, model #, so we can look one up? The issue is the "shunting" of the current, creates heat, which you need a big heatsink for. They are huge... which makes me fear the tiny router speed controllers that obviously are made to handle only a few watts, there is no real heatsink visible there.

I have found some used ones for $150, they are probably about 30 pounds, 9 x 9 x 9 and will only handle 2.6kW, or about 10A

This one is good to 20A, but the price... gahhhh, that would only control one 4500W element.
http://cgi.ebay.com/NEW-AUTOTRANSFO...emQQptZLH_DefaultDomain_0?hash=item4a9f12e79a

Here is one good to 25A at 240VAC:
http://cgi.ebay.com/STACO-VARIAC-2-...emQQptZLH_DefaultDomain_0?hash=item27afdcf3b5
Click to expand...

I was wrong, the ones we have are only rated for 15 A. They are Powerstat Model 246T. http://www.superiorelectric.com/PDF/Z40pwst.pdf

The Powerstat 1256T is rated at 28A, http://www.superiorelectric.com/PDF/Z50pwst.pdf
 
I also have access to a 240V 20,000 watt dimmer here at work. They're available, but very pricey -these particular units are made for the motion picture/lighting industry.

It would work but I'm not wired up at home to run 240v. I use my 2k heatsticks to heat mash/mash out/1st runnings then switch to propane for the boil. Works good & saves gas.
 
wilserbrewer said:
Anyone have an opinion on this...
http://www.rockler.com/product.cfm?page=10760&filter=speed control

I'm looking to control a 2000w element. I know pid / ssr is the way to go, just looking for plug and play. Claims 20 amps / 120 volt. The actual photo shows it to say 26 amps?? Found one on ebay for less $$.
Click to expand...

Curious, why is a variac so much larger and more expensive than this speed control? Arent they working on the same principle? Maybe not, anyone with any guidance on this? I am just worried that these are not capable of the wattage that we deal with.
 
wilserbrewer said:
Anyone have an opinion on this...
http://www.rockler.com/product.cfm?page=10760&filter=speed control

I'm looking to control a 2000w element. I know pid / ssr is the way to go, just looking for plug and play. Claims 20 amps / 120 volt. The actual photo shows it to say 26 amps?? Found one on ebay for less $$.
Click to expand...

That speed control is for a universal router type motor (at most 1/4 HP 110 v). They get pretty warm even running a small trim router at less than full speed. 220 would toast it. The amps from a 2000 watt heater would toast it slower. And its about the same cost as a PID (some of the PID's can switch 2000 watts without a relay)

t
 
willynilly said:
Curious, why is a variac so much larger and more expensive than this speed control? Arent they working on the same principle?
Click to expand...
No, a variac is a variable transformer, which changes the voltage of the AC waveform but leaves it more or less a clean sine wave - one that can handle high power is going to be a huge iron core and a whole lot of copper wire; lamp dimmers and router speed controls are solid-state devices that switch the AC waveform on and off, modifying its shape to vary the effective power. Variacs have their applications - sometimes you need a clean sine wave - but for a heating element it doesn't matter.
 
So, that still begs the question, will a $20 Harbor freight router speed control, control a 2000W heating element without melting down?

Id like to see someone try it, but I also dont want to see someone get hurt, or start a fire.
 
willynilly said:
So, that still begs the question, will a $20 Harbor freight router speed control, control a 2000W heating element without melting down?

Id like to see someone try it, but I also dont want to see someone get hurt, or start a fire.
Click to expand...

Sounds like a job for the MythBusters! Or you could sacrifice a heatstick and a Harbor Freight router controller to the cause. ;)
 
Since the HF says the speed control is good for "15 amps and under", and a 120 volt 2kw element is about 18 amps, I really don't think we need the Mythbusters for this one.
 
I think the point we are driving at here is, will a cheap Harbor Freight type speed control handle an element that falls within the amperage range.

Obviously we know that an 18A draw on an element will exceed the 15A speed control, bad example. You can get 20A speed controls, so will a 2000W element work on a 20A speed control... there, that is better.

Is this speed control like a dimmer then? 2000W dimmers are quite pricey, that makes me wonder if a speed control will work, there may be more than something to it than a simple amp rating needed

We are way off the OP topic, but since this was brought up, it would be nice if someone knew, for sure, what the deal is. Maybe BrewBeemer would know, he is extremely intelligent when it comes to all things electrical.
 
willynilly said:
Is this speed control like a dimmer then? 2000W dimmers are quite pricey, that makes me wonder if a speed control will work, there may be more than something to it than a simple amp rating needed.
Click to expand...

Nope, that is, all that is to it. An element is a simple resistive device. If you really think about it, a light bulb is a simple resistive device also. A dimmer of sufficient size or a speed controller would work rather well. The router speed controller and dimmers are both pwm devices.
 
willynilly said:
Cool , for $30 you can control a 2000W element
Click to expand...

If it can handle the current. You can vary the voltage to the element but I don't know how stable the temperature would be. It could vary +/- 5 degrees, who knows. You won't know unless you try. It's more suitable for controlling the boil than providing a precise temperature for strike and mash water or maintaining the mash temperature. It's not like a control system where there is a temperature probe being read by the PID and adjustments being made by turning the element on and off.
 
Right, I think this whole thread is about the boil. Not temp. control

Though it was never really stated
 
Another thing to keep in mind about the idea of running a 2000 watt element on a router speed control. Most household 120 circuits are 15 amp, not 20. The breaker might hold for a while running a 2k element, but it's not a smart thing to do.
 

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