Heating Element Control

[CoopsOz]

Update...I bought a new triac and rewired it, nothing blew up this time, however, it doesn't work. I get 240v at the o/p regardless of where the dimmer switch is. Could I possibly have damaged the dimmer switch in my previous attempt? I measure about 14Mohms across it, is that about right? I'm gonna try wiring the 75ohm resister the alternate way and see what happens.

[GoodOleBoy]

I can't answer your question, but was the dimmer switch based controller supposed to use the same store bought 120 volt dimmer for both the 120 volt and 240 volt versions?
Also, is the household wiring in Europe 240 volts to ground? In the U.S. 240 volts for residential wiring consists of two 120 phases, neither of which is grounded. Standard receptacles and lighting consists of one 120 volt phase and a grounded neutral.

[masonjar]

Good point, GOB. What country are you in, Coops? Does Oz mean Australia? What are you doing with your ground wire?

Here's another thought - you could try reversing the dimmer switch. I wouldn't think it would matter which way the dimmer went in, but without seeing its internal schematic there's no way to tell.

I'm still suspecting the metal box. There's a real good chance that something is getting shorted out in there. You might also try taping all exposed wires with electrical tape to prevent that.

If you see 240 volts always, then that means that the gate of the triac could very well be shorted to the +240v line - or something else in there at a relatively high voltage. Hey - which schematic did you use? There have been two of them posted on this thread and it's kind of misleading. One of them will never work - no matter what dimmer switch you use, even though someone said it would. That schematic doesn't make a complete circuit with the triac gate and it would be physically impossible for it to work.

Another good point, GOB. If you are using a 120v store-bought dimmer on a 240v circuit then that 120v dimmer is very likely to get destroyed. But if you say there are 14MOhms across the dimmer, then there is no conclusive evidence about whether it's broken or not. That sounds right for a dimmer that isn't hooked up to anything.

[CoopsOz]

G'day masonjar and GOB, thanks for taking the time to help me out.

Good point, GOB. What country are you in, Coops? Does Oz mean Australia? What are you doing with your ground wire?

Yes, I'm in Australia. My ground wire is bolted to my metal box......every other piece of equipment I've worked on has a chassis earth, so I figured this would need one as well. Is that correct?

Here's another thought - you could try reversing the dimmer switch. I wouldn't think it would matter which way the dimmer went in, but without seeing its internal schematic there's no way to tell.

I need a new dimmer switch, I did in fact blow the first one up.

I'm still suspecting the metal box. There's a real good chance that something is getting shorted out in there. You might also try taping all exposed wires with electrical tape to prevent that.

I don't think it's the box, I have either heatshrink or screw connectors on every connection.

If you see 240 volts always, then that means that the gate of the triac could very well be shorted to the +240v line - or something else in there at a relatively high voltage. Hey - which schematic did you use? There have been two of them posted on this thread and it's kind of misleading. One of them will never work - no matter what dimmer switch you use, even though someone said it would. That schematic doesn't make a complete circuit with the triac gate and it would be physically impossible for it to work.

I used this one from PintoShine.


I'll let you guys know after I buy a new dimmer, Its gonna kill me though...the cheap 500w ones aren't so cheap, about $50.00

[GoodOleBoy]

On page 4 of this thread, Pintoshine stated that when using the 240 volt unit, he used only the TO-220 package from the dimmer. He replaced the potentiometer and the capacitor. This wasn't necessary on the 120 volt unit.
A quote from page 2 of this thread by Pintoshine:
" Whenever I build the 240 volt ones, I replace the pot and the cap. The off the shelf ones are not rated high enough on the capacitors. I tried it with disasterous results. The caps exploded and stank the place up really bad."
If it was me, I would replace the pot and cap. as he suggested. Even though your dimmer may be listed at 240 volts, maybe the pot and capacitor can not handle the power required. Would hate to see you blow up another dimmer.

[pintoshine]

The only reason I replace the pot and cap in the 120 volt triacs is for the fact that the resistance needs to be doubled going from 120 to 240 volts, of which I don't think CoopsOz will have a problem, and also the cap in most of the 120volt dimmers is only rated for 200 volts. Peak to peak 240VAC is actually 340vpp. So I increase the cap to a 400VAC one.
I think the dimmer CoopsOz is using should work fine.
I am sure curious, why would a 500W dimmer cost so much? They are only about $8.00USD.
A thought did occur to me though. It takes 1/2 the current at 240 volts to get the same power rating. I should more precisely state that the dimmer needs to be able to handle about 4 amp. A 500 watt dimmer at 240vac is only able to handle just a little over 2 amps. The resistor at 75 ohms is able to supply 3.2 amps to the triac pair. The large triac at 4.5kw should need about 3 amps to trigger it correctly. I am sorry I was not clear. The 240VAC European and Australian voltages confuse me a bit, and assumptions I have grown up with do not work well. I am learning a whole new mind set.

[CoopsOz]

The dimmers definitely cost more than $8.00 around here, I've found a few on ebay, take note of RRP on this listing.....they reckon $70, that might be a bit rich but $50 to $60 is about right.

http://cgi.ebay.com.au/ws/eBayISAPI.dll ... &rd=1&rd=1

[GoodOleBoy]

Thanks Pintoshine, for the clarification. It sounds like to be on the safe side, a 240 dimmer should be rated near 1000 watts. If a 500 watt dimmer is going for 50 bucks in Australia, and may not be of sufficient amperage rating, it may be cheaper just to start from scratch. I certainly don't understand the wild price differences. I was going to suggest he try Ebay, even with the increased shipping cost, it may be worth it. But after searching, I found only 120 volt dimmers available unless you get into ridiculously priced theatre equipment. Even 1000 watt 120 volt dimmers can be had in the U.S. without breaking the bank, there MUST be a European supplier that has 240 dimmers at a somewhat reasonable price? I know that Lutron and other manufacturers make them so it's not a matter of rarity.....very strange.

[GoodOleBoy]

Just a quickie. For those who want to roll their own, this link has a 230 volt 1000 watt light dimmer schematic with parts list.
http://www.epanorama.net/documents/ligh ... ml#1kw230v" onclick="window.open(this.href);return false;" rel="nofollow

[CoopsOz]

Thanks for the link GoodOleBoy......This is getting way too complicated for my little brain. It's getting to the point where I'm just gonna get a smaller element.

[bourbonbob]

Thanks for the link GoodOleBoy......This is getting way too complicated for my little brain. It's getting to the point where I'm just gonna get a smaller element.

That's the way to go Coops, it can be quite costly in Aus to set up a controlled electrical system, I have a 1500w 240volt in a 20lt boiler and it works ok, but I will put a 800-1000w in as well. The 1500w works well but I need the 1000w for stripping runs as I loose a bit of vapour. I might pack the the condenser with some SS scrubber and see if it cuts the vapour loss (I don't lose much but it is noticable)

I got the elements out of cheap jugs (actually they were free)

[CoopsOz]

I ended up buying another dimmer switch (I got it new from ebay for $30), wired it in and once again nothing. This time all that happens is the cct breaker trips. I've now officially got the shits with it. Today I ended up wiring my two elements in series, I get about 850w. I ran a failed attempt at sugar wash through my potstill ( it finished at 5%) and the 850w works a treat. The distillate comes out cold and after 3hrs my cooling water was still running cold. YEHAH.
Although the resulting pot stilled tomato vodka is less than appealing , I'm finally ready for a UJSM!

[Brian Murphy]

What about a Router Speed Controller....? I believe they are just HD rheostats, not the preferred variac.However, because they are designed to regulates the speed of a router motor, probably up to 3 HP at say 10-15 amps, wouldn't that do just as well...? Easy to plug into wall, and plug heating element into Speed controller....??? Not too pricey either..... Anybody ever done that??? Feed back............??

Thanks,

CW

So did anyone ever answer your question? I read though the thread but all I seemed to find were a variety of schematics. I use the speed controller to control large lights for television shoots quite effectively for any lamp up to a 15 amp draw.They are easier for us to transport than a Variac They are cheap. $9.99. But since I am brand new here and have yet to decide on which design I will build I thought I would ask if your question ever got answered.
http://www.harborfreight.com/cpi/ctaf/d ... mber=43060" onclick="window.open(this.href);return false;" rel="nofollow

[Dog Meat]

What is the wattage rating? will it do 2000?

I think this may be the exact same thing that they are building here for 110-120V US application.

[Brian Murphy]

What is the wattage rating? will it do 2000?

I think this may be the exact same thing that they are building here for 110-120V US application.

It would depend on the exact voltage but around 1800 watts I believe.

[Dog Meat]

Well let me rephrase that. If you download the manual there is an exploded parts veiw that shows everything in the pictures here. I can't tell if its the exact same ones though.

My element is exactly 1800 watts. sweet.

Close enough so for $10 I will let ya know if it smokes.

[spaine]

OK guys I just built a still - Bokabob mini still but with 3ft 2inch column. I am using a 26 litre hot water urn with a 2500w element - the thing is just too hot - I am distilling water like it's going out of fashion, I have read all the posts re Triacs and it looks like this might be the way forward - what I am confused about is the wattage required for the dimmer switch - I read people discussing needing a 500 or 1000w dimmer - but does that mean I need to find a 2500w dimmer - seems unlikely. I live in Hong Kong and access to electronic parts is limited (if you don't speak Chinese) so I use the Hong Kong RS components http://www.rshongkong.com onclick="window.open(this.href);return false;" rel="nofollow which is in english. Hong Kong uses the UK standard for mains power ie 230-240V. I saw the various posts from Pintoshine I am just a little confused which diagram in which post to use and which parts to buy from the Hong Kong RS website, any help welcome as I have 25litres of Wash needing distiling and the still is just going to destroy it.

[castleclr]

so, this router speed controler,,i can convert my 1500w hot plate to by pass the temp control knob (to circumvent cycling), plug this router speed controller into the 120 ish wall outlet and the hot plate into the router speed controller and be able to adjust the hot plate to whatever temp i desire (or the speed controller or hotplate is capable of) and it will not cycle,,ie: will run at full output, non cycling on and off, or i can set it down to a nice cozy warm steady non cycling low temp,,all wilthout burning up the hotplate, router speed controller, the cords to each item or the wall outlet or its wires? and no heat sinks, triacs, dimmer switches, brainiacs, screwed up schematics or other crap is neeeded? Or do i just not understand this at all. ty in advance.

[masonjar]

There's no way to know if the router speed controller will work or not without seeing a schematic and parts list. My guess is that it would destroy the speed controller. There is also the possibility that the speed controller would turn the burner on - but the speed knob would have no effect on the power output of the burner, or maybe only a tiny bit of heat would come out.

Here are the reasons:

Electric motors don't consume a constant amount of power like electric heaters do. Motors will only use as much power as they need. The instant you turn on the motor, a very large inrush of current flows into the motor, (notice the lights dimming) but once it gets up to speed, it doesn't use nearly as much power. The speed controller may be designed to provide short bursts of power but may not be able to handle large continuous loads.

Electric motors are inductive - since the motor has a coil of wire inside it, it is a large inductor. Any time the output transistor switches on, the amount of current flowing through it steadily ramps up to its DC value. That means that the control circuity can switch the transistor off before the current reaches its maximum value and regulate the amount of current going through the transistor - and the load. With an electric heater, the current will rise almost instantly and the control circuitry may not have time to turn the transistor off before it blows up. If the transistor has a suitable current rating, then this may not be a problem.

There are several different types of motors also. Some motors require 3-phase input, and the frequency of the AC signal is what determines the output speed of the motor. If you connect a heater to the output of two of the 3 phases, then you will get the same power going to the heater regardless of what position the knob is at - because the knob only changes the AC frequency. The heater doesn't care what frequency the power is, it just converts the power coming in to heat.

The speed controller may also step the voltage down to accomodate a specific motor. If it steps the voltage down in half then your 1000 watt heater is now a 250 watt heater. If it steps the voltage down to 1/4th then the 1000 watt heater is now a 60 watt heater. If it steps the voltage up by a factor of 2 then your 1000 watt heater becomes a 4000 watt heater and the speed controller will definitely burn out.

Anyway, my point is that it's not quite as simple as just swapping a motor for a heater. It may work, but it may not. If you have a cheap router that you don't care about it, then go for it - but at least make sure that the power rating of the router is higher than that of the heater.

[pintoshine]

I agree with all you said Masonjar. I would like to add if you purchase a device that is rated very near your element it will have a shortened life because it will always be running hot. In engineering the term is headroom or more technically derating. You want to actually run a controller that is rated twice your element. 5kw controller for a 2.5kw element.

[HookLine]

CoopsOz
Mon Mar 05, 2007 11:21 pm

The way you have those resistors all bunched up like that will seriously de-rate their power handling capacity. That arrangement WILL NOT safely handle 80 watts. In fact I would be surprised if it safely handled half that power. All that heat has no way to escape.

Solution: First, there has to be large air gaps around the resistors about the same size as the resistors; second, don't vertically stack them like that, use horizontal rows; third, the box they are in has to be well vented, or have a good heat sink.

-----------------

I agree with all you said Masonjar. I would like to add if you purchase a device that is rated very near your element it will have a shortened life because it will always be running hot. In engineering the term is headroom or more technically derating. You want to actually run a controller that is rated twice your element. 5kw controller for a 2.5kw element.
pintoshine

True, but that gets expensive. An off-the-shelf 5 kw controller is a lot more money than a 2.5 kw, and is not necessary. Simply bypass the controller and run the element direct from the power outlet for boil up (2.5 kw), and then plug into the controller for the main run (about 0.6-1 kw).

Also, in the 'The Compleat Distiller' (page 129, 2nd edition), it says "NEVER use a motor speed controller for heating element control." One of the authors (Nixon) is a member of the Institution of Electrical Engineers, so he should know what he is talking about.

[Home Distiller]

third, the box they are in has to be well vented, or have a good heat sink.

Old PC power supply boxes, but swap the fan for a 240v, you can grab these for under $30 usually... The power supply also comes with heat sinks that connect to similar components etc as a bonus.

[CoopsOz]

Wow, this thread has opened up again.

Hookline, I was under the impression the resistors were only there as a fail safe. It's moot anyway because after I let the smoke out of two dimmer switches and three trics I gave up. Now I just put my 2.2kw and 1.3kw in series and get approx. 800w for cook-off.

[HookLine]

Old PC power supply boxes, but swap the fan for a 240v, you can grab these for under $30 usually... The power supply also comes with heat sinks that connect to similar components etc as a bonus.
HomeDistiller

 
That would work. Just the fan in a vented box, and plenty of air space around the resistors, is usually more than enough cooling.

-------------------

CoopsOz

Hookline, I was under the impression the resistors were only there as a fail safe.

They limit the power (ie the voltage and current) to the light dimmer, which can't handle those power levels on its own. The resistors are operating (more-or-less) all the time, if you ever get the circuit working you will notice they get pretty warm, even when set up properly.

It's moot anyway because after I let the smoke out of two dimmer switches and three trics I gave up.

Once you let the magic blue elekatronikal smoke escape the damn thing won't work no more. Don't worry, it is all part of the learning experience with electronics. Done it myself a few times, it's real easy. The important thing is that nobody got hurt.

That smoke has a distinctive smell, don't it?

Now I just put my 2.2kw and 1.3kw in series and get approx. 800w for cook-off.

If I was building my still again I probably wouldn't use electronic control, I'd go for dual elements.

[cwood]

OK, I need somebody to take a look at this item. It's a Surface Mount Temperature Controller. The website is chromalox.com
Punch in part number 305314 (it's the 30002-001 model).

I believe they cost $67.00, but look how compact. Does anybody see why this wouldn't work as a temperature controller for a water heater element????

Thanks,

cwood

[cwood]

Ooooops.....I looked closer.........nevermind..........not such a good idea.

[brewzz]

I have been using a PID controller for 6-7 years now and have had no problems.I think I paid about $60 for it and one ss relay

[defcon4]

I have been using a PID controller for 6-7 years now and have had no problems.I think I paid about $60 for it and one ss relay

I have been looking at those PID controllers for ages! (I currently use a ranco etc 111000 model on/off temp controller for my still)

Is there a way you can wire a household female plug to a PID (with a SSR in between the PID and the plug obviously). So you could plug in a household electric hotplate/burner to the PID?

How or can you wire this? Is it easy to wire the thermocouple? Do you have to do any computer programming in the PID to make it work, or can you get one that is pretty intuitive?

[brewzz]

Well,I had help with the wiring but it is pretty simple.I control 220v, one hot to one side of the element,the other thru the ss relay to the other side of the element.There should be instructions with the PID to show where to connect the ss relay and the thermocouple...It's really simple wiring.My PID as I think most,has a learning setting and I used that when I first used it.You can go thru settings on it and fine tune if you know what you are doing,but I tried that and only succeded in screwing it up..so I went back to the learning setting and left well enough alone...Works fine .I set it to 180 to start and keep an eye on it,that way if i'm not right there when it gets to around 172 it just equilizes until I open the valve and start collecting foreshots.I then set it to around 200 and it slowly gets there while I make the cuts.After that I set it to 208 and let it run till the product is so weak it's not worth collecting and shut her down...pretty simple.Maybe someone here knows more about PIDs that could enlighten us to making some adjustments?

[defcon4]

Well, after a frustrating weekend trying to get a Ranco Electronic Temperature controller to work, I'm gonna save up some money and get a PID controller from omega.com. I hope I can figure out the wiring, I guess I'll try to thumb through some household wiring books.

If anyone has any advice on PID temperature controllers, especially how to wire them properly, please enlighten me.

(Note; this is my current set up
Pot still
Heater: 1000watt proctor silex fifth burner (plugs into a household outlet)
My electricity service: standard American residential electrical system, so I guess its 120V.

Any help would be greatly appreciated