Diy Curing Oven Electrics? Need Some Guidance Please.

[Notrace13]

[SIZE=10pt]Hi All,[/SIZE]

[SIZE=10pt]I need help/advice/guidance (drawings and diagrams welcomed too)[/SIZE]

[SIZE=10pt]Backstory: I'm in the fabrication stage of building a small curing oven made out of a old metal cabinet. I'm planning to line the cabinet with some thermo-tec heat insulation matting.[/SIZE]

[SIZE=10pt]The part that I need assistance with is the electrics surprise surprise. I have decided to (although this may change based on feedback/advice I receive here) use the following parts for the control and heating elements of the build (see below). I have watched a few videos online where other diy-ers have used similar equipment and parts but they are all based in the States so thus there is only so much info I can take away from it with regards to wiring configs etc. and ultimately I would feel a whole lot better taking advice from people who know what they are talking about with regards to electrical DIY projects.[/SIZE]

[SIZE=10pt]3 x AC 220V 500W 10mm x 200mm Electric Heating Element Cartridge Heater[/SIZE]

[SIZE=10pt]REX-C100 Digital PID Temperature Control + 40A SSR + K Thermocouple[/SIZE]

[SIZE=10pt]I guess what I'm hoping to find out here is how to connect all together safely for use with UK mains supply. I have come across a video on YouTube by a TV engineer who appears to have a similar set up and uses it fir a similar purpose. This is the video of his wiring solution and also a modification that he made to the PID unit . As I don’t have spare parts of TV’s lying around so I would like to know what else I need to buy in order to make my set up work properly and most importantly safely. [/SIZE]

[SIZE=10pt]I have seen someone using a DROK® AC 110V 3000W SCR 110VAC Electronic Voltage Regulator Speed Governor Thermostat Dimmer to control the heating elements but I would like to have a more accurate method for achieving the required temperatures in the oven hence me replacing it with a PID controller.[/SIZE]

[SIZE=10pt]Anyway this is where I'm at so I guess it's over to all of you.[/SIZE]

[SIZE=10pt]Thanks for taking the time to read my post (if you have made it this far lol) and I look forward to your responses.[/SIZE]

[SIZE=10pt]Kind regards[/SIZE]

[SIZE=10pt]Usif[/SIZE]

 

[Andy™]

Whats the oven for? what temp does it need to go to & how accurate? is this personal /DIY use or for a business?

basically you will need heating elements & a thermostat, & possibly a fan. other than that, its probably a fairly simple build

as for insulation, fibreglass works well

 

[ProDave]

The controller you seem to be suggesting looks like it's for 110V not 230 so won't be any good.

Unless the oven heats up / cools down very quickly, or you need very accurate temperature control, then a normal on / off thermostat should do.

What is your target temperature for this oven? that's needed before anyone can suggest how to control it

 

[Notrace13]

Hi Andy,

The oven will be for curing Metal and Plastic airsoft parts painted in a product called Cerakote. Temps that it needs to reach are between 150 - 250 Celsius and as accurately as possible. It will solely be used  for personal usage.

I have thought about a fan system to circulate the air but not sure it will be needed as the internal space of the oven is not huge - 85cm x 45cm x 39cm

I have seen some people use fibreglass as insulation and I admit i have not really research that as an option as the thermo tec heat shield insulation seems to fit the bill.

Hi ProDave,

Thanks for your reply. Sorry I should of mentioned that although I stated a 110v AC regulator, there is a 220v version.

Temps that I need to reach are between 150c and 250c (maybe 300c once in a blue moon, if i need to cure something quickly) I would like the temps to be as accurate as possible and as consistent as possible.

 

[Andy™]

fan might be better - circulate the air better and more accurate temp control

for that size oven, 1.5kw might not be enough to get it to temp properly, mine is about 80x80x110cm and 7.5kW, although it would work on 2 elements instead of 3

all i use is a simple oven thermostat to switch a contactor for the elements

 

[Notrace13]

fan might be better - circulate the air better and more accurate temp control

for that size oven, 1.5kw might not be enough to get it to temp properly, mine is about 80x80x110cm and 7.5kW, although it would work on 2 elements instead of 3

all i use is a simple oven thermostat to switch a contactor for the elements

Hi Andy,

Not sure if I follow you? 

Heating elements totaling 1.5kw in power may not get the oven to temp properly, but using 2 elements totaling 1kw would work?

Is is a case of trying to to get 3 elements up to full power may not be possible but only sharing the power between two elements is more like to achieve a higher heat output?

Maybe this will help you all visualize what I'm going for

https://www.youtube.com/embed/2NpcMycHDvk?feature=oembed

 

[Notrace13]

Firstly thanks gents for coming back to me on my questions so quickly.

While sitting here at my desk at work I have had a thought. Would it be better to use a oven/Grill heating element instead of the multiple cartridge heater elements?(although i assume they are essentially the same thing)

 

[Andy™]

i was referring to mine, i have 3x 2.5kW circular oven elements, but it would work on 2 but take a bit longer to get to temperature. i just think 1.5kW wont be enough for the size of yours

 

[Notrace13]

i was referring to mine, i have 3x 2.5kW circular oven elements, but it would work on 2 but take a bit longer to get to temperature. i just think 1.5kW wont be enough for the size of yours

 Oh okay I follow what you are saying.

 

[Sidewinder]

Hello Notrace13.

First of all this needs to be safe, please ensure that you are happy that you can do this build safely.

If you are using a metal cabinet then please ensure that it is correctly connected to the building earth at all times it is in use, remember electricity kills.

Also, I believe that you should put some kind of fail safe over temperature protection on this to ensure that if the main temperature controller fails, you will have a back up that will stop the unit from simply heating up until it catches fire.

Now there are some heat loss calculations that can be done to see how much heat input you need to get the oven up to temperature in how long, do you have any idea on how quick you want it to heat up?

Once it is at temperature, if it is well insulated then the elements will be kicking in and out just to make up for the heat lost through the housing.

How accurate to you need, the temperature control to be?

As Andy has said, without a fan you will get different temperatures through the unit, heat rises & all that.

Yes, btw, oven elements are essentially cartridge heaters bent to shape with a connection either end.

The controller & scr you have indicated is a very cheap version of a typical industrial controller to achieve this function.

However, it will need putting in a box to make it safe, and, the SCR may well need a heat sink, such as a cold metal box (not your oven) to keep it's operating temperature down so that it keeps functioning.

The single thermocouple would only take the temperature at ine point in the oven, if at the top, the bottom would be colder, if at the bottom, the top would be hotter.  So, you need to decide how this gradient will work for you and the maximum hysteresis you can accept.

A little more information is needed, but there is a start here.

One last thing, does this curing "stuff" give off any fumes? If so are these fumes flammable? Do you need to consider this with regard to your element positions and controlling the temperature so that anything that is flammable is kept below its auto-igntion temperature.

However, I can't stress enough, please be safe when you do this.

I would want you to come back to tell us how well it went, rather than to perhaps learn of your demise through electrocution because something went wrong, or the unit overheated and caught fire!

A lot of the guys on here are professionals and deal with electricity all the time, we know it can kill, some of us do domestic, some commercial, some industrial, some of us do machinery, and some do more than just electrics.  Most of us know the risks and hazards and how to mitigate them to an acceptable level.

We don't know your ability so we may well take for granted some things that we know and understand well, so please, please be safe.

Wouldn't something like this be easier?

http://www.argos.co.uk/static/Product/partNumber/2445261.htm

 

[roys]

Good points sidewinder has brought up regarding especially flamable fumes and the risks associated with that.

I must admit when I first started reading the thread I though why not just buy a decent 2nd hand fan assisted oven?

 

[Andy™]

what he wants to paint probably doesnt fit into a normal oven

 

[Notrace13]

Hi Sidewinder,

Thank you for the point by point reply, it is much appreciated.

Responding in reverse to yours and Roy's comments, I would love to have been able to just pick up a 2nd hand oven on fleabay, but the internal dimensions of the majority of house hold ovens are not really large enough for the types of parts that I'm likely to be painting. The cost of buying 2nd curing ovens as found in labs or  professional paint applicators is rather prohibitive as the start at around £700-800

As the paint in question can is designed to be oven cured and the relatively low temps needed to cure to it I quite confident that flammable fumes will not be an issue. The temps in question are lower than are about 20-30c lower than needed to heat a quiche ! Max temp I will require is 300F or about 148c, the regular temps that I will be looking to achieve with any consistency will be 250f and 180f or 121c and 82c  respectively (water cant even boil at that temp) I have just checked the safety sheet for the paint it has a N/A next to Flammability, Burn rate and autoignition.

Well the PID comes with thermal prob which I was planning to place in the middle of the oven and I was planing to place a oven thermometer probably  in top portion and allowing me to get and average temp.

I concluded that I would need or should use one of those electric plastic project boxes as I was not particularly enthused about having all those exposed terminals and parts just out in the open. I don't know if you had time to watch either of the two vids concerning the PID but I was planing to go down a similar route of soldering any wires to the PID directly.

Safety is a above all else is what i want to get nailed down first and foremost, hence me finding a suitable forum like this one, sanity test my idea and to to get input from good people like yourselves who have alot more knowledge about the electrical aspects. 

I 100% want to be alive to report back on my diy oven and say, "hey Andy or Sidewinder or ProDave, thanks for all your help, everything worked a treat" I have no wish to end my life or anyone in the vicinity of something i built and deffo don't want to burn down my house, p****** the wife off on that kinda scale would make death by misadventure seem like an easy out!

So just to reiterate, SAFETY FIRST

My skill level is that of someone who possesses a hopefully decent amount of common sense. Yes I can change a plug or light bulb, I'm confident if I had to connect batteries in a car to jump start one of them, installing new connectors in LIPO batteries or rewiring electronic speed controllers on rc cars etc or realising that when looking at this build/project I hoped that someone would mention things like making sure the "  " is earthed ! or that I need to have some a saftey fuse somewhere in that loom.

At this time I have never constructed anything that required mains power and so I'm putting my hand up and asking for help/advice etc

Sidewinder, you mention some kind of fail safe temperature protection - what would you suggest as I assume by your comment that simply unplugging everything is not going to cut it.

I'm don't need the oven to reach the specified temps quickly, less than an hour would be nice. Its not a production line that I'm running to if it needs more time to reach the right temp then more time it will have.

The SSR comes with a heat-sink see here

You mentioned that the PID is a cheap version of and industrial version, if you can recommend an alternative that wont break the bank then I would be happy to hear about it. Yes I'm building this on a budget but not at the expense of my safety or those around me. (although I'm pretty sure I will be the only one using this once completed.

I would really appreciate if some would be kind enough to say " okay I see you what you are trying to do but you will also need these parts" and here is diagram of what needs to be connected when in order to not kill yourself and blowup then neighborhood 

As far as questions you may have, ask away and I will answer them to the best of my ability

Once again, thanks all for your observations, questions and feedback thus far.

 

[Sidewinder]

The expensive PID controllers will simply be more reliable/accurate in other words higher commercial performance, I would hope, anything for sale in the UK must under statute law comply with the LVD or the MD etc. as appropriate, for a PID controller, it would be the PID, if it does not, then the seller is committing an offence.

So hopefully the only lowering of cost will be on the reliability front rather than the safety front!

There is no way to tell as far as I know.

 

[Notrace13]

Andy, you mentioned earlier that you have built your own curing oven and that you use a fan. would you mind sharing some more info on this please?

The expensive PID controllers will simply be more reliable/accurate in other words higher commercial performance, I would hope, anything for sale in the UK must under statute law comply with the LVD or the MD etc. as appropriate, for a PID controller, it would be the PID, if it does not, then the seller is committing an offence.

So hopefully the only lowering of cost will be on the reliability front rather than the safety front!

There is no way to tell as far as I know.

Hi Sidewinder,

The issue then is not so much about safety angle with the PID I have selected, more just the hit and miss nature of the reliability of cheap electrical goods that orinate out of our favorite Far Eastern Red Block country.

 

[Andy™]

basically, i wanted to paint my van rims but they didnt fit into the small oven... so instead of taking them somewhere else i built a bigger oven...

3x 2.5kW elements controlled via a universal thermostat switching a contactor. fan is always on regardless of temperature. for my use, it was easier to wire as TP with 1 element per phase, but it could have been done single phase. its set at 200º, takes about 10 mins to heat up, and still at 150+ after an hour of being switched off. insulation is fibreglass stuffed into 60mm gap. stat controls temp fairly well, usually within 5º of my 200 target

pic during the build with elements & fan in place (note. the elements are actually at the top, its up-side down in this photo)



the finished oven, ready for its test run



and one of the rims in the oven...

 

[Blue Duck]

Nice work Andy!

just one thing.... why ain't them rims banded?

:lol:

http://www.bandedsteelwheels.co.uk

 

[Andy™]

that would just be too much more work... and require new tyres to go with it...

 

[Blue Duck]

Blimey Andy, you built the oven to cure them in banding them shouldn't be much trouble for you!

 

[Andy™]

im sure i could do it... just dont really have a need for them to be