Adding a brain to a Kiln.

[JimDawson]

You would not be able to switch the kiln heating element directly with the controller relay, it is only rated at 3 amps. You would have to have switch a heavy power relay with the controller relay. I assume that the kiln would operate on 230V single phase.

Something like this: http://www.automationdirect.com/adc...n-Style,_40A_(AD-PR40_Series)/AD-PR40-2A-240A

 

[LEEQ]

So the fancy box sends a low voltage signal to the big solid state relay. The coil wires are connected to this relay. Could I hook up 2 separate coils to the one relay? Switch both kiln sections off of the one relay? Or maybe spilt the low voltage signal wire to another relay to power the other kiln section? Ebay has some reasonably priced looking kits that come with everything but an enclosure if anyone else is interested in this sort of thing. I don't know if their quality is up to the automation direct components.

 

[uncle harry]

You would not be able to switch the kiln heating element directly with the controller relay, it is only rated at 3 amps. You would have to have switch a heavy power relay with the controller relay. I assume that the kiln would operate on 230V single phase.

Something like this: http://www.automationdirect.com/adc...n-Style,_40A_(AD-PR40_Series)/AD-PR40-2A-240A

Do you have 3 phase current available ? If you do you can use a 3 phase contactor with each phase & power 2 or 3 heating elements. If you only have single phase current & 220 you will need a contactor with 2 contacts, one for each line. I successfully constructed a vacuum former heater this way back in the mid '60s. Otherwise, heater elements can be parallel-wired to a single output controller contactor. For ease of wiring a relay output controller would be the more simple way to operate the kiln. If you have access to sheet metal fabricating equipment you could make your own kiln using kaowool or a similar ceramic-based insulation.

There are many internet articles & videos that could be of help.
Check out McMaster-Carr for material info. Their website is very instructional.

 

[JimDawson]

So the fancy box sends a low voltage signal to the big solid state relay. The coil wires are connected to this relay.
Yes. In this application I would use a standard power relay(contactor) rather than a solid state relay.

Could I hook up 2 separate coils to the one relay?
Yes

Switch both kiln sections off of the one relay?
Yes, if the total current is within the relay rating

Or maybe spilt the low voltage signal wire to another relay to power the other kiln section?
Yes

Ebay has some reasonably priced looking kits that come with everything but an enclosure if anyone else is interested in this sort of thing. I don't know if their quality is up to the automation direct components.

I'm not necessarily suggesting Automation Direct components, I am just using their site as an illustration. I know their web site well, so it is easy for me to find the components.

 

[williamyjk]

Here is a pretty good article on adding a PID to a kiln:

http://www.mdpub.com/kilncont/index.html

 

[gregg]

I feel just throwing my 2 cents in.
my son has give as Christmas 3 yr ago the wire, pid relays? to build oven just have not got to it.:whistle:
If I remember right there a lot good information on internet and you-tube..
pids are somewhat cheap like on e-bay? bricks can be bought and shipped in local just build your frame. The heater wire can be bought on line. there vid and information on amp draw per inch or foot? I guess I'm just being a cheer leader .. Go for it .. )

Here is a pretty good article on adding a PID to a kiln:

http://www.mdpub.com/kilncont/index.html

 

[LEEQ]

Thanks for the help guys. I don't have three phase unless I rob the mill vfd. I was thinking single phase 220 like the kiln runs on now. I Like the kiln for the oven basis for many reasons, frugality being the primary one. It's cheaper to get a hold of a couple used kilns and rework the controls from what I've see. Cooling rates also. Reading on Ray's build it seems like the wool furnaces are very efficient. The first thing I need to do requires a stepped cool down over a set time period. I'm afraid I need my furnace to be inefficient enough to ensure the pid is able to add heat to keep within the parameters, rather than needing a cooling system also. I like that the coils are in the walls and are somewhat protected too. I look forward to checking out the link on adding a pid to a kiln)

 

[LEEQ]

Oh, I forgot to ask why not use a solid state relay? The kits all seem to have one. I'm not knocking your choice, but rather trying to learn.

 

[LEEQ]

Here is a pretty good article on adding a PID to a kiln:

http://www.mdpub.com/kilncont/index.html

This is a very helpful article on the subject at hand. It's now in my favorites so I can refer back to it.

 

[JimDawson]

Oh, I forgot to ask why not use a solid state relay? The kits all seem to have one. I'm not knocking your choice, but rather trying to learn.

When working with 240V it is my preference to switch both sides of the line. That way the load, in this case the heating element, is completely de-energized, rather than still being electrically hot relative to ground. It would take 2 solid state relays to create a double pole relay to do the same thing. Also with a SSR there is always some leakage current, not much, but they really never turn off 100% thus could be a safety hazard under some conditions. An electro-mechanical relay is better in this regard, not 100% fool proof, but better.