PID controller and wiring questions

M

m1helmethead

Joined
May 7, 2012
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I have a Skutt 818-208 I'm currently converting over to work on 240v instead of 208v and it is currently a manual kiln with 4 elements. Two dials with low, med, and high settings and a timer. I'd like to convert it to a Digital PID. I have looked on Auberins and I think have figured out what I need to put it together.

My current list:

PID Temperature Controller w/ Ramp/soak, Kiln (SSR Output)
http://www.auberins.com/index.php?main_page=product_info&cPath=1&products_id=4

40A SSR
http://www.auberins.com/index.php?main_page=product_info&cPath=2_30&products_id=30

High Temperature Thermocouple for Kiln
http://www.auberins.com/index.php?main_page=product_info&cPath=20_3&products_id=39


Will these components do what I need? Some wiring diagrams have shown the use of two SSRs vs one? Why? Will I need two? Can anyone tell me the difference between a PID with SSR output and built in SSR output? Also can I hook my 240v wire from the wall into the PID or will be have to do a 220v for the PID and a 240v for the elements?
 
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I'll leave the wiring questions to the guys on your side of the pond.

I don't recall seing PID controllers with inbuilt SSRs capable of handling high currents.

The one you want will have a low-voltage DC pulsed output able to switch the 40A SSR.

I have seen PID controllers with low-current SSR outputs able to be used in much the same way as the alarm output relays: these will handle the small currents needed for things like alarm lights and are usually rated for only an Amp or two. I personally prefer the relays to SSRs for this.
 
It really would help if you filled out your profile here. Knowing if you are in Europe/UK, Africa, or in Canada/USA is crucial to a good answer.

That PID will be run by any voltage input between 85VAC and 265VAC, so just connect it to the 240 VAC line.
The SSR will need a good heat sink. That is a must at the current usage of a kiln.
PIDs with built in SSR control are for less tan 1 amp current. They will control a solenoid or a fan, but not a heating coil.

I am curious why you are referring to 208, 220, AND 240 volt current? What is the supply voltage at your home/shop? It isn't all of the above...only one of them.
Often 208 volt devices are three phase, BTW.

Some equipment can run on 208 as well as 220VAC. 240VAC is a bit too much above the allowable variance of 10%. What happens is that kiln will run hotter and draw more current than it was designed for. With PID control, the hotter part may not be as much of an issue, but the current draw may be. You could contact the manufacturer and ask the tech guys if the coils you have are OK for the extra current, or replace the coils. In either case , you will need to know the real and true voltage at your home/shop. Either ask the power company or take a reading with a good voltmeter. Many times people say 220-240VAC or 110-20VAC as a range, but when you are making changes and calculating amps, watts, and coli resistance requirements...you need to know what voltage you are really working with.
 
bladsmth said:
It really would help if you filled out your profile here. Knowing if you are in Europe/UK, Africa, or in Canada/USA is crucial to a good answer.

That PID will be run by any voltage input between 85VAC and 265VAC, so just connect it to the 240 VAC line.
The SSR will need a good heat sink. That is a must at the current usage of a kiln.
PIDs with built in SSR control are for less tan 1 amp current. They will control a solenoid or a fan, but not a heating coil.

I am curious why you are referring to 208, 220, AND 240 volt current? What is the supply voltage at your home/shop? It isn't all of the above...only one of them.
Often 208 volt devices are three phase, BTW.

Some equipment can run on 208 as well as 220VAC. 240VAC is a bit too much above the allowable variance of 10%. What happens is that kiln will run hotter and draw more current than it was designed for. With PID control, the hotter part may not be as much of an issue, but the current draw may be. You could contact the manufacturer and ask the tech guys if the coils you have are OK for the extra current, or replace the coils. In either case , you will need to know the real and true voltage at your home/shop. Either ask the power company or take a reading with a good voltmeter. Many times people say 220-240VAC or 110-20VAC as a range, but when you are making changes and calculating amps, watts, and coli resistance requirements...you need to know what voltage you are really working with.
Click to expand...

The reason I am referring to 208v is because that's what the kiln is rated for 220v and 240v is a typo but really 220v and 240v are the same anyways. I'm going to make a wiring diagram would you mind looking it over? Thanks for the info.
 
Anyone taking a look over the wiring diagram is going to need to know where in the world you are.

Power supply systems differ across the world, as do the acceptable/appropriate wiring methods.

I am in the UK, where we have one live (hot) wire at nominally 230V RMS relative to a Neutral at Earth/Ground potential. This needs to be wired differently to the North American system, which I gather consists of 2 "hot" wires, each at 110V, but 180 degrees out of phase to give 220V hot-to-hot.

A single SSR on the UK live will interrupt the current flow through the elements and leave the elements at Earth/Ground potential; safe to insert/remove a workpiece.

A single SSR on a North American hot wire will also interupt the current flow through the elements, but will leave the elements at the voltage of the other hot wire. Not safe when inserting/removing a workpiece.
 
timgunn1962 said:
Anyone taking a look over the wiring diagram is going to need to know where in the world you are.

Power supply systems differ across the world, as do the acceptable/appropriate wiring methods.

I am in the UK, where we have one live (hot) wire at nominally 230V RMS relative to a Neutral at Earth/Ground potential. This needs to be wired differently to the North American system, which I gather consists of 2 "hot" wires, each at 110V, but 180 degrees out of phase to give 220V hot-to-hot.

A single SSR on the UK live will interrupt the current flow through the elements and leave the elements at Earth/Ground potential; safe to insert/remove a workpiece.

A single SSR on a North American hot wire will also interupt the current flow through the elements, but will leave the elements at the voltage of the other hot wire. Not safe when inserting/removing a workpiece.
Click to expand...

Apologies I'm in the US. I guess my diagram will be based on how I mount the components so I need to know if I can mount the SSR and the PID in one of the boxes that hook to the side of the kiln or do I need to run it away from the kiln and put it in a project box?
 
Lots of folk mount everything in a box on the side of the kiln. It works.

It's nice to arrange a gap between the box and the outside of the kiln for air circulation, as it keeps down the temperature of the box. An inch is plenty. If using a plastic project box, this is a particularly good idea. Also, if using a plastic box (poor heat conductor), you may need to pay a bit more attention to the heat sinking of the SSR than with a steel box.

Personally, I prefer to build a separate control box and use plugs and sockets for the power to the elements, the door switch circuit and the thermocouple. That way, I can use the same control box for anything else I might want to control (so far, a mini-salt-pot and a crucible furnace, but at some point I'll build a tempering-only oven).
 
220 and 240 are OK to consider as the same if the device is a 220 rated device. If it is truly a 208 rated device, then it should run OK on 220, but could be over the range limit at 240 - that is 15% overvoltage.
It maters a lot more in motors than in resistive loads like heating coils...but it does matter.

I still am wondering if the oven was a 3 phase unit ( which really doesn't matter if you are replacing the coils). Many resistive devices are rated 1Ph or 3Ph. I really would like to see a close up of the plate on the kiln, and to know the make, model, etc..

I can't speak for Appalachian Power Co in Roanoke, but VA Power in Norfolk/Va.Beach has 120/240VAC.

Post your wiring diagram and lets see what you have planned.
 
bladsmth said:
220 and 240 are OK to consider as the same if the device is a 220 rated device. If it is truly a 208 rated device, then it should run OK on 220, but could be over the range limit at 240 - that is 15% overvoltage.
It maters a lot more in motors than in resistive loads like heating coils...but it does matter.

I still am wondering if the oven was a 3 phase unit ( which really doesn't matter if you are replacing the coils). Many resistive devices are rated 1Ph or 3Ph. I really would like to see a close up of the plate on the kiln, and to know the make, model, etc..

I can't speak for Appalachian Power Co in Roanoke, but VA Power in Norfolk/Va.Beach has 120/240VAC.

Post your wiring diagram and lets see what you have planned.
Click to expand...


Stacy, I know there's a big difference between 208v and 240v. I will likely be changing the elements. The Kiln is a Skutt 818-208 as I said. You are correct most 208v devices are phase 3 but they also make them in single phase. The data plate reads 208v Single phase.
 
timgunn1962 said:
Lots of folk mount everything in a box on the side of the kiln. It works.

It's nice to arrange a gap between the box and the outside of the kiln for air circulation, as it keeps down the temperature of the box. An inch is plenty. If using a plastic project box, this is a particularly good idea. Also, if using a plastic box (poor heat conductor), you may need to pay a bit more attention to the heat sinking of the SSR than with a steel box.

Personally, I prefer to build a separate control box and use plugs and sockets for the power to the elements, the door switch circuit and the thermocouple. That way, I can use the same control box for anything else I might want to control (so far, a mini-salt-pot and a crucible furnace, but at some point I'll build a tempering-only oven).
Click to expand...

Tim, thanks for the info. I wanted to make sure the PID itself would not suffer from the heat.
 
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Hello, everyone just wanted to let you know I didn't forget about you all. I ended up wiring it all up and it worked like a charm. Thanks to all of you for your help!
 
Good to hear.

Funny thing is that this thread and the 208 vs 240 discussion came up yesterday at the welders supply. We were talking about a TIG welder and the requirements for coolers, etc. and the difference in operation depending on the power where you were in town came up. Seems there are still industrial areas here with 208 power. The bigger shops have transformers installed that step it up to 240.
 
bladsmth said:
Good to hear.

Funny thing is that this thread and the 208 vs 240 discussion came up yesterday at the welders supply. We were talking about a TIG welder and the requirements for coolers, etc. and the difference in operation depending on the power where you were in town came up. Seems there are still industrial areas here with 208 power. The bigger shops have transformers installed that step it up to 240.
Click to expand...


Yes, most industrial plants and apparently its pretty common for schools to have 208v.
 
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