kiln controller question - WarmGlass.com

kiln controller question

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Terry Gallentine
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kiln controller question

Postby Terry Gallentine » Thu Mar 28, 2019 8:48 am

I have two kilns which I seldom use at the same time. I would like to build ssr boxes on the wall by each kiln and then use a portable controller made with an RTC-1000 (containing low voltage receptacles and plugs for signal voltage, thermocouple and a separate power source). Does anyone have any experience with this type of thing?

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Re: kiln controller question

Postby Brad Walker » Thu Mar 28, 2019 10:23 am

You should be able to set up a standalone controller into which you can plug whichever kiln you're using. Probably work best with a switchable two-in-one plug.

Terry Gallentine
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Re: kiln controller question

Postby Terry Gallentine » Thu Mar 28, 2019 11:31 am

Thanks Brad. Do you have any idea of how long a thermocouple lead can be before you lose accuracy on the temperature?

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Re: kiln controller question

Postby Brad Walker » Thu Mar 28, 2019 11:55 am

Terry Gallentine wrote:Thanks Brad. Do you have any idea of how long a thermocouple lead can be before you lose accuracy on the temperature?


That's more of a question for someone like Tony Smith, but I did find this:

The length of a thermocouple has no effect on its measurement accuracy or its ability to transfer the signal to the instrument.


For more, check out this link:

http://rdccontrol.com/thermocouples/the ... le-wiring/

Terry Gallentine
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Re: kiln controller question

Postby Terry Gallentine » Thu Mar 28, 2019 12:36 pm

Thanks again Brad. I was more concerned about the length of the wire leading to the thermocouple than the actual length of the thermocouple. The article that you sent me seems to suggest that the length of the wire shouldn't be much of a problem if it is less than 150' or so. I am thinking about centrally locating the controller and running low voltage wire to the thermocouples and to the ssr's.

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Re: kiln controller question

Postby Brad Walker » Thu Mar 28, 2019 1:06 pm

That's above my pay grade. I'm familiar with situations where you simply plug the kiln into the standalone controller and just plug in a different kiln as needed (as well as move the thermocouple), but don't have any experience with what you're wanting to do instead, other than to think it's a lot more complicated.

Kevin Midgley
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Re: kiln controller question

Postby Kevin Midgley » Thu Mar 28, 2019 1:18 pm

Digitry have as part of their system, little sending unit boxes which are fed by the thermocouple and then can be sent via 3 conductor 14/2 house type wire to the controller. No need to be close to the kiln with the digitry controller. The sending units also have a feature where they will buzz loudly should there be a thermocouple failure and alerting you to the problem and the controller is protected by Tiny Fuses. Sending unit wires from it to the controller must not be located beside regular building current wiring so as to avoid signal loss.
Without the sending units I might be worried about voltage drop from the thermocouple signal to the controller.

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Re: kiln controller question

Postby Terry Gallentine » Thu Mar 28, 2019 6:54 pm

Thanks everyone. I think that it is time to do some simple testing to see if the longer wires to the thermocouple maintain the same temp readings as the shorter wires.

Baxsie
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Re: kiln controller question

Postby Baxsie » Fri Apr 12, 2019 11:44 pm

The important thing about thermocouple leads is that you do not splice them.

Thermocouple wire has one wire made of one kind of metal and the other made of a different metal. (ref https://en.wikipedia.org/wiki/Thermocouple )

A thermocouple measures the temperature by the change in voltage generated by the junction of two metals where they are welded together (the Seebeck effect, if you are keeping score).

If you splice the thermocouple with, for instance, copper speaker wire, you essentially make two more thermocouples with your two splices.

The same thing goes for connectors. You need to have special connectors where the parts are made of the same metals as the thermocouple's conductors. For example, if you have a Type K thermocouple, this connector might work:
https://www.amazon.com/Uxcell-a14032200 ... B00MJSLLCW

Also, note that the connector's two terminals are not the same. Each needs to be connected only to its corresponding wire of the same type of metal in the thermocouple wire.

It looks like kilns use either Type K or Type S thermocouples (ref: http://www.bigceramicstore.com/info/cer ... uples.html ) you would want to verify your thermocouple type, then purchase matching connectors.

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Re: kiln controller question

Postby Terry Gallentine » Sat Apr 13, 2019 12:18 am

I have already gotten the type K connectors and type K extension wire. I am going to have a single length from the thermocouple to the controller. I am going to run some tests on a 25' run to make sure that the thermocouple is reading the same as with a much smaller run (5').

Kevin Midgley
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Re: kiln controller question

Postby Kevin Midgley » Sun Apr 14, 2019 12:44 pm

I was also told 40+ years ago that you were supposed to scrape the connector wire ends before making the connection with thermocouple leads.
And as well to tighten the connections and to re-tighten them an hour or so later.
The sending units with Digitry are nice.

Terry Gallentine
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Re: kiln controller question

Postby Terry Gallentine » Sun Apr 14, 2019 6:27 pm

Thanks Kevin. That is good information that I will use when I set up my thermocouples.

Bert Weiss
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Re: kiln controller question

Postby Bert Weiss » Thu Apr 25, 2019 9:39 pm

I’ve done pretty long runs of thermocouple wire with no issues.

The idea of one outlet wired to the controller and plug either one in to run it is the simplest approach I know of. This can be hard wired with some sort of knife switch or something so you can divert the power to one side or the other.
Bert

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Terry Gallentine
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Re: kiln controller question

Postby Terry Gallentine » Thu Apr 25, 2019 10:27 pm

Thanks Bert,
I think that I am going to wire a single female to the controller and switch out thermocouple lines when I need to. I am going to use a low voltage toggles to switch signal voltage lines but I would be worried about doing the same thing with the thermocouple lines where current accuracy is extremely important.

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Re: kiln controller question

Postby Bert Weiss » Fri Apr 26, 2019 12:20 am

Terry Gallentine wrote:Thanks Bert,
I think that I am going to wire a single female to the controller and switch out thermocouple lines when I need to. I am going to use a low voltage toggles to switch signal voltage lines but I would be worried about doing the same thing with the thermocouple lines where current accuracy is extremely important.


Thinking about this, you should be able to set up a box with 2 sets of wires coming in, and switch back and forth between sets. I would ask Krumor about it. They sell thermocouples, wire, and hardware. Their custom made thermocouples are top notch and not expensive. https://krumor.com/
Bert



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Terry Gallentine
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Joined: Mon Jul 19, 2004 2:08 pm
Location: River Falls, WI
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Re: kiln controller question

Postby Terry Gallentine » Fri Apr 26, 2019 11:58 am

Thanks again Bert.


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