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Thermocouple replacement for old Evenheat kiln


kylies.clay

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1 minute ago, kylies.clay said:

I’ll be honest, I’m not sure how I would check the ground. I know the panel to the kiln has good ground. Also when you’re talking about the transformer, do you mean the 240 to 24 transformer? 
 

I’m in Georgia so I was about to go head to Olympic and pick up a V6-DF as I’m only 40 minutes away. Should I hold off? 

The controller is normally grounded through the transformer, but sometimes theres more nose than it can handle and you have to add another ground wire that goes directly from the controller Center Tap tab to the grounding screw in the control box. You'll need a wire (14 or 16 gauge) with a .25 female disconnect on one end, and a ring terminal on the other end, and you'll have to put a new connector on the tab that allows you to attach two wires. But honestly, if you've got the money for a new controller just get it. It'll have more functionality and be more dependable. If you've got the money for the Genesis touch screen then get that.

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17 minutes ago, High Bridge Pottery said:

If it was noise wouldn't it be happening throughout the firing?

There are electromagnetic fields (or something like that) coming off the kiln, and they get worse as the kiln gets hotter. The two kilns I've had to add a ground wire to didn't have any problems until about 1900F. I remember talking with an engineer from Skutt once and he said the bricks make all sort of electrical noise as they get hotter.

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Well I stopped at Olympic and got the v6-cf. Sarah in sales that helped me was super handy, she said that this issue is normally because of the thermocouple but since that didn’t fix it, it’s almost always the connections on the back of the board after that. When I get home I’ll be wiring it up and throwing on a test fire! Or maybe wait until tomorrow, so I’m not up til 1 watching it! 

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4 minutes ago, neilestrick said:

There are electromagnetic fields (or something like that) coming off the kiln, and they get worse as the kiln gets hotter. The two kilns I've had to add a ground wire to didn't have any problems until about 1900F. I remember talking with an engineer from Skutt once and he said the bricks make all sort of electrical noise as they get hotter.

Interesting about the 1900°, that’s around where my issue started as well. While I of course didn’t really want to let the $380 go for the controller, I figured that it would give me greater reliability and longer use of my kiln. I got the kiln from a friend who bought it off the original owner and only paid $300 for it so it’s not like I’m out a whole bunch of cash. Still under half the cost of a new one. 

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I hate to say this but my best idea would be shielded cable for the thermocouple lead. This is all very speculative as a relay is worn enough to create lots of arcing noise and the guess is the noise is getting into the thermocouple circuit. Almost all circuits have noise suppression built in on board to combat this.

So if I had spare relays, I would swap them out just to see if I had a particularly noisy worn relay. (Even with a new controller) Even so, how to guard against our new relay contacts from wearing and causing issues in the future? Sort of a total random thing actually if true. The shielded cable is my lowest cost idea that all kilns could benefit from but are almost not necessary these days due to onboard filtering etc…

This is really hard to figure out without some really good test equipment and as such is very speculative. If you have a spare relay, change it. Try and route your thermocouple leads as far away from high voltage wiring as possible to decouple potential noise sources. Good grounding always helpful, especially the circuit board ground, however that is developed. It might be one of the screws on the board that fastens the board to the metal case is corroded and is designed to be the ground but no longer is a good ground because of the corrosion.

Edited by Bill Kielb
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4 minutes ago, Bill Kielb said:

I hate to say this but my best idea would be shielded cable for the thermocouple lead. This is all very speculative as a relay is worn enough to create lots of arcing noise and the guess is the noise is getting into the thermocouple circuit. Almost all circuits have noise suppression built in on board to combat this.

So if I had spare relays, I would swap them out just to see if I had a particularly noisy worn relay. Even so, how to guard against our new relay contacts from wearing and causing issues in the future? Sort of a total random thing actually if true. The shielded cable is my lowest cost idea that all kilns could benefit from but are almost not necessary due to onboard filtering etc…

This is really hard to figure out without some really good test equipment and as such is very speculative. If you have a spare relay, change it. Try and route your thermocouple leads as far away from high voltage wiring as possible to decouple potential noise sources. Good grounding always helpful, especially the circuit board ground, however that is developed. It might be one of the screws on the board that fastens the board to the metal case is corroded and is designed to be the ground but no longer is a good ground because of the corrosion.

Alright. I will order shielded wire for the thermocouple as well just for preemptive care. I’ll check all the screws as well for corrosion, and do my best to route thermocouple wire as best I can but there’s not much room in there. 
 

I don’t have any spare relays sad to say, but I’m going to wait on ordering new ones to replace my current ones until I see an issue arise, or if my current issue continues… the whole concept of electrical noise is a bit above my head, I won’t lie. I can somewhat understand the concept but don’t really have a clear idea of how it would impact the workings of other parts. My electrical knowledge is limited to how to run wire and install fixtures and switches, I never have to deal with the issues that come after that. 

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I really don't think this is a relay issue, otherwise this would be a common issue as relays fail. If the thermocouple wire is as old as the controller it would be good to replace it whether it's the source of the problem or not, but try the added grounding wire first since it's stuff you can get at the hardware store.

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