Duncan EA-820-2 Teacher Plus Kiln suddenly won't get to cone 6

[coreydbush]

Hi,

I have a Duncan EA-820-2 kiln that I would consider to be in very good shape. No cracks or disorder inside of the kiln, the wiring and outside all look very good. The person that owned it before me said it was never used and just sat in their house since they bought it new many years ago. 

I have used it for roughly 15 firings to cone 6. It typically hits cone 6 in about 5-6 hours. 

My problem: 

My last firing failed to reach cone 6 after 12+ hours. I checked connections inside the control panel and tried again. Still failed to reach cone 6 on hi-fire.

Things I have tried/checked/noted:

• I measured the resistance of each of the 8 elements and they are all between 4.8-4.9 (literature I've found online says they are 4.6 new).
• I have timed the interval of on/off for the elements at different positions on the infinite switch. It's always about 55 seconds on, 55 seconds off no matter where the switch is (low vs. hi-fire doesn't matter). Should this be the case or should the on/off interval be changing based on switch position? Possibly a problem with the repeat cycle / fixed interval timers? 
• If the switch is on low, only the bottom elements glow. If the switch is on hi-fire, all of the elements glow but the bottom elements glow slightly brighter for the first couple cycles then they are equal brightness after that. 
• I measured total resistance for the top elements and bottom elements combined and got 18.9. 
• I measured total resistance for the kiln itself and got 9.4.
• I checked voltage coming from the outlet and its 240v. 

Here are some pictures of the internal wiring: https://imgur.com/a/fHe1Yg9

Any help on what could be causing this? 

 

Edited January 2, 2023 by coreydbush
Wrong cone number in title

[neilestrick]

1 hour ago, coreydbush said:

Should this be the case or should the on/off interval be changing based on switch position? Possibly a problem with the repeat cycle / fixed interval timers? 

The timers keep it at a low temp for two hours before they allow it to run hotter, which is probably why they are on for the same amount of time regardless of the setting at first. Since all of your elements are apparently in good condition, that means the problem is either one of the timers at the bottom of the control box or a switch. My guess is that the problem is one of the timers since you're still getting power to the elements on high. Do you have a thermocouple to track how the temp is changing? Once it is hot enough that all the elements are glowing, do they continue to glow for the remainder of the firing?

[coreydbush]

17 hours ago, neilestrick said:

Do you have a thermocouple to track how the temp is changing? Once it is hot enough that all the elements are glowing, do they continue to glow for the remainder of the firing?

I do not have a thermocoupler unfortunately. Once it gets hot enough the inside of the kiln does stay bright orange when I look through the peephole. 

The big thing is that even after a few hours, Im still timing 55 second on, 55 second off (based on the audible hums and popping I hear). This is the problem correct? 

The schematic for my kiln shows a Model 4600 and Model 4300 timer from Artisan brand. I've found similar timers on ebay, but they seem to have more posts on them to connect to vs. the ones I am seeing in my kiln.

For example here is a 4600 timer: https://www.ebay.com/itm/203316305476?hash=item2f56989e44:g:WxAAAOSwLSJgWkJG&amdata=enc%3AAQAHAAAAoBu%2BveuNQjnhuI7HNrBy0CpSZTCpzawvgQ7PSpR3FzbrA92NbJ25ZWt2quGyucM4Y%2FDJKGH0Rt6eu79Ggz7l1YX80x7IwZ2MS0251VpEwHLpfIAd59nJdVjiiBiKLTfEuRojFQP%2BViRgB3a2cflzycMW9wGPgpt4%2BH0n60D0%2BnhFzIhMjKSNSpgSKNupSJPiFgD%2FYrY3Wk%2BIBvNH2zJPWPk%3D|tkp%3ABk9SR8iYuIGvYQ

Here is the 4600 timer on my kiln: 

 

Can I just take off the additional prongs? Are they actually the same timer functionally? Thanks.

My plan is just to buy the 4600 timer, 4300 timer, the relay, and the switch all at one time (if we are confident one of these will fix the issue) so I can tinker and get this kiln back up and running at one time because I'm getting behind on pottery orders unfortunately. 

Edited January 3, 2023 by coreydbush

[neilestrick]

You'll have to look at the specs of the timer HERE and see if it'll work. I think it will if you get the right one. You'll need to make sure you get one with the correct voltage, as they are available in a wide range of voltage options. For your kiln it all depends on how it's wire up. Does it have a 3 prong plug or 4 prong? If it's 3 prong then you probably need the 240V model. If it's 4 prong then you might need the 115V model. I really can't say for sure without seeing the kiln, though. 

I was talking with a customer last week who said that his timers are dead and Paragon (who serviced Duncan for a long time) said they're no longer available. Not sure what the deal is there, because clearly they are still available, however they're solid state now instead of mechanical. I'm going to be looking at his kiln on Thursday to see what I can do to rewire it without the timers just to simplify the system and make trouble shooting easier in the future. With all the different parts on these kilns it can be difficult to diagnose problems and expensive to maintain.

[coreydbush]

1 hour ago, neilestrick said:

Does it have a 3 prong plug or 4 prong? If it's 3 prong then you probably need the 240V model. If it's 4 prong then you might need the 115V model.

I was talking with a customer last week who said that his timers are dead and Paragon (who serviced Duncan for a long time) said they're no longer available. Not sure what the deal is there, because clearly they are still available, however they're solid state now instead of mechanical.

This kiln is a 240V kiln. Older 3 prong plug, yep. 

Yeah, I consulted with Paragon before posting here and their kiln tech told me the same thing... Well she said they do have the timers for the ones with two timers (like mine), but apparently some of these Duncan kilns had a single, combined timer that they don't have available anymore. Just saying this to spread the knowledge...