Kiln taking longer and longer to fire

[PeterH]

2 minutes ago, cadenrank said:

They don't list the resistance for the 180 model on the website (I just looked for it too).

You're quite right, I missed the semantically important comma!

[cadenrank]

4 minutes ago, Bill Kielb said:

I would agree, the math doesn’t work 24 X 240 = 5760 watts so I still say measure each element and make sure one side is disconnected. Let’s figure out what they are and should be. Take a picture of the element posts so we can see how many and how they are wired.

I think another important thing to add, is that it's actually stamped 230v on the kiln plate. Which would theoretically make Duralite's wattage rating at 5,520 wats, 24 amps correct, right? 

[Bill Kielb]

4 minutes ago, cadenrank said:

I think another important thing to add, is that it's actually stamped 230v on the kiln plate. Which would theoretically make Duralite's wattage rating at 5,520 wats, 24 amps correct, right? 

Yes, but they list them at 240v, 5520 watts so back to I still suggest, what do they actually measure and what exactly is on the equipment tag. That knowledge gets us to what is actually happening. The equipment tag gives us the design intent. 

[Bill Kielb]

47 minutes ago, neilestrick said:

Wired in parallel shouldn't they be 40 ohms each? That would be 6 amps per element, 12 amps per section. Typically kilns of this size are wired in series, with infinite switches and 10ish ohm elements.

Yes, maybe, who knows, his drawing shows two elements which might be four which might be two in series which might be 5000 + watt range or maybe two sets at 10000 + watts. At this point I strongly suggest , measure what ya got, post a pictur. From there I think it’s easy to solve.

[neilestrick]

13 minutes ago, cadenrank said:

The 180, and 180D are different models. They don't list the resistance for the 180 model on the website (I just looked for it too). The 180D model had a 17ohm model, and a 35ohm model, which is what they're giving there. 

By the math:

The 17 ohm elements are meant to be wired in parallel, with 120 volts to each section of the kiln. It would have a 4 prong plug- 2 hots, 1 neutral, 1 ground. Total 28 amps. 3 heat switch.

The 35 ohm elements are meant to be wired in parallel, 240 volts. 3 prong plug, 2 hots and a ground. Total 27.4 amps. 3 heat switch.

10 ohm elements are meant to be wired in series, 240 volts. 3 prong plug, 2 hots and a ground. Total 24 amps. Infinite switch.

None of this explains why your firing time is increasing, though.

You'll need to unhook your elements from the switch and measure them individually and then we can figure out if it's set up properly.

 

[cadenrank]

24 minutes ago, neilestrick said:

None of this explains why your firing time is increasing, though.

That's what I was thinking. This set up hasn't changed, and I was getting good firing times a year ago, And certainly nothing has changed over the past 3 weeks, besides ambient air temperature in the room the kiln is firing in. 

29 minutes ago, Bill Kielb said:

Yes, maybe, who knows, his drawing shows two elements which might be four which might be two in series which might be 5000 + watt range or maybe two sets at 10000 + watts. 

There are two sections. Each are 9 inches tall, totaling 18 inches. two elements in a 9 inch section, 4 elements in the 18 inch kiln. 

39 minutes ago, Bill Kielb said:

I still suggest, what do they actually measure and what exactly is on the equipment tag.

The equipment tag shows 24amps, 230v, 5,520 watts. 

24 minutes ago, neilestrick said:

You'll need to unhook your elements from the switch and measure them individually and then we can figure out if it's set up properly.

39 minutes ago, Bill Kielb said:

That knowledge gets us to what is actually happening.

I unhooked the side of the switch that the two element feeder wires come into, and separated the ends. Each element measures 10 ohms separated from the switch. 
 

[cadenrank]

20 minutes ago, neilestrick said:

10 ohm elements are meant to be wired in series, 240 volts. 3 prong plug, 2 hots and a ground. Total 24 amps. Infinite switch.

I believe from my diagram you had said mine was wired parallel? In regards to the switch, I've seen other pictures of kilns with the same model number and manufacturer plate, that have the same 3 position switches. Which would make me believe that the switches were intended to be 3pos. I'm not basing that on anything that has really any evidence behind it though. There aren't any manuals or anything that I was able to find for this kiln. 

[cadenrank]

So I actually have some verified information now that I think is important. I'm going to explain it, as well as draw on my diagram where I got these values from, and let me know if/how this makes any sense. 

So, I mentioned this when I believe @Bill Kielb and I were talking on another topic. I'm getting voltage measuring of 120v at the elements on the top section. (I didn't test the bottom section, it's a lot harder to get off, and I don't have the time at the moment.)

The incoming power to the top box measures 240v at the switch, but any combination that I tried at the switch only resulted in 120v out of the terminals. Which doesn't make any sense at all to me. I brought this up before, but it had been a while since I tested it so I figured I remembered wrong, but I just double checked, and I was correct. 

There is no neutral, so I don't get how this is possible, unless it's using the ground wire, which would theoretically mean the stainless steel jacket would be energized, correct? Which it isn't.  This was how it was when I measured it a year or so ago as well, so this isn't part of the problem of lengthening firings, but still something I'm curious about.

[Bill Kielb]

Do to Neil’s point, this would be 240v 4 wire, or 240v with a neutral and ground for safety. You could be running the kiln using the ground as a 4th wire which would potentially cause very random results depending on how your ground is run and bonded. So a real good picture of that equipment tag might do wonders. If each section is tagged then that would be good to know as well. If each element is 10 ohms then two in series would be 20. (10+10). When operating 240v/20ohms = 12 amps per section and 24 amps for two sections  or in high -  2 sections  combine to 10 ohms  at 240 v or 24 amps total.

So again, a few pictures and we don’t need to keep speculating but…… assuming all that is true

• Did they measure exactly 10 ohms? (It’s important)
• are they wired in series? (Post a picture)
• Post a picture of the three way switch (back pin out and any model number written on it)
• Post a picture of the equipment tag(s)
• Does each section have a switch?
• post a picture of the wires where they come in to the kiln and land on terminal blocks if possible.

I am posting a picture of a typical 3 way switch, just to show if it needs that neutral, it needs it and you will need to rectify, which means what size is the ground currently and is it hooked up in your panel as a ground or is it hooked as a neutral. Anyway I think pictures are  key at this point to understand how this should work so the suggestions here are accurate for your situation.

So accuracy is everything and without pictures, it’s really speculation. Sounds like you need a neutral if you are able to measure 120v at the switch some way.

 

[neilestrick]

The way a 3 heat switch works is that on low it runs the two elements in series. On medium it turns one element on, the other off. On High it runs both elements on. So 1/4 power, 1/2 power, full power. If you have 10 ohm elements, then on low each section would pull 12 amps, 24 total. On medium it would pull 48 amps total. On high it would pull 96 amps total. So if you do indeed have 10 ohm elements, and there's a 3 heat switch on each section of the kiln, then it's not wired up properly or you'd be flipping the breaker every time you switched it to medium.

 

[Bill Kielb]

25 minutes ago, neilestrick said:

there's a 3 heat switch on each section of the kiln, then it's not wired up properly or you'd be flipping the breaker every time you switched it to medium.

See above, I think it needs a neutral and we just don’t know right now how it’s really wired.

[neilestrick]

7 minutes ago, Bill Kielb said:

See above, I think it needs a neutral and we just don’t know right now how it’s really wired.

The neutral is only needed if the elements are set up to run on 120 volts, which with 10 ohm elements the math doesn't work out. It's all very odd!

@cadenrank post some pictures.

[cadenrank]

15 minutes ago, Bill Kielb said:

See above, I think it needs a neutral and we just don’t know right now how it’s really wired.

Also, I appreciate all of you taking the time to put input into this! 

There is one manufacturer plate, and it's on the top section, each section has it's own switch, and the manufacturer plate reads
"Blue Diamond Kiln Co. (their address)
Model: 180
Volts: 230
Max Temp: 2300
Serial number 
Amperes: 24
Watts: 5520"

Coming from the panel, is a black, a red, a white, and a thin bare copper wire. The thin gauge bare copper wire is not utilized in the panel, or on the receptacle. The white wire is 'acting' as a ground, and it's tied to the neutral bus bar in the panel. (there is no ground bus bar, all the neutrals and grounds are tied to the same bar) 

There really aren't any terminals inside the kiln besides the terminal block on the sitter, and then some kind of junction (labeled as J on my diagram) that looks like it's protected with some type of insulating tape (i don't know what's under the tape, I just know the ground wire from the power cord goes in, and then 3 other 12ga high temp wires come out) that splits off to the various grounds in the main panel.

But inside of the kiln, the green wire from the plug (three wires, three prong) ties together to ground the switches, the receptacles, and then to the side of the control box. This happens the same way in the top section of the kiln. The black, red and ground come in from a NEMA 6-20 plug, the black and red wires go to the switch as shown in the wiring diagram, and the ground goes to the switch, and then to the jacket. What I'm not understanding is how I'm measuring 120v on the elements. Technically, yes, the wall receptacle is supplying a neutral, but the switches shouldn't be using it as a neutral, right? It should be using it as a ground? 

I only have a few pictures, and I'm not sure how well they show anything, and I'm no longer with the kiln at this moment, but the diagram is 100% accurate to the way it's wired at the moment, and the way it's been wired since I received it. I believe the photos I have are all of the old wiring that has since been removed, but it's all wired the exact same way still. I'll have to find them on my phone, but I'll attach them in another message. At least the ones that show anything valuable. 

[cadenrank]

https://imgur.com/a/XLI5FJT
This is the top control box, looking at the back of the switch, the incoming wire, and the element connections. Again, all of the wires in this box have been replaced. This was a year ago. 

https://imgur.com/a/lBUSKcI
This is the bottom control box (main control box in my diagram), and again, all of the wires and receptacles and everything besides the grounding junction have been replaced in this box as well. 

https://imgur.com/a/QC65yhX
This is a close up of the back of the switch in the top control panel. 

Things look a lot different now, but everything is wired exactly as it was in these photos still. There's just more asbestos in this picture, where there's fiberglass insulation now, lol.

[neilestrick]

40 minutes ago, cadenrank said:

The black, red and ground come in from a NEMA 6-20 plug

Aside from whatever other issues are at play here, this kiln should have a 30 amp power cord and plug.

I have never seen that switch before, so I can't say if it's wired correctly. Can you take the switch out and get a photo of the model number so we can find out more about it?

[cadenrank]

1 minute ago, neilestrick said:

Aside from whatever other issues are at play here, this kiln should have a 30 amp power cord and plug.

This is just the sectional cord. The kiln has a 50 amp power cord for the whole thing, the one section has a NEMA 6-20. 
 

2 minutes ago, neilestrick said:

I have never seen that switch before, so I can't say if it's wired correctly. Can you take the switch out and get a photo of the model number so we can find out more about it?

That was another problem. I had tried in passing to figure out how to get the switch out, and was unable to figure it out. The front dial has nothing that I can see holding it in place, but it won't come off. 

[Bill Kielb]

Looks like old 66b idea where the kiln needs 2-120v circuits. You are measuring 120v at the switch and it appears wired as the old 66b. So the diagram I posted above  and the one below look to be pertinent. 
 Now time to think and compare ………

[cadenrank]

10 minutes ago, Bill Kielb said:

Looks like old 66b idea where the kiln needs 2-120v circuits. You are measuring 120v at the switch and it appears wired as the old 66b. So the diagram I posted above  and the one below look to be pertinent. 
 Now time to think and compare ………

The depiction of the switch in that diagram definitely looks like the back of it. 

This would just imply that the kiln is using what I was expecting to be the ground, as a neutral. This works of course (I've gotten to cone 6 hundreds of times now) but it means that there is no actual ground. I also don't understand how the jacket isn't affected somehow, since if this is the case, the neutral is attached to the jacket too. I guess the path to the panel is the path of least resistance? 

I'm also assuming they don't make the 4 way rotary switches like that anymore?  Or is it just a normal 4 way switch, that's just wired differently? 



 

[cadenrank]

9 minutes ago, Bill Kielb said:

 

Everything in this diagram is the same, except there's no fourth wire anywhere inside of the control box. 

[Bill Kielb]

I think you can find the switch, popular kiln item of the era. Yes that is a neutral and also bonded to the shell which we have not done forever. In the interim, old washing machines etc… would be separately grounded to a water pipe. Now a separate continuous ground needs to be run. So testing this would need to follow the diagram posted several threads above.
 The forth wire would be your bare copper you mentioned. It would be a separate path to ground it should be hooked to your ground buss in the panel, but an old panel probably just the neutral buss and the buss has a bonding screw inserted through it bonding the cabinet. We don’t do that quite that way anymore, everything has some separate grounding path.

[cadenrank]

While this all solves my curiosity about the 120v readings I got,  and just generally more about how this kiln functions it still doesn't answer the problem of lengthening firing times. 

Does the separate ground just need to run to the jacket? There's nothing else inside that could be grounded (even based on that diagram), besides the section receptacles, which I just replaced with NEMA 6-20's. and would I un-bond the neutral that already exists from the jacket? I'm also realizing that the 6-20 receptacles in place ground themselves to the jacket too, which is not actually a ground, but a neutral if all of this is the case. So, I'd likely have to switch those out again for something with the neutral in place if I brought this up to code, since if I just brought a separate ground to the jacket, it'd also be touching neutral technically 
 

[neilestrick]

I agree, it looks to be very similar. I think you have a kiln with the wrong wiring and the wrong elements. The problem is that in order to wire it like that with the neutral it's going to need different elements, different power cord, different outlet, etc. To keep changes to a minimum, you should be able to just change both switches to 15 amp infinite switches and wire the elements in series. 10 ohms in series = 20 ohms, 240/20 = 12 amps per section, 24 amps total. The downside there is that it's going to be slightly under-powered compared to the other possible setups (going by the elements that are available from Duralite). If you go with the 35 ohm elements then you'll get 27.4 amps, which is a pretty good power jump for a kiln that size, but you'll have to change out the switches for Skutt-style 3 heat switches.

You could, for starters, just do the infinite switch change for now and see what happens, see if the weird firing times go away. If it works like that then you could just leave it like that. I think you'll get better element life with the 27.5 amp elements, though, and shorter firing times. But you could always make that conversion later when you need elements again.

[neilestrick]

1 minute ago, cadenrank said:

still doesn't answer the problem of lengthening firing times. 

True. But there's so much other goofy stuff going on that it's impossible to say. Get the kiln right, then we can figure that out.

[cadenrank]

6 minutes ago, neilestrick said:

I agree, it looks to be very similar. I think you have a kiln with the wrong wiring and the wrong elements. The problem is that in order to wire it like that with the neutral it's going to need different elements, different power cord, different outlet, etc.

Well, I think it already is wired like that. It's just missing a separate ground, right? It's using what I thought were grounds (in regards to wires, and the ground prong on the receptacles), as a neutral already. 

[neilestrick]

2 minutes ago, cadenrank said:

Well, I think it already is wired like that. It's just missing a separate ground, right? It's using what I thought were grounds (in regards to wires, and the ground prong on the receptacles), as a neutral already. 

It needs a 4 prong power cord and outlet, and different elements.