Trying to achieve cone 6 on old manual Paragon SNF-24 electric kiln

[Sandy A]

Help please! I have an old Paragon SNF-24 that I’ve never been able to successfully fire to cone 6. It bisques just fine. It stalls at about 1980F though. Since I’m about 115 ft from fuse box I had a #3 gauge copper wiring added, new disconnect box and hard wired the kiln. Now it stalls at @ 2080F. Electricians have tested voltage, ohms, and newish coils, new wires, barrels, etc. Never has it tripped the breaker.  Just ordered ceramic blanket to add to space between kiln and floating lid to keep heat in. What am I missing? Or do I just give up? 

[Bill Kielb]

This kiln should make cone six but it Is interesting when I look it up there are two variations. One is 208 v and the other 240v . Both are lowfire 2300 deg max at 10800 watts. I guess are all your elements good and what resistance do they measure?

Since you ran heavier wire it has improved which means the wire itself was heating and consuming some of you useable wattage so it did improve. If your elements are 10% higher in measured value  than new then at 10800 watts it is likely new element time.

A decent kiln tech should be able to diagnose fairly easily and probably makes the most sense. If you have a diy attitude, post a couple pics of the kiln with nameplate, closeup of elements, and wiring with control box open.

I would not give up on it, however it is a lowfire kiln with 2300f max temp so at cone six, 2232 will probably be doable with nice new elements and not a bunch of leaks. If you intend on firing a lot of cone six, this probably will not be a great kiln.

 

 

[Sandy A]

Hi Bill, Mine is the 240v, 10800 watt version. Yes my elements are good and wired properly, I also have this diagram. We don't have any good techs here, so I've been working with a great electrician and DIYing it. I'm not sure what resistance measurement you're referring to, but he measured the ohms, voltage with and without load and I'm good.

What do you mean by "elements 10% higher"? 

Everyone I've spoken to feels that this kiln should fire just fine, and I've never heard about the other version with 11500 watts. Paragon feels that upgrading the wire (as I did) should take care of the problem but obviously it didn't. I have photos but can't seem to reduce them small enough to share. I've rewired this kiln  a couple of times so I feel confident in my wiring. (electrician checked it as well for me)

What do you feel is the max cone that this kiln will handle on a regular basis? I can't afford to buy a new kiln, especially after paying $2,ooo to rewire this (since the original electrician did it wrong the first time). Thanks for you help!

 

[neilestrick]

Probably time for new elements. With digital kilns there are often things that go wrong as the electronics heat up, but on manual kilns the switches pretty much work or don't, so that leaves elements. Since it's not a cone 10 kiln, the elements cannot wear as much before they need replacing, so the 10% change in resistance may be too high for when the elements should be replaced. It should work fine for cone 6, you'll just have to replace the elements a little more often than a cone 10 kiln.

[Sandy A]

The elements have been replaced though. Ugh

[neilestrick]

58 minutes ago, Sandy A said:

The elements have been replaced though. Ugh

Well that changes things. Are you sure they're wired up properly?

Did the kiln stall out at 2080F and you shut it off, or did the timer on the sitter shut it off? How long did it take to get that hot?

Do all the elements glow when you have it on high?

[Bill Kielb]

On 12/18/2019 at 10:44 AM, Sandy A said:

Hi Bill, Mine is the 240v, 10800 watt version. Yes my elements are good and wired properly, I also have this diagram. We don't have any good techs here, so I've been working with a great electrician and DIYing it. I'm not sure what resistance measurement you're referring to, but he measured the ohms, voltage with and without load and I'm good.

What do you mean by "elements 10% higher"? 

Everyone I've spoken to feels that this kiln should fire just fine, and I've never heard about the other version with 11500 watts. Paragon feels that upgrading the wire (as I did) should take care of the problem but obviously it didn't. I have photos but can't seem to reduce them small enough to share. I've rewired this kiln  a couple of times so I feel confident in my wiring. (electrician checked it as well for me)

What do you feel is the max cone that this kiln will handle on a regular basis? I can't afford to buy a new kiln, especially after paying $2,ooo to rewire this (since the original electrician did it wrong the first time). Thanks for you help!

 

Generally considered cone 8 max.  
I agree That with new elements it should reach cone six It is somewhat under powered so let me ask these questions

• New  elements, if yes about how many firings?
• What  was the measured fully loaded voltage?
• What was the measured fully loaded amperage?
• What were the measured resistances  (to a tenth of an ohm please)
• I think  you mentioned leaky lid,  provide some idea of how leaky? Fiber is a good idea for this kiln.
• Does the infinite switch perform as intended and how was it checked? It should remain on,  full powered when turned all the way up, no clicking noise.
• Do the timer switches work as intended and how were they set and how were they checked?
• Do you have the manual for this kiln as the timer switches work a bit differently than may be intuitive, switch two and three are hottest when The timers are off.  These timers are actually count down timers until the element set will actually start.  More confusing still is element set three will not operate until  element set two counts down to zero.  Setting  the timers to less time will actually make them begin heating earlier. For absolute maximum speed, everything very dry and no preheat set the top switch to max and switches two and three to 0.

If you know these answers great, if not we can markup a diagram above reflecting the minimum they should be.

 

.

[Sandy A]

Yes I'm sure they're wired properly. 

Yes, all my elements glow on high, paper test done as well. 

After new #3 gauge wire installed, I ran 2 cone 6 firings. First one with 4 hour preheat, I turned off kiln after 11 additional hours. It maxed out after 7-8 hours at 2116 F then hovered at 2027F-2076F. Second test, while warm from previous evening, I turned all switches to high and after 12 hours I turned it off at 2054F. 

 

[neilestrick]

Since the temp reached a max and then fluctuated, I wonder if one of the switches is cycling when it shouldn't.

[Bill Kielb]

19 minutes ago, Sandy A said:

Yes I'm sure they're wired properly. 

Yes, all my elements glow on high, paper test done as well. 

After new #3 gauge wire installed, I ran 2 cone 6 firings. First one with 4 hour preheat, I turned off kiln after 11 additional hours. It maxed out after 7-8 hours at 2116 F then hovered at 2027F-2076F. Second test, while warm from previous evening, I turned all switches to high and after 12 hours I turned it off at 2054F. 

 

See firing instruction note above for switch operation I think this might be your issue

[Dick White]

I'm getting confused now. I looked up the SNF-24 manual, and Bill beat me to posting it. The top switch is an infinite switch with variable settings between low and high, for 4 rounds of elements distributed evenly throughout the kiln. The middle and bottom switches are timers that set a delay before turning on additional sets of 4 elements, also evenly distributed throughout the kiln. But these switches are full on as soon as its time delay has expired. The design intent is that the infinite switch sets an amount of heat to first turn the kiln on slowly, and then by the end provide just enough heat together with all the other elements to get to the desired cone. When the delay for the middle switch expires, those elements add heat as if medium, and then when the delay for the bottom switch expires (usually longer than for the middle switch, but need not be) the remaining elements turn on for maximum heat, until the kiln sitter kicks off (or preferably, you observe the witness cone(s) bend and you turn it off yourself). By "high" for the middle and bottom switches, do you mean "on" (which essentially is zero hours delay).  My guess is with Neil, something faulty with the switches that some part of the kiln craps out when it gets hot (but not yet hot enough). I presume you are getting your temperature readings from an external pyrometer.

[Sandy A]

11 minutes ago, Bill Kielb said:

Generally considered cone 8 max.  
I agree That with new elements it should reach cone six It is somewhat under powered so let me ask these questions

• New  elements, if yes about how many firings?
• What  was the measured fully loaded voltage?
• What was the measured fully loaded amperage?
• What were the measured resistances  (to a tenth of an ohm please)
• I think  you mentioned leaky lid,  provide some idea of how leaky? Fiber is a good idea for this kiln.
• Does the infinite switch perform as intended and how was it checked? It should remain on,  full powered when turned all the way up, no clicking noise.
• Do the timer switches work as intended and how were they set and how were they checked?
• Do you have the manual for this kiln as the timer switches work a bit differently than may be intuitive, switch two and three are hottest when The timers are off. If Not I pasted  the relevant instructions below,

If you know these answers great, if not we can markup a diagram above reflecting the minimum they should be.

.

Hi Bill,

• New  elements, if yes about how many firings? ****Not as new as I originally thought, 18 successful bisque firings at cone 04, 17 firings at cone 6 that all failed. 
• What  was the measured fully loaded voltage? ****not measured after new wire
• What was the measured fully loaded amperage? ****Before load - 243 (not tested with new #3 gauge, but 6amp loss before)
• What were the measured resistances  (to a tenth of an ohm please)****don't remember, but were very close to specs, because I was told if they increase they are going bad
• I think  you mentioned leaky lid,  provide some idea of how leaky? Fiber is a good idea for this kiln.****ok - its ordered  but I don't know how leaky
• Does the infinite switch perform as intended and how was it checked? It should remain on,  full powered when turned all the way up, no clicking noise.****I think so, but shows some wear so ordered another new one
• Do the timer switches work as intended and how were they set and how were they checked?****yes - set as your firing instructions attached
• Do you have the manual for this kiln as the timer switches work a bit differently than may be intuitive, switch two and three are hottest when The timers are off. If Not I pasted  the relevant instructions below,****yes. 

If you know these answers great, if not we can markup a diagram above reflecting the minimum they should be.

[Sandy A]

45 minutes ago, neilestrick said:

Since the temp reached a max and then fluctuated, I wonder if one of the switches is cycling when it shouldn't.

how would I find out?

[Sandy A]

28 minutes ago, Dick White said:

I'm getting confused now. I looked up the SNF-24 manual, and Bill beat me to posting it. The top switch is an infinite switch with variable settings between low and high, for 4 rounds of elements distributed evenly throughout the kiln. The middle and bottom switches are timers that set a delay before turning on additional sets of 4 elements, also evenly distributed throughout the kiln. But these switches are full on as soon as its time delay has expired. The design intent is that the infinite switch sets an amount of heat to first turn the kiln on slowly, and then by the end provide just enough heat together with all the other elements to get to the desired cone. When the delay for the middle switch expires, those elements add heat as if medium, and then when the delay for the bottom switch expires (usually longer than for the middle switch, but need not be) the remaining elements turn on for maximum heat, until the kiln sitter kicks off (or preferably, you observe the witness cone(s) bend and you turn it off yourself). By "high" for the middle and bottom switches, do you mean "on" (which essentially is zero hours delay).  My guess is with Neil, something faulty with the switches that some part of the kiln craps out when it gets hot (but not yet hot enough). I presume you are getting your temperature readings from an external pyrometer.

Hi Dick, yes you're correct for the timers and delay timers. |When I said "high" I meant on to the max setting for the top infinite switch and "on" for the other two. Yes, I'm using an external pyrometer.

[Dick White]

Can you get your hands on a clamp meter? It has "fingers" that encircle an electric wire to determine how much amperage is flowing through the wire. Per the design specs, the kiln, with good elements, should be drawing 45 amps when full on. A clamp meter on the main power wire should have a reading in this neighborhood. Check it while the kiln is maxing out and stalling to see if it is still drawing full power.

[Bill Kielb]

26 minutes ago, Sandy A said:

Hi Dick, yes you're correct for the timers and delay timers. |When I said "high" I meant on to the max setting for the top infinite switch and "on" for the other two. Yes, I'm using an external pyrometer.

Most important, at top temp does the top infinite switch still cycle on and off and make a clicking noise? It should not btw, once on max temp the elements on top remain on all the time. Short of that idea  some of the numbers above would help. I can annotate the drawing if that helps so when someone comes you will know what is acceptable.

[Sandy A]

16 minutes ago, Bill Kielb said:

Most important, at top temp does the top infinite switch still cycle on and off and make a clicking noise? It should not btw, once on max temp the elements on top remain on all the time. Short of that idea  some of the numbers above would help. I can annotate the drawing if that helps so when someone comes you will know what is acceptable.

That makes complete sense, that the switch should be on max and not click on and off. I will check for that when I test it again. Thank you. 

[Sandy A]

27 minutes ago, Dick White said:

Can you get your hands on a clamp meter? It has "fingers" that encircle an electric wire to determine how much amperage is flowing through the wire. Per the design specs, the kiln, with good elements, should be drawing 45 amps when full on. A clamp meter on the main power wire should have a reading in this neighborhood. Check it while the kiln is maxing out and stalling to see if it is still drawing full power.

Ok. I have to get my electrician to be here at the right time, since I don't have a clamp meter. It did not pull the full 45 last time, but that was before my new #3 gauge wiring. Thank you I'll try that

 

[Bill Kielb]

1 minute ago, Sandy A said:

Ok. I have to get my electrician to be here at the right time, since I don't have a clamp meter. It did not pull the full 45 last time, but that was before my new #3 gauge wiring. Thank you I'll try that

 

We will get you a drawing of the things to be measured later today so when he comes now or in the future you can make him measure and write down the values which should make this a whole bunch easier.

[Sandy A]

7 minutes ago, Bill Kielb said:

We will get you a drawing of the things to be measured later today so when he comes now or in the future you can make him measure and write down the values which should make this a whole bunch easier.

Awesome thanks!

[Bill Kielb]

On 12/18/2019 at 1:30 PM, Sandy A said:

Awesome thanks!

Alright, best we could do. This should have meaning to your electrician and if we knew all these numbers then likely we could point you in the right direction. Normal replacement would be a change of 10% of the specified value, you have a cone 8 kiln  that will be fired to cone 6  so I made a 5% (conservative ) chart for your reference.  I checked through this pretty thoroughly,  but if I have a mistake someone will likely correct me.

 

 

[Sandy A]

1 hour ago, Bill Kielb said:

Alright, best we could do. This should have meaning to your electrician and if we knew all these numbers then likely we could point you in the right direction. Normal replacement would be a change of 10% of the specified value, you have a cone 8 kiln  that will be fired to cone 6  so I made a 5% (conservative ) chart for your reference.  I checked through this pretty thoroughly,  but if I have a mistake someone will likely correct me.

 

Hi bill, this is awesome! Wow - thank you so much for this diagram! I know that my electrician checked everything before, but am not sure if he checked the three switches with a full load. Is it best to check the ohms with or without load? Thx, Sandy

[Bill Kielb]

1 hour ago, Sandy A said:

Hi bill, this is awesome! Wow - thank you so much for this diagram! I know that my electrician checked everything before, but am not sure if he checked the three switches with a full load. Is it best to check the ohms with or without load? Thx, Sandy

Hard to check ohms fully electrically  loaded, ohms are the resistance so generally a reading taken with no power applied to the machine.
You are spot on though as when the elements heat up their resistance will change slightly especially at top temperature but ordinary meters cannot measure resistance with power applied so what are we to do. This is a good reason to measure amperage and voltage while the machine is fully on and has been full on for some time.

So for resistance unpowered and cool.

For voltage and amperage best fully powered for some time which will be more representative of the full loading that we see at the very end of the firing when the elements and relays and switches are on at or near 100%.  As all the connections and contact points carry at or near their maximum load over time the weakest or most undersized will heat  up the  most. You directly experienced this with the undersized wiring. It was too small so over the course of a firing it cost you 100  or so degrees at the top end. That wiring was heating up instead of the power going into your kiln.

Sorry to drone on,  but we use this fact to preventatively troubleshoot bad connections and relay contacts in advance by measuring operating temperatures with an infrared camera or even a non contact thermometer.

here a simple video,  while not for everyone, it is something potters can learn to do