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PF code on Skutt KM 1018


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Hi all, my kiln was doing a cone 5 1/2 glaze firing today. Last time I checked on it, the temp was in the 1400 range, climbing. Well, a few hours later it's displaying "PF" now, which, according to the manual, means power failure longer than 2 minutes. By my estimation, it should have reached the temperature about 3 hours ago. There was no power failure in the house. The kiln lives in a detached workshop that has a separate 100Amp panel (feeding from the house's main panel).

Not sure what to do. I'm letting it cool right now. I guess I'll only find out whether it has reached the temperature after I can open it, is that right? I do have a couple of witness cones to see how hot it ended up getting.

My question is - what could have caused this code? What can I do to prevent it in the future?

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For most momentary power failures it will automatically restart. A power failure can simply be a momentary outage that many do not notice.  The lights blinked! The likely solution was just to restart the program since if it only made 1400 degrees your wares were nicely dried but that’s about it.
Really the majority of the heatwork happens within the last few hundred degrees of the firing. Until you add enough energy to begin the fluxed reaction pretty much nothing has happened and the work is reversible meaning cool it down and ya basically got what you started with. . One rule of thumb we use is if it didn’t make it within a few hundred degrees of final temp just refire it after the problem is fixed. Nothing much likely  happened to it yet with respect to melting.

So if it was a momentary outage such as a line switch by the utility or some momentary line issue, nothing you can do about that except be aware your controller may not auto restart. So when the lights dim or flicker for a second, probably time to double check your firing. This all assumes your control is working properly.

Edited by Bill Kielb
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Posted (edited)

I opened the kiln and the cones tell me that it did reach the temperature, so I won't have to refire. 

But is there anything else that could have caused the PF code I wonder...

Edited by 2Relaxed
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Hmm, My best guess is it reached  temperature, then the power failure which explains why there was no restart, then cooled to the temp you saw it at. If my guess is true, pretty rare to happen that way. So the built in two minute outage / restart catches 99.99% of these occurrences. So if my assumptions are right, awfully rare for this to occur in that way. Not sure you can do anything except confirm you are seeing the shutdown temp instead of the current temp which often gets lost when the PF error is acknowledged.

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When you get a power failure, the kiln will decide whether or not to restart, depending on how much it cooled. So it may have failed while going up, then started up when the power came back on and completed the firing. I believe it'll read PF until you clear it, though. Or it may have had the failure during cooling, in which case you'd also have the PF. Some Skutt controllers will read PF any time you kill the power, even if it's not in a firing cycle. I see that all the time during repair work.

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I'm really puzzled because there was no outage on that day in the house. The kiln's panel, like I mentioned, feeds from the main panel in the house. I was home all day, working on my computer. Plus if there's an outage, there several appliances that let me know there had been one (blinking lights, beeping) - nothing like that happened.

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Well maybe a brief flicker on that circuit And maybe keep an eye on the controller. From your first description it didn’t sound like a two minute solid outage so  a brief enough outage on that phase at the right moment  is a thought.

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A quick flicker won't always affect all electronics the same. Some are more sensitive to flickers than others. It's also possible that there's a problem with that circuit, like maybe the breaker is having issues. It could also be a bad fuse holder on the kiln. I've seen those go bad several times.

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Thank you for all the replies. If I don't do anything about it, do you think I can proceed with the next firing? It'll be a bisque, might be a good way to try and see what happens, no?

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17 minutes ago, 2Relaxed said:

t, do you think I can proceed with the next firing? It'll be a bisque, might be a good way to try and see what happens, no?

That’s what I would do. No other way than to test and that’s a reasonable safe way to do so IMO. Always put witness cones in and that should virtually always help.

Edited by Bill Kielb
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So... I got the code again today. Bisque fire to cone 04 and the kiln didn't reach the temperature this time.

I emailed Skutt support, will see what they have to say. My son (an electrical engineer) is offering his help in fixing the issue. His theory is that it's the old capacitors that are to blame. The kiln is over 25 years old btw. I don't fire often, less than once a month and have had it for les than 3 years. Replaced all elements and thermocouple after I got it.

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5 hours ago, 2Relaxed said:

My son (an electrical engineer) is offering his help in fixing the issue.

Seems like a logical theory as the AC power needs to be rectified, smoothed and turned into DC  power so marginal filter capacitors are a nice guess IMO. He ought to be able to check any of the 12vdc outputs to see just how stabile they are. Electrolytic caps don’t last forever and often show visual signs of failure as well. Probably not a bad time to check the output of the transformer and it’s connections as well. Absent all that I think 25 years is a nice life for a controller, new ones can be had for 250.00 - 350.00 bucks if you are handy at installing. Might be a nice time for a retro kiln to go touch screen

If you fit a new controller, just a suggestion to keep it as cool as possible for long life. Today’s designs really isolate or shield the circuit board to stay as cool as possible. 25 years ago, not so much.

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Thank you Bill, I'll convey your insight to my so and research the controller prices here in Canada, I suspect they might be quite a bit more expensive here than 250-350!

And will keep this thread updated with what help Skutt has to offer.

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I would suspect the transformer, fuse holder, or breaker before the controller. It's not impossible, but I've never seen a controller put up a PF code because of a bad controller. Although at 25 years old you never know. A new transformer is a cheap swap to rule it out, as is the fuse holder and breaker.

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On 7/28/2021 at 7:21 PM, neilestrick said:

I would suspect the transformer, fuse holder, or breaker before the controller. It's not impossible, but I've never seen a controller put up a PF code because of a bad controller. Although at 25 years old you never know. A new transformer is a cheap swap to rule it out, as is the fuse holder and breaker.

We checked all three and they appear to be fine. The transformer test shows correct voltage. Our next suspect is a chip on the board (or the circuit around it) that detects power failure.  

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20 minutes ago, 2Relaxed said:

We checked all three and they appear to be fine. The transformer test shows correct voltage. Our next suspect is a chip on the board (or the circuit around it) that detects power failure.  

Nice, next step is close examination of all the solder connections.  I have been able to bench replicate on rare occasion with judicious heat gun / freeze spray application. That new control is likely looking more attractive.

Edited by Bill Kielb
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On 7/28/2021 at 9:35 AM, 2Relaxed said:

and research the controller prices here in Canada, I suspect they might be quite a bit more expensive here than 250-350!

 

Yes they are! I bought a used one from Pottery Supply House (aka Euclids) in Ontario a couple years ago. I'ld give them a call and ask if they have any if you decide to replace it, if you have wiring questions ask to speak with Jay Clarke. Their shipping is $12.50 if it fits in a clay size box. 

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Update. I think we managed to fix it. 

My son replaced the super capacitor which was bad. Not sure why he discounted his own initial theory about capacitors but we did circle back to it and figured it was the one directly related to the PF code. The kiln has completed the previously unfinished bisque firing yesterday.

However, it underfired by about 2 cones when it normally slightly overfires. Not a big deal for bisque, it probably ended up at soft cone 06, which is fine. But it would be a big deal for a glaze fire and  now I don't know what to think of that! Was it because of the hot weather? Was it because the new capacitor is bigger than the old one? (even though it shouldn't be involved in temperature regulation, only in running the board while the power is out...) Any ideas?

Also, I should say that I have used the same cones that were in the kiln when it gave me the PF code. I realize now that adding a new cone pack would probably have been a good idea but I hadn't done that...

I think I'll have to do another bisque before I'm brave enough for a glaze fire!

 

Min, thanks for the tip for the future! The new one at Greenbarn is about $500 as it turns out.

Edited by 2Relaxed
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2 hours ago, 2Relaxed said:

Also, I should say that I have used the same cones that were in the kiln when it gave me the PF code. I realize now that adding a new cone pack would probably have been a good idea but I hadn't done that...

I think I'll have to do another bisque before I'm brave enough for a glaze fire!

Very likely new cone is the ticket. Nice job on the capacitor! I like the idea of confirming with a bisque firing though, seems like an appropriate precaution.

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1 hour ago, Bill Kielb said:

Very likely new cone is the ticket. Nice job on the capacitor! I like the idea of confirming with a bisque firing though, seems like an appropriate precaution.

Unloaded the kiln just now. I had a bunch of small, glazed  low fire pieces on the bottom shelf;  I single-fire them sometimes together with bisque. The glazes look mature on them, but still not a definitive confirmation of the temperature as they are for cones 07-03. Oh well. At least they're done for sure.  :)

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One more update. After sitting unplugged for a while, the PF code shows up by default when I plug the kiln back in. I'm able to clear it and enter the program and start the firing cycle. Not sure what's up with this though...

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56 minutes ago, Dick White said:

That is normal behavior. In this situation, the power failure is from being unplugged, and it will immediately report the failure upon receiving power again, i.e, you plugging it back in. Press #1 and the error code will clear.

Interesting, and you're probably right I don't remember it doing this before but maybe I just didn't pay attention to such a silly little thing.:D I'm on high alert now!! :lol:
OK, I will assume that aside from the undefiring issue, which may not even have been real, we actually did fix this kiln!

 

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