Emergency help...Just discovered mid firing @ 543 C that 1 to 2 elements are dead! Student work inside

[feistyfieryceramics]

Hi all,

I have a used oven. It performed well during 3 test firings. Now is the first time I have student work in the kiln (of course). We are 2 weeks into the launch of our small business. I ran the kiln overnight at 93. At 11 am I started a bisque firing going up 60 C/hr to 475 and then 150 C/hr to 985 C.

I left the studio when we were at 430 C and when I came back the kiln should have been at about 700 C but it was only at 543 C. I checked the peeps (there are only two and there are 3 elements) and I see no glowing coils in the bottom peep. So either one or two elements are dead, I guess! And the temperature is not able to rise...

What to do at this point?!? I'm in a total panic.

Thanks,

Caitlin

[neilestrick]

@feistyfieryceramics If it's not climbing, then you'll have to shut it down and diagnose the problem. However at that low a temp the elements may not all be glowing yet. Is the temp still climbing? If so, let it run, and maybe they'll start glowing later.

If the elements are truly dead-depending on how it's wired up, you either have elements that have actually died, or you have a relay that has died. The relay is the switch that sends power to the elements. Usually when we see more than one element not working, then it's a case of a dead relay since relays typically feed more than one element. it could also just be a bad wiring connection in the system.

[Denice]

It is just a bisque so you can let is run awhile and see how high you can take it.    Let the forum know what temperature  you got your bisque fired to,  maybe it will be fired enough that your students can go ahead and glaze while you fix the kiln.   Bisque can always be refired,  students can be pretty understanding when equipment breaks it happens to everyone.     Denice

[feistyfieryceramics]

1 hour ago, neilestrick said:

@feistyfieryceramics If it's not climbing, then you'll have to shut it down and diagnose the problem. However at that low a temp the elements may not all be glowing yet. Is the temp still climbing? If so, let it run, and maybe they'll start glowing later.

If the elements are truly dead-depending on how it's wired up, you either have elements that have actually died, or you have a relay that has died. The relay is the switch that sends power to the elements. Usually when we see more than one element not working, then it's a case of a dead relay since relays typically feed more than one element. it could also just be a bad wiring connection in the system.

Hmmm. I let it run for an hour after I noticed that the bottom element wasn't glowing and it climbed just 18 degrees to 563 C. When I had left the studio earlier in the day, the temp was rising at 60 C per hour. If it were simply that the elements were not hot enough to glow yet (I really wish it were that even  though I'd feel a bit dumb )  the temp rise shouldn't have slowed so much? Also the air coming out of the bottom peep was much cooler than the top peep.

This is great info about the relay vs the elements! There are two peeps and 3 elements. If I unload the kiln and turn it on while empty, I may be able to see the middle set of elements from the two peeps... What temp should I go to to make sure the elements were glowing (I thought it was 500C). If I can't see all the elements through the peeps, how do I tell if it one or two sets of elements that aren't working? My husband has a multimeter? The paper test? Also, when I read about the paper test, it says to keep the kiln lid open, but my kiln turns off if I open the lid. 

I should also try tightening connections?

Thank you so much!

[feistyfieryceramics]

58 minutes ago, Denice said:

It is just a bisque so you can let is run awhile and see how high you can take it.    Let the forum know what temperature  you got your bisque fired to,  maybe it will be fired enough that your students can go ahead and glaze while you fix the kiln.   Bisque can always be refired,  students can be pretty understanding when equipment breaks it happens to everyone.     Denice

Thank you for responding! I ended up turning it off after the first person on Redit recommended that  But I let it run for an hour after I noticed that the bottom element wasn't glowing and it climbed just 18 degrees to 563 C. When I had left the studio earlier in the day, the temp was rising at 60 C per hour. Do you know how fragile are these things going to be when I take them out to try to fix the kiln? I hope people will be understanding. I feel so sad, and bad and disappointed. I'm also feeling overwhelmed about opening up the back of the kiln and having to learn all that... I hope it is just the elements. But whatever it is should be fixable right? It's just a very well insulated box with replaceable electrical stuff...right?

[Bill Kielb]

What make and model kiln is it? We potentially can look up the wiring diagram   and suggest some things to test. I have done this routinely with studio kilns, especially bisque runs. The easiest would be a  faulty relay which can be replaced from outside (power removed from kiln) then the kiln restarted without unloading to finish the firing.

The relay is generally an easy fix. Elements require unloading the kiln

here is an old relay video, the replacement part is pretty easy https://youtu.be/c7HZlAn4nZw

 

[neilestrick]

If you have a meter and are comfortable with running live tests, then you can use the meter to figure out where the power stops. Open the panel, turn on the kiln, and check for power on both sides of the relays, and check the elements for continuity. As Bill said, tests can be done in the control box without unloading the kiln. If you're not comfortable with live tests, then do the paper test with the elements. If one or more are out, then unplug the kiln and open up the control panel and see how the elements are connected to the relays. If there are multiple elements hooked to each relay and all of those elements are out, then it's probably a dead relay. If there are multiple elements hooked to each relay and only one element is dead, then it's an element problem. If it's one element to one relay, then you can use the meter to check if the element is broken without turning on the power. If the element isn't broken then it's the relay.

[feistyfieryceramics]

8 hours ago, Bill Kielb said:

What make and model kiln is it? We potentially can look up the wiring diagram   and suggest some things to test. I have done this routinely with studio kilns, especially bisque runs. The easiest would be a  faulty relay which can be replaced from outside (power removed from kiln) then the kiln restarted without unloading to finish the firing.

The relay is generally an easy fix. Elements require unloading the kiln

here is an old relay video, the replacement part is pretty easy https://youtu.be/c7HZlAn4nZw

 

Good morning. Thank you for replying! It is a Cromartie CTL 75, 5 KW kiln. We have a document for the computer controller but not one for the kiln (the ad for the used kiln said they had the manual...but then they didn't). We have this document https://isaunders.files.wordpress.com/2009/11/h4520206020kiln20instructions2017-08-2004.pdf but it is not really for our kiln...and I don't really know what I am looking at, but I'll look though this document and the video you sent with my husband today and hopefully learn a lot! I'll report back here!

[feistyfieryceramics]

7 hours ago, neilestrick said:

If you have a meter and are comfortable with running live tests, then you can use the meter to figure out where the power stops. Open the panel, turn on the kiln, and check for power on both sides of the relays, and check the elements for continuity. As Bill said, tests can be done in the control box without unloading the kiln. If you're not comfortable with live tests, then do the paper test with the elements. If one or more are out, then unplug the kiln and open up the control panel and see how the elements are connected to the relays. If there are multiple elements hooked to each relay and all of those elements are out, then it's probably a dead relay. If there are multiple elements hooked to each relay and only one element is dead, then it's an element problem. If it's one element to one relay, then you can use the meter to check if the element is broken without turning on the power. If the element isn't broken then it's the relay.

My husband says he is only comfortable with interacting with the control pannel when the kiln is unplugged. We will do our best and report back  Thank you for your help! 

[Bill Kielb]

Yes of Course, no power.
This diagram is not for your kiln, however Skutt has built many for Cromartie so can you post a picture of the kiln, controller and equipment tag. The manual / diagram you have is for the 3kw  so it likely doesn’t match your 5kw kiln. With a little luck we will be able to get a diagram off the Skutt site. We don’t know till we try though so pictures very important.

[feistyfieryceramics]

@neilestrick @Bill Kielb @Denice

OMG! I think we figured it out! We will walk you guys through the process, here in case someone else has a similar problem some day and it could be useful to them. Also, we still have a couple questions. 

After having the kiln off/unplugged over night we opened up the control box on the back of the kiln this morning. We used a multimeter to check the continuity of the elements and none of them seem to be broken.

We checked the resistance as well. The top element was 26.2 Ohm. The middle 27.5 Ohm. And the bottom was 27.8 Ohm. In the video that Bill posted, the resistance of the elements was about 12 Ohm, but if I understood correctly, he also said that the element manufacturer would be the one to tell you what the correct resistance should be. We have not been able to find such a number for Cromartie CTL75, 5 KW elements. But is there a normal range?

At this point we wondered if there was enough difference in resistance between the elements that that the bottom element could be lagging enough behind the top element that one would be glowing and the other not.

Next we checked the relay. It seems that there is just one relay for all three elements. (We are assuming this Brook Crompton HR0910 is the relay. This thing has a plastic bit in the middle that goes up and down I guess turning on and off the elements in response to the kiln temp). At this point we thought the relay must not be broken. Based on what you guys said, it sounds like if the relay were broken, none of the elements would have been working.

Then my husband checked the wires going into and out of the Brook Crompton HR0910. In the on position, there was continuity though the relay for all 3 elements and the resistance was low (0.2-0.4 Ohm).

Then we traced the wires coming out of the relay. They go to a switch that is connected to the kiln lid. There is a piece of metal shaped like a pac man (like the video game) that turns when the kiln lid is up and it compresses 3 small metal arms (one per element) to turn off the elements.

There was continuity though this thing only with the top element!!! We were able to turn the large bolt that the Pac Man and lid are attached to in order to leave a small gab between the small metal arms and the Pac Man.

When we did that, we got continuity though the switch for each of the elements!!! OMG. We were thrilled (still are)!

I guess that with opening and closing the lid, between the last successful test firing and now, and maybe with the expansion of the kiln during heating, two of the 3 metal arms got pushed by the Pac Man which turned off two of elements!

I have attached a photo.

We are re firing now. The temperature seems to be going up correctly.

Thank you soooo much for your help! Without it I might have panicked and bought a new kiln! Or at best I would have replaced the elements and then found it still wasn’t working and panicked a second time still having not discovered what the issue was and thinking my kiln was destroying elements.

[feistyfieryceramics]

21 minutes ago, Bill Kielb said:

Yes of Course, no power.
This diagram is not for your kiln, however Skutt has built many for Cromartie so can you post a picture of the kiln, controller and equipment tag. The manual / diagram you have is for the 3kw  so it likely doesn’t match your 5kw kiln. With a little luck we will be able to get a diagram off the Skutt site. We don’t know till we try though so pictures very important.

Hi @Bill Kielb. I think we figured it out. But it would still be amazing to have the diagram for next time. I am sure there will be a next time. And now we have to confidence for next time! That is great to know about the 3kw vs the 5kw too. Thank you. Here are some photos. Are these what you need? Also, do you think we should buy the equipment that is in the You Tube video you recommended? The infared thing, the temp reading gun, and the amp probe?

[Bill Kielb]

Yes, this is an old Cromartie and those kiln switches interrupt each element group when the lid is open. They must connect when the lid is closed so realigning them  should fix it. Nice catch, nice work! And yes the element resistance is specific to the kiln and, it’s not uncommon for the top element to have a bit more power.

[feistyfieryceramics]

4 minutes ago, Bill Kielb said:

Yes, this is an old Cromartie and those kid switches interrupt each element group when the lid is open. They must connect when the lid is closed so realigning them  should fix it. Nice catch, nice work! And yes the element resistance is specific to the kiln and, it’s not uncommon for the top element to have a bit more power.

You think I can find a Skutt diagram that is similar to our kiln? Do you think the Cromartie people will be able to tell us what the resistance should be on this old kiln? They do sell replacement elements made to order for this model.

[Bill Kielb]

Yes Cromartie would be the ones to request a manual and element resistance, this is prior to their deal with Skutt. This is a pretty good picture of your kiln. A closeup of the black contactor at the bottom with wiring connections and the wiring on the back of the zone switches pretty much tells us everything we need to know actually. 

[feistyfieryceramics]

46 minutes ago, Bill Kielb said:

Yes of Course, no power.
This diagram is not for your kiln, however Skutt has built many for Cromartie so can you post a picture of the kiln, controller and equipment tag. The manual / diagram you have is for the 3kw  so it likely doesn’t match your 5kw kiln. With a little luck we will be able to get a diagram off the Skutt site. We don’t know till we try though so pictures very important.

@Bill KielbYay! I should maybe hold my excitement until we complete a successful firing , but we are feeling so happy and impressed with ourselves  I know there will be a lot more to learn, but we got past the first barrier of even trying. All thanks to the wonderful advice here.

[Bill Kielb]

You guys did the work, deserve the credit, nice! Have fun firing!

[neilestrick]

Nice work finding the problem! That's an odd way to do a lid safety switch. 3 times the chances of something being out of alignment, as you just found out. But hey it works when everything is right!

2 hours ago, Bill Kielb said:

This diagram is not for your kiln, however Skutt has built many for Cromartie so can you post a picture of the kiln, controller and equipment tag. The manual / diagram you have is for the 3kw  so it likely doesn’t match your 5kw kiln. With a little luck we will be able to get a diagram off the Skutt site. We don’t know till we try though so pictures very important.

I don't think Skutt has anything to do with these old Cromartie kilns. I think Cromartie used to make their own, and now they just sell Skutt kilns instead. 

[feistyfieryceramics]

1 hour ago, Bill Kielb said:

Yes Cromartie would be the ones to request a manual and element resistance, this is prior to their deal with Skutt. This is a pretty good picture of your kiln. A closeup of the black contactor at the bottom with wiring connections and the wiring on the back of the zone switches pretty much tells us everything we need to know actually. 

@Bill KielbI think we already asked Cromartie for the manual and they couldn't provide it because the kiln is so old.  I think it is from 1990. We might have gotten that 3 Kw kiln manual from Cromartie actually. But I will try again and maybe include these photos. Then I can ask Skutt as well if they have something similar. And now I'll know what I'm looking at if I browse some Skutt manuals online! So that's exciting and promising!

[feistyfieryceramics]

3 minutes ago, neilestrick said:

Nice work finding the problem! That's an odd way to do a lid safety switch. 3 times the chances of something being out of alignment, as you just found out. But hey it works when everything is right!

I don't think Skutt has anything to do with these old Cromartie kilns. I think Cromartie used to make their own, and now they just sell Skutt kilns instead. 

@neilestrickI believe you are right about Cromartie not making their own kilns anymore. I've never seen the lid mechanism on any other kiln, but this design is clearly problematic  I remember now that when I was doing test firings, the lid starts flush but then there must be some warping at a certain temperature because a small gap develops at higher temperatures between the lip of the kiln and the lid. Even when it is latched and you can't just push it down to close the gap. So the Pac Man bolt thing must have migrated a bit with all the students asking to see inside the kiln and me wanting to keep it closed as much as possible for dust to not get in AND then that usual lid pop must have happened and shut off two elements. Interesting that it doesn't shut off all three. Now that we know how this mechanism works, we can also adjust it so that we can intentionally leave the top ajar while candeling. We learned soooo much today.

[Roberta12]

1 hour ago, feistyfieryceramics said:

@Bill KielbYay! I should maybe hold my excitement until we complete a successful firing , but we are feeling so happy and impressed with ourselves  I know there will be a lot more to learn, but we got past the first barrier of even trying. All thanks to the wonderful advice here.

Congratulations!!!  Great diagnostic!  Yes, there will be another time.  At night, on a holiday when it is really cold and you are tired and you have custom work  in the kiln.  This forum and my kiln support guy have calmed my nerves more than once.   I hope your load fired properly.

Roberta

[neilestrick]

1 minute ago, feistyfieryceramics said:

@neilestrickI believe you are right about Cromartie not making their own kilns anymore. I've never seen the lid mechanism on any other kiln, but this design is clearly problematic  I remember now that when I was doing test firings, the lid starts flush but then there must be some warping at a certain temperature because a small gap develops at higher temperatures between the lip of the kiln and the lid. Even when it is latched and you can't just push it down to close the gap. So the Pac Man bolt thing must have migrated a bit with all the students asking to see inside the kiln and me wanting to keep it closed as much as possible for dust to not get in AND then that usual lid pop must have happened and shut off two elements. Interesting that it doesn't shut off all three. Now that we know how this mechanism works, we can also adjust it so that we can intentionally leave the top ajar while candeling. We learned soooo much today.

There are definitely simpler ways to deal with a lid/door shutoff switch. But now that you have it figured out you'll know what to watch for. Good job!

Assuming the resistance on your elements should all be the same, they should be measuring at 29 ohms. Typically when they do graded elements (made to compensate for cold areas of the kiln), we see both the top and the bottom element running hotter than the middle, plus in a kiln this small is would be unlikely to have graded elements, so I'm betting they should all be the same. At their current resistance and runnning on 220 volts you're at about 5348 watts. Higher than what it should be according to the serial plate, but that just means it's running hotter, which is not really a problem since it's only about a 1.5 amp difference. Is the kiln on a 30 amp breaker? 

[feistyfieryceramics]

4 hours ago, neilestrick said:

There are definitely simpler ways to deal with a lid/door shutoff switch. But now that you have it figured out you'll know what to watch for. Good job!

Assuming the resistance on your elements should all be the same, they should be measuring at 29 ohms. Typically when they do graded elements (made to compensate for cold areas of the kiln), we see both the top and the bottom element running hotter than the middle, plus in a kiln this small is would be unlikely to have graded elements, so I'm betting they should all be the same. At their current resistance and runnning on 220 volts you're at about 5348 watts. Higher than what it should be according to the serial plate, but that just means it's running hotter, which is not really a problem since it's only about a 1.5 amp difference. Is the kiln on a 30 amp breaker? 

@neilestrick

I know 0 about electricity! Maybe after some exchanges with you I'll be able understand some of electric kiln videos that I've watched but just totally overwhelmed me!

How did you find the 29 ohms number? What does it mean if the resistance is lower than it is supposed to be? I thought that the resistance becomes higher in older elements and I thought that was one way you know you need to replace them?

We are in Sweden. Does that change anything?

We had a special 3-phase outlet  put in by the building companies electrician, I think it uses 3 breakers (11, 12, 13 in photo). I see that the plate on the side of the kiln says 220 V, but this big 3-phase plug says 200/346 V and 240/415V. I don't really know what that means actually, but I point it out because when we were looking at new elements online, one thing you have to choose is 220 V vs 240 V, I believe. 

How did you calculate the 5348?

Thanks!

[feistyfieryceramics]

4 hours ago, Roberta12 said:

Congratulations!!!  Great diagnostic!  Yes, there will be another time.  At night, on a holiday when it is really cold and you are tired and you have custom work  in the kiln.  This forum and my kiln support guy have calmed my nerves more than once.   I hope your load fired properly.

Roberta

@Roberta12Thank you! Currently the kiln is right on target! The temperature has been rising appropriately this times and the bottom elements are glowing, although they did take longer to start glow than the top element. This forum has been a dream come true every time I've posted here.

[Mark C.]

Your kiln looks to be three phase

goggle (3 phase explained)

Its used world wide

your elements are 220 on the plate I think