Alondene Posted October 30, 2016 Report Share Posted October 30, 2016 I have an LL Feugo kiln which has been fired around 12-14 times to cone 4/6. Recently it stopped reaching the right heat so I contacted the supplier who said check the element wires. Turned out one was broken, so they replaced it and I fitted it in. First firing was fine, no issues. Second firing which was to cone 10 shorted out at 1260. The plug started to melt in the socket and blow the RCD socket and circuit. I have a separate circuit 100amp for the studio with a 50amp slot for the kiln which is 30amp. The double socket was ruined but the studio circuit board is fine. After refitting the plug, it's been tried again in different sockets and each time trips the circuit the minute you flip the little switch on the front panel? I've spoken to the supplier to check why this is happening and they say it because theres a wire touching some part of the kiln inside. Go check. All wires in the kiln have been checked with a multimeter by electrician and there's no break. Nothing looks damaged, melted, loose, etc. No wires touching inside. Elements are connected and no breaks and no glaze on elements. The electrician can't see any fault with the studio to main circuit wiring either. Other thing work fine from the socket the kiln was tried on. The supplier says they don't know what the problems is and say they don't think it's a parts issue ( the Kilns is only on parts warranty now as 2nd year of warranty) and the charge for getting it looked at is £70 per hour, that's after I get it to them which is 340miles away, so likely carriage cost both ways will be near £140. Has anyone had anything similar happen to their kilns or have any suggestions what might be causing it to short each time? I'm really missing my kiln and don't have the knowledge to know what it could be. All suggestions and advice very much welcomed. Link to comment Share on other sites More sharing options...
Dick White Posted October 30, 2016 Report Share Posted October 30, 2016 A short circuit is happening somewhere only when the kiln gets hot? Open the control panel and look for connections that have black smudges around them or pinched wires. Link to comment Share on other sites More sharing options...
Mark C. Posted October 30, 2016 Report Share Posted October 30, 2016 I'm a bit unclear on why the plug/socket melted-thats usually a loose or poor wire connection . The other item you mentioned is a wire thats touching somewhere. I suggest as Dick said above check the circuit board and control panel . You need to inspect every wire connection from circuit breaker back thru control and elements .Look for loose or black or burned or funny color connections. Make sure that are all tight and clean. Link to comment Share on other sites More sharing options...
neilestrick Posted October 30, 2016 Report Share Posted October 30, 2016 I'm having a hard time following some of your terminology. So just to be clear, when you say socket do you mean the outlet that the kiln plugs into, or are you referring to the location of the switch in the breaker panel? When you say you have a 50 amp slot for the kiln which is 30 amps, do you mean it's on a 50 amp breaker? According to the L&L site, your kiln pulls either 13 or 15 amps depending on which model you have, which means it should be on a 20 amp breaker. Some clarification will help determine the cause of the problem. How many amps does your kiln pull? It will say on the serial plate on the control box. What size breaker is the circuit for the kiln? Other appliances plugged into the same outlet work fine, correct? That means the problem is in the kiln. When it flips a breaker immediately upon starting the kiln, that means something is grounding out or connected wrong. Double check that everything was wired properly Compare the wiring connections on each ring of the kiln and make sure you didn't change something when you put the new element in. If everything looks good and all connections are tight and there's no loose wire contacting the metal of the kiln jacket or control box, then I would look at the power cord. Did you replace the plug, or the cord, or both? Link to comment Share on other sites More sharing options...
glazenerd Posted October 30, 2016 Report Share Posted October 30, 2016 I have a separate circuit 100amp for the studio with a 50amp slot for the kiln which is 30amp. That is a really bad and hazardous set up. The whole point of matching a 30 amp breaker to a 30 amp rated kiln is for the breaker to trip if the circuit demands greater than 30 amps: which it has. The evidence of that is your burnt out receptacle: which was rated for 30 amps, but obviously drew more than 50 amps (breaker size) and burnt it up. Everything was checked by an electrician as you stated: so that leads me to believe that you have a faulty relay. It is stuck in the "open/on" position because it is demanding full power as soon as you turn it on. However, as Dick stated: you may very well have two problems occurring at the same time.The only way this kiln would exceed maximum amperage rating is a short somewhere. For safety sake, I would only touch this kiln during operation with shielded rubber gloves. If by chance this circuit is grounded out or shorted out in contact with the metal housing: you could easily cook yourself. The electrician needs to pull the relay (with breaker off) and test the leads individually. A wiring schematic should be included with the kiln purchase, and would show which contacts on the relay are power leads. A simple continuity tester would tell (them) if the relay is stuck open. If that proves to be the problem: once repaired then the kiln needs to be rechecked before firing while idle. If that checks out, then set the kiln on full power, and check the element leads to see if they are drawing more power than what they are rated for. Nerd Link to comment Share on other sites More sharing options...
Alondene Posted October 31, 2016 Author Report Share Posted October 31, 2016 Language difficulties: indeed, plus I'm no electrician, so I'm getting an overload trying to decifier posts. Thank you all, for your responses. No sure how to pull out individual points so going to respond to as much as I can in once. I will show this to the electrician and ask for additional checks. On the parts I could clarify( well I think I am, but it may still make little sense but here goes:- I have a separate consumer unit( circuit breaker USA? ) that comes from the houses main consumer unit. It has apacity for 100amps and have 4 slots for MCB's. Three slots are used, one for lighting, one for power sockets and one for the kiln. Pic's attached for consumer unit and Fuse- MCB (Miniature Circuit Breaker) (MCB) Miniature Circuit BreakerAn MCB is a modern alternative to fuses used in Consumer Units (Fuse Boxes). They are just like switches which switch off when an overload is detected in the circuit. See pictures. When the studio was wired up by the electrician I was asked to confirm watts of the kiln. It is 3000 watts, 13amp plug and uses 240volts. They said it required 30amp generally but safer to have spare capacity, hence 50amp fuse. UK cookers are similar and require between 30- 50amp fuse. These also have 13amp plugs or are directly wired into the wall socket. The plug - I mean attached to the kiln has a 13amp fuse. The socket - I mean as in the one fitted in the wall The socket on the wall has slight blackening in one of the three pin holes (the blue neutral wire) The plug also is slightly melted on one of the three pins ( the blue neutral wire ) The wires within the kiln have all been checked for damage, blackening, melted sections, breaks, touching the casing. Nothing found all fine. All connections within the kiln checked with milimeter and no breaks or issues found. Same with the kiln wire to plug. The circuit between the wall socket and consumer unit not checked. This socket no longer works. However The kiln has had the plug refitted (13amp) and tried against a seoerate power socket and it trips immediately the switch is clicked up or dowm( can't remember if it's up on or down on) either way, that's where the trip happens. Would this not indicate the issue is with the kiln in someway? Rather than with the socket to circuit section. Other items used in these sockets are all fine, no problems with working them. I'll take suggestions away to the electrician and get further checks carried out. In the meantime, the kiln remains unplugged, lacking life (but saving mine) , looking forlorn and awaiting diagnosis and treatment. Thanks everyone. Link to comment Share on other sites More sharing options...
neilestrick Posted October 31, 2016 Report Share Posted October 31, 2016 The fuse/breaker whatever you want to call it is way too large at 50 amps. A 13 amp kiln should only have a 20 amp breaker. When it shorted out before, it allowed 50 amps to flow through the kiln system that is only set up to handle 20 amps. There's a reason we use breakers/fuses- they prevent too much amperage from going through the system. By using a 50 amp breaker they've pretty much negated the benefit of having a breaker at all. It's not at all safer to have a larger breaker. I would replace the entire power cord because it may be fried inside where it's not visible. I would also double check the whole kiln system for damage. It's tough to diagnose these things over the internet, though. It may be worth having a kiln tech check it out. Link to comment Share on other sites More sharing options...
glazenerd Posted October 31, 2016 Report Share Posted October 31, 2016 Alon: the picture on the left is called a circuit breaker in the States: MCB on your end. The picture on the right is called a sub-panel in the States: consumer unit on your end. You deal with DC current, and we deal with AC current (electrical.) However, rather called a MCB or circuit breaker: the function is the same. The MCB trips (disconnects) if a greater electrical load is placed on it than what it is rated for. Kiln makers already allow a certain amount over the actual amperage demand the kiln actually makes. In this case your kiln requires 15 amps peak: so they specified a maximum of 30 amp MCB (breaker.) By installing a 50 amp MCB breaker, you allowed nearly double the maximum amperage to come to the kiln Here is why I think the relay started this problem: 1. You said it fired 12-14 times when you first got it with no problems. This means everything was functioning properly. 2. Then you had an element burn out and it was replaced: then it fired one time without problems. 3. The next firing after you replaced an element is when the plug and receptacle burnt. You replaced the plug and receptacle: but it trips every time you turn it on. My personal opinion is the relay: which governs the amount of power the kiln requests/demands when firing. However, the relay is only rated to 30 amps, and you were allowing 50 amps to come to it: thereby burning it out prematurely ( after 12 firings.) I also think your electrician did you a big disservice by installing a 50 amp MCB on a device that specifically stated a maximum of 30 amp MCB. When the studio was wired up by the electrician I was asked to confirm watts of the kiln. It is 3000 watts, 13amp plug and uses 240volts. They said it required 30amp generally but safer to have spare capacity, hence 50amp fuse. The kiln maker stated a draw of 13 amps, and specified a 30 amp MCB: which gives you " room to spare." and your electrician stated: They said it required 30amp generally but safer to have spare capacity, hence 50amp fuse. >> Actually by installing a 50 amp MCB, they created a fire hazard and an electrical shock hazard.. making it unsafer, not safer...I also think the 50 amp current allowed by the 50 amp MCB also fried your relay prematurely, and created a short within it. ******** words and opinions about this electrician the moderators would bounce me and slap my hands over...****** use your imagination. Nerd Link to comment Share on other sites More sharing options...
neilestrick Posted October 31, 2016 Report Share Posted October 31, 2016 I agree with Nerd. You should find a different electrician. Link to comment Share on other sites More sharing options...
neilestrick Posted October 31, 2016 Report Share Posted October 31, 2016 The big question here is why the kiln fried out in the second firing after replacing the element. I suppose the relay could have taken a hit when the element died and then gave out a couple of firings later, but if the relay was fried enough to cause the system to overheat and now short out whenever it's turned on, I would expect to see some visible damage to the relay, like fried out tabs and melted plastic. When they get that much extra amperage in them they always melt out. Plus I've never seen one cause a short like that, even when totally melted. I reread your original post and realized that you said it was blowing the breaker when you turn on the power switch to the controller, not when the firing is started. If it was a relay that was fused and shorting, it should cause the breaker to flip when the kiln is first plugged in, regardless of whether or not the switch was on or off, because that switch only controls power to the controller. When a relay is fused on, it doesn't matter if the controller is powered up or not, power will flow through the relay. So it has to be something with the power path to the controller, which means the controller, transformer or power cord. The transformer takes the 240 volts (or 220 or whatever you have there) from the main power supply and knocks it down to low voltage 24 volt power for the controller. The controller itself can't cause the short that you're getting, so it's either the power cord or the transformer. In 12+ years of kiln repair I've only ever replaced one transformer, so it's unlikely that it is causing the problem, especially because it would not have been affected by the amperage surge that happened before- it's not part of that system. That leaves the power cord, which we know overheated when the plug melted. I fixed a kiln a couple of weeks ago that was blowing the fuse due to bad terminal ends where the cord connects inside the kiln. So it could be the cord itself or just the terminal connections. Nerd, double check my thinking on all that. This still leaves the question of why it overheated in the first place. My theory is that you didn't get the nuts tight when connecting the element pigtails to the ceramic block. When those aren't tight you'll get arcing there that causes the system to overheat all the way back to the plug. I've had it happen a couple of times on my big kiln. I have to check the nuts every few months because they like to loosen up over time on that kiln for some reason. When they get loose the power cord heats up and blows fuses. When they get hot enough it will melt out the element connection, but that doesn't always happen. Check it all out and see what you find. It's an interesting case for sure! Link to comment Share on other sites More sharing options...
PeterH Posted October 31, 2016 Report Share Posted October 31, 2016 UK resident (so very shaky on US electrical practice) A UK "13A" plug contains its own fuse, whose rating is selected to protect the connected device. So there shouldn't be any mechanism for more than ~13A to pass to the kiln during the incident [*qualification]. This is confirmed by the OP: The plug - I mean attached to the kiln has a 13amp fuse. >Neil: The big question here is why the kiln fried out in the second firing after replacing the element. Alondene: after the incident: - was the plug's 13A fuse blow? - was the supply-side MCB (circuit-breaker) tripped? - what exactly had happened to the RCD? Was it tripped, or just fried? - was there any evidence of tracking/shorting/singeing/arcing/failed-insulation/etc when you opened the 13A plug? If there was melting on the neutral pin I would expect to see something inside the plug. Alondene: After refitting the plug, it's been tried again in different sockets and each time trips the circuit the minute you flip the little switch on the front panel? What exactly is tripping? Is it the RCD? Just to confirm that your kiln is a K-F-1418/41 cf http://hotkilns.com/f1418-international?quicktabs_24=1#quicktabs-24 Regards, Peter PS Just to confirm that the standard UK supply is AC not DC as suggested earlier. * At least through the live wire to the kiln under normal failure modes. Of course some sort of short-circuit within the plug could conceivably result in higher currents through the socket and the supply-side wiring, and theoretically even permit a live connection to the kilns earth/neutral wires. Link to comment Share on other sites More sharing options...
neilestrick Posted October 31, 2016 Report Share Posted October 31, 2016 I totally missed the fuse on the power cord. If it's not blowing, but the 50 amp breaker is, then maybe the problem is in the wires between the outlet and the breaker. It's possible they were damaged when the outlet melted. It's odd that the 13 amp fuse didn't blow and prevent that outlet meltdown in the first place. Link to comment Share on other sites More sharing options...
PeterH Posted October 31, 2016 Report Share Posted October 31, 2016 If true, this is interesting! http://www.theiet.org/forums/forum/messageview.cfm?catid=205&threadid=37963 Reading an article in issue 18 of 'Switched On' (Electrical Safety Council) concerning overloading of 4 way extension leads.The article explains that by product testing a BS1362 13A Fuse is required to operate at 1.9 times rated current (24.7 A) within 30 minutes, and also that the fuse shall have a non-fusing current of 1.6 times rated current (20.8 A). It goes on to say that it is therefore possible for an extension lead (or anything else for that matter protected by a 13A fuse) to carry a total current of 20 A for an indefinite period! The point seems to be backed up by http://www.aboutelectricity.co.uk/images/photoalbum/bs1362fusingtime.png This is in the same ballpark as Neil's US figures: a 13 amp kiln should only have a 20 amp breaker. ...but could be rather hard on a 13A plug and socket if the excess power is drawn for an extended period. Alondene: it might be an idea to look at the inside of the failed socket, in case there was a heat-induced short there. PS Clamp ammeters are looking more and more attractive as a way of seeing what's actually going on. Link to comment Share on other sites More sharing options...
glazenerd Posted October 31, 2016 Report Share Posted October 31, 2016 Nerd, double check my thinking on all that. Got my vote: transformer would also be on the list. Regardless, no way should there be a 50 amp breaker (MCB) in the panel for this circuit. It's odd that the 13 amp fuse didn't blow and prevent that outlet meltdown in the first place. Very odd...something in this circuit line is not closing (tripping the breaker/ or fuse) as designed. PS Just to confirm that the standard UK supply is AC not DC as suggested earlier. Peter, when did this change occur? I know years back it was DC, and often see DC schematics on kilns destined for the UK. Did I miss something? Neil: if power cords in the UK have in-line fuses in them: then it should have tripped- but did not. Do not like this scenario either. I would be installing a 20 amp MCB (breaker) to service this kiln until I was sure the problem was resolved. Nerd Link to comment Share on other sites More sharing options...
PeterH Posted October 31, 2016 Report Share Posted October 31, 2016 >Peter, when did this change occur? I know years back it was DC, and often see DC schematics on kilns destined for the UK. Did I miss something? I think there is some confusion somewhere, we had a large national AC grid in 1930s. Had a personal interest since the 1950s and DC was always odd-ball or niche. Any chance of me seeing one of the schematics? Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted October 31, 2016 Report Share Posted October 31, 2016 I thought DC power was only used in america by Thomas Edison until AC was shown to be much more useful. It is very strange that the 13amp fuse didn't go. Does it have tinfoil wrapped around it ? Did the electrician rewire the kiln? They always seemed to stump any electrician I had look at mine. One wired live back to itself and left neutral going nowhere... Nice incomplete circuit. Link to comment Share on other sites More sharing options...
Alondene Posted October 31, 2016 Author Report Share Posted October 31, 2016 Wow! I am bedazzled and thank you all for all of the thoughts and suggestions. I think however I need a kiln repairer to come and look at this rather than get the electrician back at this point. I don't like messing with electrics at this type of level, it's way above my current understanding. I can clarify a few points though. The refitted plug is a 13 amp and the fuse has fired and has not foil wrapped round it. New from the store. When the kiln was retried after fitting the plug, it was tried on a seperate socket for power socket circuit (20amp in consumer unit). An RCD was fitted in the socket and then the plug. When the kiln was turned on at the switch, it tripped the RCD. When this was tried in the same socket without the RCD, same process the whole circuit was tripped I will definitely look at the element connections but nothing obvious seen previously but another looked seems advisable. LL kilns suggest checking the resistance if the element (unplugged) , so planning to do this in the next day or so. Interested in whether there is an issue with the cord to plug but multimeter didn't show a break or if the relay is the issue. Looking for a good recommended kiln repairer via supplier / or if anyone knows one in UK London area, please let me know. Amazing how you all know so much and work through these things, truly in awe. I'd like to develop a more in depth knowledge, though this kiln is certainly helping me learn a it more. Will keep you posted once I have someone in to check it over throughly. Link to comment Share on other sites More sharing options...
Alondene Posted October 31, 2016 Author Report Share Posted October 31, 2016 Hi Peter, replied as best I can in line below. Thank you Alondene: after the incident: - was the plug's 13A fuse blow? - yes, blackened, melted. - was the supply-side MCB (circuit-breaker) tripped - no as double socket had built in RCD however that socket is completely fired and needs replacing completely.MCB fine, consumer board fine. All working fine. - what exactly had happened to the RCD? Was it tripped, or just fried? - as above - fired, blackened, plug had slightly melted in socket. - was there any evidence of tracking/shorting/singeing/arcing/failed-insulation/etc when you opened the 13A plug? If there was melting on the neutral pin I would expect to see something inside the plug.( yes, in the neutral pin, that's wher the melted blackened section is focused. Alondene: After refitting the plug, it's been tried again in different sockets and each time trips the circuit the minute you flip the little switch on the front panel? What exactly is tripping? Is it the RCD? - when tried with RCD, yes just the RCD tripping, when tried without RCD, consumer unit tripped. Just to confirm that your kiln is a K-F-1418/41 cf http://hotkilns.com/...=1#quicktabs-24- Model on document, warranty states: F1418-UK , 230 volts, 13 amps, 3000 watts Regards, Peter Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted October 31, 2016 Report Share Posted October 31, 2016 Sorry the foil was a bad joke Was there never a problem before you replaced the element with it tripping the circuits. RCB's trip I think when there is a mismatch between what is coming in live and going out neutral so it sounds like something is not right. Also the plug melting is a strange one for a kiln fault, normally I have found it would be the relay or something closer to the kiln. The only thing I can see that's changed is the element. How was the element broken in the first place? Also weird that 12-14 firings breaks one. Could it have arrived broken? Link to comment Share on other sites More sharing options...
Mark C. Posted November 1, 2016 Report Share Posted November 1, 2016 I know a fair amount about electrical and the language problem in terminology here is massive. I'm just enjoying the fact that in England it completely different. No DC in England well I leaned something new today. I think I'm going out and putting some slate on my roof and putting in some cobble stones to the studio. Link to comment Share on other sites More sharing options...
glazenerd Posted November 1, 2016 Report Share Posted November 1, 2016 Neil: Do you have this handy wall sheet for NEMA outlets? http://www.paragonweb.com/files/manuals/NEMA_Config_Chart1.pdf Looking for DC schematic Peter, have it around here somewhere. Nerd Link to comment Share on other sites More sharing options...
PeterH Posted November 1, 2016 Report Share Posted November 1, 2016 Marc, ref to historic use of DC in mainland UK areas. It appears to have continued rather longer than I would have expected. http://www.vintage-radio.net/forum/showthread.php?t=41380 From what you say I gather that DC is still supplied in the US today. About what % of US domestic consumers use DC? Link to comment Share on other sites More sharing options...
PeterH Posted November 1, 2016 Report Share Posted November 1, 2016 Back to the OP. Is my summary consistent with the facts? 1) Despite differences between UK & US practice it seems that the results would have been broadly similar in both cases. The kiln seemed to have being drawing 20A+ when it was disconnected ( by plug's fuse rather than a breaker). [reservations in a ps.] 2) Trying to reconnect the kiln is OK until you try to switch it on. Hence the cable doesn't seem to be an immediate cause of any problems. (I leave it to the experts to indicate if its replacement after a high current excursion would be good practice.) 3) If an RCD is fitted, it trips immediately after the kiln is switched on. This indicates a (possibly small) difference between the current in the live and neutral wires. 4) If an RCD is not fitted, the breaker trips immediately the kiln is switched on. I presume that this is the 100A studio breaker? To me this looks awfully like a short between the live input and earth, somewhere "behind" the kiln's on/off switch. UK specific issues covered? ... back to the kiln experts. PS As the plug & socket seem to have been pretty well fried, I cannot say that the UK 13A-ring-main practice has come out of the exercise looking good. It's fair to say that it was not designed with loads like kilns in mind, but I'm disappointed with the outcome. PPS Wiring diagram seems to be on p33 of http://hotkilns.com/sites/default/files/pdf/fuego-robin-uk-10-22-16-web.pdf ... my printers dead at the moment, so I have not tried to follow it. Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted November 1, 2016 Report Share Posted November 1, 2016 I don't understand why they have done it with 4 elements. Mine just has one big one that runs around the kiln for 240v 13amp. Seems like more connections to go wrong. Maybe they do not like angled grooves. ( turns out I am forgetful and it has 2 elements ) A few pictures of the kiln wiring inside the box would be good. I always find making a sound connection tough. Link to comment Share on other sites More sharing options...
Mark C. Posted November 2, 2016 Report Share Posted November 2, 2016 Marc, ref to historic use of DC in mainland UK areas. It appears to have continued rather longer than I would have expected. http://www.vintage-radio.net/forum/showthread.php?t=41380 From what you say I gather that DC is still supplied in the US today. About what % of US domestic consumers use DC? I know of no DC supply for domestic use here. Its used in electronics ,cars and pottery wheels,kiln controls etc- all via a step down transformer or generator/alternator Link to comment Share on other sites More sharing options...
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