Kiln Firing Slowly

[jordan mcd]

Hello, 

I'm a little stumped - I have an Olympic 2518 Oval 240 V 35Amp - rated to fire to cone 8

I regularly fire to cone 6. 

I recently replaced my elements, and right after that my kiln was firing slowly - cone 6 fast glaze took 13 hours. And after that initial firing, I started getting an Error 1 after 14 hours. 

So, then I replaced the relays and still got an error 1 message. 

Then I checked the voltage at the shut off/breaker - it's 240. Tested voltage at the elements - they're 240, but drop to about 232-235 or so when the kiln is firing. 

I've tightened the element connectors... I even ordered a replacement plug and receptacle that connects the center/main panel to the bottom box, because the plug seems a little hard to insert. But, again, when the kiln is firing, I'm getting decent voltage at the elements.. 

The kiln fires relatively fine up until 1900F and then kind of stalls after that. The kiln errors out at around 2100-2170, which is frustrating because it's almost finished. 

The kiln draws roughly 38 amps while firing, I set my amp meter up to high/low and let it measure throughout one firing. So I don't think there's an element out.. 

I'm getting a little overwhelmed here and wondering if anyone has any ideas for what I can do to fix the issue. 

Thank you 

[Bill Kielb]

Well that’s too much drop for sure so where is the drop? CAUTION Live testing requires proper safety practices, when the kiln is firing do you have 240v at the breaker or does it drop there as well. If it does, check the breaker, is it hot? If not, then the voltage drop is in the wiring between the kiln and breaker which points to a bad connection or undersized wire.

So this is a 3-4% drop which might be enough to cause you trouble, normally a cone ten kiln has trouble at a 10% element change so I would definitely remedy your electrical situation this being a cone 8 kiln and starting off with a 4% disadvantage. If rectified by an electrician I often specify 1% or less drop for kilns. The 3% rule of thumb is just too much..

The chart below shows what the manufacture recommends for your kiln with respect to wire, breaker, plug …. So 50 amp circuit breaker and likely #4 wire. The distance (40 ft)  is the two way wire distance, so if 20 ft one way, then its 40 ft.

[oldlady]

jordan, have you contacted Olympic?   do not send an email, call them and talk to a tech expert.  

[neilestrick]

If it was firing fine before at that voltage, then it should still fire fine at that voltage, especially with the new elements. Most manufacturers roll their elements a little strong to account for possible drops. And since it's pulling 38 amps, which is above the specs, then I'm not convinced the voltage is the issue. Check the voltage again, as I've seen lots of voltage fluctuations on a service. I had a school recently that was measuring 228 when I was there, but runs at 240 most of the time. So it's possible that you had a fluctuation, but that wouldn't require pulling new wire. Check the plug and outlet and any jumper cords after the kiln has been running for a while to make sure they're not overheating. I had a customer where the kiln was measuring the proper voltage and amperage, but the plug was overheating and causing problems. Go ahead and replace the relays in case one is sticking when it gets hot. Also take a look at the controller and see if there's a ground wire going directly from Center Tap on the controller to a grounding screw. Sometimes they just ground them through the transformer, which doesn't always work great.

[jordan mcd]

Thanks for the replys- 

I should clarify that I changed my elements from the cone 10 version of the Olympic (42amp) to the cone 8 (35 amp). To explain: the landlord installed the kiln for the previous tenant (I bought the kiln and took over the space) - it worked 'ok' for years but I'm on a 60 amp service that also powers 4 other studios (no big equipment in those).. so occasionally we'd run into trouble tripping breakers off a main panel.. and other things you can imagine going wrong cutting it so close (42 amp on 60amp service). So I called Olympic and bought the 35amp/cone 8 elements so we weren't cutting it so close and I could sleep at night not worrying about an electrical fire.

What I can't really understand is why on the first firing I had OK results (it took about as long to fire as the previous elements), only to fail after that.. 

I'll double check the voltage at each spot and the controller as you suggested, Neil. I've checked the voltage at the elements when the kiln is cold and when it's stalling around 2100F and I don't recall any difference. When the kiln is off I get 433volts at the breaker. 

I'll call Olympic again - they've been helpful so far. Their initial idea was to re-crimp the element connections- but I have those removable connectors. I went through and tightened the crap out of them but perhaps I should use the crimps that olympic supplies. 

Maybe I need to invest in running a heavier wire  (I think we're on #6?). 

Thanks again 

[Bill Kielb]

45 minutes ago, jordan mcd said:

I'll call Olympic again - they've been helpful so far. Their initial idea was to re-crimp the element connections- but I have those removable connectors. I went through and tightened the crap out of them but perhaps I should use the crimps that olympic supplies. 

Maybe I need to invest in running a heavier wire  (I think we're on #6?). 

 

That makes a bit more sense, but I would get the electric portion solidified for sure. I assume you meant 233 v at the main not 433 v.  233v would be bad though as it will automatically reduce your capacity further. Electric services in the US are pretty reliable. Voltage fluctuations occur but ought to be pretty rare and reasonable in range. When they are not, there is almost always a real reason.

 None of your measured stuff is consistent with what we would expect. Elements that should draw 35 amps should draw less than 35 amps with lower voltage yet yours draw 38 amps. So either a measurement accuracy thing or you will find a reason for the inconsistency. With less wattage to do the job, dense loads may take excessive time in a large kiln as well. If there is not excessive drop in the wire, it will help but is also likely not the cause of your issues so bigger wire will be better but not likely the cause.

An interesting possibility would be they sent 208v elements, your first firing fired somewhat ok but the elements overproduced as 230 plus volts and are possibly worn to this current level. It’s easy to mix up voltages, current etc… try and be exact, measure the element resistance with reasonable care. 240 volt elements all in parallel operation should read 6.86 ohms, 208 v elements all in parallel operation should read 5.15 ohms. Not a giant difference when measuring,

consistency and precision in measurement will move you in the right direction, and paragon hopefully will be asking for these measurements. Suggesting recrimping  elements when voltage drop is excessive is a bit of a strange ask actually if they knew the system voltage was dropping. An infrared thermometer is pretty good at spotting overheated connections btw.

[jordan mcd]

I'm sorry, I meant 243v at the breaker. 

You're right about accuracy - I'm getting a little antsy since I'm falling behind in production. 

Yes, I thought it was odd that I'm drawing 38 amps. 

Thanks again Bill

[Mark C.]

since your 60 amp breaker supplies other spaces and has tripped is it now heating up during firing? Bad breaker can mess things up.I have fried a 60 amp breaker

The screw connectors are not your issue-Crimped ones are no better

#6 wire should handle 38 amps with ease-see whats getting hot-like the plug -are the connections clean inside receptical? and plug-look for losse connections or tarnished connectors 

[neilestrick]

So the 60 amps are for your kiln plus all of the lights, etc, in 4 studios?  That's not great.

According to the Olympic web site, that kiln is 8.8 cubic feet. 35 amps/8,400 watts for a kiln that size is terribly underpowered IMO. Even at 42 amps/10,080 watts it's underpowered. If you look at the L&L e28M-3, it's 8.4 cubic feet and cone 10 at 48 amps/11,520 watts. And having talked to them about it, it's just at the bottom end of a cone 10 kiln in terms of power to size ratio. I have a hard time believing that your oval was a cone 10 kiln at 42 amps, especially since it has such a large surface area for the floor and lid. Lots of heat loss there compared to a circular kiln. It was probably a cone 8 kiln before at best, and it's a cone 6 kiln now at best, and with the voltage drop it can't do the job. I don't know why they didn't make it a 48 amp kiln. No good reason not to.

Talk to Olympic and see if they have any ideas.

[Bill Kielb]

On 9/23/2021 at 8:24 PM, neilestrick said:

I had a school recently that was measuring 228 when I was there, but runs at 240 most of the time

Most schools would have three phase 120/208 which would be 208v L-L. Just asking, they had single phase service? Might be a reason for the 228 v measurement. Anyway, just mentioning in case it has future value.

[neilestrick]

Just now, Bill Kielb said:

Most schools would have three phase 120/208 which would be 208v L-L. Just asking, they had single phase service? Might be a reason for the 228 v measurement. Anyway, just mentioning in case it has future value.

Lots of schools around here have 240V 3P. I've even got a customer (art center) that has 208V and 240V in the same building.

[Bill Kielb]

48 minutes ago, neilestrick said:

Lots of schools around here have 240V 3P. I've even got a customer (art center) that has 208V and 240V in the same building.

Interesting, fairly rare as the transformer winds are very different and cost to install both  usually very pricey. Good to know though.

[neilestrick]

1 hour ago, Bill Kielb said:

Interesting, fairly rare as the transformer winds are very different and cost to install both  usually very pricey. Good to know though.

Older building, I figure they brought in a second service from the street at some point when they expanded/remodeled. Who knows? Lots of goofy stuff done over the years in Chicagoland.

[Bill Kielb]

On 9/25/2021 at 9:59 PM, neilestrick said:

Older building, I figure they brought in a second service

This may help for reference. I am posting because three phase 240v service (High leg) is old but presents some special risks when working around it, plus a floating neutral. Anyway maybe good for reference and safety. Hopefully your old building contained a single phase service, then a three phase 4 w addition later. The last two diagrams are most common.