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Kiln Amps Labeling Conflict

Amps Amperage Kiln LT-4K Kilnsitter Badge

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#1 mkregor

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Posted 17 August 2014 - 01:36 AM

Hi all!

 

I found a large old AIM Kiln at a thrift store for $50 :) , and it looks in good condition (pics attached).  Based upon the badge specs of 230v 20amps, I had an electrician install a 240v outlet on a 30amp circuit.  I fired it up and everything worked for a few minutes until it shut down, and wouldn't restart.  After checking continuity through all the wiring, I decided to check voltage on the outlet.  Sure enough it was out of whack.  I called the electrician back and he confirmed that the circuit was fried.  After connecting the kiln directly to the power drop at the circuit breaker we discovered that it was pulling 45-50 amps.  The electrician pointed out tiny print on the label for the Kilnsitter indicating 45 amps!  So, we were both confused.  Why does the badge on the control box indicate 20 amps if the Kilnsitter, which is the distribution point for electricity to all three rings, needs 45?  Even if it's simply extremely deceptive labeling (which is actually indicating that EACH RING requires 20 amps) wouldn't the sitter need at least 60 amps to function? Also, almost every kiln I've seen made by almost every manufacturer has an LT Kilnsitter indicating 45 or more amps -- regardless of the amp specs for each individual model (some as low as 15 amps).  Is it true that any kiln with a sitter will require wiring up a 50 amp circuit (at a cost of around $800)? And finally, why would a Kilnsitter, which is simply a heat sensitive shut-off switch, dictate amps drawn?  Can anyone shed some light on this seemingly ubiquitous contradiction in specs?

 

Thanks!

Matt

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#2 PSC

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Posted 17 August 2014 - 04:06 AM

Not a expert but in the kiln room at the place i teach we have smaller 25 amp kilns and larger 50-60 amp kilns but the stamped metal plate indicates this. Not sure why your plate says something different. Going to aims site it looks like that model 1718 originally only came with 2 rings perhaps someone added a 3rd that boost the amperage up.

#3 High Bridge Pottery

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Posted 17 August 2014 - 07:31 AM

Somebody could have put in the wrong elements or something wrong with the wiring. Could be an extra ring too.

 

Is the 45 stating operating amps or max amps for the switch? My guess is they might have a rating like a relay but I have never used or seen a kiln sitter before.

 

Do you know the resistance of the elements and how they are wired up? $50 is cheappp. Hard to tell the size of the thing but it looks similar to my 30amp 240v kiln.



#4 Marcia Selsor

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Posted 17 August 2014 - 09:07 AM

The stamp on the kiln plate says Model 1718, 20 amps and the plate on the kiln sitter says Model LT-4K  45-amps.

Maybe sometime during the history of the kiln things got changed..like the kiln wiring and sitter.

 

Marcia



#5 Dick White

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Posted 17 August 2014 - 10:39 AM

The rating plate on the kiln sitter specifies the maximum amperage that can be run through the switching mechanism of the kiln sitter. It does not  mean that is how much the kiln is rated for. You didn't state the diameter of the kiln, but it looks like about 23"? I've never seen a 3-ring 23" kiln that draws only 20 amps, most are in the 45 amp range (which requires a 60 amp circuit to allow for the 125% overage requirement in the electric code). Some more research is necessary.



#6 schmism

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Posted 17 August 2014 - 10:58 AM

 

 I fired it up and everything worked for a few minutes until it shut down, and wouldn't restart.  After checking continuity through all the wiring, I decided to check voltage on the outlet.  Sure enough it was out of whack.  I called the electrician back and he confirmed that the circuit was fried. 

This statement is somewhat concerning.  A properly wired circuit, with properly sized over current protection should cause no damage if you over current the circuit.   Which is to say,  if it was wired correctly,  the 30 amp breaker should trip in plenty of time to prevent any damage on the circuit should you pull more than 30 amps through it.  

 

IS the nameplate the rateing?  meaning the ring is rated to withstand the power output of 20 amps @240v (4800w)  but in reality the element inside only uses 15 amp per ring which is why the controller is rated at 45 amps.  Which means it needs to be on a 60 amp breaker.



#7 Mark C.

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Posted 17 August 2014 - 12:09 PM

The rating plate on the kiln sitter specifies the maximum amperage that can be run through the switching mechanism of the kiln sitter. It does not  mean that is how much the kiln is rated for. You didn't state the diameter of the kiln, but it looks like about 23"? I've never seen a 3-ring 23" kiln that draws only 20 amps, most are in the 45 amp range (which requires a 60 amp circuit to allow for the 125% overage requirement in the electric code). Some more research is necessary.

Yes I agree 100% on this statement. My guess is its a 3 phase or a misplaced plate? Neil could get to this mystery fast.

This kiln is to large for 20 amps .

Mark


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#8 Dick White

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Posted 17 August 2014 - 07:03 PM

Ok, looked at the AIM web page and figured out their numbering system. The first 2 digits of the model number is the kiln diameter and the second 2 digits is the height. The sections are 9" tall. The rating plate on yours is for a 1718, which logically would be a 17" diameter 18" high 2 section kiln. Their current catalog shows it as a cone10 kiln requiring 240V, 22 amps. You have a 3 section kiln. But still 17" in diameter. That would be the same as their model 1727 kiln, which in their current line of kilns is rated as 240V 33 amps (also now speced as a cone 10 kiln). 

 

The 2 mystery parts are the 230V rating and the cone 8 spec. First, US single phase voltage is generally 208V in commercial settings and 240V in residential settings. Some other countries have voltages in the 220-230 range. Second, older kilns with smaller element coils that pulled less amperage sometimes only went to cone 8. Yours is old and maybe was originally manufactured for a foreign market. The combination of these factors lead to a reasonable view of the original rating plate - a cone 8 17" diameter two section kiln pulling 20A at 230V. And then somebody stacked an additional ring on it. These things can be adapted from one voltage to another simply by changing the elements.The trick is determining the resistance and wattage that each element is designed to produce and then multiply that by the number of elements in play. The problem you face in solving that trick is you really don't know what elements are in there (surely not the original). It is entirely possible that a previous owner obtained replacement elements suitable for the current 240V model, and was running it on a 40A (just shy of the necessary 41A circuit needed for a 33A device) or proper 50A circuit. At a minimum, your 30A dryer circuit is absolutely inadequate. You need to install a new circuit with much heavier wire. And yes, $800 is about right for that.

 

The AIM company seems to still be in business in Nevada.  Give them a call and see what they can tell you about elements for that model.

 

dw



#9 SmartsyArtsy

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Posted 17 August 2014 - 08:12 PM

It is not clear from any of these posts that the extra ring has any elements. In a small kiln this size, a blank ring is often inserted. that would make a difference in the assumptions of Dick White. Also, my 18x23 with extra ring runs fine on a 30 amp. I certainly do not have an answer for the different ratings, but the replies here make assumptions about that extra ring and therefore the probable amps  needed.



#10 Dick White

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Posted 17 August 2014 - 10:44 PM

The first picture show all three rings having switches and indicator lights.



#11 mkregor

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Posted 18 August 2014 - 12:46 AM

Thanks for all the replies.  The kiln is indeed 17x27, and there are elements in all three rings.  I like Dick's logic, especially if AIM's current model 1718 is claiming cone 10 from 22 amps.  That makes cone 8 at 20 amps sound about right.  Also, schmism, no need for concern about the circuit.  When I mentioned that it was 'fried' I was actually quoting a service rep from the electrical company. (I couldn't be at the house when the electricians were there, so I got the report second hand).  After checking the box, the breaker is fine and the outlet is back to outputting 240v, so there really wasn't any damage.

Now the big decision is whether I shell out the money to upgrade the amps for a big manual kiln that may or may not function properly, or spend a little more to purchase a new automatic one rated for fewer amps, but with less space.  Hmmm......

 

Matt



#12 Mark C.

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Posted 18 August 2014 - 02:30 AM

I'd go with a newer unit with newer controlls-easy to fire.

Mark


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#13 High Bridge Pottery

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Posted 18 August 2014 - 06:55 AM

You could try taking off the extra ring for a smaller kiln till you decide what to do. How many elements are in each section? Do you know the resistance of each element and how they are wired i.e. series or parallel. Once you know this it is easy to work out the amp draw and change things or just work out in theory what is meant to be happening with the electricity. What cone are you wanting to fire it to?

 

I cant see how the wires bridge each section.

 

I would pay $50 for just the structure. That is only £30, enough for 2 maybe 3 bags of clay.



#14 neilestrick

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Posted 19 August 2014 - 08:39 AM

You've got a Frankenkiln. Someone added a third ring but never changed out the serial plate to reflect the change.

 

The amperage rating on the sitter has nothing to do with the actual draw of the kiln. It's just a switch that power goes through, and it can handle up to 45 amps. The actual draw is determined by the service voltage and the resistance of the elements.

 

It's odd that a kiln of that size with 3 rings is pulling 45-50 amps. It should be around 35 amps. Someone's definitely been tinkering with it. I'd get new elements in it that are properly sized for that kiln.


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