Increasing kiln temp

[Tati]

I have a refurbished AFC kiln.  The elements are running perfectly and I just replaced the thermocouple (type N).  I was told it could reach 1280 periodically so assume 1220c wouldn’t be a problem.  However, getting to cone 6 takes 17-18hrs.  It’s manual so I do ramp rate of 100/hr till 1000c hold for soak 30mins then an just leave on full till cone 6.  Once it hits about 1100 it won’t ramp more than 30c/hr and even less ramp after 1150.  Essentially I’m soaking till the cone 6 goes down.  Is this normal?  I’m worried about ruining my elements with such a long firing and would like to cut this time down to 14/15hrs. 
It’s been suggested to either increase the insulation on the floor and back wall to see if it’ll hold more heat. And also or potentially replace my top elements with a lower resistance ones to supply more heat.

any thoughts would be appreciated as I’m not sure what to do.

TIA

[Bill Kielb]

The basic problem, the amount of energy you are putting into the kiln is not sufficient to offset the energy leaving through the kiln shell and that required to heat the wares to temperature all at a reasonable speed. The shell looks decent, no holes, missing insulation So, was the kiln designed or is rated to fire to your desired cone? Are all the elements working? Are they within 10% of the original resistance? Is it operating on the design voltage ….

Maybe start with the what it’s designed for part, does the kiln equipment tag state top temperature? Usually a cone 6 kiln needs to be rated more (cone 10 preferred) to be able to repeatedly hit cone six as it wears. If maximum temperature is cone six, then after a few firings and regular element wear it will not. So good to find out the rating first which often is on the equipment tag.

Next, if rated appropriately can you measure the element resistance and compare to new. If the elements have worn by 10% typically they will need to be replaced to make it to the intended design temperature in a reasonable amount of time. Generally elements wear together so all are replaced when found worn.

Edited September 21, 2023 by Bill Kielb

[Tati]

Thanks for your reply, that all makes perfect sense.  Unfortunately the kiln doesn’t have an equipment tag. So I’ll try tracking down the person who rebuilt it.  Do u know  if  there is another way to find out it’s rating should I not be able to track down them down?

Edited September 21, 2023 by Tati

[neilestrick]

What's the volume of your kiln, wattage, voltage and phase?

[Tati]

Hi there,

It works on a 20A, single phase, 220V, 2.2kW, 120L

Thanks,

[Bill Kielb]

10 hours ago, Tati said:

It works on a 20A, single phase, 220V, 2.2kW, 120L

It seems to have three phase specifications: 3 phase 220v expect 2.2kw. And so on. Although I think I am looking at a contactor though, not necessarily the kiln rating. Understanding how this is currently wired, it’s actual measured operating amperage would be helpful along with the measured resistance of the elements and how they are connected to get to the actual wattage being supplied. From there We have typical watts per interior area conditions that would give an idea of capability.

Maybe easiest: If you can measure the actual amperage we can just figure the wattage.

Edited September 22, 2023 by Bill Kielb

[Tati]

Hi Bill,

Sorry its taken a bit.  I measured the amperage today and it was 236V

I'm not quite sure how to measure the resistance of the elements as when i did it I kept getting a number like 2.1 (that doesn't seam right especially since I found a hand written note indicating that the OHM tested in 1984 is 14.4 .   Attached is also a picture of how they are connected and the writing.

Thanks

[Bill Kielb]

You have measured the operating voltage and that is great, but we really need to know the amperage to calculate the wattage. These measurements really take place around energized conductors which requires solid electrical safety practices. I would suggest having someone help here - someone who is used to measurement of live circuits. I really hesitate to suggest more, additionally this kiln could be of an age when asbestos insulation was fashionable. For me, you really need the help of someone local. Any chance you have someone who could help?

Edited October 16, 2023 by Bill Kielb