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Paragon Kiln Voltage Conversion 240v to 208v


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Hello All,

So last year I had an old Paragon S-23-3 240v kiln installed in my my studio without realizing that the electric available in this building is 3-phase 4 wire 120v/208v (old mill building). Electrician basically said it was fine to do so and it would just take a bit longer to get up to temp but the kiln is definitely quite underpowered as it struggles to get up to 04. I would love to be able to get to mid-range temps but not to excited about replacing the whole kiln so I'm curious about rewiring/converting this kiln to work better at 208v single phase. I'm aware that I'll have to swap the elements, which is something I'm comfortable doing myself, but I'm not sure if there's anything else I'll have to change. I emailed Paragon, no response. Thoughts?

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Electricians don't generally understand kilns unless they've worked on them before. The difference between 208 and 240 volts is a big deal with kilns, but not so much with other electrical systems.

If you're just switching from 240 to 208 volts, then it's most likely just an element change. You'll need to check with Paragon to see what the amperage draw is on 208 volts though. If I'm looking at the correct wiring diagram, it pulls 40 amps on 240 volt service, which means it should be on a 50 amp breaker. On 208 volts it may pull higher amperage depending on how they set up the elements. If it bumps it up over 40 amps then you'll need a 60 amp breaker to be in code. As for hooking it up to 3 phase power, that gets a lot more complicated if its got a kiln sitter, as the sitter can't directly control 3 phase systems. Ask Paragon about it, but it would be easiest to leave it as a single phase kiln.

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59 minutes ago, Hope_Street_Clay said:

I emailed Paragon, no response. Thoughts?

I would do the elements although you could do a buck and boost transformer in boost mode but probably even harder to find and old enough electrician to do that properly and your primary wiring (kiln branch circuit) would need all sorts of resizing and probably a fused disconnect at the kiln for good measure. You are likely resizing your wire and breaker either way, elements would be easiest IMO. Most electricians don’t know that when kiln power drops by as little as 10% they can’t make top temperatures. Brand new they are only designed at about 110% so his comment about it taking longer is probably typical of most.

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On 1/19/2022 at 3:35 PM, Bill Kielb said:

I would do the elements although you could do a buck and boost transformer in boost mode but probably even harder to find and old enough electrician to do that properly and your primary wiring (kiln branch circuit) would need all sorts of resizing and probably a fused disconnect at the kiln for good measure. You are likely resizing your wire and breaker either way, elements would be easiest IMO. Most electricians don’t know that when kiln power drops by as little as 10% they can’t make top temperatures. Brand new they are only designed at about 110% so his comment about it taking longer is probably typical of most.

It is easy to add a transformer to boost the voltage. Plenty on ebay and it's not a complex wiring challenge and if done carefully completely safe. The power is proportional the square of the voltage so 208 compared to 240 is 208/240 squared or 0.75 that's only  75% power into the kiln

 The transformer has to supply 240 -208 = 32. Volts. Assuming the power is 10 kW then the current will be 10000/240 amps or 42 amps. The transformer will need to be 32 volts at 42 amps. Input to transformer will be 208volts. If you need more EE help email me. You could just get new elements of course...probably simpler and cheaper...but..

rdoctors ,at,gmail.com

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What is the wattage and amperage on the equipment tag. Thought being it was designed to work with X amount of energy (heating) so order new 208 v elements that make that wattage so the kiln performs as originally designed. From there wiring size will be per the amperage draw of the new elements to achieve the design wattage and what is available for elements. A picture of the nameplate gets us the info. Incidentally 3 phase 120/208 v is pretty common for commercial service so even moving to another commercial location, this works. Post a picture of the equipment tag.

To answer your question, if it’s a 10000 watt kiln at 240 v it draws 40 amps. If we order 10000 watt elements at 208 v  so the kiln heats the same, it draws 48 amps.The kiln needs the design wattage to make top temperatures and offset the shell losses and firing load inside, else peak temperature cannot be made or cannot be made fast enough to fire consitantly.

Edited by Bill Kielb
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57 minutes ago, Bill Kielb said:

If we order 10000 watt elements at 208 v  so the kiln heats the same, it draws 48 amps

They don't necessarily keep the wattage the same, though. Often they let the kiln run at lower wattage on 208 volts so they can keep the amperage the same, so at 208 volts it's not as powerful, but still powerful enough. It all depends on how they set it up.

1 hour ago, Hope_Street_Clay said:

Well still haven't gotten a reply from paragon regarding whether or not the kiln would draw more amps at 208v.

Have you called them or just sent an email? Give them a call, call them again, etc. 

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Ebay . There are transformers that would raise 208 to 240. Cost about  $1000.  new elements cost?

It's not hard to wind your own . KANTHAL wire and some time..

Getting the correct wire size is a calculation that might be tricky but doable.

BTW have you asked your electrical distributor if they can hook you up for 240 ? When I drew so much juice that my neighbors lights dimmed my supplier put a transformer specially for me.

 

 

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40 minutes ago, rondoc said:

Ebay . There are transformers that would raise 208 to 240. Cost about  $1000.  new elements cost?

It's not hard to wind your own . KANTHAL wire and some time..

Getting the correct wire size is a calculation that might be tricky but doable.

BTW have you asked your electrical distributor if they can hook you up for 240 ? When I drew so much juice that my neighbors lights dimmed my supplier put a transformer specially for me.

I guess my idea here is to figure out the simplest and lowest cost way to get into cone 6 territory. A the cost of a transformer and installation seems like it would cost way more than installing new elements. Of course, another idea which might be the easiest would be to find a second hand kiln on CL or FB marketplace that was set up for 208v in the first place... I've seen some decent looking kilns go for under 300.

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2 hours ago, Hope_Street_Clay said:

I guess my idea here is to figure out the simplest and lowest cost way to get into cone 6 territory. A the cost of a transformer and installation seems like it would cost way more than installing new elements. Of course, another idea which might be the easiest would be to find a second hand kiln on CL or FB marketplace that was set up for 208v in the first place... I've seen some decent looking kilns go for under 300.

My vote is change the elements to 208 volt maintaining at least 9600 watts (32736 btuh) which is the energy you need to heat this kiln and offset the shell losses. Go to the 60 amp breaker and pull new wire as necessary. 9600 watts is not a whole bunch and again brand new kilns are only designed at about 110% capacity. Running the kiln at 208v is currently a bit over 13% reduction in wattage (Prox. 8300 watts) which we already know is not working for you.  No surprise, it’s like running a kiln with elements worn beyond 10%. New kilns on the right voltage only fire 100–150 times before they lose that 10% and just don’t fire to cone with less power. If you could easily insulate the shell then this all could be done with less energy and probably left as is, but as of yet there is no good easy way to do that in my experience.

Edited by Bill Kielb
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48 minutes ago, Bill Kielb said:

My vote is change the elements to 208 volt maintaining at least 9600 watts (32736 btuh) which is the energy you need to heat this kiln and offset the shell losses. Go to the 60 amp breaker and pull new wire as necessary. 9600 watts is not a whole bunch and again brand new kilns are only designed at about 110% capacity. Running the kiln at 208v is currently a bit over 13% reduction in wattage (Prox. 8300 watts) which we already know is not working for you.

If it pulls 40 amps on 240 volts, it's going to pull about 34.6 amps, 7210 watts on 208 volts with those same elements. On 208 volts with a 40 amp draw it'll produce 8300 watts, but it's not pulling a full 40 right now.

If you math out the element resistance shown on the wiring diagram it's actually pulling 10,000 watts.

@Hope_Street_Clay Don't do anything until you find out from Paragon if they have 208 volt elements for this kiln, and what the actual amperage draw will be. Hopefully they do keep the same wattage, because it would be a bit underpowered if not.

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6 hours ago, neilestrick said:

it pulls 40 amps on 240 volts, it's going to pull about 34.6 amps, 7210 watts on 208 volts with those same elements. On 208 volts with a 40 amp draw

Maybe I said this incorrectly but thermodynamically it’s super important. My vote is change the elements, make sure that the 208v elements are rated the same wattage as what you have currently, (whatever that is) to make sure it performs as expected.

The example would be a 10000w kiln where the elements have gone up in resistance from a starting point of 5.76 ohms to 6.336 ohms or 10%. The kiln now cannot make cone quick enough and we suggest changing the elements. This worn kiln is only supplying 9090 watts (an approx 9% drop btw) and it don’t work no more.

Hopefully Paragon will do the math and realize there are 10000w of elements in there, correct their drawing and suggest 10000w Of 208v elements.

Unfortunately producing 10000w of heating at 208 volts will be about 48 amps. If not, and they suggest something around 9000 w or less at 208v, then I would NOT expect it to work well at cone 6.

I would be sure to point out the error in the diagram, it appears this is a 10000w kiln, not 9600 w but also measure what you have in the kiln because we really don’t know what is in error. It’s possible this kiln works well at 9600 w and that’s what we should match. 
………………………….whatever the wattage is new, match it for the same heating performance.

Edited by Bill Kielb
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As I use a Silicon Carbide element that changes resistance with temperature and life I built a very simple power controller. This has the advantage that provided you have high enough voltage then you can get the power you need. The controller has 16 levels so I start at 1 level and as kiln temp rises I just up the level to maintain the slope I want. I use J-K Thermocouples and a Fluke digital meter. I also put in cones so I can be sure. I have used this setup for 35 years with no problems. I fire to cone10 . I have another kiln that I fire to about cone 20 for making structural parts. Also SiC element. For any new kiln I would consider MOSI elements as they will accept a reduction atmosphere. Kanthal is a great wire but not for a custom built kiln. Using the SiC element means no grooves etc so inside is just plain 2600 board.. I am happy to share my experience with anyone.

RdoctorsAAAGMAIL.COM

 

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As far as transformers go it is possible and electrically ok to use a welding transformer. They put out about 40 volts. Many older welders are simply dumped or sold for peanuts for their copper.

Problem is that shipping costs are high due to their weight. I do have access to them should anyone want to pursue this.

 

 

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