Need advice on electrical for new used Bailey kiln - extension cable or no?

[Msheffield]

Hi you all, I just purchased a used Bailey PL-2327, 240 V, 48 AMP, single phase kiln in good condition. It has a 3-prong dryer plug, and I'm currently wired for a 4-prong dryer plug. I'm going to upgrade my breaker from 50 to 60 amps, and the wire going from my switch box to the outlet is 8-gauge, so hopefully that's enough. 

Part of my debate is whether to use an 8-gauge cable going from my house kiln outlet up to my barn so that I could have it up there, but I've always heard not to use an extension cord because of power loss over distance and possible fires? My dad is wondering why it wouldn't work if the electric wires coming into the switch box are already traveling a distance from the telephone pole. I already seem to be having some voltage loss at the outlet (113-ish instead of 120), which I'm going to investigate, but I definitely don't want to make it worse than that. This kiln is double-insulated, so even with some lower voltage, I think it will still do better than my other kiln. 

Another question is whether to try to replace the 3-prong plug with a 4-prong, since I've read that's safer, or to get a 3-to-4 prong adaptor. I do have a spare 4-prong dryer plug which I could potentially hook up to the kiln, but it is 8-gauge, and the existing kiln plug is 6-gauge. The kiln is rated to Cone 10, but I plan to use it for 5/6 since my clay and glazes are that temp. 

Any thoughts are much-appreciated! 

 

EDIT: It is actually 43 amps,  not 48. I misread the plate. 

Edited July 28 by Msheffield

[neilestrick]

To meet code the kiln will need to be on a 60 amp breaker. It will need 6 gauge wire. Smaller wire will be a fire hazard. No extension cord, no adapter- neither is safe to use with a kiln.  Swap out the outlet for a 3 prong. Definitely check out the voltage drop issue. Getting 226 volts instead of 240 is a really big deal for a kiln. The added insulation isn't going to make such a big difference that a large voltage drop won't have an effect.

[HenryBurlingame]

For continuous loads a breaker has to be rated for 125% of the continuous load. So you have to use a 60 amp breaker for your 48amp kiln. A 50amp breaker would probably trip. While 8awg wire can technically handle 50amps, changing the breaker to 60 amp without upgrading the wire to 6awg would not be to code and would be a fire hazard as Neil said.

It sucks to upgrade the wiring, but you HAVE to do it. I just upgraded from 6awg to 4awg in my studio for a new kiln and right now copper wire prices are through the roof and they are going up every week. My local hardware store had to put fencing around the wire area and now keeps it under lock and key. Total for just materials cost me over $10/ft and I had to run it around the side of our house and out to our barn omg lol.

[Msheffield]

7 hours ago, neilestrick said:

To meet code the kiln will need to be on a 60 amp breaker. It will need 6 gauge wire. Smaller wire will be a fire hazard. No extension cord, no adapter- neither is safe to use with a kiln.  Swap out the outlet for a 3 prong. Definitely check out the voltage drop issue. Getting 226 volts instead of 240 is a really big deal for a kiln. The added insulation isn't going to make such a big difference that a large voltage drop won't have an effect.

Thanks for your input Neil! I misread the plate--it's actually 43 amps. I had seen the newer model online as being 48 amps. Does that change anything, or would you still recommend going to 6-gauge and a 60 amp breaker? 

[Msheffield]

5 hours ago, HenryBurlingame said:

For continuous loads a breaker has to be rated for 125% of the continuous load. So you have to use a 60 amp breaker for your 48amp kiln. A 50amp breaker would probably trip. While 8awg wire can technically handle 50amps, changing the breaker to 60 amp without upgrading the wire to 6awg would not be to code and would be a fire hazard as Neil said.

It sucks to upgrade the wiring, but you HAVE to do it. I just upgraded from 6awg to 4awg in my studio for a new kiln and right now copper wire prices are through the roof and they are going up every week. My local hardware store had to put fencing around the wire area and now keeps it under lock and key. Total for just materials cost me over $10/ft and I had to run it around the side of our house and out to our barn omg lol.

Dang, I know, the wire is ridiculous! Thanks for your confirmation. I misread the kiln plate, and it's actually only 43 amps, which is not a huge difference, but I wonder if that would mean I don't have to upgrade. 

[Hulk]

The online wire calculators I'm seeing all spec #6 for 43 amps continuous - even a short run, e.g. ten feet

I'm curious what the wire experts will recommend for 43 amp rated kiln.
How long a run in feet?

I pulled 6-3
The kiln doesn't require it (three wires only), however, if ever in future something did require 120v, the spare/extra wire is there*.
The vendor** price is less now, $3.86/; it was $4.10/ft.
We bought sixty feet. The shipping was $30.60

Their price on #4 ("#4-3C THHN-PVC Tray Cable with Ground") is $5.59 today

*We had to rewire our son's wellhouse to run the 120v UV appliance.
We put in a light and an outlet while we were at it.
The 240v well pump requires three wires only. Half the run had four wires, half did not. We weren't happy.

** Wire & Cable Your Way: Electrical Wire By the Foot (wireandcableyourway.com)

[Bill Kielb]

3 hours ago, Msheffield said:

Dang, I know, the wire is ridiculous! Thanks for your confirmation. I misread the kiln plate, and it's actually only 43 amps,

I see 48 amps for the round 2327, so I believe 48 amps is correct. Breaker sizing: 125% minimum breaker is a 60 amp breaker, 150% maximum is a 72 amp breaker. So 60 amp breaker. Wire sizing is limited by terminal temperature. Breakers terminals are rated 75c these days so a number 6 - 75c or greater appears to fill the bill. The ampacity is limited by the 75c column. Using heavier gauge wire is really good practice  if for no other reason to minimize voltage drop and maximize heating in your kiln rather than heating in your wires.

Cone art used to make these kilns for Bailey - your circuit diagram is likely http://coneartkilnsshop.com//wp-content/uploads/Wiring_Diagrams/pottery/BXGX_2327D_1240rev21Aug23.pdf

Bailey specs I found on their website  below.

 

Edited July 28 by Bill Kielb

[Dick White]

There is some confusion between 43 and 48. Maybe the stamped "8" looks like a "3"? To confirm, what is the wattage listed on the plate. Ohms Law math will indicate the correct amperage.

[Msheffield]

9 hours ago, Hulk said:

The online wire calculators I'm seeing all spec #6 for 43 amps continuous - even a short run, e.g. ten feet

I'm curious what the wire experts will recommend for 43 amp rated kiln.
How long a run in feet?

I pulled 6-3
The kiln doesn't require it (three wires only), however, if ever in future something did require 120v, the spare/extra wire is there*.
The vendor** price is less now, $3.86/; it was $4.10/ft.
We bought sixty feet. The shipping was $30.60

Their price on #4 ("#4-3C THHN-PVC Tray Cable with Ground") is $5.59 today

*We had to rewire our son's wellhouse to run the 120v UV appliance.
We put in a light and an outlet while we were at it.
The 240v well pump requires three wires only. Half the run had four wires, half did not. We weren't happy.

** Wire & Cable Your Way: Electrical Wire By the Foot (wireandcableyourway.com)

I think I need something like 10-16 feet of wire. I'm tempted to just install a 60 amp breaker in a new slot and put the kiln right on the other side of the wall that contains the breaker box... It would be inside the house, but it came with a vent, so I could just run it a short distance outside. 

When you say you pulled 6-3, what do you mean? That you originally had 6-3 or went to it? 

[Msheffield]

8 hours ago, Bill Kielb said:

I see 48 amps for the round 2327, so I believe 48 amps is correct. Breaker sizing: 125% minimum breaker is a 60 amp breaker, 150% maximum is a 72 amp breaker. So 60 amp breaker. Wire sizing is limited by terminal temperature. Breakers terminals are rated 75c these days so a number 6 - 75c or greater appears to fill the bill. The ampacity is limited by the 75c column. Using heavier gauge wire is really good practice  if for no other reason to minimize voltage drop and maximize heating in your kiln rather than heating in your wires.

Cone art used to make these kilns for Bailey - your circuit diagram is likely http://coneartkilnsshop.com//wp-content/uploads/Wiring_Diagrams/pottery/BXGX_2327D_1240rev21Aug23.pdf

Bailey specs I found on their website  below.

 

That was what initially confused me as well--the modern TL-2327 model DOES use 48 amps. The seller bought my kiln in the 90's and said the model was "PL"-2327, so that's something I need to confirm with Bailey. I calculated though that even if my kiln does pull 43 amps, 125% is still 53.75 amps, and I probably still have to upgrade. 

[Msheffield]

4 hours ago, Dick White said:

There is some confusion between 43 and 48. Maybe the stamped "8" looks like a "3"? To confirm, what is the wattage listed on the plate. Ohms Law math will indicate the correct amperage.

That was my intial thought, that it just looked like a 3. But the wattage is 10.3 kw, and my electrician neighbor came over yesterday and calculated that as 52.5 amps. He seemed to think my current setup would be okay for the new kiln, but I wanted to check with you guys since you have a history working with kilns specifically. 

[PeterH]

18 hours ago, neilestrick said:

Getting 226 volts instead of 240 is a really big deal for a kiln.

To emphasize Neil's point.

Power is V^2/R

Supplying 226V rather than 240V  reduces the power to (226/240)^2 = 88.7% of its original/design value.

For comparison, elements are usually swapped out when their resistance increase by 10%, which reduces the power to 1/1.1 = 90.9% of its original/design value. So a >10% loss of power would be a really big deal.
 

[Bill Kielb]

5 hours ago, Msheffield said:

That was my intial thought, that it just looked like a 3. But the wattage is 10.3 kw, and my electrician neighbor came over yesterday and calculated that as 52.5 amps. He seemed to think my current setup would be okay for the new kiln, but I wanted to check with you guys since you have a history working with kilns specifically. 

Hmm, just reading the voltage issue here. All above are right, losing approximately 10% of your capacity means you likely can’t make cone 6 at a speed that works or without a controller error. Since this is a double insulated kiln it is very likely a cone art design. Tucker used conventional IFB backed by a medium density fiber which performed like 3” IFB or maybe a bit better. Kilns require a certain amount of thermal energy to make cone effectively based on their interior surface area and losses or ….. shell losses. The 2327 size at cone art has always been an 11.5 kw kiln to my knowledge so 10.3 kw seems odd and double insulated or not represents an approximate 10% or greater reduction from design energy requirements given the interior size and losses. So it would seem something is amiss here and already under powered for cone 6 operation with 10.3 kw.

226 volts vs 240 volts is also a bit odd (especially if measured unloaded) but puts you in this 10% reduced power range so it seems amiss as well. I would check this with another meter for sure, just seems very odd and inconsistent for mains voltage.

only way to know the actual wattage is to measure the total resistance and apply ohms law with the true operating voltage. Using the design voltage and design resistance gives the design wattage which can be compared with the actual. Generally if 10% low, it’s not gonna work as designed.

Home circuit breakers are made to only be loaded 80% max for cooling reasons, so hopefully your electrician knows this. Kilns present a special type of load called a continuous load that can operate continuously for three hours or more. Hence the 125% minimum breaker requirement (the reciprocal of 80% is 125%) a 50 amp off the shelf breaker can only be loaded to 40 amps before exceeding its 80% restriction to keep it reasonably cool. A 60 amp breaker can only be loaded to 48 amps to keep it reasonably cool

I mention because some of this is new to electricians or specific to kilns so hopefully helpful. Often rule of thumb voltage drop allows 3% as acceptable. I suggest 1% or less because most kilns need all the power they can get. Watts lost in the wire - heat the wire - not the kiln. Brand new, most kilns are designed with about 110% capacity meaning don’t skimp on wire size even for short runs and especially for long runs.

Grounding requirements: Your kiln ought to use two hot wires and one ground (no neutral). The grounding requirement for 60 amps is no 10 copper. So if in raceway, 2-#6 & 1-#10 ground wire (all copper). NEC ground wire table requirements:  http://wiresizecalculator.net/tables/groundconductortable.htm

My thought is - none of this seems quite right or ok and needs some research to sort it out. The wire to the barn very likely needs to be #4 copper if any length at all.

I suggest: post a picture of the kiln information tag, kiln lid and kiln interior. Tucker (cone Art) has always had a unique lid lifter design as well as an element routed into  the floor of most models.

 

 

Edited July 29 by Bill Kielb

[neilestrick]

There were a lot of 43 amp, 7 cubic foot kilns made in the past, so not terribly unusual. It may only be rated for cone 8, though. Still need a 60 amp breaker, and still need to deal with the voltage drop issue.

[Hulk]

"When you say you pulled 6-3, what do you mean?"

Sorry,
pulled == installed
as in pulled through the various walls, conduit, et cetera into final installed position.

I'm not seeing where #8 would be sufficient, was curious what the expert members would recommend.
My kiln requires the three wires only.
We ordered higher quality cable at less $/foot from the vendor indicated, (which at least one other Forum regular had also noted within the last year or so).

[Bill Kielb]

6 hours ago, Hulk said:

was curious what the expert members would recommend

Copper wire - 2 #6 & a #10 equipment ground he must use 75c terminal limit and at least 75c wire. Anything of length then likely 2-#4 & a #10 equipment ground - copper, qualified above. Suggest figure out low voltage and actual kiln rating as well.

Edited July 29 by Bill Kielb

[Msheffield]

I am definitely going to upgrade the breaker and wiring, and I'll work on figuring out the voltage issue in the process. I'll plan to keep it on the back porch rather than running #4 or #6 up to the barn, since that would cost a ton and be tricky. Thank you all so much for your input! I really appreciate it

Here's the kiln spec plate: 

 

[Bill Kielb]

Hmm, definitely a cone art kiln (says so). Definitely marked cone 10& 10.3 Kw @240 Volts. Still curious about the lid and bottom element. I believe Tucker added the bottom element to many of his kilns to improve performance.

43 amps - Minimum breaker size 1.25 X 43 = 53.75 amps, max breaker 1.5 X 43  = 64.5 amps, so 55 Amp breaker minimum. And 60 amp maximum. 60 A likely best choice especially if upgraded to today’s elements assuming they fit. ( another reason it would be nice to know if the bottom element was added since)

This is old so I would say likely 60c terminal design or 75 c max so # 6 (copper) regardless and the speculation - this kiln now days is likely 48 amp element set so it probably needs that energy to get a decent cone 10 rating and longevity. Replacement with the new higher wattage elements likely desirable anyway, so I would design this to accommodate for the near future …… wherever the placement ends up.

I think you need to figure out the out of tolerance voltage regardless. If it is  low at the mains you are starting off at about a 10% deficit. Hopefully just a bad meter used to measure, but could indicate a poor connection or worn main breaker or even  overhead splice going bad somewhere along the way. Should be able to spot it with a non contact infrared along the way or this should be easy for an electrician to track down.

I think I would treat it as if it will someday be a 48 amp kiln. Cone art is still in business, a call or email could clarify your options.

Edited August 1 by Bill Kielb

[Mark C.]

50 or 60 amps =#6 copper wire. Better to be safe

25% upgrade for safety- continuous load

[Msheffield]

1 hour ago, Bill Kielb said:

Hmm, definitely a cone art kiln (says so). Definitely marked cone 10& 10.3 Kw @240 Volts. Still curious about the lid and bottom element. I believe Tucker added the bottom element to many of his kilns to improve performance.

43 amps - Minimum breaker size 1.25 X 43 = 53.75 amps, max breaker 1.5 X 43  = 64.5 amps, so 55 Amp breaker minimum. And 60 amp maximum. 60 A likely best choice especially if upgraded to today’s elements assuming they fit. ( another reason it would be nice to know if the bottom element was added since)

This is old so I would say likely 60c terminal design or 75 c max so # 6 (copper) regardless and the speculation - this kiln now days is likely 48 amp element set so it probably needs that energy to get a decent cone 10 rating and longevity. Replacement with the new higher wattage elements likely desirable anyway, so I would design this to accommodate for the near future …… wherever the placement ends up.

I think you need to figure out the out of tolerance voltage regardless. If it is  low at the mains you are starting off at about a 10% deficit. Hopefully just a bad meter used to measure, but could indicate a poor connection or worn main breaker or even  overhead splice going bad somewhere along the way. Should be able to spot it with a non contact infrared along the way or this should be easy for an electrician to track down.

I think I would treat it as if it will someday be a 48 amp kiln. Cone art is still in business, a call or email could clarify your options.

Oh right, I forgot about those--there is an element on the floor, yes, and I'll have a look at the lid in the morning. 

Good to know about the terminal and the higher new element rating. Definitely upgrading the breaker. 

Yeah, my voltimeter is a cheap one, but I also know I'm getting low voltage because my current kiln is firing very slowly in spite of a change in elements not super long ago. I've checked and cleaned all connections, and it's still having trouble, so I'm suspecting something with the outlet wiring. 

[Bill Kielb]

7 hours ago, Msheffield said:

Oh right, I forgot about those--there is an element on the floor, yes, and I'll have a look at the lid in the morning. 

 

It’s definitely a cone art (no question about that anymore)  - so hopefully you have the element routed in the floor from a replacement aspect.

[Msheffield]

Hi you all, just an update (after a long hiatus of not doing pottery or getting anything wired up) that I think I figured out my problem with my older kiln. I tested the voltage this morning, and it was 238 or 239 instead of 240 (but up from 226 some months ago--maybe a summer voltage drop I've read about??). Then I opened the outlet box and the back part was disconnected and crumbling, and you can see the burn marks on the wires. I will go get a new outlet box today, but my question is whether or not I need to replace the wires, or if there is something I can wrap them with (electrical tape??), or if there is anything I should take into consideration. My dad suggested that I get a 60 amp outlet box rather than the current 50, just to be safe. 

I still want to wire up the bigger cone art kiln, but for the sake of time, I want to get the little paragon functional again in the meantime. 

 

 

[neilestrick]

At the very least those wires need to be cut back to fresh copper. But if it we my I'd pull all new wires. No need to get a 60 amp outlet, as the kilns aren't going to pull anywhere near 50. The issue here is simply corrosion and/or age.

[Msheffield]

Thanks Neil! Yes, the outlet box is 55 years old, so makes sense it would wear out. If I'm about to rewire with 6 gauge wire for the bigger kiln, do you think I could just cut back these wires and use as-is for a few firings? 

[Msheffield]

Also, my dad just noted that the wire is actually aluminum but connected to copper fittings, and he was thinking maybe that was a bad combo? I have no idea. But when I get the new wires, should I get copper?