Kiln Circuit

[mbrooke]

What circuit and breaker size would a 17.8 amp 240 volt kiln need? #12 with a 20 amp breaker? .............

 

[electrofelon]

It depends on if it is a continuous load. I used to doubt that they were continuous loads, but last time this came up I talked to a potter friend and I now would consider it continuous. In that case, I would go 10 on a 30.

 

[LarryFine]

. . . I would go 10 on a 30.

That's what I'd do. In my opinion, #12 would get too warm.

Almost exactly the same situation as a 4500w water heater.

 

[mbrooke]

That's what I'd do. In my opinion, #12 would get too warm.

Almost exactly the same situation as a 4500w water heater.

Warm isn't hot though.

 

[mbrooke]

It depends on if it is a continuous load. I used to doubt that they were continuous loads, but last time this came up I talked to a potter friend and I now would consider it continuous. In that case, I would go 10 on a 30.

Anything explicit in the NEC? I swear that you would be correct code wise.

 

[infinity]

Anything explicit in the NEC? I swear that you would be correct code wise.

Depends on whether or not the load is at its maximum current level for at least 180 straight minutes. If it cycles off or to a lower current level at any point in that 3 hours it is not a continuous load.

Continuous Load. A load where the maximum current is expected to continue for 3 hours or more.

 

[GoldDigger]

Depends on whether or not the load is at its maximum current level for at least 180 straight minutes. If it cycles off or to a lower current level at any point in that 3 hours it is not a continuous load.

And a kiln coming up to its set temperature is quite likely not to cycle off at any point during that stage of operation. If a kiln has a thermostat rather than being manually controlled (using melting cones next to the pottery to determine when the desired temperature has been reached and then turning the kiln off completely to cool slowly), it is still not likely to cycle while the temperature is on the way up, at least during some parts of the increase program.

Firing Electric Kiln | Instructions, Tips and Issues

Firing Electric Kiln (Oxidation) - electronically and kiln sitter models with bisque and glaze firing - how to, tips and knowledge sharing

www.lakesidepottery.com

 

[infinity]

And a kiln coming up to its set temperature is quite likely not to cycle off at any point during that stage of operation. If a kiln has a thermostat rather than being manually controlled (using melting cones next to the pottery to determine when the desired temperature has been reached and then turning the kiln off completely to cool slowly), it is still not likely to cycle while the temperature is on the way up, at least during some parts of the increase program.

Firing Electric Kiln | Instructions, Tips and Issues

Firing Electric Kiln (Oxidation) - electronically and kiln sitter models with bisque and glaze firing - how to, tips and knowledge sharing

www.lakesidepottery.com

Would it take more than 3 hours to reach the proper temperature?

 

[GoldDigger]

It certainly could.

 

[Dennis Alwon]

A water heater doesn't need 3 hours to get to temp. and it is considered continuous. My understanding is if there is an electric element than we need to consider 125%.

 

[infinity]

A water heater doesn't need 3 hours to get to temp. and it is considered continuous. My understanding is if there is an electric element than we need to consider 125%.

That is because the NEC specifically requires that for a hot water heater. A kiln would need to be specifically required also if the intention was to add the 25%.

 

[electrofelon]

Would it take more than 3 hours to reach the proper temperature?

My Potter friend said it would. Of course, it likely varies from kiln to kiln.

 

[LarryFine]

Even if you went with a 20a breaker, I'd want #10 so more heat is generated in the kiln, and less in the wire.

 

[petersonra]

It depends on if it is a continuous load. I used to doubt that they were continuous loads, but last time this came up I talked to a potter friend and I now would consider it continuous. In that case, I would go 10 on a 30.

I don't see how it will ever be over 20 Amps. The silliness over continuous and non-continuous loads ought to go away.

What is the point of making the wire bigger because the load is "continuous"?

 

[electrofelon]

I don't see how it will ever be over 20 Amps. The silliness over continuous and non-continuous loads ought to go away.

What is the point of making the wire bigger because the load is "continuous"?

I mostly agree with you that the continuous load thing is silly. At least, I would think the time should be shorter than 3 hours. If we are worried about heat, you are going to have that heat in a lot less than three hours. Three hours seems like a long time.

OTOH, I have dont some grows where there is a full panel with every breaker operating at 80%, and it gets alarmingly hot. I think they would start tripping with 100% amps. Seems like maybe it is a bad design and there should be space between breakers and/or vents in the cabinet.

 

[mbrooke]

I mostly agree with you that the continuous load thing is silly. At least, I would think the time should be shorter than 3 hours. If we are worried about heat, you are going to have that heat in a lot less than three hours. Three hours seems like a long time.

OTOH, I have dont some grows where there is a full panel with every breaker operating at 80%, and it gets alarmingly hot. I think they would start tripping with 100% amps. Seems like maybe it is a bad design and there should be space between breakers and/or vents in the cabinet.

Minus lighting panels you have load diversity.

 

[petersonra]

I mostly agree with you that the continuous load thing is silly. At least, I would think the time should be shorter than 3 hours. If we are worried about heat, you are going to have that heat in a lot less than three hours. Three hours seems like a long time.

OTOH, I have dont some grows where there is a full panel with every breaker operating at 80%, and it gets alarmingly hot. I think they would start tripping with 100% amps. Seems like maybe it is a bad design and there should be space between breakers and/or vents in the cabinet.

I don't know how warm "alarmingly" is. But TM breakers can get very warm before they trip. It can be uncomfortable to the touch kind of warm.

 

[Dennis Alwon]

Some kilns are called continuous kiln however here is the specs for an electric kiln. The amps is 39.4 multiply by 1.25 and you bet 49 amps-- hence a #6 and a 50 amp breaker.

Electrical Requirements
240 Volts 39.4 Amps 9460 Watts
208 Volts 40.0 Amps 8320 Watts
Copper Wire Size: 6
Breaker Size: 50
NEMA Receptacle Configuration: 6-50

 

[mbrooke]

Some kilns are called continuous kiln however here is the specs for an electric kiln. The amps is 39.4 multiply by 1.25 and you bet 49 amps-- hence a #6 and a 50 amp breaker.

#8 wire, 40 amp breaker, 0.375Ω max loop.

 

[LarryFine]

I wired pair of kiln circuits for an artist last year, one 30a on #10 and one 50a on #6. Breakers can be replaced easier than wire.