Need help troubleshooting heat treat oven

K

KracknCorn

Joined
Mar 29, 2010
Messages
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The problem I'm having is my heat treat oven trips a 50amp breaker at 1900f degrees. Using a 230v outlet and a single 18.5ohm 18gauge kanthal wire. I should only be drawing 12.43amps. Everything seems work until it gets into 1800 to 1900 degrees. I don't see any shorts or exposed wires. Anyone have any idea what could causing the problem?

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Interesting
I'm assuming that if the oven is operating for that length of time to get to temp it isn't likely to be a dead fault but more likely a overcurrent fault.

12.43 amp (2858 watts) x 125% = 15.53 amps and within the 80% usage of a 20 amp breaker so a 50amp should be no problem

( I run 13.6 amps(3130 watts) on a 20 amp breaker with no issues)

1. if you have access to a amp probe you can measure the current and monitor while you bring the oven to temp to see if you remain within target amps or you catch a high current spike.

2. If it remains within your target amps and the breaker goes in trip you might want to change breakers.

3. There is a possibility you have a high current fault.phase to phase or phase to ground somewhere.

a. Either in one of the relays itself.

b. or somewhere between the frame and the load side wires going to the element.

c. possibly a carbon track in the terminal block at the element

That's everything I would do faced with the same problem.
 
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Jax really answered that well.


Is the "single 18.5ohm 18gauge Kanthal wire." measured or calculated ?
If it's calculation based on wrong wire dia or length would do it.


Weak breaker is all I can think of and verifying with an amp clamp meter is a great test first.
 
My educated "guess" would be a weak trip sensor in the present breaker. But I hate giving people suggestions without facts/proof and tell them to just throw parts/money and a problem and be wrong. I'd rather give you the tools/knowledge and let you verify it through test and find the source of the problem without buying a pile of parts you don't need.
 
I talked to a master electrician and he said it might be because the outlet has 8 gauge wire from breaker to outlet, but he wasn't there to inspect. The continuous load is probably what is causing the tripping because of the built up heat, but it can still be a weak breaker. Gonna change out the wire to 6 gauge and see if it fixes the problem. Thanks for the suggestion guys, i'll let you guys know if it works and help anyone else that has this problem.
 
Assuming your posted info is correct and the oven draws about 20 amps:
8 gauge wire doesn't even get to 50% load rating at 20 amps. It is rated for 40-50 amps at 125°F ( depending on wire type). At 20 amps it should not even get warm, much less near the 195°F that it is rated up to. Also, current capacity increases as the wire warms up.
6 gauge will handle 55 to 65 amps at 125°F - depending on whether solid (65) or stranded (55).

Perhaps you need to talk to a different "Master Electrician".
 
KracknCorn said:
I talked to a master electrician and he said it might be because the outlet has 8 gauge wire from breaker to outlet, but he wasn't there to inspect. The continuous load is probably what is causing the tripping because of the built up heat, but it can still be a weak breaker. Gonna change out the wire to 6 gauge and see if it fixes the problem. Thanks for the suggestion guys, i'll let you guys know if it works and help anyone else that has this problem.
Click to expand...

The load is heavier when starting not while maintaining or increasing temperatures at the/to the set point, the oposite of what you are experimenting.
Think of it like a car, it takes more power to cold start than to keep moving. If it trips when hot, and the cables all the way to the breaker are the gauges you described, its probably the breaker...

Pablo
 
KracknCorn said:
I talked to a master electrician and he said it might be because the outlet has 8 gauge wire from breaker to outlet, but he wasn't there to inspect. The continuous load is probably what is causing the tripping because of the built up heat, but it can still be a weak breaker. Gonna change out the wire to 6 gauge and see if it fixes the problem. Thanks for the suggestion guys, i'll let you guys know if it works and help anyone else that has this problem.
Click to expand...
I"ve been a industrial electrician 40 plus yrs , specifically in industrial controls over 20 yrs and hate to question another tradesman.. As already intentioned 8 gauge is rated at 40 amps over twice the amperage of your oven. I really doubt that is your problem. In reality your oven should easily run on 20 amp breaker and 12 gauge wire and that's rated at 125% for continuous load and right at 80% of the rated capacity of the breaker.

Not to mentio, replacing with #6 wire depending on length to find out you need a breaker might be a pricey little adventure.

good luck.
 
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That kinda sucks, cause I already bought 30ft of 6ga wire that I can't return. So you guys think the breaker is the problem, can you guys recommend a breaker? I have this one

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You’ll have to get a breaker that matches your box. GE breakers only fit in GE breaker boxes. Same for Westinghouse and square d. Take your old breaker to the store with you and they can match it up to the one you need if you’re unsure.
 
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KracknCorn said:
That kinda sucks, cause I already bought 30ft of 6ga wire that I can't return. So you guys think the breaker is the problem, can you guys recommend a breaker? I have this one

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As I mentioned in a earlier post I gave you trouble shooting advice to determine the source of the problem first to avoid buying a pile of parts you don't need and can't return.

I guess it's up to you now how you want to approach it now that you bought wire you can't return.

1. you can follow your master electricians advice and replace the wire and test your oven and his theory.

2..You can buy a new breaker( or use the one you have if it fits your panel) leaving the old wire and test the oven

3. you can replace the breaker and the wire and test the oven.

Basically now your just throwing parts and the problem until something works.
 
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Jax knives said:
Interesting
I'm assuming that if the oven is operating for that length of time to get to temp it isn't likely to be a dead fault but more likely a overcurrent fault.

12.43 amp (2858 watts) x 125% = 15.53 amps and within the 80% usage of a 20 amp breaker so a 50amp should be no problem

( I run 13.6 amps(3130 watts) on a 20 amp breaker with no issues)

1. if you have access to a amp probe you can measure the current and monitor while you bring the oven to temp to see if you remain within target amps or you catch a high current spike.

2. If it remains within your target amps and the breaker goes in trip you might want to change breakers.

3. There is a possibility you have a high current fault.phase to phase or phase to ground somewhere.

a. Either in one of the relays itself.

b. or somewhere between the frame and the load side wires going to the element.

c. possibly a carbon track in the terminal block at the element

That's everything I would do faced with the same problem.
Click to expand...

So if I measure a current spike, what could be causing it and is there a way to fix it?

Is there a way to test the relays?
 
There is a funny coincidence here. On of the ladies at work has had her lights go out in her condo about weekly for a while. She would turn off all the breakers and turn them all on and it would be fine ... until the next time. The management people sent out electricians twice. One said the place was wired with the wrong wire and that was tripping the breakers (totally bogus). The other said the new microwave was bigger than the old one and that was the problem (it is a 1200 watts unit on a 20 amp circuit, and has been working fine for a year). I told her how to tell which breaker was the one tripped, and to have the electrician change the breaker. Problem solved.
 
KracknCorn said:
So if I measure a current spike, what could be causing it and is there a way to fix it?

Is there a way to test the relays?
Click to expand...
Explained in my very first post.

Measuring the current/amps of your oven will point you toward the direction of the problem. If the amperage reading is constant and within range and your breaker is trippinng, obviously the breaker needs replaced.

If the amperage is high and way over the projected amp or is spiking at high amps and breaker is trippong your problem is likely to be somewhere in the oven

I was just giving you a guide /option to test to confirm your problem. I didn't want to tell you to go buy a breaker even tho that's my educated guess. I'm not there to test and confirm that.
 
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Stacy E. Apelt - Bladesmith said:
There is a funny coincidence here. On of the ladies at work has had her lights go out in her condo about weekly for a while. She would turn off all the breakers and turn them all on and it would be fine ... until the next time. The management people sent out electricians twice. One said the place was wired with the wrong wire and that was tripping the breakers (totally bogus). The other said the new microwave was bigger than the old one and that was the problem (it is a 1200 watts unit on a 20 amp circuit, and has been working fine for a year). I told her how to tell which breaker was the one tripped, and to have the electrician change the breaker. Problem solved.
Click to expand...
I see that all the time. A microwave not on its own dedicated circuit combined with a lighting or receptical load eventually weakening a breaker and over the 80% capacity of the.breaker.
 
Yeah we had a breaker keep tripping and it was faulty. Breakers do get weak over time.
 
Seems odd for a breaker to go bad after 2 yrs. Yah, I just bought a replacement breaker from amazon and see if anything changes. If it doesn't, i'll just return it.
 
Ha, I’ve had a breaker go bad on one of our grain bin motors after a few days. Never underestimate the shoddy craftsmanship of a lot of today’s products.
 
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