blowing breakers

[Marty Kremer]

My homemade fusing kiln keeps blowing a breaker. It's been fine for about 8 years of steady use but is getting cranky. I swapped out the thermocouple and the controller (no change) and the relay is only a year old. My hope is that the breaker is faulty but I think it's the elements- does the resistance increase with use/age?

[Steve Stadelman]

Check to see if corrosion at the heater entries into the heating chamber is causing occasional shorts or something along those lines, also check any and all electrical connections. Have you been using the breaker as a switch? shutting the kiln on and off when not in use?

[Victor Chiarizia]

check the breaker itself. i had one go bad. after removal from the panel, smack the breaker in your hand. it should not go to the off position. old electrician tole me so. v

[Ben Rosenfield]

This may sound silly, but you may wish to check all of the screw terminals in your breakers. Changes in temperature can loosen the connections and allow the incoming wiring to shift and slip out.

[Mike Aurelius]

If the load on the circuit is greater than 80% of the rating of the breaker, then it is possible that the breaker itself is failing.

All of the above will increase the resistance, and hence the load.

Check to see if the breaker itself is warm or hot.

Hang an ammeter on the circuit to check your load.

I'd double check all connections, clean and retighten, and if the breaker continues to trip, replace the breaker.

[Rosanna Gusler]

like they said. i had one go wimpy on me. it felt different to turn on/off than the others. rosanna

[Dave Hilty]

Originally posted by Mike Aurelius
If the load on the circuit is greater than 80% of the rating of the breaker, then it is possible that the breaker itself is failing.

All of the above will increase the resistance, and hence the load.



Not sure that last statement is correct for resistive loads. Seems to me that the load (current) drops when element resistance increases. (assuming the voltage remains the same)

[Mick Owen]

Increasing resistance always lowers the load for a given voltage (Ohms law). Since your voltage hasn't changed, any increase in resistance would cause a lower current flow. Therefore, loose screws etc. are likely not to cause increased current draw in the overall circuit.

Shorts as Steve suggested is one possibility or the problem may lie in a worn out breaker. Breakers do go bad --and more frequently as the circuits load approaches the breaker's current rating. I have replaced 3 or 4 for friends in the past 5 years.

[Steve Stadelman]

I have to disagree, loose connections can easily cause an increased current draw because the can get extremly hot.

[Mick Owen]

Heat in metals reduces conductivity, or increases resistance, slightly. The atoms scatter the electron waves carried by the electrons in the conductor. When current causes a conductor (connection or whatever) to get hot, this would increase the resistance.

[Mike Aurelius]

yup, as do dirty connections...the power has to work that much harder to get to where it wants/needs to go.

The more you push, the harder it gets, and the hotter it gets.

(Is that why rocket engines are so hot? Ohhhhhh...it IS rocket science!!!)

[Ben Rosenfield]

Originally posted by Mike Aurelius
The more you push, the harder it gets, and the hotter it gets.
Sounds like you're trying to blow your own breaker! :D

[Marcel Braun]

As nichrome elements age they draw slightly more juice. Basically the metal oxidizes away making the element smaller (shorter) the draw increases slightly. The bonus is that the kiln has more power...lol

[Steve Stadelman]

I have seen it plenty of times in both careers where loose wire connections pop breakers and fuses, start housefires and wreck equipment.

[Mick Owen]

My intention of pointing out that poor connections increases resistance was only to eliminate it as the cause of the circuit drawing more current and thus popping the breaker. Poor connections can cause vastly different amounts of resistance, and if more resistance did in fact increase current, this could easily have been a factor.

Although I'm not sure, I would think the current increase from an eroding element to be minimal and therefore unlikely the cause of the popping breaker.

A loose wire could result in a short, and the increased resistance resulting from a loose wire would likely generate heat (and could cause a fire), but a loose wire would not cause an increased current draw unless it also providing a short.

[Pete VanderLaan]

Originally posted by Steve Stadelman


, start housefires and wreck equipment.
*************

Another excellent logo for the T Shirt.

[Mike Aurelius]

Originally posted by Mick Owen
My intention of pointing out that poor connections increases resistance was only to eliminate it as the cause of the circuit drawing more current and thus popping the breaker. Poor connections can cause vastly different amounts of resistance, and if more resistance did in fact increase current, this could easily have been a factor.

Although I'm not sure, I would think the current increase from an eroding element to be minimal and therefore unlikely the cause of the popping breaker.

A loose wire could result in a short, and the increased resistance resulting from a loose wire would likely generate heat (and could cause a fire), but a loose wire would not cause an increased current draw unless it also providing a short.

Actually Mick, here's the issue...

If you have stranded wire, the screw device holding the wire in the connector tightens the wire together, and forces full contact with the connector.

As the screw loosens, the bundle of strands "opens up" and there is less surface area making contact with the connector. Resistance increases because there is less of a "pipe" for the current to flow through. As the resistance increases, the temperature increases, and viola, heartbreak hotel.

With sold wire, the issue becomes the wire actually moving inside the connector, arcing and re-welding itself, thus creating heat and once again, heartbreak hotel.

[Mick Owen]

The issue has been: “What keeps blowing the breaker”. As you are restating, it is not an increase in resistance which results in a decrease in current.

To sum up the issue, chances are that there is either a short or the breaker is bad.

[Marty Kremer]

I cleaned and tightened the connectors- eureka!
Am still going to keep an extra set of elements handy though.

[Marty Kremer]

No Eureka- the second firing started tripping the damn breaker again.
New breaker. Another firing going on now.
Replacement elements on the way from Duralite, just in case.
Don't wait up for this- I'll post results in the morning.
Brisket for breakfast anyone?

[Marty Kremer]

Good firing.
Previous breaker rated at 70 amps, kiln drawing 75. New breaker is 100.
No brisket today, maybe over the weekend.

[Rosanna Gusler]

um marty, did you just 'over breaker' your wiring? i hope not. rosanna

[Mick Owen]

The purpose of the breaker is to limit current to that which the wire can handle easily. I hope you have at least a #2 copper wire between the panel and the kiln, or you may at some point find that the wire becomes a heating element setting your building on fire.

[Marty Kremer]

the wire beats the breaker- had an electrician in to check.

[Mick Owen]

Great, you should be fine then. I'd save the new elements until one burns out.

Mick