Quick Question about Breakers.

[Scott Novota]

First off is is possible that a breaker can start to wear out with the use a furnace puts on it?

This breaker worked really well for about 2 years then it would pop maybe once every once in a while. Always on a charge I toss a little to much in on. I chalked it up to long term load on the breaker and it heated up and popped. It has slowly started to get much more sensitive over the last couple of months to the point that I am trying to find the issue. Rebuild did not help the issue.

After rebuilding the furnace it is still popping under a load but it seems to be getting worse with time. I realize that a breaker is pretty cheap fix I just have never actually had a breaker wear out on me. Seems like if it is heating up and cooling with over 3 years of use on it that could very well be what is going on here.

Any advice would be welcome.


Thanks,

Scott.
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[Hugh Jenkins]

Two things about breakers;

1) you are supposed to exercise them once or twice a year, on-off, on-off, since they can corrode and not respond as they are supposed to.

2) they do tend to get more sensitive if they are overloaded. Replace the touchy bugger and most likely all will be well for a while. But, you might need to look at how close to circuit capacity you are pushing.

[Scott Novota]

Where I was leaning.

It gets pretty hot when charging and must be pulling more amps than the stated amount on the furnace. That would take it over the 80% rule of thumb if it was pulling as little as 5 more amps while charging. Have three years of constant furnace use on this breaker at or just above the 80% rule. Plus it is about 98f outside and it always seems to pop more in the summer months. Maybe it is just pissed off.

I will have my electrician look at it and upgrade the breaker if needed.


Thanks,


Scott.
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[Thomas Chapman]

Speaking of which. . . I just got back in town. For my annealers I use Watlow 982 controllers. I just flipped my breakers back on. Two turned on and the third Watlow went snap, crackle, pop. Accompanied by that little plastic-electric burny-odor. Hopefully it was just one of the high-dollar sub-cycle busse fuses. I think I better call my electrician now. Woe is me.

[Thomas Chapman]

It's cooked!
The installation of a new SSR did not fix my problem. The lights in the face of the Walow 982 do not even go on. Anyone have one to spare?

Re: Breakers failing. This might not pertain to the electric furnace use, but using a breaker as a switch is not that good. They are breakers--not switches, and as such are only designed for so many cycles, I have been told.

[Ben Solwitz]

You're not supposed to let the smoke out, that's what keeps them working.

[Pete VanderLaan]

somewhat off subject but I run a squirrel cage blower in to my transformer on my moly to keep it nice and cool. It gets really hot when cranked up, hot as in it melted an aluminum buss block.

[Dave Bross]

I know an old time phone company engineer from the days when the phone system was nearly bulletproof. He said they designed and tested everything to be sure it never got hotter than you could stand to put your hand on.

Hang an amp meter on that line and see how many amps when you charge. That way you'll know if it's wiring upgrade time or just the breaker. You can buy cheap clamp on amp meters from Harbor Freight or Ebay has cheap dial face meters with shunts for a permanent install.
Just in case you've never used one... the clamp on clamp goes around just one of the wires supplying the power, not all of them.

[Pete VanderLaan]

If I recall correctly Scott, you have an SiC system don't you? One of the many downsides of SIC is that the elements change resistivity as they age. I've probably said enough.

[Brody Shaw]

I thought Scott had a wire melter?

[Pete VanderLaan]

I think it would happen with wire as well.

[Dennis Hetland]

The increase in resistance causes the current draw to go down. Which is less of a load on the breaker. I would do what David Bross suggested and slap an amp clamp on it to see what you are drawing.
Breakers do wear out, but if it's been tripping for a while I'm not sure if that's the problem.
If you change the breaker don't put a larger one in without increasing the size of wire going from the panel to the furnace.

[Rosanna Gusler]

i have had breakers go wimpy on me. i noticed that the wimpy ones felt different when being switched off/on from a healthy one of the same amp size. rosanna

[Scott Novota]

Pete, I have two shops that I either run or am the lead guy turning the wrench.

In one I have a SiC Electroglass(140) and in the other two are wire(aim 80 and JenKen 80). So everyone is sort of right here.

Breaker problem. It seems the problem is fixed and was just the breaker getting worn the hell out over the last 3 years of 100% use. I dropped and new one in and everything seems to be humming along like a dream. It was also a bit underrated so we upgraded it as well.


Scott.
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[Pete VanderLaan]

I can totally believe that the breaker could need replacing and I totally agree that checking the current draw is appropriate to do. But, I'm confused. It seems to me if the resistivity increases that it would take more power to achieve the same temp as when the element is new. So, Dennis are you suggesting that it would actually use less power as it ages to achieve a constant temp?

[Dennis Hetland]

If your voltage stays the same and your resistance increases amps go down. Your controller will cycle on longer/more often to achieve the same temp.
My wire melter started at 32 amps. Now four months later I'm down to 26 amps. I plan on twisting new elements very soon.

[Pete VanderLaan]

But to attain the same temperature, then would it not require more pressure ( voltage) on the element, or more volume (amps)? I see your point being that the element resists flow more, drawing the amps (volume) down and subsequently it either doesn't get as hot or has to stay on longer to get as hot. My point is that the wire carrying the juice to the element would need to be more to attain the same temps as before. If the breaker was at a borderline for failing,running it longer would make it heat up more and then would throw it if it were close to maxed. Help me with my thinking here.

I get it that the element will fail.

[Dennis Hetland]

Voltage is going to stay the same. Amperage is the product of the amount of resistance put on the voltage (V/R=A). The less resistance the more power(VxA=watts).
If the wire feeding the furnace is sized properly (including derating for things like ambient temperature and number of wires in the raceway) the wire and breaker should not get hot. The breaker should only trip when too many amps are drawn on it.
If the copper wire feeding the furnace is getting hot(and making the breaker hot) it's too small and is a fire hazard.

[Eben Horton]

Originally Posted by Pete VanderLaan

If I recall correctly Scott, you have an SiC system don't you? One of the many downsides of SIC is that the elements change resistivity as they age. I've probably said enough.

scott has a wire melter

[Pete VanderLaan]

I understand that the voltage will not change unless it is run through a transformer. If the ampacity drops with increased resistivity, I have to assume that either the furnace doesn't get as hot or it takes constant lower amps at a longer draw to run the thing at the same temps as when the element is new. It just seems to me that given that there is resistance in all conductors to a varying degree, that running at a constant high amperage for a longer time will generate heat cumulatively. It seems to me that the breaker runs on something of the equivalent of a fused link which if it gets too hot, trips. True, or not?

[Dennis Hetland]

A circuit breaker uses one or both of two methods to sense a problem. A magnetic sensor that trips when a fault condition occurs and/or a thermal sensor, but even if the breaker is using a thermal sensor if the wire and all the hardware used in that circuit is sized/rated properly it shouldn't get hot enough to cause the breaker to trip.
My furnace is down to 26A from 32A and the controller is cycling on longer and more often and my breaker is not hot.

[Scott Novota]

Dennis what size is that breaker?


Just wondering. I am guessing a 40?

[Pete VanderLaan]

I suppose it's all relative. My Moly runs a 120 Amp breaker. After the transformer has worked it's magic, it draws about 385 AMPs at 36 volts or so says the meter.. Everything gets at least warm.