Pro-Melt is Tripping Circuit Breakers

[David2011]

My faithful RCBS Pro-Melt has been unused for the past four years. The lighted switch failed after 42 years (date of manufacture was stamped inside the case) and a new exact replacement was installed so, YEA! Time to give it a test run. After about three minutes of heating the circuit breaker tripped. This was on a standard trip breaker. After the furnace cooled enough to handle it I took it to another area, still on the same load center but on a combination arc fault/ground fault breaker that I expected to be less tolerant of the mechanical thermostat but it didn't seem to be a problem. This time the breaker tripped after about 18 minutes. The furnace only draws 800 watts according to the data plate and there was very little else on the first circuit. There was nothing else on the second circuit. A 20 amp breaker should be good for 2,340 watts at 117VAC. I saw that Eaton makes breakers for the same load center that are intended for a large tungsten lamp loads which made me wonder if their standard breakers might not like heating loads. In my mind there's not much difference in a lead furnace and big incandescent lights.

The shop and electrical system is less than two years old. I know even new breakers can be weak but I've used this furnace at four other homes with no issues. When it was in storage it was kept in a climate controlled area, never humid/damp or hot. If there was a dead short I would have expected the breaker to trip instantly but that wasn't the case.

Ideas?

[David2011]

A little more insight and experimenting: I took the furnace into the garage which is on the original GE load center. The available outlet is on a 20A breaker and is shared with the kitchen and one or two living room outlets. The load includes two full size refrigerators, a dorm sized fridge for water and drinks, the Internet router, the microwave oven (not in use at the time other than the display) and both ends of an Ethernet over Powerline network extender. The Pro-Melt ran for over 40 minutes during which time I melted about 6 pounds of old hollow base muzzle loader boolits, presumably more or less pure lead. That's what was readily available for a test; didn't want to melt anything with wax lube on it with the cars sitting there. They would take on that smell for almost as long as SWMBO would remind me of my misdeed.

The initial impressions are that the Pro-Melt is working as it always has and the Eaton breakers don't like the heating load.

[rancher1913]

i would put an amp meter on it before you do much else. the house breakers might be working like they should and the garage one might be frozen, an amp draw test will confirm or dispel the problem. you could have vary easily moved the heating element just enough to make it bad, elements are by nature a controlled "short".

[Newboy]

Some times the heating element insulation will absorb a little moisture when unused, which causes this issue until they dry.

On the elements we sell, we try to get the customer to apply a low voltage initially, for the first time they are used.


Sent from my iPhone using Tapatalk Pro

[Mal Paso]

2 Wire or 3 Wire Plug? On some of the older RCBS pots the heating element will uncoil a bit and short to the case. With a 2 wire cord the frame of the pot can be live 120V and not blow the breaker.

You need a meter to check the amperage draw and make sure the element hasn't shorted.

Heating elements usually do not increase in amperage draw. They draw the proper amperage or they fail. High amp draw is something else.

[Hannibal]

As others have said when the switch was replaced something might have moved or something might have been left loose. I'd check the connections at the switch and anything else that might have been moved/removed/displaced. If that reveals nothing then again as others have said the amperage draw needs to be checked. Could very well be a moisture problem in the insulation around the heating coil that is slowly resolving itself with use but an amperage draw test is the only way to know for certain.

[Walter Laich]

same thing happened to my Pro-Melt (original)

If I let it sit for a month or so, in garage, then it would trip breakers (GFI)

Plugged into another type of socket would heat fine and then would work in GFI without tripping

learned to do the above procedure and never looked back

[GLL]

Replace the breaker and see what happens ! If that does not work try bypassing the new switch.

[Winger Ed.]

Over time and use of loads close to its tripping point will wear down and 'soften' a breaker.
I used to run a 120V wire feed welder on a 20 amp.
It'd start tripping the breaker after a year or so unless I put a fresh on in.

If your 20 amp one is fairly well worn, it should still hold for a 15 amp draw.
A healthy Pro-Melt will run off a 15 amp breaker just fine.

[Hannibal]

We can speculate until the cows come home but the only way to know is to check the amperage draw. To do otherwise is akin to replacing the engine in your vehicle because it dies sometimes. Might fix it but if not it's work and expense for nothing.

[David2011]

i would put an amp meter on it before you do much else. the house breakers might be working like they should and the garage one might be frozen, an amp draw test will confirm or dispel the problem. you could have vary easily moved the heating element just enough to make it bad, elements are by nature a controlled "short".

The garage breaker IS a house breaker. The house load center is located in the garage. The workshop wiring is all new as of this time 2 years ago. There is a 3-4 foot run from the house load center to the workshop load center. It's the new-ish workshop breakers that are tripping easily. The furnace should be drawing a little under 7 amps.

I'll either get my A/C guy to come by to test the draw or purchase a clamp-on ammeter. I agree that an older breaker is more likely to trip at a lower current and far less likely to fail to trip above the indicated amperage. I agree that there is a lot of guessing until I KNOW that the furnace is not drawing more than it should.

The wiring inside the Pro-Melt is very simple and is well isolated from the case. There is a panel between the pot and the electrical parts so it would be difficult to accidentally disturb anything on the pot side. The connectors supplying power to the heating element are welded to the ends of the heating element and as can be seen in the photo the connectors are all very robust. Pending an amp draw test, I'm giving credence to the moisture idea or the Eaton breakers not being up to the task.

[David2011]

same thing happened to my Pro-Melt (original)

If I let it sit for a month or so, in garage, then it would trip breakers (GFI)

Plugged into another type of socket would heat fine and then would work in GFI without tripping

learned to do the above procedure and never looked back

It seems that Walter had the correct answer. I took the furnace back to the casting bench where the problem first occurred. After the use last night it ran until I turned it off, about 1-1/2 hours while I cast over 150 boolits at a very leisurely pace. Sized 'em immediately before they age hardened and will powder coat. I've had this furnace for a long time. This was the first time it tripped a breaker.

Thanks to all!

[wv109323]

Watch all the wire terminals to make sure they are tight. They will heat and cool and loose their "springyness" to grip on the spade of the heating element. That will draw more amperage and trip a breaker.
There is also high temperature wire terminals , if they need replaced.
Also he bare wires will degrade and become brittle with heat.

[David2011]

I learned about loose connections generating heat in the early '70s. Melted a battery clamp in my street rod due to a loose connection. My first lead melting experience! The spade connectors in the Pro-Melt were brutally tight. I've used the furnace a few more times including today. I cast 100 keeper 340 grain hollow points with a Lyman 457122E mold and about 150 158 grain .358 hollow points with a Lee C358-158SWC mold. Long casting session with those single cavity molds and zero issues so it must have been moisture as Walter Laich suggested.

[Mal Paso]

I learned about loose connections generating heat in the early '70s. Melted a battery clamp in my street rod due to a loose connection. My first lead melting experience! The spade connectors in the Pro-Melt were brutally tight. I've used the furnace a few more times including today. I cast 100 keeper 340 grain hollow points with a Lyman 457122E mold and about 150 158 grain .358 hollow points with a Lee C358-158SWC mold. Long casting session with those single cavity molds and zero issues so it must have been moisture as Walter Laich suggested.

Thank You for the info! I am close to firing up an original Pro Melt that's been in storage. I'll try to remember to put an amp meter on it when I turn it on the first time.

[David2011]

I hope it goes well. Mine has been just fine after the third heating cycle.

[deltaenterprizes]

My ProMelt was tripping the GFI receptacle so I switched to a non GFI and the problem went away!