View Full Version : moly element question -3 phase power- stadelman

Mike Stepanski
03-08-2012, 10:13 AM
Just did a crucible change on a 300# Stadelman furnace. Turned the power back on a day ago. Furnace is now at 570f degrees. Took a look inside now and two of the six elements are not glowing hot like the 4 others.
I checked for continuity over and over while putting the furnace back together but I fear that the 2 are gone?
When you look in the furnace starting to your left the first element is glowing the next 2 are not and the next 3 are glowing following around to the front on your right side.
Anyone have any other ideas what is going on?

Pete VanderLaan
03-08-2012, 10:20 AM
Isolate the elements in that pairing and check them each for continuity. I am guessing that you have three banks of two elements per bank but you don't say. It sounds like as you look at it that 1 and 6 are a pair, 2 and 3 are a pair and 4 and 5 are a pair. your problem is with the pair 2 and 3. Or is the wiring different than my guess? Are you wired in three's instead? Regardless, check each element that is out for continuity.

You have to isolate the elements from each other and the incoming heavy cables or you will do nothing more than to confirm continuity through the transformer.

Do shut off the power completely

Michael Ahlefeldt-Laurvig
03-08-2012, 05:44 PM
with the risk of sounding like a computer support guy- You dont say if youve actually checked that they are getting power

John Riepma
03-08-2012, 06:04 PM
Mike, Pete's suggestion of checking continuity on that bank is indeed correct if that is indeed one pair of elements running on one of the three phases. Be sure to disconnect the straps going to the elements before checking or you will just be checking continuity through your transformer, even with the power off. Another possibility, one that I've actually observed, is that you can't expect much of a glow from the elements at 570F. It may just be the difference in the resistance of the elements. If they're still not glowing at about 1200F you've got a broken element. I have had one shatter into rubble inside the passage brick, so you can't always tell just by looking at the visible parts.

Virgil Jones
03-09-2012, 05:42 AM
I've had an element show continuity until it heated some. Sometime during the heating process it separated just enough to show non=continuity.

Mike Stepanski
03-09-2012, 09:24 AM
Sure enough, I've got a bad element.
Thanks for your replies.
Have been told by a tech to change both elements in that bank so they draw even power.
Is this true? Or can I change out just one with no issue?

Pete VanderLaan
03-09-2012, 10:22 AM
I have yet to hear of that particular "Tech" argument and I'm the one who sells the elements. While my boat payments account would appreciate that approach, just change the one element that is broken. These are not silicon carbide elements which change resistivity as they age. Moly's are constant. Your "tech" is wrong.

So, just change the broken one. Capice? (As they say in China).

Steve Stadelman
03-09-2012, 10:23 AM
Pete is right.

Randy Kaltenbach
03-09-2012, 11:06 AM
Although, having a spare [insert name of any part here] is always a good idea...

Mike Stepanski
03-09-2012, 11:57 AM
Thanks for all the help

Joe Deanda
03-13-2012, 08:54 PM
As Pete said, isolate the elements before testing for continuity (take the power straps off) Iv had bad elements test good until someones wiggles the element from the inside of the furnace. Seems that while cold it had continuity and when heating the crack separated. These things can be tricky at times but when they run they are heaven. Good luck

Pete VanderLaan
03-14-2012, 06:03 AM
When elements get really old, they become more fragile. As the quartz layer builds up on the element and the molybdenum oxidizes they actually are more prone to cracking. I have seen ten year old elements but by the time they are about six years old, moving them is just tricky.