Furnace build regarding moly's largely

[Pete VanderLaan]

No. The transformer, assuming it is the correct unit would have an input of 480V. That would break it down to two 240V taps and a 120V tap, plus the correcting taps. You however are going to run 240V in to the thing and it can't perceive the difference between 480 and 240, so it is going to give you two 120V taps and a sixty volt tap instead. You are looking for the sixty.

So you are looking conventionally for a 50KVA transformer 480 volt input with three taps for 240 and 120 secondary outputs. It may have adjusting taps as well.

Or you can custom order a transformer with 240 volt input and 36 volt secondary output through either me or a local supplier, I don't know what your deal is there. I use the 36 volt in my furnace. That works out to two banks of three elements at 12V if wired in series.

[Dennis Hetland]

Exactly what you want is not common so it's likely to cost a lot, but a 480v to 240/120v is common. If you put 240v to the primary of a 480v transformer you'll get 120/60v out of the secondary. If the load on your secondary is 200 amps you'll draw 50 amps from your panel to you primary.(If the secondary is wired for 60v).
A 50KVA 4 to 1 stepdown transformer rated for 480volts on the the primary should work for you.
I should point out that while I have installed transformers I have not built a moly furnace yet. I think it would be worth the money to pay someone like Cheyenne Malcolm for some advice. Especially if you don't have a lot of experience with electrical installations. I'm sure he could tell you where to get the best transformer for your money.

[Dennis Hetland]

Yeah. What Pete said.
(I need to learn to type faster.)

[Dennis Hetland]

Originally Posted by Pete VanderLaan

No. The transformer, assuming it is the correct unit would have an input of 480V. That would break it down to two 240V taps and a 120V tap, plus the correcting taps. You however are going to run 240V in to the thing and it can't perceive the difference between 480 and 240, so it is going to give you two 120V taps and a sixty volt tap instead. You are looking for the sixty.

So you are looking conventionally for a 50KVA transformer 480 volt input with three taps for 240 and 120 secondary outputs. It may have adjusting taps as well.

Or you can custom order a transformer with 240 volt input and 36 volt secondary output through either me or a local supplier, I don't know what your deal is there. I use the 36 volt in my furnace. That works out to two banks of three elements at 12V if wired in series.

What about welders? I thought I heard something about people using welders for their transformers.

[Larry Cazes]

Originally Posted by Dennis Hetland

What about welders? I thought I heard something about people using welders for their transformers.

A welder is NOT a transformer. Most are not designed or built for 100% duty cycle meaning 24 hours/day. We have EZTherm furnaces at the shop I rent at. They use Miller welders. I would not suggest you go there.

[Pete VanderLaan]

Originally Posted by Dennis Hetland

What about welders? I thought I heard something about people using welders for their transformers.

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When EZ Therm built their shortlived moly, a cooperative adventure between Henry Halem and Mark Jesson from Duralite, they asked Miller for a welder that would perform continuous duty. Miller said "sure" and supplied them with a unit that supplied continuous duty- for an eight hour work shift. This was an exceptionally unfortunate miscalculation and speaks volumes for testing a product for a year before it gets put on the market. It was only one of many problems.

Use a transformer, a real one.

[Larry Cazes]

Originally Posted by Pete VanderLaan

***************
When EZ Therm built their shortlived moly, a cooperative adventure between Henry Halem and Mark Jesson from Duralite, they asked Miller for a welder that would perform continuous duty. Miller said "sure" and supplied them with a unit that supplied continuous duty- for an eight hour work shift. This was an exceptionally unfortunate miscalculation and speaks volumes for testing a product for a year before it gets put on the market. It was only one of many problems.

Use a transformer, a real one.

Yup. Even the user guide shows 100% duty cycle is actually 8 hours instead of 24 as most would assume. Specsmanship at it's best.

[Pete VanderLaan]

And I would note: Take care of your transformer or it won't last forever either.

[Lawrence Duckworth]

You guys have helped….thanks







Progress---

Originally Posted by Pete VanderLaan

I am very sure the Bowman stuff is sold and it was 208 volt three phase anyway. I would look with local demolition contractors in the Atlanta area.

Check is on the way to Jim as we speak

[Pete VanderLaan]

Originally Posted by Lawrence Duckworth

You guys have helped….thanks







Progress---

I still think the floor could use more insulation.

[Lawrence Duckworth]

Originally Posted by Pete VanderLaan

I still think the floor could use more insulation.

I finished up with the wall castings and the sill height ended up being 2’-6” off the floor. Is that height worth compromising by adding additional insulation?….

Btw, is the pot lip higher, lower or level with the sill?

[Pete VanderLaan]

a tiny bit lower is best but put the pot on a stilt that completely supports it.

[Mark Wilson]

if a transformer is designed for an input of 480 volts and has a 50 kva output power, and then is used with 240 volts, it now can only supply 12.5 kva or only 25% of the power it could before. the size of the wire used in the transformer is the limiting factor.

[Steve Stadelman]

Originally Posted by Mark Wilson

if a transformer is designed for an input of 480 volts and has a 50 kva output power, and then is used with 240 volts, it now can only supply 12.5 kva or only 25% of the power it could before. the size of the wire used in the transformer is the limiting factor.

No, 25 kva. Redo your math.

[Mark Wilson]

Originally Posted by Steve Stadelman

No, 25 kva. Redo your math.

off by a factor of 2.....the story of my life!!!!

[Pete VanderLaan]

Christine Lavin has this great song called " Don't Push Send."

[Lawrence Duckworth]

Steve S. recommended a 15kva 240 input, 45v output single phase transformer with standard 5% and 10% voltage compensation taps.

Do you guys plug the cleanout with brick and fiber?

[Tim Bassett]

My stadelman has a layer or two of hot face fibre close to the crucible and then a few layers of standard fibre to back it up. I would not suggest using bricks in case you do need to do a big cleanout. The worst case scenario is that the fibre can never be actually "glued" on place by the glass, you can always shred it and pull it out. I would hate to have to shred a brick that has been glued in place. Hopefully you will have to use the cleanout port very infrequently. I opened my cleanout port after charging at least weekly for 18 months and was surprised that there seemed to be so much glass on the floor...maybe 1/2 an inch. I spent quite a while gathering it all off the floor and it added up to be about three kilos. Best of luck with your build
Tim Bassett

[Rollin Karg]

If you want your furnace to run efficiently for a long time you should clean the bottom out on a regular schedule. At least once a month if not every other week.

[Pete VanderLaan]

and I might add, three kilo's isn't much at all. I am really encouraging people to use the cleanout to heat the lower end of the furnace when turning it on, so it's nice to keep it clean. I have folks sticking their bench torches in the cleanout on a pilot flame. This has eliminated problems with thermal shocking pots or so it seems. It's really only an issue on the 28 and 34 inch furnaces.

[Pete VanderLaan]

Originally Posted by Lawrence Duckworth

Steve S. recommended a 15kva 240 input, 45v output single phase transformer with standard 5% and 10% voltage compensation taps.

Do you guys plug the cleanout with brick and fiber?

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And while that is absolutely the best unit for the job, you aren't going to find it off the shelf. It's a custom transformer.

[David Russell]

what is the best method to clean out my port without shutting down?

[Pete VanderLaan]

Get the furnace really hot, pull the cleanout material and look it all over. If it's really bad, there is going to be a solid plug of glass to stare at. If it's clear, look up the hole. Make a little rake out of angle iron and drag the crud out. If solid, heat up the glass plug with a torch, as big as you can find. If there is really a lot of crap, be ready to contain it and keep valuable combustibles away from the cleanout.

This is not a fun job.

[David Russell]

thanks pete. alright, really hot, do i need to go as hot as 2275?

should any coating on the floor be cleaned out regardless of thickness?

in the past i have been sure to load batch real careful and wait for the pot change for a big cleanout, but the part of me that pays the bills is demanding maximum efficiency!