Can't believe I got this- (now what do I do with it?)

Bill Hubbell

Bill Hubbell

KNIFE MAKER
I am one thankful man! My brother called the other day and said his boss had a heat treat oven that they were getting rid of (as in mine for the taking!). He works at a tool & die/machine shop. His boss had bought it used, but never hooked it up. He ended up buying a new oven instead, and didn't want to fool around trying to sell this one. I didn't waste any time getting there, and I now have it sitting on my truck. It's much larger than I expected. The pictures I included here are from one listed on ebay. The one I have is a little larger but otherwise looks similar (same brand).
It came with a bunch of graphite boxes for atmospheric control. Don't let my use of the big words fool you- I had never even heard of those before, but have just been researching the company's website. That looked interesting- like a good way to avoid de-carb.
This oven is larger than I need- physically. Has a larger footprint than I wished for. But it looks like 'industrial strength'. One problem is: it's 3-phase, which I don't have, and know little about. There's a separate metal box/cabinet with it that I was hoping would be a phase splitter, but I'm suspecting that it might be a contactor?
Here's some specs:
Sentry Electric Furnace
Size 5
Model AY
33 KW
220 V
87 amps
3-phase
I think the oven measured about 9" Wide, 7" High, and 20 inches deep.
The dial goes to 3,00 degrees, but someone put a label-maker label on that says "Max Temp 2500 degrees"

I've been getting by so far with a home-built gas forge, but have been dreaming of building an oven.
I would value you guys' thoughts on this one:
Should I try to modify it to run on single phase?
Should I strip it out and install new elements and a controller to run on 1 phase,220?
Should I sell it or barter to try to work myself into a newer smaller oven?
Would the mass of the firebrick be a detriment- as in take forever to heat up if I switched out to a lesser heating element, etc?
Are the graphite boxes a good way to go for knives?

I've worked with steel most of my life, as in fabrication, etc. but have never used a heat treat oven, and I've only made a half dozen knives, so-
I would REALLY appreciate any input on this!
Thanks,
Bill

Furnace 2.JPGFurnace 1.JPG
 
I am not familiar with heat treating furnaces, not an electrician either. But I have been running phase converters in my shop for 25 years without problems. A rotary phase converter will give you true 3 phase power, but I have always seen it referred to by the horsepower of the machinery you are running. For the price you paid, consult a real electrician and get set up with a 3 phase converter on a 100 amp circuit. Not that big a deal.
There is a guy on ebay that will build you a custom control, I have 2 of his. Search for "phasecraft" on ebay.
 
Thats an awesome find! I suspect the reason it was a "give away" is the power draw. 87 amps at 3 phase is a LOT of juice. I might be off, but if I remember correctly, thats going to require either 6 or 4 gauge wire (depending on if the wire is aluminum or copper) and that isn't cheap. Then you've got the phase converter.... whew!

Depending on where you live, there's generally only 200amp service in most modern residental areas, so depending on the electrical draw of your household, you MIGHT have to put another transformer/meter in to run it.

Its hard to look a gift horse in the mouth, but in all honestly, were it me, I would try to sell that one, and use the money towards a small, more "shop friendly" heat treat oven. Depending on your circumstances, I suspect that even if you were to do all the work yourself, its going to cost a pretty penny to get it up and running in your shop.....plus running it will be a spendy venture....your electric meter will be screaming.
 
this website is driving me nuts tonight. I had a big, thorough explanation all typed up and... poof. three pop ups later it all disappeared.

The cliff notes of what I typed before:

That monster you have is 33KW. That translates to 44HP. Forty-Four (!) That's why it draws about 90 amps at 230V. To get 90 amps from a phase converter or VFD, you need to upsize the drive by the derating factor. In English, that means to get 90amps out, you need a converter/VFD rated for 87amps x 1.73 = 150 Amps. A converter or VFD rated for 150 amps @230VAC is about 60HP. You are talking thousands of dollars.



What Ed said.
 
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Thx for the input, Cabinetmaker. I might try calling the guy at phasecraft tomorrow - I thought maybe it would be a simpler task working with heating elements than with motors- because of the timing necessary for the fields to armature relationship- and the need for extra amperage on start-up- but like I said I don't know much about 3-phase. I also have a friend who's in charge of a maintenance dept. where they have lots of 3-phase equipment... Think I'll call him too.
Thx again
 
All of the elements run on single phase. (Only two connections per element, therefore single phase). However, the controls are set up for 3 phase input. If you have the schematic you could rewire the whole shebang so that the third phase is eliminated from anywhere it's currently used. In other words, you are likely going to have to gut the cabinet and start over.

At the end of the day, the amp draw of the heating elements and the duty cycle (on/off time) is what drives the total amp draw. You'll have to put in smaller elements (or less elements) to draw less amps. How small before they can't keep the box hot? How small before it takes three hours to get the furnace up to temp? How few elements can be run and still get up to temp? I don't know.
 
Thx Ed- and John-
So you're saying I might have to purchase my own hydroelectric dam to power up my free oven? It sounds like this furnace needs a new owner- someone with more budget than me, and more need for heat. The whole building my shop is in only has a 150 amp service, if that.
What do you think about just using the oven, and installing a new controller and elements? - and thermocouple, and... ? It's really well built, and I did like the large oven capacity. I guess I need to price out everything for that. I see ovens that would be more suited to my needs running on 15 amps (220).
There's a Sentry oven a little smaller than this one on ebay for $1,800- 'Buy it Now'- but who knows what it will bring -if it ever sells.
But, you guys addressed exactly what I was wondering.
Thanks a bunch
 
a hydroelectric dam or your own little reactor!

I think you've got a hell of good oven on your hands... for the industrial shop that needs such an oven. If it fell in my lap I think I'd start calling machine shops and fabricators to see if they need one or know someone who might make a trade for it. You could end up with a real nice piece of gear that you can use.
 
I get your point- and guess I can't argue that. I'll get busy and see if I can leverage it into something more suitable. Half of my motivation will be that it made my brother so glad to score it for me. He's a good ol brother!
You guys helped me make up my mind, tho.
Thx
 
I might go against the flow here and keep it if it were me. Before I bought an Evenheat, I was pretty gung-ho on building an oven from scratch, they're not that complicated. There are a bunch of guys selling PID controllers and SS relays for stuff like this and they're not very expensive. If you're a good tinkerer and a little familiar with electric work, you could do it. I ended up buying an oven just due to the time, or lack there of, of building one from scratch. But, if I had been given that one for free, I would have made it work. I will admit though, there is a lot to be said for unboxing and just plugging one in with no tinkering.
 
For 87 amps you need a minimum size 0f no# 1 0r # 2 conductors . They don't specifically make wire for 87 amp so you have to go to 100amps . Its better to go bigger than smaller . I equals E over R....
 
87 amp! man that is some juice.
It's been said but I'd sell it and get one better sized for home heat treating rather than fooling with it.
 
I see that it's too big as is- and it would be crazy to set up the power for it even if I could (I'd have to run more overhead to my shop)- and I figure the old controller probably wouldn't do what the new solid state ones do. But I keep hearing this little voice in my head that says: Gut it, install new elements, and a new controller. The structure looks great- not having to build all that from scratch is worth something, that's for sure. I actually enjoy building projects like this- up to a point- and don't have the bucks for a new one. And I can figure out basic electrical if I grunt real hard. But what about this:- with so much mass, will it take too long to heat up with the elements I'd have to use? But, then my other little voice says- The mass is the firebrick- and that is insulation, not a heat sink. Thicker should be better, right? But then an the other hand- it has a pretty large area to heat- about 20 x 9 x 7. And so on, and so forth., As I stand right now, I think I'll try to talk to one of the companies that sell controllers and elements. I remember someone (maybe here) mentioning a "helpful' guy like that and I figure someone like that could give me the final scoop as to whether running '30-plus' amps to it would suffice. Does anyone come to mind, that sells the goods and is glad to instruct? I have a 220 volt, 50 amp circuit for my 225 Lincoln welder. Hmmmm
Thanks Guys!
 
Good idea , 87 amps is what a normal household would use . Your electric bill might cause a heart attack . I used to have a huge drill press that ran on 3 phase Y , pulled over 60 amps if it became locked in some tough stuff .

When I used it , my bills were atrocious . Heat treating can be a lengthy process. I agree get something you can use without too many problems .using some equipment that consumes that much amperage is like running


7 central air units . The running load amp on a 3.5 ton AC is about 13- 14 amps. Bubba
 
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Your post seem pretty similar to what I'm engaged in now. I am rebuilding a Thermolyne 9"x10" x 18" or so.... It is from the 80's. Has a similar controller on the side for temp controls. If you want to do ramp soaks I think you may want to get some thing from the new Millennium? :-0 My controller has a Vacume tube in it btw. LOL I picked a Solo from Automation Direct.

IMO I think you'll need to rewire that bad boy! ;-) Some things I've learned in the last week. btw/ I usually hang out on Hobby Machinist but my kid has me playing w/ Knives and Axes. :) He's 17 and learning to machine and craft. All good!

The panels in mine are green wire encased in a ceramic or clay. so max of 2200F. They are $400 for the side heating panels and $350 for the top/bottoms. But you can make your own!
Here is what I did:
went w/ A1 Kanthal Wire into something like 10 Ohms per element. 3/8 coil. 10 looping coils per panel. (see my thread link below. Has pics of molds, wire, etc._) You can also buy these from Euclids elements. Jay is a very cool guy!! I Put 1 side and 1 bottom in series. And put other 1 side and a top in series and wire the 220/240 to these in parallel. This gives you like 20 Ohms and about 22-24 Amps draw on your oven. Respectable for me in the shop/home garage. This is the stock wiring from Thermolyne btw/

The link to my post and my forms and type of Clay is here. It's long. Mine is the very bottom post but this thread is my bible of sorts. I bought the book Rac C. mentioned and its great. The author is even funny. And it's easy to read. Ray C is a Sr. guy on the form w/ ME and some doctorates. when he types it , I read it.

Here is my post w/ pics. Again, very bottom post. Supplys and such all listed out too.
http://www.hobby-machinist.com/threads/heat-treat-oven.9929/page-4#post-304160


Hope is all pans out. KEep us posted. This is my first post here! Cool place gang!
Jeff aka Countryguy
 
Totally agree. After messing w/ this 80's Termolyne and trying to get all the programming going, I put a KF on order and will use the "build" unit for something or just sell it locally.
Our 27" KF series is to be picked up in a week or so. We're close to evenheat's caseville site. (for once something I do not need to drive to PA, NY or deep OH for!).
 
IT does not look all that big (as a unit) to me. My concern is the small work/heating chamber. I cannot tell the size but looks pretty small. I wonder if this is a High Temp item with all that insulating space? Anyway- To add some items to this thread related to making new encasedelements which seems to be a muffle furnace thing?

To take this and convert it into something more moden here are a few items from my own conversion going on right now:

Info on the overall build to the oven in the post above is finally to final phase.

The Soho PID temperature controller is in.($80 to 130) The TC (Thermocouple) probe is in($30-45). The TC wire obtained. ($35) The USB to 485 comms adapter ($13) is installed. Each are shown in the Circle's in the image below of the bench test setup. The new panels we poured are installed and connected. The way we hooked them up is shown in the hand drawn note (pic) below. I set it up for 24Amps. We have heated the new panels up to 500F on the bake cycle but need to get to 1200F which I could not do w/o this setup from Automation Direct. I must say I really like these guys! Great CS. No hassle on returns. Great docs and instructions (to me anyway).


To make this all work; I have 2 sets of 3A NO contacts on the SOLO PID controller. I'll use 1 set to trigger a 110VAc coil large contactor which will place the 240VAC & 24Amp draw on the coils. I know a lot of folks on the ebay PID sales use the Solid State's? I get that a mechanical & contacts will burn but is that all?

A few pics :
muffleF1Pic.JPG OvenUpgrade1.JPG PanelOhms.JPG
 
Solid state relays/contactors last longer because you don't have the mechanical throw of the contacts. Heater coils cycle on/off/on the whole time they are working (what your PID controller does). The constant cycling wears out the solenoid coil and the contacts themselves will tend to weld together over time from arcing. They will work just fine, it just adds a maintenance cost item. The flip side is a solid state relay that will handle 24amps isn't cheap. But, neither are motor starters (contactors) when you start replacing them. The bright side is a good quality contactor (motor starter) will last years with 24/7 operation. In a home heat treating unit that runs a few times a week? You might never have to replace it. Oversize the contactor one size and it will last a very long time.

Do you have thermal overload protection on your contactors? Something to think about. Overloads are way cheaper than replacing parts like contactors and heater coils.
 
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