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    Default Electric heat treating oven

    I picked up an electric heat treating oven a couple of years ago and just recently hooked it up. I am attempting to run it off a phase converter but once the oven gets to about 600F and the oven starts to "pulse" the phase converter sounds VERY bad - like I'm going to blow some caps. Any ideas on how I can smooth things out so I don't ruin something? Would this be an application for a vfd? It's rated at 208v.

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    Why go through a phase convertor? I would drive through a transformer directly from the power line. The issue is that the phase convertor wants to control the load through its internal control. Phase convertors don't like having load switching between them and the load.

    How many kva is the oven?

    Tom

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    Sounds like a triac or act phase angle control on the oven. Convert it to single phase and run it from the line.

    Or replace the pid controllers and use a relay. Heating element life may not be as long.

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    Quote Originally Posted by Joe Miranda View Post
    I picked up an electric heat treating oven a couple of years ago and just recently hooked it up. I am attempting to run it off a phase converter but once the oven gets to about 600F and the oven starts to "pulse" the phase converter sounds VERY bad - like I'm going to blow some caps. Any ideas on how I can smooth things out so I don't ruin something? Would this be an application for a vfd? It's rated at 208v.
    I just send my heat treating to Winston Heat Treating in Dayton. Super fast turn around, Great work, they forgot more about heat treating than I will ever know and so cheap I don't know it could ever pay to do it yourself.

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    Tom - not sure how many kva. Its says 30 amp on the tag. It also says 208v 3 phase. Is it still a candidate for a transformer to run off supplied power?

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    Johansen - if only you were closer! I'm afraid most of what you said is far beyond my understanding. You made it sound so simple!

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    moonlight - thanks, I will certainly keep them in mind. We have a couple heat treaters near me and one of them has a truck that passes our shop a couple times a week and we usually use them. They do good work but we had a couple of instances where it was hard to get our parts done from them. They kept saying they were too busy to get to our small order. I get it...you have to cater to the ones that pay your bills...we're so small and occasional we're more of a nuisance than a help to them.

    I have done a lot of heat treating over the years and can get pretty good results on the simpler stuff ... 4140, A2 etc. I had a really good Metallurgy teacher from the old J&L Steel Co. Plus a lot of the repair stuff we do requires us to be as responsive as possible so being able to pull some of that back in house would be helpful. As always...thanks for your thoughtful responses!

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    My suspicion is that your heater could be converted to single phase fairly easily. This would be no more than 10kw . . . do you by any chance have a schematic?

    If you had a VFD, you could with some effort connect directly to the heater coils (bypassing the kiln’s contactors) and use the signal that normally goes to the contactor to control the VFD.

    Or . . . most VFD’s have an analog input that a signal conditioned thermal signal could be brought into and you could program a very nice temperature controller using the VFD to vary the power delivered to the heater coils.

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    Quote Originally Posted by Joe Miranda View Post
    moonlight - thanks, I will certainly keep them in mind. We have a couple heat treaters near me and one of them has a truck that passes our shop a couple times a week and we usually use them. They do good work but we had a couple of instances where it was hard to get our parts done from them. They kept saying they were too busy to get to our small order. I get it...you have to cater to the ones that pay your bills...we're so small and occasional we're more of a nuisance than a help to them.

    I have done a lot of heat treating over the years and can get pretty good results on the simpler stuff ... 4140, A2 etc. I had a really good Metallurgy teacher from the old J&L Steel Co. Plus a lot of the repair stuff we do requires us to be as responsive as possible so being able to pull some of that back in house would be helpful. As always...thanks for your thoughtful responses!
    One part one hundred parts, never more than a day or two. No excuses, they are on time. UPS is no problem

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    Quote Originally Posted by moonlight machine View Post
    One part one hundred parts, never more than a day or two. No excuses, they are on time. UPS is no problem
    Moonlight - sounds good! I will certainly keep them in mind. These days I think UPS gets stuff shipped faster than I could drive it there myself!

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    Quote Originally Posted by motion guru View Post
    My suspicion is that your heater could be converted to single phase fairly easily. This would be no more than 10kw . . . do you by any chance have a schematic?

    If you had a VFD, you could with some effort connect directly to the heater coils (bypassing the kiln’s contactors) and use the signal that normally goes to the contactor to control the VFD.

    Or . . . most VFD’s have an analog input that a signal conditioned thermal signal could be brought into and you could program a very nice temperature controller using the VFD to vary the power delivered to the heater coils.
    mg - I do not have the schematic but I can probably find one because it is a Cress furnace and I can still read the serial number on the tag. It's probably 30 years old or more but I will start searching around.

    Thanks! How's the new building working out for you?

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    Here is the name plate
    Attached Thumbnails Attached Thumbnails cress-name-plate.jpg  

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    Quote Originally Posted by Joe Miranda View Post
    Thanks! How's the new building working out for you?

    I imagine that you know what it is like to move into a new home, the garage gets stacked full of boxes . . . that describes our new shop pretty well.

    The city has some fairly stringent permit requirements for pallet racking including fire suppression provisions, fire egress / access considerations, licensed PE designed anchoring plant, etc. We weren't prepared for this so we have been stalled in getting our racking put to use which means literally tons of stuff is still sitting on the floor.

    Apart from that, we are getting settled and our employees are pretty jazzed with the new facility. We purchased a Butler planer mill at auction 2 weeks ago so re-arranging our shop layout to optimize it for the new 72,000 pound machine.

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    Quote Originally Posted by motion guru View Post
    I imagine that you know what it is like to move into a new home, the garage gets stacked full of boxes . . . that describes our new shop pretty well.

    The city has some fairly stringent permit requirements for pallet racking including fire suppression provisions, fire egress / access considerations, licensed PE designed anchoring plant, etc. We weren't prepared for this so we have been stalled in getting our racking put to use which means literally tons of stuff is still sitting on the floor.

    Apart from that, we are getting settled and our employees are pretty jazzed with the new facility. We purchased a Butler planer mill at auction 2 weeks ago so re-arranging our shop layout to optimize it for the new 72,000 pound machine.
    Haha! That whole packing and unpacking thing sounds like a nightmare! And fire suppression for the pallet racking? Huh... who woulda thunk it. A 72,000 pound planer mill...I'm drooling! Do you need to dig a foundation pit for it?

    Best wishes KB and may God continue to bless and prosper your efforts!

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    Quote Originally Posted by motion guru View Post
    I imagine that you know what it is like to move into a new home, the garage gets stacked full of boxes . . . that describes our new shop pretty well.

    The city has some fairly stringent permit requirements for pallet racking including fire suppression provisions, fire egress / access considerations, licensed PE designed anchoring plant, etc. We weren't prepared for this so we have been stalled in getting our racking put to use which means literally tons of stuff is still sitting on the floor.

    Apart from that, we are getting settled and our employees are pretty jazzed with the new facility. We purchased a Butler planer mill at auction 2 weeks ago so re-arranging our shop layout to optimize it for the new 72,000 pound machine.
    Soon you will be out of space! Is there room on your property for an addition?

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    Quote Originally Posted by motion guru View Post
    My suspicion is that your heater could be converted to single phase fairly easily. This would be no more than 10kw . . . do you by any chance have a schematic?

    If you had a VFD, you could with some effort connect directly to the heater coils (bypassing the kiln’s contactors) and use the signal that normally goes to the contactor to control the VFD.

    Or . . . most VFD’s have an analog input that a signal conditioned thermal signal could be brought into and you could program a very nice temperature controller using the VFD to vary the power delivered to the heater coils.
    I'd like to hear more about this. Never would have thought of this use for a VFD.

    Sent from my SM-G973U using Tapatalk

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    Resources - Cress Manufacturing Company Inc.


    It appears to me that your furnace has solid state relays. They are essentially triacs or scrs back to back. They typically wait until there is 30 volts or so present before they conduct, that is why your phase converter is making noise.


    anyhow, converting to single phase should be easy. simply disconnect the third phase, and reconnect the 3 heating elements to run off line 1 and 2. each element is in series with its own solid state relay.

    It is likely that all three solid state relays already have the inputs connected in parallel, directly driven by the temperature controller.

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    cress-wiring-diagram.jpg
    Quote Originally Posted by johansen View Post
    Resources - Cress Manufacturing Company Inc.


    It appears to me that your furnace has solid state relays. They are essentially triacs or scrs back to back. They typically wait until there is 30 volts or so present before they conduct, that is why your phase converter is making noise.


    anyhow, converting to single phase should be easy. simply disconnect the third phase, and reconnect the 3 heating elements to run off line 1 and 2. each element is in series with its own solid state relay.

    It is likely that all three solid state relays already have the inputs connected in parallel, directly driven by the temperature controller.
    johansen - ok - I was able to find the diagram:

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    johansen - can you take a look at this and see if this looks like what you would do? I eliminated L3, brought L1 to the right side of the toggle switch then up to the top terminal of the POTTER BRUMFIELD relay, jumper L2 to both terminals of lower POTTER BRUMFIELD relay (although I could probably eliminate that one altogether - yes?). Thanks for your help!
    Attached Files Attached Files

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    Your issue is that a phase converter would need to be connected to the thermostate of the furnace, and controlled by that, not relays switching the load lines. An RPC would handle your issue fine, or the rewiring you are considering.


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