How to Rewire 3-phase 240VAC Resistive Device for 240 Single Phase Power?

LJ, can you provide a schematic, possibly? Alternatively, the make and model? It may be possible to snag the schematic off the web.

If the load is purely resistive, it may be possible to rewire the element connections for single-phase service. Without a schematic in hand it's hard to say. There is also the temperature controller wiring to consider.

-e

Hi "e"

Not sure I can get the schematic but it's worth calling the manufacturer to ask how it differs from their single phase units.

Temperature control is a standard Kiln Sitter, a popular aftermarket add-on, which I do not use. Instead I have an external Bartlett digital controller with thermocouples to monitor and regulate temps.

Thanks

L.J.

It would be basically the same thing...The resistive heat has a 120v line to each terminal, the lines connected to each heater are different phases, you have two connections for each heater...

I suspected as much

That is very encouraging. It makes it deffinately worthwhile to contact the manufacturer of the kiln.

It also means I should bid on it as others seem to be put off by a paper tiger.

Thanks Eagle!

L.J.

How many watts? Can you tell if it is wired in delta or star? (If delta, it will be easy to rewire as 3 single-phase elements in parallel, but the total amps may be fairly high.)

How many watts?

I don't know but I will ask.

Can you tell if it is wired in delta or star?

I do not know what that means but since I have not yet purchased the kiln in question, I'll have to call the manufacturer and ask.

(If delta, it will be easy to rewire as 3 single-phase elements in parallel, but the total amps may be fairly high.)

My current panel will support 30 amps per leg on the existing circuit and the wire is of sufficient gauge that I can change the CBs to higher values safely if needed. I anticipated that there would be a bump in current if the wiring changes.

Thanks

L.J.

We can decide it by removing one phase wire

if it is in star only two phase resistors will get on

If it is in delta only one resistor will get on

the other way which gives rough idea is by checking and calculating the resistance of resistor per phase

Hi Tornado!

I was able to get the amps and wattage for the same model but wired differently for single and three phase power.

240V Single Phase, 48 amps,

240V Three Phase, 34.6 amps

The wattage for both is the same at 11520 watts

Thanks

L.J.

Tidy sized load, just don't use it when the wife is cooking Sunday lunch otherwise you'll be in big trouble.

As has been said if it's connected three phase delta then a bit of rewiring and you're sorted. At that sort of load I would assume a contactor is used.

Hi Tony!

A Honeywell contactor is driven by a smaller 24 volt relay. Both are housed in the same cabinet that houses the Bartlett V6 digital controller.

Thanks

L.J.

Hi Mate

You could probably change it to single phase quite easily, but the biggest problem you would be facing is if you have enough of a power supply to power it.

Most of the time elements are connected in star so all you could possibly have to do is rewire the elements in delta and then hope like hell that your power supply will hold out.

Best Regards

Joe

If you don't need to operate the kiln at its rated temperature and/or you don't need to get it to temperature as fast as it was designed to get there, you can operate it at lower than design voltage and power after converting to single phase. Another option is to use a dedicated single to 3-phase converter. There are several types available and they work very well. I use one in my machine shop.

I think that you have a very good chance of rewiring the kiln to work the way you want. You may have to partially disassemble it to get to the wiring. Be careful, the wiring and connections used to connect to the heating elements must be able to withstand the heat.

Make sure the wiring you use is capable of handling the total current load, from the kiln to the breaker box. From the breaker box to the service entrance the kiln load in addition to normal house usage, not just the kiln by itself. The current capacity of the wire is based on it's size/gauge not the breaker size. The breaker is sized to protect the wiring 'downstream' not the load. If there is a short in the wiring, you don't want to burn down the house by melting the wires because an oversized breaker doesn't trip.

How many amps do you have available with your single phase?

It would need to be connected to 3 different circuits between the live and the neutral and fused at each connection of the (same) phase.....in the UK for example you would usually get 3 x 13 amps, not enough.......but maybe its possible to up the ampage even there with a knowledgeable electrician.

You don't need different phases as you would for a motor, each at 120° to each other as its only a resistive load....but you do need at least 16 amps per phase and a bit more would be even better.....all wiring between the main fuse box and the oven needs to be beefed up properly.....safety, safety, safety.

The rewiring will be easy, but do get an electrician to check it out once done (if you do it yourself).....all wires must be heat shielded etc....

Best of luck.

I was able to purchase the kiln at a substantially reduced price. . . . $140! Typically, this size unit, used, but in excellent condition, would sell for somewhere around $550. It's seen very little use in the high school who abandoned the ceramics program for lack of interest.

It appears I was correct: the 3 phase lable scared off the uninformed.

I will be driving out to pick it up in the next 48 hours. Not certain when I will attempt the wiring mods. When I do, I will report back my findings and my success, or failure.

Thanks. . . . . . . everyone, for the generous support.

BTW, unless some of you are familiar with my history, you have no way of knowing what I am melting.

I am a professional mechanical designer and in my spare (sic!) time, I make honeycombed and meniscus shaped telescope mirrors. I also design and build large aperture telescopes.

Laughing Jaguar

I'm looking forward to the updates and pics.

Good luck, and may all your troubles melt away....