240v to 208v question

[vrinner]

So in another thread I mentioned I got a kiln but it's 208v 3 phase however my garage is 240v single phase. So getting a quote from manufacture to do the proper swap of everything that is needed and it's just under a grand for all the parts.

Someone else mentioned getting a buck boost step down transformer and I have a question on getting the right thing.

Below is the data plate from the kiln. 208v, 3W 2phase, 23.1 amps and 8320 watts. Manufacture suggests a 40 amp breaker (even though the plate says 23.1 amps)

When looking online at buck boost transformers, most of them say Power Rating of x.x kVA and don't mention watts or amps. Is there some conversion from amps or watts to kVA?

 

[BillK]

The stepdown transformer isnt going to help you because it does not address the 3 phase vs single phase issue. The kiln might have three separate heating elements, one for each phase. You really need to find out exactly how it is wired internally. Depending on how it is setup you might actually just be able to run it on the 240 without any transformer but it will change the amount of heat the elements will generate.

Do you have a wiring diagram of the kiln ???

 

[BillK]

I just took a quick look at their web site and it looks like a lot of the kilns have digital controls instead of old school mechanical ones. That will probably complicate the situation. I dont know enough about VFD'd but that might be your only option if you want everything to work properly.

In the overall scheme of things you might be better off selling the 3 phase one and getting a single phase unit.

 

[wyliesdiesels]

Yup a buck-boost transformer only bucks or boosts the voltage. It cant generate the needed third leg

You will need a VFD or an RPC...

 

[cannuck]

If it has a control circuit, it will probably be tapped off of one leg to ground so you might be alright. 99% likely it has 3 elements, one between each leg/phase of the circuit. To go 240 single phase you would have to go with 3 parallel heater circuits - and that would require more like 70A breaker, not 40. Now keep in mind I am the mechanical guy, not the sparky, but pretty sure this is what you will find.

 

[walta]

This is a quote from the OPs original thread.

“Picked up this glass fusing kiln. In great condition and a killer price however the guy told me it was 240 3 phase. Manufacture said no problems converting it to 240 single phase with a couple of parts.”



If true I think it will draw 40 amp at 208 single phase and will need a 32 volt 1.5kW buck transformer.

Something like this?

https://www.amazon.com/dp/B007V6HBTE/?tag=atomicindus08-20

Walta

 

[walta]

Used transformer $45 shipping $160

Buck boost transformer t113074 | eBay

Find many great new & used options and get the best deals for Buck boost transformer t113074 at the best online prices at eBay! Free shipping for many products!

www.ebay.com

Edit
I just noticed the used eBay transformer is 30 minutes away from the OPs location more or less.

Walta

 

[Norcal]

Either 3 phase power is going to have to be supplied w/ buck/boost transformers, (2 or 3), the heating elements replaced w/ ones rated for 240V, & reconnect the kiln for single phase input, which may not be allowed/possible, it's not a motor load so a VFD is not going to work, & not sure a RPC would work either.

 

[Bert_]

It's just a resistive load. No reason to create 3 phase if the machine can be converted to single.

It will have elements wired in 3 banks. If those connections are accessible it's not a big deal to convert to single phase. Will need a bigger contactor if that's what it used to control the elements.

A 1.5kva 240x32v transformer would reduce the 240v line down to 208v.

 

[vrinner]

Manufacture did give me a small parts list to convert to single phase so that's not a problem.

Thanks for the replies. I'll check them out.

 

[alfredeneuman]

If it has a control circuit, it will probably be tapped off of one leg to ground so you might be alright.

That would be not only dangerous but a Code violation.

 

[cannuck]

That would be not only dangerous but a Code violation.

Aw shucks, did I actually write ground instead of neutral???

 

[alfredeneuman]

Aw shucks, did I actually write ground instead of neutral???

It says on the nameplate "208 Volts AC 3 wire" so there is no neutral.

 

[BillK]

So getting a quote from manufacture to do the proper swap of everything that is needed and it's just under a grand for all the parts.

I think that everyone is missing this comment in your original post.

This comment tells me that it isnt a simple swap.

 

[rsanter]

First off let’s look at what 208 three phase really is,It is three separate legs of 120v separated by 120 degrees between the phases.
240 singlphase is two legs of 120v separated by 180 degrees between the phases.

This being a resistance load you really cannot use VFD but if you know the wiring diagram of the kiln you may very well be able to change it to work on your 240 volt single phase.
Sleep if you can get their Wirig diagramming for th model you have and the model that would run on 240 single ph

 

[Bert_]

What parts are they quoting you to convert to single phase?

 

[American Locomotive]

Please answer the following questions:

- What is the $1000 kit doing, is it converting the unit from three phase to single phase, or 208 > 240v?
- What is the "small list of parts doing" - is it converting from 3 phase 208v to single phase 208v? Or is this the $1000 kit?

 

[cannuck]

It says on the nameplate "208 Volts AC 3 wire" so there is no neutral.

I work with large transformers, so neutrals are common in my world (sorry for the pun)

 

[alfredeneuman]

I work with large transformers, so neutrals are common in my world (sorry for the pun)

All the large transformers I've worked on have had 3W primaries.

 

[Norcal]

I work with large transformers, so neutrals are common in my world (sorry for the pun)

When it is 3Ø with a neutral it would be 4-wire.

 

[ez-duzit]

The kiln's wiring will also be unfit for sufficient single phase power.

 

[alfredeneuman]

The kiln's wiring will also be unfit for sufficient single phase power.

Manufacture did give me a small parts list to convert to single phase so that's not a problem.

 

[cannuck]

All the large transformers I've worked on have had 3W primaries.

Power plants are Y not delta, and then the LV is the "primary". HV to transmission is delta. Large to me is 100 to 400 tons. BUT: I am the mechanical guy - Materials, fasteners, cooling, insulation - NOT one of the electrical people as you might guess.

 

[vrinner]

Please answer the following questions:

- What is the $1000 kit doing, is it converting the unit from three phase to single phase, or 208 > 240v?
- What is the "small list of parts doing" - is it converting from 3 phase 208v to single phase 208v? Or is this the $1000 kit?

The $1000 in parts is a entirely new lid with heating elements ($750) and the one more heating element for the body to make it 240v compatible and the some wiring parts to go from 3 phase to single.

They don't suggest trying to just replace the heating elements in the lid as it usually destroys the brick in the lid and then when you heat things up the brick can crumble and fall onto your work.

I think if I can find the right transformer to go from 240 single to 208 single and then get the small parts that would be the way to go.

 

[Bert_]

This transformer can be wired to buck 240 down to 208v https://www.ebay.com/itm/174401467562?epid=1900562860&hash=item289b2334aa:g:VOEAAOSwmGVhfFIl

 

[vrinner]

This transformer can be wired to buck 240 down to 208v https://www.ebay.com/itm/174401467562?epid=1900562860&hash=item289b2334aa:g:VOEAAOSwmGVhfFIl

So 16/32 is 208? Just making sure.

 

[American Locomotive]

240 - 32 = 208

So yes, that would work.

 

[Bert_]

When you need a small-ish change in voltage wiring a transformer buck or boost let's you get away with a much smaller transformer than a normal isolated primary x secondary transformer.

A transformer with a 240v primary and a 208v secondary would need to be nearly 10kva to run this kiln. With a bucking transformer we only need 1.5kva. That's because only the secondary of a buck/boost transformer needs to handle all the current of the kiln.

240-208= 32 so we want to lower the voltage by 32. We can that with a 32v secondary. But how big does it need to be?

8320w / 208v 1ph = 40amps so 40a through the secondary of the transformer.
40amps x 32 volts = 1280va closest larger size is 1500 or 1.5kva

 

[walta]

I think the first step is to get the instruction from the manufacture to make the machine operate on single phase and confirm the current requirement will be 40 amps at 208 volts.

Once we are sure about the current requirement, we can size the transformer needed. My guess is 1.5kW will be about 10% over the minimum

Yes, a standard transformer will work but it will weigh more than the kiln and take up almost as much floor space.

I am recommending a Buck/ Boots transformer it is wired to add or subtract some voltage from the line voltage. In your case we will subtract 32 volts from the 240 volt supply giving you the 208 volts you require. The buck transformer will be about 80% smaller and lighter. Used transformers are not uncommon and with no moving parts transformers rarely fail.





Walta

 

[ez-duzit]

This transformer can be wired to buck 240 down to 208v https://www.ebay.com/itm/174401467562?epid=1900562860&hash=item289b2334aa:g:VOEAAOSwmGVhfFIl

It cannot create 208V 3-phase.

 

[Norcal]

It cannot create 208V 3-phase.

Nobody said it did.

 

[walta]

Changed my mind the first step is to disconnect and ohm out all 3 elements one at a time because if one is bad you will be buying a new lid.

Walta

 

[alfredeneuman]

If the kiln is a continuous load it would change the current requirement.

 

[vrinner]

OK...so I was able to pickup the Acme T113074 transformer for $45 bucks. It was actually for two of them mounted on a steel frame so I got two and a frame for $45 bucks!

So looking at the schematic, here is what I believe I need to do.

On the input side
Connect H2 & H3 together
Connect one leg from my panel to H1 and the other leg to H4 (Does it matter which leg I connect to H1 or H4?)
Instead of wiring it directly to my panel, can I just put a 6-50 connector on the end and plug it into an existing 240 outlet?

On the output side
Connect X2 and X3 together
Connect one leg of my outlet to X1 and the other leg to X4 (Does it matter which leg I connect to X1 or X4)

Do I need to run a ground wire from my panel to the case or frame of the transformer?

Is it OK for me to mount the 208v outlet directly onto this frame or do I have to mount it to the wall (for code or whatnot)?

 

[ez-duzit]

That will not produce 208v 3-phase.

 

[vrinner]

That will not produce 208v 3-phase.

I need single phase, not 3 phase.

 

[walta]

I still think the first step is to disconnect the wires from one end of each heater and test each element. There is no point in wiring up the transformer if one of the elements is bad and the lid needs to be replaced.

This diagram seems to line up with the tags on your transformer.

I would power it up and measure the output voltage there is a 50% chance that the transformer will increase the voltage output from 240 to 273. If that happens switch the wires on the X1 connection with the wires on the X4 connection and measure again.

YES, you must ground the box the transformer is in.

To me the question will the kiln be hard wired to the building making it difficult the move or will there be a plug and socket and will the plug be before or after the transformer?

Hard wired install requires the transformer be attached to the building and a disconnect unless you have a line of sight to the circuit breaker for the kiln from the kiln.

Plug after the transformer means the transformer and a disconnect box would need to be attached to the building.

Plug before the transformer means you need to attach the transformer to the kiln but the plug could serve as the disconnect.

Walta

https://hubbellcdn.com/ohwassets/HCI/Acme_Electric/Literature/SECTION-7.pdf

 

[vrinner]

I still think the first step is to disconnect the wires from one end of each heater and test each element. There is no point in wiring up the transformer if one of the elements is bad and the lid needs to be replaced.

What is the proper way to test those...I'm assuming a multimeter. Not being an electrical guy I'm not 100% sure but I do have a couple of different multi-meters (I "regular" one and one of those clamp ones).

Plug before the transformer means you need to attach the transformer to the kiln but the plug could serve as the disconnect.

Yes...I'm thinking plug before transformer means I can just plug it into an existing outlet so I can then just attach the transformer to the outside of the kiln then.

 

[BillK]

What makes you think that you can get 208 from that transformer ??? Everything I see on the data plate looks like the output is either 16 or 32 volts. Unless I am looking at it totally wrong. Here is a link to the product brochure:

https://hubbellcdn.com/brochure/BuckBoostTransformerBrochure.pdf

This shows the output at 16 or 32 volts.

 

[Bert_]

What makes you think that you can get 208 from that transformer ??? Everything I see on the data plate looks like the output is either 16 or 32 volts. Unless I am looking at it totally wrong. Here is a link to the product brochure:

https://hubbellcdn.com/brochure/BuckBoostTransformerBrochure.pdf

This shows the output at 16 or 32 volts.

At least make an attempt to read the thread, this is exactly what has been suggested.