# 208vac 3ph to 24vdc solution ?



## wildleg (Apr 12, 2009)

you might have 120 at the transformer but if you didn't check for a neutral you'll never know.

anyhows, to answer your question: 
https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=208%20to%2024v%20transformer


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## emtnut (Mar 1, 2015)

martindag said:


> Hi guys,
> 
> i have to rebuild a control for a very old equipment and the main power is 208vac 3ph 60hz. so i got 3 ph and a ground. All my control component are prety much all 24VDC.... and was wondering what would be the best solution to get that 24vdc?
> 
> ...


If you have 208V 3ph and a neutral, then you have 120V phase to neutral ... Am I missing something here ?

**edit ... Is it a wye or delta you're working with ?


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## martindag (Oct 30, 2009)

Well... i got 3 phase of 208vac and a ground ....

i do have a neutral to my electric panel but not on the actual receptacle that im using which is 50 ft away from it.

So im wondering with 3 phase 208vac and a ground what is the easiest way i could get a 120vac AND a neutral... without pulling it all the way from my panel and changing all my cable and receptacle.


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## Service Call (Jul 9, 2011)

Is it in conduit?


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## KennyW (Aug 31, 2013)

No reason you cannot buy a 24v power supply that will take a 208v input from two of the phases...


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## emtnut (Mar 1, 2015)

martindag said:


> Well... i got 3 phase of 208vac and a ground ....
> 
> i do have a neutral to my electric panel but not on the actual receptacle that im using which is 50 ft away from it.
> 
> So im wondering with 3 phase 208vac and a ground what is the easiest way i could get a 120vac AND a neutral... without pulling it all the way from my panel and changing all my cable and receptacle.


The best way ... Since your only 50' away, is to run a new 120V circuit from your panel.

If not, If you post the model# of the wiedmuller supply, I could take a look:thumbsup:

Depending on the power supply, it may not mind the 32 volts less.

What style receptacle is it? Wondering what used to be plugged in it


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## AK_sparky (Aug 13, 2013)

KennyW said:


> No reason you cannot buy a 24v power supply that will take a 208v input from two of the phases...


I agree. Get a power supply that will take a 208V input. No futzing around with neutrals.


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## JRaef (Mar 23, 2009)

Most newer 24VDC power supplies will accept a really wide input voltage range, likely 85-265VAC input, and give you a stable 24VDC output. The one you have now might already be like that, and it will not care if it's L-L or L-N for the incoming. That's because they are all what are called "Switch Mode Power Supplies" now, and they can adjust the output voltage from just about any input, as long as it is higher than the output needs and lower than the flashover point of the terminals.

As for the 120V, since you don't have a Neutral brought out to the machine, you will need to use a transformer and tap off of two legs of the 208V. Even though at some point up stream of your machine, there WILL be a grounded neutral to give you 120V Ph-N, you legally cannot use the Ground as a current carrying conductor. If your 120VAC load requirement is more than a few amps, you might consider pulling a neutral into that conduit because the transformer, plus the primary and secondary protection, may end up costing more than the wire pull would.


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## emtnut (Mar 1, 2015)

JRaef said:


> Most newer 24VDC power supplies will accept a really wide input voltage range, likely 85-265VAC input, and give you a stable 24VDC output. The one you have now might already be like that, and it will not care if it's L-L or L-N for the incoming. That's because they are all what are called "Switch Mode Power Supplies" now, and they can adjust the output voltage from just about any input, as long as it is higher than the output needs and lower than the flashover point of the terminals.
> 
> As for the 120V, since you don't have a Neutral brought out to the machine, you will need to use a transformer and tap off of two legs of the 208V. Even though at some point up stream of your machine, there WILL be a grounded neutral to give you 120V Ph-N, you legally cannot use the Ground as a current carrying conductor. If your 120VAC load requirement is more than a few amps, you might consider pulling a neutral into that conduit because the transformer, plus the primary and secondary protection, may end up costing more than the wire pull would.


I'm wondering if there even is a machine there ... why the existing receptacle ? ... seems odd


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## martindag (Oct 30, 2009)

Well i was planning to use a old receptacle around for this equipment but i guess pulling a new 50ft with a neutral wound be the best option. But it's good to know that my actual power supply could possibly take a L-L 240v ! 

Thanks for all the advice!


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## micromind (Aug 11, 2007)

KennyW said:


> No reason you cannot buy a 24v power supply that will take a 208v input from two of the phases...


I've connected a lot more than one of them this way. 

That don't care about voltage to ground, only what appears at the input terminals. 

I've even connected them to the high leg and one of the other phases of a 240∆ system.


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## martindag (Oct 30, 2009)

here just in case its the link of the power supply im using....

http://newsroom.cuthbertstewart.co.nz/wp-content/uploads/2016/02/14781100009999.jpg


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## emtnut (Mar 1, 2015)

martindag said:


> here just in case its the link of the power supply im using....
> 
> http://newsroom.cuthbertstewart.co.nz/wp-content/uploads/2016/02/14781100009999.jpg


Input range is 85 to 277 Vac. So you'll be fine with 208v :thumbsup:


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## martindag (Oct 30, 2009)

Perfect thanks alot !


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## telsa (May 22, 2015)

The old ATX PC computer power supply could give you 24VDC

Though, not so much.

You'd have to use the -12VDC and +12VDC rails.

&&&&&&

Due to solid state switching circuits and capacitors --

All of the 'old rules' have been obliviated.


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## martindag (Oct 30, 2009)

I got also a Temperature controler from Omega a CNi16D33 and the input is 110v-240v just like my power supply, do you think it can take a L-L 208vac ?


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## psgama (Oct 26, 2015)

Most likely it will be fine.


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## triden (Jun 13, 2012)

martindag said:


> here just in case its the link of the power supply im using....
> 
> http://newsroom.cuthbertstewart.co.nz/wp-content/uploads/2016/02/14781100009999.jpg


That's a good supply. Pheonix is another candidate that makes good supplies.


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## Jhellwig (Jun 18, 2014)

A little late but they do make 480volt 3phase to 24vdc power supplies. I would imagine that they might also make a 208 3phase version.


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## oliquir (Jan 13, 2011)

Jhellwig said:


> A little late but they do make 480volt 3phase to 24vdc power supplies. I would imagine that they might also make a 208 3phase version.


yes they exist, almost any popular brand of power supply have them, phoenix, weidmuller, meanwell,... 
heres one not too expensive Mean Well DRT-240-24


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## MechanicalDVR (Dec 29, 2007)

What is the reason you want a 3 ph power supply as opposed to a single phase 208v to 24v ? What type controls are you using ? Why a power supply instead of just a transformer mounted in your control panel on the equipment ? Why is the 120v needed ?


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## Jhellwig (Jun 18, 2014)

A three phase powere dc power supply has less ripple that needs corrected and can handle more power on a smaller foot print. It is the same type of thing with drives. The single phase powered ones are larger than the 3 phase ones.


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## MechanicalDVR (Dec 29, 2007)

Jhellwig said:


> A three phase powere dc power supply has less ripple that needs corrected and can handle more power on a smaller foot print. It is the same type of thing with drives. The single phase powered ones are larger than the 3 phase ones.


I missed the vdc in the first post and the swapping out an outlet sounded odd as well.


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## JRaef (Mar 23, 2009)

oliquir said:


> yes they exist, almost any popular brand of power supply have them, phoenix, weidmuller, meanwell,...
> heres one not too expensive Mean Well DRT-240-24


I've always thought that was a terrible name for a company. 

"It doesn't work, but they mean well..."


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## micromind (Aug 11, 2007)

Jhellwig said:


> A little late but they do make 480volt 3phase to 24vdc power supplies. I would imagine that they might also make a 208 3phase version.


As far as I know, no one does. They're all single phase.


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