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Old 09-08-2008, 08:05 AM   #1
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Connect 120/240 clothes dryer to 3-phase panel - possible?


There is a clothes dryer appliance that bears a NEMA 14-30 plug. We all know that it draws both sides of the standard household 120v, single phase two-wire power, which produces a potential of 240 volts across the hots. However, I have been asked if this appliance can be connected to the nearest panel, which is a 3-phase panel.

Mechanically, the installation of a breaker and a 14-30 receptacle would be exactly the same. But the resulting voltage would not be 240 - it would be 208 volts due to the 120 offset of the phases, correct? (I'm trying to remember back a few years on this, so I might not have all the numbers correct.)

So the question is, can this appliance be connected to this panel? I have read some entries on the internet where people seem to hint that they have 240v appliances connected to a 3-phase panel, but such intimations can never be trusted.

I will consult the appliance's owner/operator documentation when I can, but in the meantime, what's the straight dope - can this be done? Or must a commercial, 3-phase appliance be used?

Thanks to all for your consideration...

- Gamm.

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Old 09-08-2008, 08:37 AM   #2
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Connect 120/240 clothes dryer to 3-phase panel - possible?


Double check the nameplate on the dryer to make sure it can be run on 208v, it should be able too. To answer your second question, it's very common to pull single phase pwr from a 3 phase panel. No worries.

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Old 09-08-2008, 08:56 AM   #3
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Connect 120/240 clothes dryer to 3-phase panel - possible?


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Originally Posted by Gamm View Post
However, I have been asked if this appliance can be connected to the nearest panel, which is a 3-phase panel.
Are you sure this is three phase? Residential or commercial.

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But the resulting voltage would not be 240 - it would be 208 volts due to the 120 offset of the phases, correct?
It depends on what the transformer secondary is, i.e. wye or delta.

Honestly, and not to sound like a jerk, but if you are asking these questions, do you really think that you are qualified to complete the installation?
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Old 09-08-2008, 10:07 AM   #4
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Connect 120/240 clothes dryer to 3-phase panel - possible?


I'm not sure I'm prepared to be questioned by someone who misquotes the great George Carlin. :o)

Hey, I can understand your concerns - it's very common on these types of message boards, especially those concerning electrical work. I won't bother typing out a resume, but yes - I'm comfortable with this type of work.

Thanks for the suggestion, Cow. I looked over the dryer initially, but haven't had a chance to do so in the last week or so. If it can operate on 208, then that would naturally be the easiest solution.

- Gamm.

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Old 09-08-2008, 10:15 AM   #5
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Connect 120/240 clothes dryer to 3-phase panel - possible?


If what you have is a 120/208 panel, then the dryer will work. It won't get quite as hot as it would at 240, but it will work.
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Old 09-08-2008, 10:38 AM   #6
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Connect 120/240 clothes dryer to 3-phase panel - possible?


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Originally Posted by Gamm View Post

Mechanically, the installation of a breaker and a 14-30 receptacle would be exactly the same. But the resulting voltage would not be 240 - it would be 208 volts due to the 120 offset of the phases, correct? (I'm trying to remember back a few years on this, so I might not have all the numbers correct.)


- Gamm.
No it's not correct. The transformer connection determines the nominal voltage. Have you measured across the three phases. This tells you what the voltage is. 240 or 208.
Do you have a four wire or 3 wire system? If its a three you need another XFMR to get 120 volts. Or should I say IF you need 120.
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Old 09-08-2008, 12:32 PM   #7
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Connect 120/240 clothes dryer to 3-phase panel - possible?


208/240....whatever it takes

If it is 120/240 delta, STAY OFF the high leg. Dryer motors are commonly 120V while the elements are 240V.


Even though is is 240V between phases, the high leg is 200ish volts

Last edited by 220/221; 09-08-2008 at 12:34 PM.
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Old 09-08-2008, 12:59 PM   #8
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Connect 120/240 clothes dryer to 3-phase panel - possible?


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No it's not correct. The transformer connection determines the nominal voltage. Have you measured across the three phases. This tells you what the voltage is. 240 or 208.
So, it's not that it's not correct. It's just that it's not necessarily correct. As BigJimmy pointed out above, it depends on the type of secondary transformer.

This is pure speculation until I meter the panel myself, but I suspect it is Wye, not Delta. I believe the original panel configuration has 120 volt circuits running from all three legs. A highleg delta system would have 208v on one of those three legs, and I don't believe that to be the case. Pity, actually - I'd have access to 240v that way. But anyway - we'll just have to see.

Thanks again for all the input, it is truly appreciated. Also, great reference, 220/221. (I'm assuming Michael Keaton?)
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Old 09-08-2008, 01:22 PM   #9
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Connect 120/240 clothes dryer to 3-phase panel - possible?


Gamm-

Sorry about the mis-quote. I'll take care of this blasphemy immediately!

Where is the washer being installed? Is this a commercial install? My guess is that you're probably dealing with a 4W wye secondary but this is simply a guess.

And yeah, 220-Is that a nod to Mr. Mom? I always figured that it was but never asked.

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Old 09-08-2008, 04:12 PM   #10
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Connect 120/240 clothes dryer to 3-phase panel - possible?


When I signed up on the electrical boards, I was surprised that no one had taken the name.
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Old 09-09-2008, 01:48 AM   #11
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Connect 120/240 clothes dryer to 3-phase panel - possible?


Let me add little more with Delta and wye colour codes

typical delta will have Black , orange , red { or bleu depending on the type of wire used however.,, if you see black red bleu somecase old delta system used to be marked red { in very old system but modern delta system will marked orange or will warn wildleg there }

a quick giveaway with breaker box if you see every third one is skipped that will tell ya is delta but some area they keep single and three phase panel sepratated so you don't get single or three phase delta load mixed up espcally with some equiment that need 120v netural

typically delta line to line is 240 volts while line to netural., A phase to netural is 120 and C phase to netural is 120 but B phase to netural is 208 volts { yeah there is other name called for wild leg but I will keep it G rated here }

If you hook up anything that required 120 volts and landed on wild leg phase the result will useally destory something once you throw breaker or turn on something POOF that it.

typically on the breaker the wildleg will useally be founded in B phase { some case in C phase }

The wye system is not a issue with wild leg due it is non exsting due the phase sequice all the phase between the lines are useally 208 volt and line to netural is 120 volts

typical colours are Black Red Bleu { there are other colours but please verify with voltmeter to make sure you know what you stand on it }

Merci,Marc
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Old 09-09-2008, 03:30 AM   #12
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Connect 120/240 clothes dryer to 3-phase panel - possible?


My house has a 120/208 3 phase 4 wire wye service. Seriously, it does, I have a bunch of 3 phase shop equipment, and this was far better than a phase converter.

My dryer, a basic Maytag that is about 30 years old, has run on 120/208 for about 12 years now. Not the slightest problem. It takes a bit longer to dry a load of clothes, you get used to it quickly.

Lower voltage means lower current, which would likely translate to longer life. A 240 volt heating device operated on 208 will consume 25% less watts. And produce 25% less heat.

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Old 09-09-2008, 08:37 PM   #13
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Connect 120/240 clothes dryer to 3-phase panel - possible?


Not bad Rob.,,

My home have 3 phase system as well {208Y120} while the shop used 480Y277 system between the two I do have transformer to downstep the voltage.

All of my system is run from one meter but it can be converted to seprated if need to.

Yeah any equiment espcally with heating elements will work fine on 208 volts as Rob mention it will take longer to get up full heat due lower wattage.

Motors that diffrent story it depending on the nameplate if can run on 208 system or not.

Merci,Marc
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Old 09-10-2008, 01:59 PM   #14
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Connect 120/240 clothes dryer to 3-phase panel - possible?


Continued thanks to all who are taking the time to contribute...

Regarding phase color coding: There are certainly standard practices, but to my knowledge there is no mandated standard for color coding of three-phase systems. Neutral and ground, of course - but not the phases. I've never trusted color coding anyway. You only have to have your three-phase motors start running backwards once before you realize you can't trust color coding!

The panel in question is exactly as I suspected - a 120/208Y. Next I'll check the dryer and see if it can operate at 208v. If the dryer is not listed to run at 208v, then I'll discuss options with the client. Either get a new dryer, or be satisfied with extra-long drying times.

We'll see - thanks again all...

- Gamm.
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Old 09-10-2008, 09:38 PM   #15
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Connect 120/240 clothes dryer to 3-phase panel - possible?


That dryer should work fine on a 208Y/120 volt supply. Since it has a NEMA 14-30P cord on its end, it requires a neutral connection, most likely for the timer, any lights, and the motor.

The element will operate at 25% less wattage, so your drying cycles may take a bit longer. But, your element should last longer on that setup.

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