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Old 06-04-2010, 11:50 PM   #1
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120/208 120/240 high leg delta panel


whats the difference between a 120/208 and 120/240.
i have 3 hot legs coming in over head, and i have 120/120/208.
tester ,120 with 120=240 and 120 with 208=240.

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Old 06-05-2010, 12:17 AM   #2
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120/208 120/240 high leg delta panel


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Originally Posted by florint23 View Post
whats the difference between a 120/208 and 120/240.
i have 3 hot legs coming in over head, and i have 120/120/208.
tester ,120 with 120=240 and 120 with 208=240.
There are few ways you can indentify if you have wye connected or delta conneted system.

One way is you can tell the numbers of breaker if they skip every third space then you have delta system however with wye it will use all phases.

To order to read the voltmeter on delta or wye system here the way you do it.,,,

DELTAsystem

get the voltmeter and read from line to netural each phases so here the example :

Phase A - 120 volts
Phase B - 208 volts
Phase C - 120 volts

That is from line to netural reading and if you are reading line to line it will read 240 volts.

WYE system

Phase A - 120 volts
Phase B - 120 volts
Phase C - 120 volts

Again that from line to netural and line to line will read 208 volts

The other thing I will warn you if you have delta system make sure you do not hook anything on 120 volts to wild leg { 208 volts } otherwise you will make magic smoke real quick.

Merci,Marc

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Old 06-05-2010, 01:15 AM   #3
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120/208 120/240 high leg delta panel


Quote:
DELTAsystem

get the voltmeter and read from line to netural each phases so here the example :

Phase A - 120 volts
Phase B - 208 volts
Phase C - 120 volts
Marc must be snoozing. He never leaves out important information like this.

along with the voltage readings listed, you will also get 240 volts from A-B, B-C, and C-B

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Old 06-05-2010, 01:33 AM   #4
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120/208 120/240 high leg delta panel


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Originally Posted by frenchelectrican View Post
get the voltmeter and read from line to netural each phases so here the example :

Phase A - 120 volts
Phase B - 208 volts
Phase C - 120 volts

That is from line to netural reading and if you are reading line to line it will read 240 volts.

The other thing I will warn you if you have delta system make sure you do not hook anything on 120 volts to wild leg { 208 volts } otherwise you will make magic smoke real quick.

Merci,Marc
Nap I did not leave anything out and I will print in bold that where I did mention line to line voltage.

Merci,Marc

P.S. it is 08:40 Paris time when I am typing and I am awake allready
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Old 06-05-2010, 01:50 AM   #5
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120/208 120/240 high leg delta panel


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Merci,Marc (The other thing I will warn you if you have delta system make sure you do not hook anything on 120 volts to wild leg { 208 volts } otherwise you will make magic smoke real quick. )
what do you mean by that?i got a 3 phase a/c unit 120/120/208 . is that not hooking 120 to 208, i cant do that
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Old 06-05-2010, 02:05 AM   #6
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120/208 120/240 high leg delta panel


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Merci,Marc
(The other thing I will warn you if you have delta system make sure you do not hook anything on 120 volts to wild leg { 208 volts } otherwise you will make magic smoke real quick. )

what do you mean by that?i got a 3 phase a/c unit 120/120/208 . is that not hooking 120 to 208, i cant do that[/QUOTE]

I just want to make it clear on what you are getting there.,

The normal three phase A/C unit is wired for either 208 or 240 volts as I mention above you will read 240 volts between hot lines and I know you read 120-120-208 that is normal to read that and that is on Delta system.

The way you read is from line to netural that is correct.

However if you have outdoor or indoor older breaker box this get very instering from time to time I ran into delta breaker it is a odd item you may not see it anymore at all { the only way you can replace the old delta breaker is replace the whole panel box or mount a subpanel next to it for three phase breaker } The old style delta breaker will have two tabs mounted to the single phase load centre while the third leg have specal connection there it will have two screws one for incomming and second one for outgoing circuit. { I will look around for the photo what it look like }

Merci,Marc
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Old 06-05-2010, 02:27 AM   #7
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120/208 120/240 high leg delta panel


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Originally Posted by frenchelectrican View Post
Nap I did not leave anything out and I will print in bold that where I did mention line to line voltage.

Merci,Marc

P.S. it is 08:40 Paris time when I am typing and I am awake allready
I guess it's me that has to wake up. I missed that in your post. sorry about that.

what marc is warning you about is; if you use a standard panel, it is possible to hook up something to that 208 to neutral leg easily by mistake. If you forget about it and put a single pole breaker in the space for that phase, using that will feed 208 volts to what you thought was feeding 120 volts.

It has happened to a lot of seasoned electricians that aren't paying attention.

Last edited by nap; 06-05-2010 at 02:32 AM.
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Old 06-05-2010, 02:47 AM   #8
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120/208 120/240 high leg delta panel


one more thing, i want to put a new 120/208 high leg 150 amp panel just for the a/c, so every 3rd space is the 208, i have to leave it blank. or does the 208 have to be in the center? cause i have a stove and a dryer with a double pull breaker .

ya i know about that breaker, i found out about that for the first time today. but the one that i found was 250 dollars used , and they couldnt sell it to cause it was defective . they dont make them anymore , so im putting a new high leg delta panel.
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Old 06-05-2010, 07:08 AM   #9
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120/208 120/240 high leg delta panel


Also be sure that your 3 phase equipment, 120/2xx volt equipment, and 2xx volt equipment is specifically rated for the voltage of the feed. Some household and light industrial equipment takes either 208 volts or 240 volts.

A 240 volt 3 phase circuit has 240 volts phase to phase and may have a neutral producing 120 volts phase to neutral for two of the phases (and 208 volts phase to neutral for the third -- high leg; wild leg; orange -- phase).

A 208 volt 3 phase circuit has 208 volts phase to phase and almost always has a neutral producing 120 volts phase to neutral for each phase.

A 13,200 volt 3 phase circuit has 13,200 volts phase to phase (distribution circuits are off topic here).

Master electrician's license or Ph.D. in electrical engineering needed. Three phase equipment using both 120 volts and 2xx volts e.g. 120/120/208, that is, having a neutral connection, and also rated for both 208 and 240 volts must indicate which of the three phase wires is to be connected to the wild leg. All single phase equipment using both 120 and 240 volts (having a neutral lead) must be connected to the non-wild legs if you have a 240 volt 3 phase system; do not try to balance these loads about all three phases.
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Last edited by AllanJ; 06-05-2010 at 10:30 AM.
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Old 06-05-2010, 08:48 AM   #10
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120/208 120/240 high leg delta panel


ya the 208 is going directly in to the a/c and the 120 is at a single phase disconnect on the a/c. at the panel , the 208 is just passing throw what use to be a disconnect with fuses and the 120 is coming off from the sub panels lug nuts and passing throw also to the disconnect to the a/c.
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Old 06-05-2010, 10:27 AM   #11
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120/208 120/240 high leg delta panel


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one more thing, i want to put a new 120/208 high leg 150 amp panel ... does the 208 have to be in the center?.
The 120/208 volt 3 phase feed (208 volts hot to hot) does not have a high leg so the feed wires can be connected up top in any order.

The 120/240 volt 3 phase high leg feed wires have to be arranged in the correct order at the top of the panel in order that the 120 volt hot to neutral legs match up with the breaker slots down below.

Equipment that has two hot leads and neutral must not be connected to the wild leg of a delta 120/240 volt system unless the instructions specifically allows it. Equipment using 208 volts only (two hot leads and no neutral) may be connected to wild leg and neutral.
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Old 06-05-2010, 11:54 PM   #12
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120/208 120/240 high leg delta panel


The standard pratice with delta load centre the wild phase will be on the C phase but few case I ran into it will be on B phase so that is the extra step you have to be carefull which phase you will take and use it.

Merci,Marc
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Old 06-06-2010, 11:38 AM   #13
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120/208 120/240 high leg delta panel


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Originally Posted by florint23 View Post
ya i know about that breaker, i found out about that for the first time today. but the one that i found was 250 dollars used , and they couldnt sell it to cause it was defective . they dont make them anymore , so im putting a new high leg delta panel.
If you are installing a new panel anyway you might consider this:

Buy a smaller 3 phase panel with enough spaces to feed your 3-phase loads plus a few extra spaces. Then install a new 1-phase panel next to it fed with the 2-120-volt phases protected by whatever size breaker your load requires. Then you can relocate your single phase loads to that panel. This way you don't have to worry about someone in the future accidentally tying into the high leg.

You should identify the Delta high leg panel with a label or something highly visible as being such! This is required by code if you are in the US!
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Old 06-06-2010, 12:52 PM   #14
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120/208 120/240 high leg delta panel


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You should identify the Delta high leg panel with a label or something highly visible as being such! This is required by code if you are in the US!
If I remember correctly, it is with an orange marking.



and around here (SW MI/ N Cent IN) we put the high leg on B phase typically. In one area, the POCO feeds it as C phase because their meters have to have it that way but we still put it on B in the panel.
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Old 06-07-2010, 07:17 PM   #15
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120/208 120/240 high leg delta panel


now the single phase are 4/0 size wire and the 208 is 2 awg wire , is it that 208 capable for a 150 amp 3 phase panel? cause some people told me that the 2 amg wire could not be big enough for a 150 amp 3 phase main .

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