3 phase upgrade questions

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  #1  
Old 12-19-10, 09:08 PM
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3 phase upgrade questions

My house currently has 100A 3 phase 240Δ120 4 wire (red leg) service. I do not have anything that uses 3 phase right now (nothing is even wired to the B phase), but since I am not paying any premium to have it, I don't see any reason to drop it, especially since I eventually want to build a wood shop in the garage. My current setup has the mast/meter, with a 125A QO 3 phase breaker box underneath. This has a 100A main breaker and nothing else in it. This spring, I am going to have the POCO change my service to underground, and I figure it is as good a time as any to upgrade it to 200A.

Here's what I've done so far:

* Replaced 'house main' panel in basement - upgraded to 200A with main breaker.
* Run new 2 1/2" conduit from basement panel, through garage, then (via LB) through the wall to the exterior main breaker.
* New conduit contains 3x 2/0 copper + #4 ground. (It has #2 pigtails in the outdoor box to fit the 100A breaker lugs and busbar.)

Here's what I want to do:

* Install 200A 3 phase meter pan
* If necessary, install new 200A 3 phase main breaker (or a meter/main combo)
* Install 200A 3 phase main breaker panel in garage (back to back with meter or outdoor main)
* Feed basement panel from this panel via 225A fuseless lug block (phase A+C).
(I know about the high leg being 208V L-N, not being used for single phase loads, needing to be Phase B, and being colored orange.)

This will allow me to have either 1 or 3 phase branches in the garage, but eliminates the need for a large 3 phase panel (with lots of wasted spaces) in the basement. It also avoids having to run garage circuits to the basement.

Here's my questions:

Anyone see any issues with what I want to do? We are still on NEC2002 here.

I've already found out that you can't get 3 phase anything at a big box (even a QO breaker). I am also about 200 miles from the nearest supply house. Can anyone recommend an online supplier that caters to the public with good prices?

Do I need (or should I have) an outdoor main? There will only be about 3 cable feet between the outdoor and indoor equipment, and it will be in conduit through a solid brick wall.

Is there any issue using those fuseless lug blocks, given the fact that it is wired for 200A and both the 3 phase panel and the subpanel both have 200A main breakers? I would prefer to use them if at all possible, because it'll save me several hundred dollars over buying a 200A 3 pole branch breaker (the 2 pole version requires 4 stabs, therefore is incompatible with a 3 phase panel). Am I going to have to explain them to the inspector?

The existing ground is obviously going to have to be upgraded (single rod, 10ga). Right now it goes into the outdoor breaker box. If I don't use an outdoor main, is it still acceptable to run the ground wire into the meter pan and through the conduit into the 3 phase panel (since that would be the first disconnect)? If so will I have to bond the pan since the ground wire will be passing through it?

Thanks
 
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Old 12-19-10, 10:37 PM
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Before you do any upgrading to your system check with POCO to see what they say about upsizing your service to 200 amp and do this three phase transfomer is served to your house only or shared to other house or bussiness near by ??

If it was your own three phase transfomer set up some POCO will give you a couple options one is coverted to single phase or go with three phase Wye connection

This what most POCO rather have to use the wye connection it safer and you can able use full pointeal of three phase supply due you can get 120 volts from each leg to netural but only gotcha is you will only get 208 volts line to line so just give you a head up if you have any electrical heating devices that run on 240 volts they will reduce the heating performace to 25% so expect that if you go this route.


Normally with three phase supply I really discourage most DIYers to mess around with delta supply unless you really understand the system. the Wye is not too bad at all.

The big box can make a specail order for your three phase load centre but it will not be cheap otherwise you can call the electrical supplier they can work something out and Oui of course they can ship it to you and expect to be mid 300 to 400 Euros for it on SqD QO series with main breaker.

If you have more question just ask one of us which we are famuair with triphase supply.

Merci.
Marc

P.S. my house and shop have triphase supply as well but I get the power to shop first then go to the house { main supply is 480Y277 volts } then go to transfomer to downstep to 208Y120 for part of shop and the rest go to the house. { that in wisconsin location }
 
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Old 12-20-10, 12:10 AM
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Your absolute first step is to consult with a customer service rep (and possibly also an engineer) at the utility. Three-phase into a residence is rare and if you are making a major change (going to an underground service is major as is going to a 200 ampere service) the utility may cease to serve you with the three-phase UNLESS you already have three-phase equipment needing to be supplied.

Most residential customer service reps won't have a clue when it comes to a three-phase service so be prepared to be shuttled around and play telephone tag when you call.
 
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Old 12-20-10, 04:45 AM
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Thanks for the feedback.. Let me give you a better picture..

I know residential 3 phase is rare.. I didn't even know I had it until about a year after I moved in, and I took a good long look at the drop one day and realized that it was quadplex and there were 4 wires going into the mast head, then I opened the breaker box and verified voltages. The pole behind my house serves mine plus 6 others (basically they stick a single pole in the alley in the middle of each block), and mine appears to be the only 3 phase. Everyone else's service is connected to the same pole feed as mine, but mine is the only one that connects to all 3 phases.

I never took notice of where the transformer is (it's definitely not just mine), but I'm literally 4 blocks from the power plant (the generating plant, not a substation), so it may very well be there. It's definitely nowhere near the pole.

The POCO actually made an offer to all the town residents that they will convert you to underground for just the price of the wire. They are making a push to put all the utilities underground to minimize storm damage. Two of my neighbors had it done over the summer, and their underground feeders are now much larger than the drops to the rest of the houses.

As for changing to single or wye, I wouldn't want to do either.. It's there, so I might as well take advantage of it. If it means borrowing my dad's compressor and slapping a receptacle on a 3 pole breaker to say I have a need for the 3 phase, so be it. I'd also rather not take the voltage cut because I have an electric stove and oven. I'm not scared of the extra wire, and I know how it works, so I would need a better reason to change it than it being easier to work with.

But I'll definitely call them and find out.
 
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Old 12-20-10, 08:44 AM
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Originally Posted by JerseyMatt View Post
* New conduit contains 3x 2/0 copper + #4 ground. (It has #2 pigtails in the outdoor box to fit the 100A breaker lugs and busbar.)
This could be a problem. The table 310.15(b)(6) only applies to single-phase 120/240 services. You might need to go up to #3/0 cu for a full 200A or drop the main to 150A. That's probably at the discretion of the inspector/plan reviewer. The also might want you to split the single phase loads into two or three smaller panels rather than one 200A panel to keep the load more balanced on their transformer.

I've already found out that you can't get 3 phase anything at a big box (even a QO breaker).
Home Depot has a big special order catalog you can get at the contractor's desk which should give you access to many three-phase items.

Do I need (or should I have) an outdoor main?
NEC does not require the main to be outdoors, but some local jurisdictions do.

is it still acceptable to run the ground wire into the meter pan and through the conduit into the 3 phase panel
No, it should go in a separate PVC conduit or if protected from damage, tie wrapped to the outside of the service conduit.

As for changing to single or wye, I wouldn't want to do either.
I suspect they may make you change to 208Y120V if they let you keep the three-phase. Many utilities consider the high-leg delta to be obsolete and will only re-install it if absolutely necessary. The wye service is a safer alternative and easier to understand for the electrician and line crew.
 
  #6  
Old 12-20-10, 10:43 AM
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The 3-phase service would be justified only if a 200 amp, 240/120 volt 3-wire system is inaduquate--- this determination is based on the existing loads + and any additional loads.

In general, the existing load calculations involves the square-foot area of the premises and the power ratings of specific loads for cooking / kitchen apliances, laundry appliances, domestic hot water appliances, and air conditioning .

Also ,the 1-phase / 3 -phase selection depends of the HP rating of the largest motor that will powering machinery and AC compressors.
 
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Old 12-20-10, 12:13 PM
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Originally Posted by ibpooks View Post
This could be a problem. The table 310.15(b)(6) only applies to single-phase 120/240 services. You might need to go up to #3/0 cu for a full 200A or drop the main to 150A. That's probably at the discretion of the inspector/plan reviewer. The also might want you to split the single phase loads into two or three smaller panels rather than one 200A panel to keep the load more balanced on their transformer.

This conduit serves a 1 phase 240/120 panel. It would be fed off the 3 phase panel, but that wiring would only see 1 phase. As for splitting the panels to balance the transformer, being as they have everyone else's single phase pulling from the same two legs, I can't see it being an issue...

Home Depot has a big special order catalog you can get at the contractor's desk which should give you access to many three-phase items.

Good to know, thanks.


NEC does not require the main to be outdoors, but some local jurisdictions do.

That's what I thought, I'll check with the inspector.

No, it should go in a separate PVC conduit or if protected from damage, tie wrapped to the outside of the service conduit.

Nitpicky I know, but "should" or "must"? Right now it is in a conduit that runs from the dirt up to the bottom of the breaker box. I want to do the same thing with the new ground into the new meter pan (which will be connected to the panel on the other side of the wall via a 2 1/2" nipple), and just pass it through the nipple to the panel. Basically I don't want to have to drill a separate conduit through the brick for the ground if I'm allowed to run it through the pan.

I suspect they may make you change to 208Y120V if they let you keep the three-phase. Many utilities consider the high-leg delta to be obsolete and will only re-install it if absolutely necessary. The wye service is a safer alternative and easier to understand for the electrician and line crew.
I understand it's obsolete, but as I said it's not just my transformer. I would assume if multiple customers are using the same high leg service, they can't just change out the transformer unless EVERYONE'S panels were reconfigured to balance a Wye system. They would also have to go pole by pole and reconfigure balance out all the customers who are all lumped onto the same two phases for their 240/120 (which would become 208/120)... I'll go take a walk around and see if I can figure out where the transformer is, but I guarantee it's serving a bigger area than you think.. I can't imagine them going through that expense to force me to change to wye...
 
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Old 12-20-10, 12:31 PM
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Originally Posted by JerseyMatt View Post
run it through the pan...
In my area it would not be allowed; only the phase and neutral conductors are allowed in the meter pan.

I can't imagine them going through that expense to force me to change to wye...
No they won't, they'll just force you to change to single phase or give you the option of paying the ridiculous cost installing the three-phase wye if you really want it. They usually are not very accommodating in this unless you have a stamped plan from an engineer detailing the three-phase service specs.
 
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Old 12-20-10, 12:32 PM
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Originally Posted by PATTBAA View Post
The 3-phase service would be justified only if a 200 amp, 240/120 volt 3-wire system is inaduquate--- this determination is based on the existing loads + and any additional loads.

In general, the existing load calculations involves the square-foot area of the premises and the power ratings of specific loads for cooking / kitchen apliances, laundry appliances, domestic hot water appliances, and air conditioning .

Also ,the 1-phase / 3 -phase selection depends of the HP rating of the largest motor that will powering machinery and AC compressors.
Wouldn't just having something 'existing' that requires 3 phase be justification enough? Like I said my dad has a 10HP compressor that I can lug over here if need be..
 
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Old 12-20-10, 12:44 PM
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Not really, especially given that the B phase isn't even used. The compressor might be enough though. You have to establish the need for it, and that is usually done with the size of the HVAC system. I suppose a big shop tool like the compressor might do it.
 
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Old 12-20-10, 12:52 PM
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Originally Posted by ibpooks View Post
Not really, especially given that the B phase isn't even used. The compressor might be enough though. You have to establish the need for it, and that is usually done with the size of the HVAC system. I suppose a big shop tool like the compressor might do it.
Like I said, B phase is unused right now because I didn't even realize I HAD 3 phase until about a year after I moved in. After I found out, visions of large shop tools danced in my head! If it came down to it, the compressor wouldn't just be there for looks, I would actually hook it up. I might be able to get his lathe over here too, but that's his baby and god forbid I get a scratch on it, so that would be a last resort, not to mention it's a lot heavier than the compressor!
 
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Old 12-20-10, 01:00 PM
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Where I live, if people want 3 phase, they get a phase converter.
 
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Old 12-21-10, 02:46 PM
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A very important advantge realized by installing either a 200 amp single-phase service ,or a 100 amp 3-phase 4-wire service, is that the voltage-to-ground for both types is limited to 120 volts; this in VERY important in reducing shock hazards to a minimal level.

If the "Neutral" point of the Delta 240 volt phase winding that is connected to supply 120 volt circuits is Grounded, then the result is a "High ( voltage ) Leg " with a voltage-to-Ground which exceeds 240 volts. The Code requires that this "High Leg" be indentified as such at any and all connection-points by the color orange.
 
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Old 12-21-10, 05:20 PM
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One thing that has not been mentioned is, if you have a 240 volt piece of equipment that does not need a neutral (most do not) I would try to utilize the high leg by placing the two pole breaker so it uses the B phase.
 
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Old 12-21-10, 06:09 PM
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Originally Posted by Tolyn Ironhand View Post
One thing that has not been mentioned is, if you have a 240 volt piece of equipment that does not need a neutral (most do not) I would try to utilize the high leg by placing the two pole breaker so it uses the B phase.
If you were to install a 2 pole breaker to include the "B" phase, wouldn't the circuit breaker have to be rated for a full 240 volts and not 120/240 as the typical residential 2 pole breaker is rated? Square D calls them "H" rated breakers (Example: QO220H - 20A 2 Pole) and the cost is about 10 times that of a regular QO220 breaker ($160 vs. $16).
 
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Old 12-21-10, 06:57 PM
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Originally Posted by PATTBAA View Post
A very important advantge realized by installing either a 200 amp single-phase service ,or a 100 amp 3-phase 4-wire service, is that the voltage-to-ground for both types is limited to 120 volts; this in VERY important in reducing shock hazards to a minimal level.

If the "Neutral" point of the Delta 240 volt phase winding that is connected to supply 120 volt circuits is Grounded, then the result is a "High ( voltage ) Leg " with a voltage-to-Ground which exceeds 240 volts. The Code requires that this "High Leg" be indentified as such at any and all connection-points by the color orange.
The high leg on 240 delta is 208v.. And let us not forget it is not the volts that kill you.. 120 can kill you just as easily as 208/240/277/480 can.

I know about using orange. Although that raises another question: On the feeder conductors (3/0), could I spraypaint the insulation orange? I know you can't repurpose loose wire smaller than #6, but is there any restriction on the METHOD of changing the color? IE: is spraypaint OK or do I have to use tape or spaghetti?
 

Last edited by JerseyMatt; 12-21-10 at 07:17 PM.
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Old 12-21-10, 07:08 PM
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Originally Posted by Tolyn Ironhand View Post
One thing that has not been mentioned is, if you have a 240 volt piece of equipment that does not need a neutral (most do not) I would try to utilize the high leg by placing the two pole breaker so it uses the B phase.
That was my plan for the garage circuits. But Joe raises an interesting question about it, so what say you?


Originally Posted by CasualJoe View Post
If you were to install a 2 pole breaker to include the "B" phase, wouldn't the circuit breaker have to be rated for a full 240 volts and not 120/240 as the typical residential 2 pole breaker is rated? Square D calls them "H" rated breakers (Example: QO220H - 20A 2 Pole) and the cost is about 10 times that of a regular QO220 breaker ($160 vs. $16).
I don't see why it would matter, as the high leg is only 'high' with regard to a line-neutral load. Line-line A-B, B-C, C-A are all 240v. But you couldn't use A-B or B-C for a 120/240v load or subpanel. In a regular 1 phase panel, you don't use a $160 breaker for a straight 240v load, so why would it be different?

Not arguing, it just doesn't make sense to me and I'm always open to learn!
 
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Old 12-21-10, 10:21 PM
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There is a reason why for a straight voltage breaker for delta system due the netural to ground will be 208 volts and they will change the interal parts a little inside the breaker and have diffrent rating so that why it drive the cost up and per NEC code it have to be straight voltage breaker I know they are not cheap as someone else mention if this system wired in Wye format then it will be NO issue at all due all legs to netural will be 120 volts { on 208Y120 system }

Is there any possibe way if you can take a quick photo of your transfomer ?? due one of us will have a idea or two how to address this.

Merci.
Marc
 
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Old 12-22-10, 12:46 PM
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Originally Posted by JerseyMatt View Post
That was my plan for the garage circuits. But Joe raises an interesting question about it, so what say you?
You only need a breaker that is rated for 240 volts so a standard two pole breaker is just fine. As mentioned, the high leg is 208 volts to ground/neutral and below the rating of the breaker.

This will not work for your garage if you plan to install a single phase panel. Your one leg will still be 208 to ground/neutral.

Another option is to get a delta to wye transformer and install it in your garage. This might be a bit on the costly side though.
 
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Old 12-22-10, 06:11 PM
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Originally Posted by Tolyn Ironhand View Post
You only need a breaker that is rated for 240 volts so a standard two pole breaker is just fine. As mentioned, the high leg is 208 volts to ground/neutral and below the rating of the breaker.

This will not work for your garage if you plan to install a single phase panel. Your one leg will still be 208 to ground/neutral.

Another option is to get a delta to wye transformer and install it in your garage. This might be a bit on the costly side though.
My point is that a standard 2 pole breaker is rated 120/240 volts meaning 120 volts per pole (1 pole to ground or neutral) or 240 volts across the poles. If the high leg is 208 volts to ground, the high leg will exceed the 120 volt per pole rating of a standard 2 pole breaker. To get a 240 volt rated 2 pole breaker you must buy the "H" rated breaker. This isn't an issue if you are using a 3 pole breaker in a 3 phase configuration because 3 pole breakers are rated a full 240 volts and not 120/240 volts.
 
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Old 12-22-10, 09:24 PM
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Originally Posted by CasualJoe View Post
My point is that a standard 2 pole breaker is rated 120/240 volts meaning 120 volts per pole (1 pole to ground or neutral) or 240 volts across the poles. If the high leg is 208 volts to ground, the high leg will exceed the 120 volt per pole rating of a standard 2 pole breaker. To get a 240 volt rated 2 pole breaker you must buy the "H" rated breaker. This isn't an issue if you are using a 3 pole breaker in a 3 phase configuration because 3 pole breakers are rated a full 240 volts and not 120/240 volts.
Line to line doesn't work like that. It's 240V line to line no matter which pair of phases you use. A-B isn't going to be 32V from A and 208V from B. It's the same exact 240V as A-C. The 208 only comes into play with regard to B-neutral, because the neutral is center-tapped on A-C.



And Marc, I haven't found the transformer yet, but again, it's not just MY transformer. It serves (from the little walking around I did today) at least 8 blocks (6-8 houses per block), and I have come across several other houses that tap all 3 legs. Two have the new underground service.
 

Last edited by JerseyMatt; 12-22-10 at 09:49 PM.
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Old 12-22-10, 09:57 PM
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That allright and if you can take a photo of your POCO post where you have the three phase connection is there I can able indentify it one way or other.

Did you have a volt meter with you and verify that the thrid phase is still engerized ??

If so keep it by all means and verfiy with POCO to see what they have in their mind with the exsting locations.

Merci.
Marc
 
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Old 12-23-10, 02:32 AM
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Yes I have tested it, and there is 240v between any two phases, and phase B to neutral is 208v (actually I think it was 210, but that still identifies it as a wild leg).
 
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Old 12-23-10, 05:48 PM
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Line to line doesn't work like that. It's 240V line to line no matter which pair of phases you use. A-B isn't going to be 32V from A and 208V from B. It's the same exact 240V as A-C. The 208 only comes into play with regard to B-neutral, because the neutral is center-tapped on A-C.
Yes, you are right, it's 240 volt phase to phase no matter which 2 phases you use. Install the breaker to "A" and "B" pases and connect the circuit and now with your meter, check phase "A" at the breaker to ground and then check phase "B" at the breaker to ground. What readings do you get from each phase? Unless I am mistaken, you'll get 120 volts from "A" and 208 volts from "B". Check voltage across the 2 phases and I am sure you'll get 240 volts. If you get anything higher than 120 volts to ground from any of the phases you'll need to use a breaker rated at a full 240 volts and not rated for 120/240 volts.

It's a little like a 3 phase grounded "B" 240 volt sysytem in that you get 240 volts across any 2 phases, but phase to ground is also 240 volts and requires a 240 volt rated breaker, not a 120/240 volt rated breaker (like you find at a Big Box) that is just rated at 120 volts per pole. You have to watch your phase to ground voltage when selecting the proper circuit breaker and not just the voltage across the poles.
 
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Old 12-23-10, 07:29 PM
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But given the fact that one wouldn't be using a A-B load in a manner that references to ground (a 120/240 device or subpanel), it shouldn't matter. It's only referencing to the other pole, which equals 240V. It is still giving you 120V phase to phase even on A-B and B-C. If the high leg was contributing 208V, the phase to phase would be 328V. I don't see how it's any different than a straight 240V load on a single phase panel.

Say you have a water heater. It's hooked pole to pole with no neutral. On single phase it takes 240V. On any combination of phases it still gets 240V. It wouldn't get 328V if you were to use the B phase. So it does balance at 120V per pole.
 
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Old 12-23-10, 08:39 PM
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I have submitted this question to the manufacture. Waiting on their reply.

You have a 120/240v rated breaker. All the parts of the breaker are rated for the higher voltage, 240 volts. the breaker doesn't know if difference if it is phase to phase or phase to ground. It is designed to handle a maximum of 240 volts through its inter parts.

BTW Matt, a two pole breaker is not 120 volts per phase. It is the difference of potential which is 240 volts

I still like my idea of getting your own delta to wye transformer and installing it in your shop. The you only run 3 hots and a ground from your delta panel to your the transformer and from the transformer to your new shop three phase panel.
 
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Old 12-24-10, 08:21 AM
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Thanks, TI. I was about to suggest the same thing. Just curious, which manufacturer did you submit the question to? I think JerseyMatt mentioned he had a Square D QO panel. I have to admit, I am not familiar with the 3 phase 240/120 4 wire service and have had no experience with it, but I have had experience with services that provide 240 volts to ground or 480 volts to ground per phase. In my experience with Siemens, these services (generally Grounded "B") required breakers with each pole fully rated for the voltage per pole so my opinions are just that, my opinions. A Square D Digest might provide the answers, but I don't have one here at home.
 
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Old 12-24-10, 10:46 AM
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I sent the question to Square D (Schneider). Still no reply but considering the holidays I'm betting everybody is gone so I will expect a reply on Monday. I am also, by no means, a circuit breaker expert which is why I am looking into this.

I did some digging on the net and found some good info which confirms Joe's posts. Looks like you need a straight 240V breaker for a two pole on the B phase. Makes no sense to me but again, not a breaker expert. :

"Although the Code permits you to install a 120/240V slash-rated breaker on a 120/240V 3-phase, high-leg delta system, you cannot install it on the ďBĒ phase (high-leg), because the nominal line-to-ground voltage of the high-leg is 208V. This exceeds the 120V line-to-ground voltage rating of the 120/240V slash breaker."

Source: Understanding Circuit Breaker Markings
 
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Old 12-24-10, 03:41 PM
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Good article, TI. And the article probably explains it a little better than I did too. To borrow from your article, I also saw this:

Two-pole breakers can be either slash or straight voltage-rated, whereas 3-pole breakers are all straight voltage-rated.
This is why I was saying the Square D 2 pole breaker must be an "H" breaker. I think the full number would be QO220H. I believe Siemens uses an "R" suffix to the catalog number, but a quick look in the Siemens catalog would confirm it. I don't think GE makes a straight 240 rated 2 pole and am not sure about C-H. IIRC, this is one of the reasons single phase loadcenters (the ones that used to be U.L. Listed for Grounded "B" 3 phase systems) are no longer listed for Grounded "B" 3 phase use. I have seen many a good electrican install 120/240 rated breakers in those panels thinking they were the proper breaker. Some inspectors don't even understand the breaker ratings either. The bottom line is that learning is a good thing and I have learned a lot from reading the posts on this forum and hope everyone else has too so I hope all of you moderators keep up the good work on here.

BTW Hope everyone reading the board has a Merry Christmas!!
 

Last edited by CasualJoe; 12-24-10 at 03:43 PM. Reason: fix typo
  #30  
Old 12-24-10, 07:25 PM
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That why I mention before about straight voltage breakers on delta system but once you go in Wye format that will not be a issue at all.

CJ .,

I did recall the GE breakers do have straight voltage breakers give me a jour or duex { day or two } to confirm this number.

again that is a special order items that one reason why many stright voltage breakers are special items even on larger three phase breakers it can get ya if not pay attetion to the rating { It did happend to moi once after that got wise up with it }

You can get a 15 KVA detla to wye transfomer after that you can use standard single or two even three pole breakers without issue at all which I will recomended anyway.

Yeah you can get larger one like 30 KVA but I doubt you need that big for your useage I know 15 KVA is reltive common item which it will handle more than what you will load it up in your shop but before you can go this route make a quick load demand figure before you order the transfomer the closeset size to fit your exsting 100 amp three phase supply is 41 or 45 but 30 is more common which I used pretty often.

If have more question just holler one of us will help ya.

Happy Holidays .,


Merci.
Marc
 
  #31  
Old 12-25-10, 06:55 AM
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I have also learned quite a bit on this thread. This is why I keep hanging around here, because there is always somebody who knows more then me and is willing to share. (as opposed to some of the "pro" sites)

I also found a code reference on this issue: 240.85

To the OP: As Marc also posted about the transformer: If you choose to go this way, check around for a used one. These things never get thrown away.
 
  #32  
Old 12-25-10, 09:11 AM
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First, Merry Christmas to all!

Originally Posted by JerseyMatt View Post
And Marc, I haven't found the transformer yet, but again, it's not just MY transformer. It serves (from the little walking around I did today) at least 8 blocks (6-8 houses per block), and I have come across several other houses that tap all 3 legs. Two have the new underground service.
I think youíre missing something . . . I canít imagine a single transformer serving at least 8 city blocks of residential housing. Even if this is a large transformer residing in a building vault or underground below a sidewalk or roadway, I canít see why youíre POCO would string 8 or more blocks of secondary cable back to this transformer.

Look for a riser cable going up the pole near the area where you saw the two new underground services.
 
  #33  
Old 12-25-10, 12:00 PM
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I did recall the GE breakers do have straight voltage breakers give me a jour or duex { day or two } to confirm this number.
I was comparing the Square D QO series to GE THQL series, both plug on breaker styles. Perhaps I have misspoken here though. Without checking a GE catalog I don't know for sure that GE doesn't make a 240 rated Type THQL 2 pole breaker. I know they make the 240 rated 2 pole in a THQB version, bolt-on breaker. I do know for a fact though that GE doesn't do Grounded "B" phase panels. A GE rep told me that no more than 4 or 5 years ago.
 
  #34  
Old 12-25-10, 11:08 PM
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Originally Posted by CasualJoe View Post
I was comparing the Square D QO series to GE THQL series, both plug on breaker styles. Perhaps I have misspoken here though. Without checking a GE catalog I don't know for sure that GE doesn't make a 240 rated Type THQL 2 pole breaker. I know they make the 240 rated 2 pole in a THQB version, bolt-on breaker. I do know for a fact though that GE doesn't do Grounded "B" phase panels. A GE rep told me that no more than 4 or 5 years ago.
The grounded B phase which most electricians will call that corner grounded phase that part is very spooky for most peoples due the voltage reading and how it set up and the corner grounded delta is slowly dropped out of flavour for safety reason.

That part of the reason due it need straight voltage breaker on that.

I will give a quick example how the corner ground delta read like this .,

Phase A - G 240 volts Phase B to G 0 volts phase C - G 240 volts as you noted why I say Phase B to G is zero due it is allready grounded on purpose and quite few corner grounded delta panels can get confused with standard single phase panels espcally when they are NOT marked at all.

That corner ground delta work the same with 480 volts system as well

That one of few reason why POCO allready dropping out from their list for system / voltage to customers and many POCO will allowed to keep the delta system for exsting customers only but new customers will get Wye supply only {I know majorty of POCO in wisconsin do that and it is stright wye supply in France ( very limited on delta ) }

Merci.
Marc
 
  #35  
Old 12-28-10, 06:07 PM
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But high leg isn't the same as corner grounded. The A-C transformer is center tapped.

I've done a little more reading up on 240.85, and now I understand the reasoning. It is because even though there is no line-ground load, if there is a ground fault on the high leg, it will exceed the rating of the breaker. I wasn't thinking about that, I was only thinking of the 240V line to line.

I also found the transformer sets. They do appear to serve approximately 4 blocks (2x2) each. And these aren't 'city' blocks, these are 'small town' blocks.. They're only a couple hundred feet square, and there's only 6 or 7 houses around the block, with a north-south alley for utility workers down the middle. There is a single central pole in that alley that serves all of the houses on that block. In several of the alleys there is a platform holding 3 cans. Some look antiquated, some look brand new. As soon as I can find the adapter for my phone's memory card I'll get the pics uploaded.
 
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