More 3 Phase questions

[ScottReb]

Hey All,

Have a new shop in an industrial park. Im getting PG&E out to look at it next week. Im going to upgrade to a larger panel. Currently 100 amp single phase. I have 3 phase in the shop next to mine and possibly interested in that. My question is: Do they install 2 separate panels to have both 1 & 3 phase? PG&E offers 120/208, 240 and 480 I believe. Im going to have an electrician out as well since Im not well versed enough to play with 3 phase, obviously! We will be purchasing several machines with 3 phase options.

 

[mm08822]

Typically only one service will be provided to a building. Since you need 3 phase, your new service will provide that. It will require a 3 phase meter (or ct’s) and a 3 phase panel.

Your current single phase service will be disconnected and removed. Your current 120/240v panel can remain as is, but will then need to be re-fed off of a new transformer that you will own and install at your cost.

Evaluating the current 120/240v panel size (# circuits and ampacity), present loads and condition of it will determine if it too should be upgraded. It may be fine as is.

Load calcs for its current loads and planned future loads should be considered. This information will also be used to determine the xformer kva rating used to step down 480v to 120/240v.

And of course, load calcs for the 3 phase system are needed of which the single xformer load (120/240v panel) is part of.

 

[ScottReb]

Perfect. The second paragraph was part I wasn't understanding. I will pull 1 phase off the 3 phase with a transformer and then run 1 phase traditionally. Thanks so much!

 

[EOC_Jason]

Well... There's more than one kind of 3-phase that most power companies offer... You need to find out if it's a high-leg Delta or Wye 3-phase service. That will affect how your single phase is wired up....

 

[klassenl]

.... You need to find out if it's a high-leg Delta.....

I would be very surprised if a typical consumer would get this kind of service. (Wild exceptions not withstanding)

 

[ScottReb]

When I spoke to the service person on phone wye was mentioned. But I believe she was reading from the computer

 

[mm08822]

Well... There's more than one kind of 3-phase that most power companies offer... You need to find out if it's a high-leg Delta or Wye 3-phase service. That will affect how your single phase is wired up....

If he gets 480v Y or 480 delta, that wont effect how he picks off 480v (single phase ) to feed the xformer.

 

[Norcal]

If he gets 480v Y or 480 delta, that wont effect how he picks off 480v (single phase ) to feed the xformer.

240V, & 480V, 3Ø are not available to new PG&E customers, 480Y/277, 208Y/120, 120/240V, 3Ø, & 120/240V, 1Ø are. For small 3 phase services, PG&E loves 120/240V Delta. The OP is going to end up with whatever is already serving the building unless willing to spend big bucks.

 

[mm08822]

Well... There's more than one kind of 3-phase that most power companies offer... You need to find out if it's a high-leg Delta or Wye 3-phase service. That will affect how your single phase is wired up....

240V, & 480V, 3Ø are not available to new PG&E customers, 480Y/277, 208Y/120, 120/240V, 3Ø, & 120/240V, 1Ø are. For small 3 phase services, PG&E loves 120/240V Delta. The OP is going to end up with whatever is already serving the building unless willing to spend big bucks.

OP, EOC_Jason and NorCal are correct in listing the possibility of other 3Ø voltages/configurations. I somehow locked onto 480V 3Ø service in your thread and ran with it, not re-reading your post. (Plain as day now, but not last night. My bad!)

What I mentioned about 480V 3Ø service and how to possibly re-use/save your existing panel is correct, but you may not have that option. First need to know what your 3Ø service supply will be, and the current/future loads to properly determine best path forward.

My preferences for 3Ø service would be: 480Y/277 (most flexible), 120/240V 3Ø, and my least favorite 208Y/120, 3Ø. As Norcal stated, you may not cheaply get an option.

Start gathering info about the new equipment loads. Call the mfr’s of those equipments and get load values for both single and three phase configurations. POCO will probably be asking for it soon anyway.
Also get an understanding of current/future single phase loads too.

 

[wyliesdiesels]

240V, & 480V, 3Ø are not available to new PG&E customers, 480Y/277, 208Y/120, 120/240V, 3Ø, & 120/240V, 1Ø are. For small 3 phase services, PG&E loves 120/240V Delta. The OP is going to end up with whatever is already serving the building unless willing to spend big bucks.

Whats interesting in PGEs green book is they had an option for 240 corner grounded delta but not 480 corner grounded delta...

 

[wyliesdiesels]

OP, EOC_Jason and NorCal are correct in listing the possibility of other 3Ø voltages/configurations. I somehow locked onto 480V 3Ø service in your thread and ran with it, not re-reading your post. (Plain as day now, but not last night. My bad!)

What I mentioned about 480V 3Ø service and how to possibly re-use/save your existing panel is correct, but you may not have that option. First need to know what your 3Ø service supply will be, and the current/future loads to properly determine best path forward.

My preferences for 3Ø service would be: 480Y/277 (most flexible), 120/240V 3Ø, and my least favorite 208Y/120, 3Ø. As Norcal stated, you may not cheaply get an option.

Start gathering info about the new equipment loads. Call the mfr’s of those equipments and get load values for both single and three phase configurations. POCO will probably be asking for it soon anyway.
Also get an understanding of current/future single phase loads too.

Why do u dislike 208Y/120?

PGE and MID no longer offer 240/120 D or 480 D so its either 208Y/120 or 480Y/277 for us in the majority of cali for new services...of course theres still a lot of existing delta services...

 

[EOC_Jason]

Unless there is a hidden transformer outside your space you don't know about, I would almost bet with you on regular 120/240v single phase and your neighbor having 3-phase that you would have 240V Delta... Go look at the power pole, are there 2 transformers or 3?

If you get some larger machines, or even just have CNC controls, you might want to spend the few extra bucks for a transformer, even with the same voltage-in/voltage-out it gives you isolation and a little extra protection. Better to spend a little on a transformer than a lot on diagnostics & control boards...

 

[mm08822]

Why do u dislike 208Y/120?

...

The 120v piece is fine. The 208v piece seems like a built in line loss when you need to hook up 230-240v loads. Especially, when the grid sags a little during summertime loads. Been a problem a few times. I've had to put in buck-boost xformers for the seasonal dips on a couple of motors.

 

[Bert_]

I doubt the OP has any need for 480V. If he has the option of both 240 and 208, then he should look at the equipment he plans to run and base the decision off that. If it's going to be a lot of machining equipment I would rather have 240.

The 120v piece is fine. The 208v piece seems like a built in line loss when you need to hook up 230-240v loads. Especially, when the grid sags a little during summertime loads. Been a problem a few times. I've had to put in buck-boost xformers for the seasonal dips on a couple of motors.

I've got the same opinion, 208 is great... if you have lots of 120v loads. Like a retail store ect.

When there are mostly line to line loads and a few 120v. I'd take a 120/240 delta every time. It also seems like there's always some single phase 240v equipment the customer wants keep, so that is another point for the delta.

 

[Barnabas]

My shop was upgraded to three-phase just before I bought it. They added a new 600A 120/240 main panel. That new main panel feeds the old single-phase panel. The main panel also feeds a new 3-phase sub-panel with space for about 30 breakers. My 3-phase has a high leg, so I have to be careful to avoid that when installing single-phase circuits.

 

[alfredeneuman]

They added a new 600A 120/240 main panel. My 3-phase has a high leg, so I have to be careful to avoid that when installing single-phase circuits.

The high leg can be used on a 240V single phase (line to line) circuit

 

[PRH44]

The high leg potential in a 120/240 volt 3 phase delta is actually 208 volt. It should not be used for line to neutral loads.

 

[Steve from Socal]

I doubt the OP has any need for 480V. If he has the option of both 240 and 208, then he should look at the equipment he plans to run and base the decision off that. If it's going to be a lot of machining equipment I would rather have 240.

That is quite the assumption, all my machines are 480. I prefer it for several reasons.

Steve

 

[Bert_]

That is quite the assumption, all my machines are 480. I prefer it for several reasons.

Steve

Not saying a higher voltage doesn't have advantages. But unless his few pieces of new equipment has a 100hp worth of motors or an otherwise high current draw, 480 can bring some added cost and complications. If he goes that route he will need a transformer and another panel for 120 and 240v loads. That makes sense if you have a factory full of machines spread out across a huge building. Not so much if you've only got a couple machines and the rest runs on 120/240.

To do anything other than assuming we need more info about this machinery.

 

[mike93lx]

Might be worth considering the cost of vfd's for each machine... Could be a lot cheaper and simpler, plus you would have speed control

 

[theoldwizard1]

Why do u dislike 208Y/120?

What little 3 phase I have dealt with was 208Y/120. Very simple.

 

[wyliesdiesels]

The 120v piece is fine. The 208v piece seems like a built in line loss when you need to hook up 230-240v loads. Especially, when the grid sags a little during summertime loads. Been a problem a few times. I've had to put in buck-boost xformers for the seasonal dips on a couple of motors.

yeah i wouldnt want to use 208y for large motor loads...

The high leg can be used on a 240V single phase (line to line) circuit

nope. high leg is 208v and is unstable. Not recommended for any single phase line to neutral loads that are 208v or 240v.

I have heard of people using the high leg, line to neutral(208v) for 208v loads but I wont do it...

Definitely cant use it for 120v loads...unless your goal is letting the magic smoke out which i have seen people do on a high leg delta...

EDIT: Whoops. I shouldve slowed down and read what u said a little closer...
yes high leg can be used line to line, for single phase 240v loads. Just dont use it line to neutral for 208v loads...For some reason i thought u said u can use it line to neutral...

What little 3 phase I have dealt with was 208Y/120. Very simple.

yup simple and balanced for the most part...

208Y is the majority of what is used out here in cali for small commercial buildings and restaurants. We still have a lot of 240/120 Delta but is no longer available for new installs...

Ive worked on all types of 3-phase except for corner grounded Delta which is almost extinct out here...I know of one old converted plant that has it and is now a habitat restore, so it sits unused...Can tell its corner grounded from the street looking up at the pole, as the meter is housed on the H-frame poles and there is only 2 CTs. The third leg is connected to the pole ground.....My buddy works as a lineman for the local PoCo. they recently went to this service to convert it, then the engineer called and told them nevermind as the main service panel would need to be converted which the customer would need to agree to and pay for....

 

[Norcal]

The high leg can be used with any other phase for a 240V load, which is what alfredeneuman was saying, just should never use it where the load requires a neutral because bad things can happen + the 2-pole breaker has to have a 240V, not a slash (120/240V) rating which are expensive.

Have heard but not confirmed, that the use of the ******* leg & the neutral violates a PoCo's tariffs.

 

[zmaxmotorsports]

I'm guessing the would normally bring in 208 instead of 480 unless you're running some serious machinery in your shop.

 

[wyliesdiesels]

The high leg can be used with any other phase for a 240V load, which is what alfredeneuman was saying, just should never use it where the load requires a neutral because bad things can happen + the 2-pole breaker has to have a 240V, not a slash (120/240V) rating which are expensive.

Have heard but not confirmed, that the use of the ******* leg & the neutral violates a PoCo's tariffs.

yeah whoops. wasnt paying attention to what he was saying. Missed the line to line part....thats what i get for reading in a hurry... wned:

 

[ScottReb]

I have two separate shops and just got into the second one and this is what I found. Looks good! When I looked at the shop all I saw was the panel filled with single phase breakers I "assumed" there was no 3 phase. Dont mind being wrong on that one. FYI PG&E told me we would need a new pole, new transformer all to the tune of about $6-7000.

Now with one 100 Amp single and 100 Amp 3 phase I will be fine, wont need to upgrade at all. Nice cost savings for us!

 

[wyliesdiesels]

none of your images came through...

 

[FullRaceMerc]

I am not an electrician, but have worked in 2 different shops with both 3 phase & single phase panels in use. It sure has been easy to have both available.

 

[ScottReb]

Not sure what Im doing with the pics
Will try to edit

 

[ScottReb]

There we go.

Long story short my second shop has 3 Phase. They are side by side so I can put it in either one.

The outside of the panel has written in marker "high third leg." Does that mean is delta?
The meter shows 120-480, so Im assuming 480V Delta.

 

[wyliesdiesels]

There we go.

Long story short my second shop has 3 Phase. They are side by side so I can put it in either one.

The outside of the panel has written in marker "high third leg."

Does that mean is delta?

yes

The meter shows 120-480, so Im assuming 480V Delta.

nope. not good to assume. PG&E uses those "fitzall" meters for all small 3-phase services(208, 240v, and 480v) that dont require CTs....

There is no such thing as 480v delta 4-wire with a neutral and you obviously have a neutral. Any 480v delta will be 3-wire. You cannot get 120v from a 480v service WITHOUT a load side step down transformer....

You have 120/240v Delta. The high leg is 208v line to neutral so be careful. Dont use a single pole breaker, for 120v loads, on the high leg unless u want to let the magic smoke out....

One concerning thing- on the last pic, there is 2 different legs taped red, which is used to indicate the high leg.

If you feel comfortable, I would use a multimeter and figure out which leg is the high leg....

I wonder why someone wasted 3' of al for the first leg...

Is the first and third pic on the same service?

BTW where are you located in california?

 

[EOC_Jason]

The high leg can be used with any other phase for a 240V load, which is what alfredeneuman was saying, just should never use it where the load requires a neutral because bad things can happen + the 2-pole breaker has to have a 240V, not a slash (120/240V) rating which are expensive.

Have heard but not confirmed, that the use of the ******* leg & the neutral violates a PoCo's tariffs.

It's not always wise to blindly use the high-leg for 240V single phase equipment. I would take a look at the transformer(s) outside to see how they are sized. I've often seen a considerably smaller secondary transformer for the high leg because of the spec'd small three phase load for the facility. Of course I guess this falls under the general common sense / balancing your loads concept for the breaker panel...

In this case with a 100A panel it's not going to really matter, but with a larger setup it could...

 

[Mr. T]

One concerning thing- on the last pic, there is 2 different legs taped red, which is used to indicate the high leg.

The High leg needs to be orange according to the NEC. Also, while not required by code, it's a pretty common courtesy to locate the high leg as the "B" phase.

Also, Black, Red, Blue, is a common way to mark 208Y/120.

 

[wyliesdiesels]

It's not always wise to blindly use the high-leg for 240V single phase equipment. I would take a look at the transformer(s) outside to see how they are sized. I've often seen a considerably smaller secondary transformer for the high leg because of the spec'd small three phase load for the facility. Of course I guess this falls under the general common sense / balancing your loads concept for the breaker panel...

In this case with a 100A panel it's not going to really matter, but with a larger setup it could...

If theres only 2 transformers, then its an open delta with reduced capacity.

And PoCo transformer KVA is never sized to the amperage of the service... its all about demand factor and load calcs...

The High leg needs to be orange according to the NEC. Also, while not required by code, it's a pretty common courtesy to locate the high leg as the "B" phase.

Also, Black, Red, Blue, is a common way to mark 208Y/120.

Yes code is orange but hardly anyone uses orange. Out of all the highleg Delta services Ive worked on, only a few had orange taped high legs. The rest were red.

And code DOES require the high leg to be on the B phase. See 408.3(E)

 

[EOC_Jason]

If theres only 2 transformers, then its an open delta with reduced capacity.

And PoCo transformer KVA is never sized to the amperage of the service... its all about demand factor and load calcs...

Yes I know the poco requires load calcs for the initial install, but in a facility where tenants change over time, so can the demand. Just saying, better safe than sorry...

Yes code is orange but hardly anyone uses orange. Out of all the highleg Delta services Ive worked on, only a few had orange taped high legs. The rest were red.

And code DOES require the high leg to be on the B phase. See 408.3(E)

I've always seen / used orange. Likewise other legs get marked for consistency so you have a better chance of getting your rotation right first try.

 

[Mr. T]

And code DOES require the high leg to be on the B phase. See 408.3(E)

I'd say I was 3/4 right. I guess I should read that expensive book more and trust people less!

 

[ScottReb]

Thanks for all the info guys.

All pics are from my shop. The meter and the cut off are in my larger one which has single phase. The panel is in my adjacent smaller shop. It's an old park that has been bastardized many time over the years. I have 3 meters in my shop. My two and a neighbor's. Interesting.

It's in Auburn CA

I've got an electrician coming out next week or so. I'm ok wiring single phase stuff but I don't have my head wrapped around the legs and lines and how they make different phases and voltages.

 

[ScottReb]

Regarding the two transformers. Is that in the pole that goes to the service? If so it has 2. They're different sizes.

 

[wyliesdiesels]

Thanks for all the info guys.

All pics are from my shop. The meter and the cut off are in my larger one which has single phase. The panel is in my adjacent smaller shop. It's an old park that has been bastardized many time over the years. I have 3 meters in my shop. My two and a neighbor's. Interesting.

It's in Auburn CA

I've got an electrician coming out next week or so. I'm ok wiring single phase stuff but I don't have my head wrapped around the legs and lines and how they make different phases and voltages.

If u dont feel comfortable enough working on them then thats the best thing to do.

Too bad youre not closer. I could stop by and check it out for you.

Regarding the two transformers. Is that in the pole that goes to the service? If so it has 2. They're different sizes.

Yes.

2 pole mounted transformers means its an open delta. Its 3 phase but the output is only 87% of the transformers KVA ratings.

The larger trany supplies both the single phase loads and the 3 phase loads. The smaller one only supplies the 3 phase loads and this is where the high leg or stinger leg(208v) comes from.

 

[ScottReb]

Thanks Wyliesdiesels! I wish you were closer too. Thanks to everyone for the wealth of information. GJ never dissappoints