What Type Of Service Is This?

SleepnZJ

I'm turning my basement in to my work shop, I have a bunch of single phase 120/240 volt equipment and I just picked up a lathe that is 3 phase 220. I figured that I will use a phase converter for all the 3 phase equipment (1 for now and one more piece down the road for a total of 2). My question is I think that I might already have 3 phase in the house.

Now I hope you guys don't think that I am going to play with this setup my self. The truth of the mater is I already had one electrician look at it a couple of years ago and he said he wasn't sure. I will run some wire and install a outlet or two but I plan on having the meter moved outside by a pro so the utility company will stop knocking on my door to read the meter. I am just seeing if I can get a clearer picture of what I have before I call a electrician to move the meter out side.

If you open up the cabinet below the meter you see where the wires come into the house (total of 4) then they go up through the meter then through a conduit to the main breaker panel and one small breaker box for the AC.

Now I put a volt meter on the wires in the cabinet where the wires come into the hose. The wires go as follows "Red, Black, Black" and a white wire at the bottom of the cabinet which I assume is the ground. When it test across the red and white I get 210 volts, when I test the other two black wires across the white I get 120 volts. When I test across both the blacks I get 240 volts and when I test across either of the blacks to the red I get 240 volts.

The words "caution red leg first phase on block" and a 3,2,1, underneath the wires in the cabinet.

So what do you guys think, do I have 1 phase or 3 phase coming into the house.

mdshunk

Yeah, sure sounds like you have a 3-phase service already. What yours would be called in electrician trade slang is "Delta high leg". You're the envy of your neighborhood. The only thing that's wrong is that your high leg is in the first position, but that's really no big deal to a competant electrician.

A word of caution... get a good electrician to work on your place. Delta high leg installations are nothing to take lightly. I'd guess that 7 out of every 10 electricians have no business messing around with these.

Sparky Joe

Yes you have 3 phase 240volts in your house.
It's called a 'center tapped delta system' which is becoming more uncommon by the minute.
The red wire is called the high leg(hence the high reading to ground).
You can run any 3 phase 240volt machine on this system, but have to be very careful when adding new 120 volt circuits(as 1 of the legs to ground is nearly twice the 120 desired, 208 would be the mathematical reading on the high leg)

Speedy Petey

Have you guys seen the pic he linked over on the DIY site?
http://www.diychatroom.com/showthread.php?t=11320

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747

Wow that looks harcore to me. Your a big player with that in your house and your neighbors they not even in the game.

SleepnZJ

Well I am going to have a licensed electrician do most of the electrical work for me. I am going to run a few outlets my self both 120/240. I will probably run the 3 phase outlet me self because I have done 3 phase before at a old job. But installing a new pan, updated breaker box and running the new wires in from the outside I will leave to the pro. I just feel better now that I know what type of service I have for when I start making phone calls.

My big question is since I have a 3 phase and I have a lathe that is 220v 3 phase can I run it on the delta 3 phase? I always though that the 3 phase was 120 degrees apart and had equal voltage on each leg? Wouldn't the 208/120/120 be unbalanced to run directly to the lathe with out balancing the voltage?

Dustball

This explains the high leg-

http://www.kilowattclassroom.com/Arc...WYEPhasors.pdf

mdshunk

Now you're thinking too much, so you need to stop that. You haven't measured any phase angles yet. Only voltages.

The high leg only becomes a concern in three cases:

-120 volt loads
-120/240 loads, such as ranges and dryers
-3 phase, 5-wire machines that steal one leg for 120 volt internal control power.

Just get a good electrician, and quit worrying so much.

mdshunk

I only run into a 3-phase "A" base meter maybe once a year. In fact, the only one's I know about in my area that are still in use as "A" base meters are in residential homes. Might have been a fad once upon a time for rich folks. Who knows. Nowadays, you need to have a really good reason to get 3-phase in your home. Most of the time, the power company will want charge you the materials difference if 3-phase is available on your block but you have no compelling reason to need it .

mickeyco

I call it: The super deluxe, you lucky bastard, I wish I had because I have a mill that needs it, service.

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Speedy Petey

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Liquid Force

n0ob 3 phase questions...

is the reason they put delta in houses that you can still use 2 pole, 240v appliances, as well as 3 pole, 240v 3 phase motors? You would only get 120v/208v with wye, right? Also, isn't wye more common in general? Does that mean every appliance for a wye system building has to be spec'd for 208v? Water heaters air handlers everything? Do they have multi tap applainces 208v/240v? Also, is most everything on a wye system going to be 3 pole, including 3 phase resistive heating elements, and 3 phase motors, or do they use many 2 pole circuits on a wye 3 phase system? Other than just relayed lighting?

(1 of the 7 out of 10 electricians, d'Oh! )

mdshunk

No, nothing of the sort. People with wye services are still gonna run their 120/240 stuff on the 120/208 and never know the difference most of the time. Most of the straight 230 stuff has tolerances that will work fine off straight 208, such as air conditioning units. Where you start to hit trouble is with reduced capacity for electric water heaters.

The only reason a PoCo would provide a delta high leg service is because they can do it with two transformers instead of three, thus saving cost. This is how small 3-phase overhead services are most often done. Undergound, you're getting wye, because one padmount is one padmount.

Sparky Joe

You seem to know a bit about phase angles, so I'll just post the crude picture I made


A to ground 120
C to ground 120
B to ground 208
phase to phase 240

If you subtract 120 at 60 degrees from 240 you get 208(at least I think I said that right)

Sparky Joe

Here's what MD explained, called an Open Delta
works just the same, but at a lower capacity

Magnettica

Roxanne....

Turn on the Red Leg!

Roxanne....

Turn on the Red Leg!

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Magnettica

The answer is yes to using double pole breakers on any 3-phase system.

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mahlere

what does the panel look like?

mdshunk

You might want to re-evaluate that stand when you're talking about items like electric clothes dryers and electric ranges. You stand a pretty good chance of blowing up the control circuit in those if you just pop in a double-pole at random. Items such as these rob one leg to neutral for certain 120 volt loads. If that one leg happens to be the high leg, you're SOL.

Liquid Force

I guess it would be too expensive to get a 3 phase blower motor in every air handler for example, and 3 phase heating element in every water heater.... right. I have seen commercial dishwashers with 3 phase heating elements, but it was on a wye system, so no need to identify the high leg.

So the only determining factor whether a building gets delta or wye is if it's overhead or underground service?