wyliesdiesels
Well-known member
huh?
3 Phase Service Question
- Thread starter Doubled33
- Start date
You summed up what I was trying to say earlier in a much easier question.
By the way, do you mean 208(207 actually) is 10% and not 5% of 230?
Oh duh!! yes 10%. I'll fix that.
micromind
Well-known member
Some 208-230/460 motors have reserve built into them, others do not. It depends on the service factor. If the SF is 1.0, there's no reserve, it it's higher (like 1.15) then there is.
Basically, service factor goes like this......if a 10HP motor has an SF of 1.15, it is an 11.5HP motor marketed as 10HP. Provided its design parameters are not exceeded, it will produce 11.5HP continuously.
If the SF is 1.0, it is a 10HP motor marketed as 10HP and if it is made to produce more than 10HP, it'll burn up.
Some manufacturers will have a 230/460 rating and a separate 208 rating. The 208 rating usually has higher current, sometimes lower RPM and sometimes lower SF.
I'm talking about is there any reserve built into a 208-230v rated motor @ the less than 208v level. I'm not confusing that with SF.
SF is as you describe above but determined by mfr only at rated voltage and frequency and for intermittent overloads. To me that means at 230 or 460v. If there was a SF rating @208v, then it wouldn't apply @ 200v for example.
We had this happen once. Had a automatic gate opener installed by a contractor. They provided all the wiring from the panel to the opener and unknowingly landed the breaker on the "open spot" of the 3rd leg. The control board did no like that.
200V is the rated voltage for 208V, just like 230/460V is is the rated voltages for 240/480V. While the 200V rating has been around for a while, I have a couple of Rockwell machines with 200V motors from the early 1970's, NEMA changed the rating from 208V to 200V a few years back. So the current rating for a tri-volt motor is 200-230/460V.
jar944
Well-known member
Nope I'd take 277/480 myself.
nadogail
Well-known member
I have experience with both Wye and Delta systems.
With Wye systems there is a “Wild Leg” that can burn up a piece of 120 Volt equipment if you mistakenly hook up to it. I was not aware of that and the panel was not marked. Additionally the Wild Leg was not identified with Orange Tape. Fortunately I was not required to replace the radio that burned up, but I made sure to identify the wild leg and added a warning label to the panel about the wild leg.
120 Volts bites but 277 kicks, I am very happy that I no longer have to work 277 circuits Hot.
With Wye systems there is a “Wild Leg” that can burn up a piece of 120 Volt equipment if you mistakenly hook up to it. I was not aware of that and the panel was not marked. Additionally the Wild Leg was not identified with Orange Tape. Fortunately I was not required to replace the radio that burned up, but I made sure to identify the wild leg and added a warning label to the panel about the wild leg.
120 Volts bites but 277 kicks, I am very happy that I no longer have to work 277 circuits Hot.
Your post has a error, wye systems do not have a wild leg, delta does though.
nadogail
Well-known member
Thanks for setting me straight. It’s been over 20 years since I last worked on a 3 Phase system.
Anybody that opens up a 120/240 delta panel and can't figure out what it is really has no business being there in the first place. I've opened up a ton of panels. It's usually pretty obvious before you even pull off the cover. I can think of once or twice in the last 10 years where I actually pulled out a meter to verify.
I like 240v over 208v if it's mostly motor load. 208 is obviously better if you have a lot of 120v.
I like 240v over 208v if it's mostly motor load. 208 is obviously better if you have a lot of 120v.
TRWham
Well-known member
When I was in the HVAC compressor manufacturing business, we tested all motors to +- 5% of the nameplate. If it was shown as a spread voltage motor then it was tested to 5% below 208 V (197 V) and 5% above 230 V (242 V). Obviously, it would draw more current at the lower voltage at the same load, but that is just physics at work. Most motors were rated for 50 and 60 Hz as well, but at different voltage. Before that, I worked for an equipment manufacturer, and the vast majority of the systems we built were installed in 208/3 buildings.
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wyliesdiesels
Well-known member
you got it backwards. Delta has the stinger leg- 120/208/240 are the voltages on 4-wire delta
Wye is either 208/120 (120 between all 3 phases and neutral) or 480/277....
Steve from Socal
Well-known member
I have 240 delta in my shop from my 480 service. I know 'most' stuff that is dual rated runs OK on 208. I had friend in SoCal with 208 Edison power that sagged badly in the summer. Location and how critical voltage is would be the decider for service. Small low power machines that don't start under load may favor 208? Personally I still would take delta it is not that big an issue.
sparky 1971
Well-known member
I got a call today from a customer that makes well drilling and directional boring equipment in a factory that hasn't changed a thing since the 50's. The POCO wants to change out the 240D transformer and replace it with 208. In this case, I told him to tell them no and to leave it alone until they find the right transformer, which apparently it tougher than it should be. They have a plasma table and a CNC machine that I had to put buck-n-boost transformers on, but I don't remember if they are bucking or boosting due to low voltage. They also have a bunch of equipment I haven't touched that dates back to WWI that might not like 208.
wyliesdiesels
Well-known member
why are they changing the trany bank in the first place? old?
they should be able to use any 2 (open delta/reduced output) or 3 single phase 120/240v split phase cans rated for their primary system distro voltage and wire them up in delta. maybe they cant find cans with the correct primary voltage for their system??
sparky 1971
Well-known member
That would be my guess. The GM is who called me, but couldn't answer my questions of why they want to change it to begin with or the reasoning behind the 208.
micromind
Well-known member
The PUCO around here is a lot like an overgrown schoolyard bully.......if you have a ∆ system and one of the transformers burns up, they will change it to a Y. If your stuff can't handle 208, tough luck.
If it was an open ∆ (2 transformers and 3 primary wires), they will, surprisingly, upgrade their system at no charge.
If it was an open ∆ (2 transformers and 3 primary wires), they will, surprisingly, upgrade their system at no charge.
Same here.
Your 3-phase options are 120/208Y or 347/600Y. If you happened to get anything else decades ago - you are at a dead-end for upgrading.
Does the POCO typically change a 3 phase transformer and not let you know? I am almost certain years ago when we built the shop we had 240v. The other day I was checking the power to a lathe I plan on moving and converting over to a VFD to operate it on single phase power at my home shop. When I checked the power I had 2-120v legs and 1-208v leg. Its not how I remember it.
yatg
Well-known member
sparky 1971
Well-known member
That is 240 three phase. Line to line between any two of the three will be 240.
wyliesdiesels
Well-known member
Cruzan80
Well-known member
So, piggybacking of Sparky's pic, and Wylie's answer, why would you choose 3-phase Wye over a center tapped Delta design? It seems like the Delta would give you the most options (120, 208 and 240). Is it just the part where the third breaker slot can't be used for 120, and so people want easier installs, or they don't see a need for both 208 and 240, or bigger breaker panels, or ...?
Or is it that there are not always both options available, and any 3ph option is better than no 3ph?
Or is it that there are not always both options available, and any 3ph option is better than no 3ph?
That's the case here. You're NOT getting 240V Delta from my utility.
wyliesdiesels
Well-known member
You cant use the hi-leg for line to neutral loads
The voltage is not stable and running a load on it can cause weird imbalances.
You would also have to use straight rated breakers because of the higher voltage to neutral/ground.
The voltage is not stable and running a load on it can cause weird imbalances.
You would also have to use straight rated breakers because of the higher voltage to neutral/ground.
You would have to use single pole 277V breakers on the high leg, which opens up more issues.
I dealt with a utility Co on one job, added quite a bit of load to a 240v delta. Had 25kva transformers, 400A service. Told them what load I was adding and they might want to look at their transformer size.
Boy that guy started going on, have to change to 208 or 480v! Told him I'm not changing the service equipment, just adding load. Then he starts warning about a hot socket. Well it's CT metered so I'm not really worried... Finally he says the transformers are fine, they aren't changing anything.
Drove by a month later and there was 3 new 37.5 or 50 kva transformers hanging on the pole, I don't remember exactly what size. That sure made me happy after the way he went on and on.
Boy that guy started going on, have to change to 208 or 480v! Told him I'm not changing the service equipment, just adding load. Then he starts warning about a hot socket. Well it's CT metered so I'm not really worried... Finally he says the transformers are fine, they aren't changing anything.
Drove by a month later and there was 3 new 37.5 or 50 kva transformers hanging on the pole, I don't remember exactly what size. That sure made me happy after the way he went on and on.
wyliesdiesels
Well-known member
why would it have to be 277v rated breakers? 240 straight rated breakers should work
Because they don't make 240V single pole breakers.
wyliesdiesels
Well-known member
A
Aaawww i admittedly have never searched for a straight rated single pole breaker… because well Ive never needed to…
alfredeneuman
Well-known member
347/600Y service is a Canadian voltage.
If he's doing work in the US it's 277/480Y
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Last thing you would want to do is run a 230V compressor on 208V. When ordering a new compressor, I-R supplies a single voltage motor when 208V is specified, IMHO, if 3Ø power is available, it's foolish not to use it.
Common yes, exclusively Canadian, no.
My point being, your Utility decides what you can get. Then add your own transformers to make what you want.
It's enough to test a motor (unloaded). But agreed, I'm not leaving equipment in service (on a 208V supply) unless it explicitly has a 208V (or 200V) rating.
micromind
Well-known member
Just for info and yes, this is way out in left field but Square D makes a 20 amp single pole breaker rated at 240/416 volts. It's QOXD120. The bolt-on version is QOBXD120. Feel free to laugh, I did, but the AIC (Ampere Interrupting Capacity) is 3K. Not all that useful......lol.
Obviously not meant for the US market but useful in foreign countries where the supply voltage is 240/416.
P.S. These come in 16 and 32 amps too, I always wanted to get a 16 or 32 and put it in a panel that will be inspected by a royal jerk just to see what he would do..........lol
P.P.S. If the high leg system was an open ∆ and the high leg transformer was 25KVA or less and its impedance was 3.5% or more, the maximum available fault current on the high leg would be less than 3KA. Maybe not so useless after all.....
Obviously not meant for the US market but useful in foreign countries where the supply voltage is 240/416.
P.S. These come in 16 and 32 amps too, I always wanted to get a 16 or 32 and put it in a panel that will be inspected by a royal jerk just to see what he would do..........lol
P.P.S. If the high leg system was an open ∆ and the high leg transformer was 25KVA or less and its impedance was 3.5% or more, the maximum available fault current on the high leg would be less than 3KA. Maybe not so useless after all.....
alfredeneuman
Well-known member
In the Northeastern US, some POCOs get their power generated from Canada.
Where else is it used?