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Another 3 Phase question

Capt Odyssea

Capt Odyssea

In Yamalibrium
So a 3 phase 208v electrical panel, no wild leg. All show 120v to neutral.
But Leg to Leg is low at 200v.
What's up with that?
I'd expect 208 minimum, prob closer to 230v?
My month for weird Electrical issues it seems.

Another panel different site and supply, shows 125 each leg to Neutral, but leg to leg is 203.
Anyone with an idea? Again, no high or wild leg.
Klein and Fluke meters show the same.
 
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8V low would appear to be within tolerance. You won't get 230/240V on two phases of a 3 phase system, you need a split single phase system for that.

ETA: I see you're in the Bahamas, so who knows, your electrical system may be completely different from what we have in the US.
 
Standard U.S. 60hz, 120/240v single split or 208v 3 phase, have never run across a high or wild leg so I assume a WYE config?

The first above with 120v/leg to neutral and a flat 200v leg to leg is the power co supply. one Bay of a larger building with multiple tenants.

The second above w 125/leg and 203 leg to leg is a generator, 200kw, still temporary power following Hurricane dorian, just stuck me as strange to be low on the leg to leg but high on legs to neutral.

We have a serious lack of competence I'm afraid.
 
You know what, I retract my original reply, since I completely missed that you tested each leg at 120V to neutral...I was trying to come up with some scenario, such as the phases not being quite 120 degrees apart, but then some combinations would read high and others low.
 
If they all read 120v to ground, you have a WYE configuration.

Could be slightly high resistance to ground on that center leg. Might explain why its 120v to ground but 200v phase to phase.
 
True RMS meters?

Haven't played with 3-ph for a while so dunno if that would cause a non-RMS meter to read a little different phase to phase than phase to ground, or not.
 
I'm just curious.
Is this causing some kind of problem?
Usually 3 ph 208 is for motors. If it can't produce the torque at (lower than) 208 (rated current it will draw more current) power being even. If it draws too much current it will trip the heater blocks in the starter or drive or eventually the fuses or breaker. If its working right it will trip thermal though. I don't see 200v being a problem. If the unit is designed to run actual 230v 3ph, you might need boost (opposite of buck) transformers.
I've had to do that for German presses installed in NY.
I find 480v typically reading 460 or less lately. It hasn't seemed to bother anything
 
nj pheonix said:
I'm just curious.
Is this causing some kind of problem?
Usually 3 ph 208 is for motors. If it can't produce the torque at (lower than) 208 (rated current it will draw more current) power being even. If it draws too much current it will trip the heater blocks in the starter or drive or eventually the fuses or breaker. If its working right it will trip thermal though. I don't see 200v being a problem. If the unit is designed to run actual 230v 3ph, you might need boost (opposite of buck) transformers.
I've had to do that for German presses installed in NY.
I find 480v typically reading 460 or less lately. It hasn't seemed to bother anything
Click to expand...
It's also used for lighting. 10% is not a standard acceptable tolerance. I do know that the ANSI standard for 120v. is +/- 2.5%
 
ANSI C84 service voltage is 120 +/-5%. ANSI utilization voltage has a wider total tolerance, particularly the low tolerance, because it also considers drop in the inside wiring.

Screenshot_20200701-190716_Drive.jpg
 
Ok, thanks all, The issue we are experiencing is a dozen UPS units on PC/printers beeping at random, but proving to be hard to track down the voltage drop/cause
We are in the process of replacing all the old salt water wet switch gear, supply side stuff.
Service was 480v 3 phase with AC units (15 ton, 20 ton, multiples, say 8 units total) on the 480, and 6 step down Transformers giving us 208/120v. (50Kva to 75 Kva, may have been one at 120Kva)
All 480v gear got wet, and the step down transformers. Actually also the Power co transformers went under also. 14kv to 480v.
Currently installing 8 ton frequency drive AC units @208v, and distribution panels, so changing utility supply to 208 3 phase.
Will obviously drastically reduce the demand factor with no compressor hit on start up, and reduce overall consumption also.
We did the LED 4ft tubes a few years ago. That caused the power co to come and change the meter twice! they could've just asked........
Anyway, Mothers wit got us open within days of the Storm, first on a 45Kw 208v Gen and then on a 200kw 208v Gen.(that will be the permanent stby gen on auto transfer)
All the end branch circuits were not wet so we only had to reconfig the supply side stuff,running 208 through what was 480v gear.
Appreciate the input everyone.
Paradise has it's downside......
 
Presumably all the cables that used to carry the load at 480 were properly upsized to now carry the load at 208?

Your comment about the power company wanting to change the meter gave me a chuckle. I had the same thing happen with the gas company when I turned my dual-fuel heating system (natural gas & electric) to run fully on electric. Couple months later a gas company guy knocks on the door, "I have a work order to change your meter because it's not reading properly." I told him he could change it if he must but I guarantee the new one will read exactly same as the one there now. Went on to explain why, to which he said "Ahhhh...", and did not change the meter.
 
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Just thinking on that scale. CVTs my be the answer for the computer equipment.
Google constant voltage transformer.
 
surprised they're changing all of the service to 208 rather than just installing local step-down for the 208v equipment. All the stuff I have at work is done that way. 480v mains, and step-down trafos where needed mostly for 120v loads but there are some 208v items. Double the current for 208 of course, which means fatter wire.
 
I don't want to highjack anyone's thread, but it seems those knowlegable on 240 vac are here and I have a question.

I have a Sundance Marin Spa. It has four motors (recirculation, jets, jets, and blower). The thing is computer controlled, cycling itself and all of the pumps every day.

I have a twin 60 amp breaker on the main panel, and a twin 60-amp GFI breaker on a subpanel by spa, ~60 feet from the main panel.

Two weeks ago I noticed the spa was not cycling, and in fact had no display. I checked the wiring in the spa and found it to be OK. Then I checked the GFI breaker and found it tripped. I reset it and all was well... for about 2 weeks. Now it will continually trip if reset. The main breaker (no GFI) never trips.

If I remove the spa wires from the GFI breaker, it does not trip and I get 238 VAC on these pins. I get ~68 ohms across the red and black to the spa. As soon as I reconnect the spa, it trips.

At this point I ordered another GFI breaker (frickin' expensive for twin 60 amp) that I found used, but the seller would guarantee it for a year. Still $85 shipped/tax, but worth a try I guess. Should be here next week.

Is it common for these GFIs breakers to go "wonky" (~8 years old) or should I expect the problem to remain with another?

By code, pool lights (mine included) are not on GFI because they would continually trip. In fact, when my pool light is plugged into a GFI, it does trip. What is the efficacy of changing this spa subpanel to a non-GFI breaker? I don't think I can just install a non-GFI breaker in this panel because of a difference in the shape of the back of the breakers and how they latch in so would need to change out the entire box (still cheaper than a twin 60 GFI breaker).

Thanks
 
Well, it's you and yours but I most certainly would NOT do away with the GFI.

Maybe it's the GFI itself, maybe the GFI is telling you something by doing what it's supposed to do. Maybe a process of elimination by disconnecting each motor and heaters and stuff one at a time can pinpoint an offending component in the hot tub.
 
The GFCI are required for any sort of wet location / outdoor gear. Pretty certain if you check the electrical codes it will very specifically call for a GFCI on a spa.

We used to have a hot tub and when it started tripping the GFCI it was a bad heater. I was able to use an ohm meter and read from the disconnected heater power leads to the metal shell it lives in. It was pretty low resistance and when I pulled the heater out there was an obvious visible hole in the insulation. Its basically just a calrod heating element stuck in a metal pipe, nothing all that complicated but once that outer cladding goes away and exposes the wire inside its done. I'd give everything a quick ohm check to ground first just to see if it turns anything up.
 
whoaru99 said:
Well, it's you and yours but I most certainly would NOT do away with the GFI.

Maybe it's the GFI itself, maybe the GFI is telling you something by doing what it's supposed to do. Maybe a process of elimination by disconnecting each motor and heaters and stuff one at a time can pinpoint an offending component in the hot tub.
Click to expand...

The other than recirculation, the motors and heater don't come on when the power is first applied..., only when called on. Everything is controlled by the motherboard/relays.

BTW, I had replaced both the heater and recirculating pump a couple years ago. PITA!
 
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