Single phase appliance on a 3 phase panel?

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Also, it is a relatively new panel here in California. And, I just read this on the interwebs so I think @James L is correct:

"Also, use the Orange color for high leg delta hot busbar (now phase “C”, previously Phase “B” – prior NEC-2008″.

Caution:

  • The High Leg Must Terminate on the “B” Phase.
  • Utilities require the High Leg conductor in meters and box be located on the “C” Phase.
 
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Joethemechanic said:
B should be the high leg. Don't use the high leg for any of your single phase loads. Slash rated single phase breakers like 120/240 are not rated for the high leg. In my place I have single phase sub panels for my single phase loads. I only use the high leg for 3 phase loads
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Slight correction: don’t use the high leg for any single POLE loads. The “high” leg is only high with relation to neutral (and ground), leg to leg it’s just 240V.

2 pole single phase loads (that don’t need a neutral wire for 120V) are fine in the high leg.
 
A high-leg delta is a standard 1ph 120/240v source AND a standard 3ph delta source, superimposed on each other. In fact, the high-leg, open-delta service originated as a modification to existing 1ph services for new 3ph equipment.
 
don_resqcapt19 said:
You can't use "slash rated" breakers on that system. You have to find a straight rated 240 volt rated breaker,
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and it seems like most people dont know or just ignore this. I work on quite a few high leg delta in Seattle and I dont recall EVER seeing a straight rated breaker used for a two pole connected to the high leg. These breakers are not very common. For siemens, its a R added as a suffix, i.e. a Q220R is a two pole straight rated 20 amp breaker. I got a quote of $110 apiece a few months back from my siemens guy (who hadnt even heard of them). For QO it is a H between the QO and the numbers, i.e. QOH220. For the bolt on versions, it is probably cheaper to use a 277/480 breaker such as a siemens BQD, which is there common slash rated 480V breaker.
 
Hey guys, happy Friday! I got a chance to get under the hood of the Square D, 3 phase 240v high leg delta panel today. There's a plot twist.

The panel is maxed out with only a couple of slots left open that are the wild leg - I thought I was going to be able to move a couple breakers around but not the case. But below I will explain an easier way but I'm a bit confused (but I'm pretty sure I know what they did here - but want to run it by ya'll).

When I took off the dead front and metered it out, it turns out that C phase is in fact the high leg and is "phased" as PURPLE instead of ORANGE.

I got the usual delta, 3 phase - high leg readings:
  • Neutral to A phase = 120V
  • Neutral to B phase = 120V
  • Neutral to C phase = 208
  • A-B-C phase to phase were all 240V between phases

Anyway, I really got a chance to look at the bones of the electrical system at this place and it turns out that this 240v high leg delta panel is feeding another panel with more space in it - it's serving as a sub-panel but I'm confused about the panel rating and how it was metered out.

After taking off the dead front of this other panel that is an Eaton, 3 phase panel, it shows it is a 208Y/120V on the dead front. Below are the readings I got which are the same as the 240V Delta high leg it is being fed from - it is not reading out as 208Y/120V, 3 phase system - here are the reading I got:

  • Neutral to A phase = 120V
  • Neutral to B phase = 120V
  • Neutral to C phase = 208
  • A-B-C phase to phase were all 240V between phases

So to hook this single phase, 208/230V mini-split HVAC unit up, I can just grab an A&B phase on this Eaton sub panel and get an Eaton 120/240V slash rated, double-pole 40A breaker and call it a day?

I was just surprised to get the readings that I did with this 208Y/120V Eaton panel which resembled the high leg panel.

Main questions here are:

  1. Can I just grab an A&B phase on this Eaton sub panel and get an Eaton 120/240V slash rated, double-pole 40A breaker and call it a day?
  2. What are your thoughts about the readings on this 2nd Eaton sub-panel that is rated 208Y/120V but reading out as the high leg, 240V Delta?

We also have a 480V panel. Both the 480V panel and this 208Y/120V Eaton sub-panel are tied into a xformer near all the panels. The xformer ties into the high-leg Delta system which is serving as the "main".


Pics belowSquareD panel.jpg
Square D, 240V Delta 3 phase high leg panel


HighLegPhasing.jpg
Square D, 240V 3 phase high leg "phasing"


HighLegBranches.jpg
Square D, 240V high leg branch circuits


EatonSubpanel.jpg
Eaton sub-panel that is being fed with (4) #2's from the Square D, 240V Delta high leg panel


EatonFeeders.jpg
Eaton 3 phase 208Y/120V feeders from the Square D, 240V Delta 3 phase high-leg


EatonBusbar.jpg
Eaton 3phase, 208Y/120V busbar
 
(1) sounds fine to me - as long as we are assuming 10kaic is sufficient
(2) I wouldnt worry about the "mislabeling", take your label maker and fix it. I'd bet you a milkshake that there wouldnt be anything different from the factory for a 120/240 three phase panel.
 
Manufacturers labels typically show the maximum system voltage the equipment can be installed. In some case special order panels may show a specific voltage that was on the drawings.

Almost never will a manufacturer's panel label show you the actual installed voltages.

For example: In the above pictures the Square D panel label shows it is good for a maximum of 240VAC 3-phase or 48VDC. The only way to know the voltage is to use a voltmeter.
 
If this is in San Francisco purple instead of orange is actually the code requirement. It's a local ammendment. If it's not in SF maybe the electrician was originally from there.
 
Yeah never look at any panel and assume you know the voltage. For example a customer may tell you they have 120/208 , but they actually have a high leg delta.

Dealing in used machinery for years I seem to always had more 480 fused discos. Most of the people I sell stuff to have 240 or 208. At one point I had so many 480v that If someone bought a machine off of me and needed a 240 disco and I didn't have one I'd give them a 480 fused disco for free. So if you find a 480 disco and replace a motor on a machine and connect the motor for 480, and smoke the motor because it's running on 240, you can curse me
 
hillbilly1 said:
An easy way to guess is if the majority of the second or third spaces are open! Big red flag is its a delta! LOL!
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Some old residential delta panels the high leg doesn't make it to the busses, it stops at its own cb at the top of the panel, i beleive beneath the main cb for the other hots- or something like that.... I wish I had a pic. The delta meters are very different looking from a normal meter, aside from the service voltage labeled on the face of the meter of course...
 
hillbilly1 said:
An easy way to guess is if the majority of the second or third spaces are open! Big red flag is its a delta! LOL!
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So funny and true indeed - that is exactly what I was looking at when I thought I was going to be able to just move a breaker where these third space breakers were open! When I took off the dead front this was exactly what was going on! lol

rambojoe: I've said it before, you can look at the meter and know what it is...
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how so?

LarryFine: I prefer to look at the transformers.
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What do you look for?
 
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wondervamp said:
So funny and true indeed - that is exactly what I was looking at when I thought I was going to be able to just move a breaker where these third space breakers were open! When I took off the dead front this was exactly what was going on! lol


how so?


What do you look for?
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I was about to take a picture of an open delta. But stepped outside, transformers were already gone! Changed over the service a couple of weeks ago to a 480 wye. I thought I had another picture, but Google photos lose’s them!
 
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