# how does this circuit work?

How does this circuit work?
This house has 3 phase power.
I was replacing a downlight and found it having two black, two neutral, and one blue incoming wire.
If the light switch was on, the blue wire was energized. If the ceiling fan was on, one of the incoming black wire was energized.
Why/how do both light and fan work when both are on?
incoming downlight a) ================(black)------------------ b) ================(neutral)---------------- c) ----------------(blue)------------------
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On Wednesday, March 14, 2018 at 10:38:55 PM UTC-4, Oumati Asami wrote:

IDK why a house anywhere would have 3 phase power. But there is a wire for the light, a wire for the fan, two neutrals, so what's the issue?
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Sorry, the diagram was wrong. I mistakenly labelled ground as neutral. It is now corrected.
When both fan and light are on, both the blue and black wires are energized.
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On Thursday, March 15, 2018 at 6:09:18 AM UTC-4, Oumati Asami wrote:

So, again, you have a hot for the light, a hot for the fan and a neutral. What's the issue?
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On 3/15/18 6:27 AM, trader_4 wrote:

Is the equipment ground being used as the neutral? It must be tied to the neutral upstream somewhere. That's illegal at least in my world.
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On Thursday, March 15, 2018 at 7:58:01 AM UTC-4, Dean Hoffman wrote:

does a represent TWO blacks wires and only one is energized when the fan is on? what about the other black wire? are the two black wires connected together?
does b represent TWO white? are they connected together?
and c looks like it is ONE blue wire that is on when the light is on?
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On 15/03/2018 19:22, snipped-for-privacy@yahoo.com wrote:

Yes. Only one black is energized when fan is on. The two black wires are connected together. The parentheses represent a connector. It is like []=[]=[] where wires go into the [] from top and bottom (https://uae.souq.com/ae-en/mega-pvc-wire-connector-10amp-m85470-7557028/i /). To put the connector into the top diagram, turn the connector ([]=[]=[]) 90 degrees. So, from left to right is a, b, and c.
In this part of the world, ground is yellow/green. They are connected together.
There is only one blue wire and it is on when light is on.
So, when both fan and light are on, both a and c are energized.
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On 15/03/2018 18:27, Dean Hoffman wrote:

How do I test if ground is used as neutral?
The main breaker is a GFIC. I have experienced unexplained tripping. Would that have anything to do with ground being used as neutral?
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On 3/15/18 9:13 PM, Oumati Asami wrote:

Just by looking, I suppose. Assuming the motor has two wires, one wire is the hot wire feeding the motor. What is the other, second, wire coming out of the motor connected to? It should be hooked to a neutral eventually going back to your panel. It shouldn't be hooked to any metal in the motor housing or frame. The same thing applies to the light. A hot wire feeding it, a neutral going back to the panel, and a separate ground wire connecting metal to metal in the various boxes containing lights, outlets, etc. The easiest way to cheat would probably be to connect the second wires out of the devices to the metal. Then the ground would be carrying the current that should be carried by the neutral.
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On 16/03/2018 17:15, Dean Hoffman wrote:

I am not sure/don't think both black wires are from the fan. When I separated the two black wires and turned on the fan, one of the black wire was energized and the fan wasn't turning. That's all I know. the other black may serve as the neutral for both the fan and the light.

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On Thursday, March 15, 2018 at 10:13:37 PM UTC-4, Oumati Asami wrote:

e:

?             downlight

---------

--------

.
he neutral?  It must be

ld.

If the ground was used as the neutral, it would trip for sure when the ligh t or fan was turned on. It would probably trip even without being turned on . Like I said, the wire might be green, but it could be otherwise correctly used as the neutral.
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On 15/03/2018 18:27, Dean Hoffman wrote:

It never occurs to me that people would use ground as neutral. Would that make the fixture energized when on? I just tested the light fixture, it was not energized when light was on, nor when both were on.
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On Thursday, March 15, 2018 at 11:06:00 PM UTC-4, Oumati Asami wrote:

e:

?             downlight

---------

--------

.
he neutral?  It must be

ld.

The fixture would not be energized as long as the wire is connected all the way back to the panel and connected to the neutral there. But if it got d isconnected, the light and fan would not function and the metal would be en ergized. Which is why it's not allowed by code for that kind of circuit her e in USA at least.
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When both fan and light are on, there are two hots. Where is the neutral?
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On Thursday, March 15, 2018 at 10:10:11 PM UTC-4, Oumati Asami wrote:

Same place it's always been? You said there was a neutral.
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Sorry. I made a mistake in the original post. The neutral in the original should be ground. There is a blue wire, hot when light is on, two ground wires, and two black wires, one of them hot when fan is on. Please see the corrected diagram above.
The light is a ceiling recess light, not one on the ceiling fan.
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On Thursday, March 15, 2018 at 10:43:03 PM UTC-4, Oumati Asami wrote:

te:

tral,

gized.

----------

---------

ire for the light, a wire for the fan, two neutrals, so what's the issue?

l.

ral. What's the issue?

al?

The ground wire should be connected to the metal frame of the fan and light . The fan and light have a hot on one side and the other side is the neutra l. Like someone else said, if that wire is another green/yellow then it is serving as the neutral and should be marked as that. Whether it is correct ly run and terminated on the other end, who knows.
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On Wednesday, March 14, 2018 at 11:09:04 PM UTC-4, trader_4 wrote:

I can answer that for one location.
In a housing development at what is essentially a campus, we fed 3 phase power to individual houses because of going to 208V airconditioners. I think we got a better price on a bulk buy of the units.
What we found is that everybody complained their dryers didn't work right and their ovens took too long to warm up. Their appliances expected 240.
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For a straight thermal load like an over or dryer, that drop from 240 to 208 is actually pretty messy.
At first glance you'd think that 208/240 = 0.8666.., or about 13 pct, so to first approximations 13 pct longer to heat up.
However, wattage is amperage times voltage. And both of these [a] are dropping by that 13 pct.
So the final wattage is.. 0.86... times 0.86... = 0.73.
So more than 25 percent longer.
[a] neglecting the very real issue that in many of these items the resistance changes with temperatur...
As a side note, we installed a "240v" air conditioner i a NYC building that had three phase, so it was being fed at the equivlanet of 208.
We very specifically asked the sales rep AND the manufacturer if this would be a problem. They said it was fine.
It wasn't.
--
_____________________________________________________
Knowledge may be power, but communications is the key
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On 3/15/2018 11:36 AM, danny burstein wrote:

https://www.larsonelectronics.com/p-148185-1-phase-buckboost-step-up-transformer-208v-primary-240v-secondary-234-amps-5060hz.aspx
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