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I have both Blue Boards and Green (kit) boards. The blue boards all
had problems when split over the 2 phases of normal residential
power. The Green boards did not have the problem. I have not
yet tried a firmware upgrade (which may fix it). like I said,
I'm just reporting what happend to me this year when I used
2 different phases into a single controller.

Tim

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hdrigid wrote:

I'm Missing something here. The link was for 3 phase which isn't residential.

I posted the link because of the symptoms I had more than the electrical application. Hopefully someone will learn from it.

Tom
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I'm probably just going to make matters more confusing, but let me give a bit of a try...

Distribution power is 3-phase. That's what commercial uses. DEFINATELY going to have problems if you try to power these boards off of two different phases. 3-phase means that the cycle of the AC sinewave is offset between the different legs of the feed (hence the name three phase).

One of the phases of the distribution power feeds a transformer on your local power pole [or transformer vault.] The transformer reduces the high voltage down to 240VAC center tapped, which is fed to your house as two wires. Center tap on the transformer is provided as reference or neutral through earth ground. So by going from netural (ground) to >either< of the hot leads you get 120VAC; going from hot to hot gives you the 240VAC (like for major appliances).

Now, in your breaker box, each of the hot lines feed one power rail. The neutral is mechanically tied to ground in the box. The circuit breakers in the box are designed so that a 120V breaker takes a single slot and feeds off of one of hot rails; and a 120v breaker immediately below that one feeds off of the OTHER hot rail. It's arranged this way so that if a 240V breaker is installed (which is a double-wide breaker), it clips on to BOTH of the power rails to get access to the full 240v.

Normally it doesn't matter which rail any given socket in the house is being powered from since there is no interaction. But if you have one of the legs loaded a bit more than the other (which always happens in practice), then the neutral referenced to ground of tha legs moves away from true ground. (This is due to the wire resistance, etc, between where the neutral is mechanically tied to the earth ground in the circuit box and the earthground at the transformer). It's interesting to note that you share the transformers with other houses, so THEY are also affecting the load on each leg. The theory here is that everything will average out so that no leg is far out of whack of any other.

What this means is that if you power one of the dimmer boards from two different legs, one side of the board will establish a "virtual ground" for the board. This will be used by the triacs to detect "zero crossing", that is, when the sine of the voltage crosses zero which is the only time there is no load on the line. That is the only time that a triac can turn on or off. The other side of the board will have a slightly different neutral. So you get a conflict between the detected zero-crossing and the source voltage. Result is a triac misfire, or latchup.

The bottom line is: Feed a single board off of two breakers that are either directly across from one another in the panel and/or a multiple of two away vertically from each other. This assures both are on the same leg (or rail) of the feed. This is ONLY a necessity for the feeds of a single board. Doesn't matter where other boards are powered from.

[Disclaimer: I've >greatly< simplified (or at least tried to :) ) this explanation. I know the explanation is not complete. But hopefully this gives a bit of insight as to what's going on and how to deal with it.]

Joe

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I am very surprised that anyone in a residential situation has had a problem with what leg of the service is used with the two sides of a CTB16D. I do know that in the vast majority of cases it makes absolutely no difference where you plug things in.

Also the fact that there was a difference between a green card and a blue card is surprising. There are minor differences between the two cards but. We will look into this to see what is going on. Anyone that is sure that they had a problem with a controller that was corrected by moving from one leg to the other please send an email to support@lightorama.com and describe the symptoms that were seen that lead you to move the plug to a different leg.

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Joe, I just want to thank you. I am taking from your explanation that you are an electrician, and that explanation was incredible. I did have to read it twice, but thats just me.:laughing: Thank you so much for taking the time...you really helped me out with that!!

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Jeckardt, Thanks for taking the time to explain that.............But.

The board is designed for 240. So if you can put a double pole 20 amp breaker and wire its straight to the board (no receptacles) you would have the same issue. The breaker is on different hot legs in the panel with one ground. Now if you take that breaker and install 2 receptacles duplex or cut the tab off of one and have upper and lower on different legs and plugged the unit in them there would be no difference then straight wiring them. Each application is still going to share the same ground/neutral.

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Ponddude wrote:

Joe, I just want to thank you. I am taking from your explanation that you are an electrician,


Actually I'm a EE/CS, not an electrician. Part of the EE curriculum required plowing through several classes on power systems, AC machines, transformers and EM devices, and other power-related subjects. Also used to work in technical theatre (lighting and sound design, and troubleshooting 1st and 2nd generation electronic lighting systems). These days I deal mostly with low-voltage (i.e., computers).

hdrigid wrote:
Jeckardt, Thanks for taking the time to explain that.............But.

The board is designed for 240. So if you can put a double pole 20 amp breaker and wire its straight to the board (no receptacles) you would have the same issue. The breaker is on different hot legs in the panel with one ground. Now if you take that breaker and install 2 receptacles duplex or cut the tab off of one and have upper and lower on different legs and plugged the unit in them there would be no difference then straight wiring them. Each application is still going to share the same ground/neutral.

I would't think so. Presumably you've wired both wires of the 240v feed to a single set of power inputs on the board ("single feed configuration" per LOR docs). So one of those legs should become the "neutral" reference for the board, the other the hot. Ground reference doesn't come into play with 240v as neither leg of the 240v feed is tied to ground anywhere in the circuit box. Now what you are likely to find is, if you measured the voltaged of the 240v-wired board neutral to earthground (or hot to earthground for that matter) you'll probably see 120v (which is the same that you'd see measuring each rail to earthground at the circuit box).

[Disclaimer: this is entirely guesswork as I have absolutely no idea of what the board is doing as the schematic of the board is unavailable.]

Please note that I have never tried to wire these boards to 240v myself, and have never personally had any of the problems that started this thread. I chimed in only because there seemed to be confusion regarding the difference between 120v, 240v single-phase, and 240v three-phase. (I do remember how confusing this was for me in my first power-systems class in college.) Please don't think I'm any sort of expert on how these boards really work... that's Dan's territory. I could be totally off in the weeds on this.

Joe
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hdrigid wrote:

Jeckardt, Thanks for taking the time to explain that.............But.

The board is designed for 240. [snip]

That is 240 (outside the US)... In that case the 240 is Hot/Neutral like here in the US but the Hot side is 240 not 120.
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I/m sorry Dan I did not grasp what you are trying to say.

All homes are single phase. But to be clear here we need to call the hot leads legs.

Stole this from another board.

A common version of a single phase, 120/240 volt transformer will have a single core, a single primary winding, and a single secondary winding that is center-tapped to ground. The same flux from the same primary is imposed on both halves of the secondary winding, and has the same influence on each. We connect the neutral to the center tap, and a hot leg to each end. But we measure voltage of one leg as from neutral (i.e., zero reference voltage) to one end of the secondary winding. Then we measure voltage of the other leg as from neutral (i.e., zero reference voltage) to the other end of the secondary winding. If you show both of these on the same oscilloscope, you will see two sine waves 180 degrees apart.

The secondary of a transformer is a coil of wire around a core. For the sake of simplicity, let's say there are 240 turns (coils) in the secondary. This gives us 1 Volt per Turn for this transformer. As the magnetic flux travels through the core, these turns are each excited to the tune of 1 Volt. There is a center tap in this secondary. A circuit that is connected from one end to the center is connected to 120 turns. It sees 120 Volts: 1 Volt per turn. If a circuit is connected to the ends of the windings, it is connected to 240 turns. At 1 Volt per turn, this gives 240 Volts. All of these turns are in phase with one another. The center tap merely accesses half of the available voltage.


Me:

Now Grounds and neutrals are the same thing they go to the same place back to zero.

Any imbalance is transferred through the neutral. http://electrical-contractor.net/BCodes/unbalanced__neutral.JPG

So in the end you can connect each side of the controller to any outlet not being on the same leg. It doesn't effect it. You are providing the same current to each side with no imbalance because homes are single phase.

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